CA2190253A1 - Device and methods for in vivo culturing of diverse tissue cells - Google Patents

Abstract

An anatomically specific, bioresorbable, implant device for facili-tating the healing of voids in bone, cartilage and soft tissue is disclosed.
A preferred embodiment of using the implant device for facilitating the healing of a human joint lesion includes a cartilage region invested with an alginate microstructure joined with a subchondral bone region in-vested with a hyaluronan microstructure. The alginate selectively dis-persed in the cartilage region enhances the environment for chondrocytes to grow articular cartilage. The hyaluronan selectively dispersed in the subchondral bone region enhances the environment for mesenchymal cells which migrate into that region's macrostucture and which differ-entiate into osteoblasts. The microstructures can be invested at varying concentrations in the regions. A hydrophobic barrier, strategically po-sitioned within the subchondral bone region macrostructure, shields the chondrocytes from the oxygenated blood in subchondral cancellous bone.
In the preferred form, the cartilage region includes a tangential zone in-cluding a network of intercommunicating void spaces having a horizontal orientation and in communication with synovial fluid and includes a ra-dial zone including multiple void spaces oriented in both horizontal and vertical planes and providing intercommunication between the tangential zone and the subchondral bone region.

Description

WO95131157 r~ l~U.. ,~ In9 2 1 90~53 Device and Methods For In Vivo Culturing of Diverse Tissue Cells BACKGROUND _ _ _ 1. Field of the Invention:
The present invention generally relates to the LL~III yuL L and culturing of cells. Specifically, in one aspect, the present invention employs an ana~ ic~l ly specific device for regenerating at least first and second, juxtaposed tissues having different histologic patterns, lo which includes a f irst region having an internal three-dimensional architecture to approximate the histological pattern of the f irst tissue and a second region having an internal three-dimensional architecture to approximate the histologic pattern of the second tissue. In addition, 15 the present invention relates to a domain for the trapping and controlled growth of cells as such functions relate to tissue regeneration. In particular, a permeable bioLes~,L~able polymer assembly is designed in such a way as to allow tissue integration of the assembly while 20 delaying, limiting or preventing total penetration through the device by tissue cells. Such an assembly can be used to: 1) provide space maintenance and regeneration of lost tissue ~ rn;~l to the unit; and/or 2) control growth of tissue forming cells within the unit.
2s 2. Statement of Related Art The medical repair of bones and joints in the human body presents significant difficulties, in part due to the materials involved. Each bone has a hard, compact exterior ~uLL-~ullding a spongy, less dense interior. The 30 long bones of the arms and legs, the thigh bone or f emur, have an interior containing bone marrow. The material bones are ,- e' Of mainly is calcium, phosphorus, and the connective tissue substance known as collagen.
Bones meet at joints of several different types.
3s ~fJV~ L of joints is ~nh;lnl Pcl by the smooth hyaline cartilage that covers the bone ends and by the synovial membrane that lines and lubricates the joint. For example, consider a cross-section through a hip joint.

Wo9SJ3115-f 21 ~0,~53 -2- P.,lf .~ 109 ~
1 The head of the femur is covered hy hyaline cartilage.
Adjacent to that cartilage is the articular cavity.
Above the articular cavity is the hyaline cartilage of the acetabulum which is attached to the ilium. The ilium s is the expansive superior portion of the hip bone.
Cartilage damage produced by di5ea5e such as arthritis or trauma is a major cause of physical deformity and dehabilitation. In ~ ;ne today, the primary therapy for loss of cartilage is replacement with a prosthetic lo material, such as silicon for cosmetic repairs, or metal alloys for joint realignment. The u5e of a prosthesis is commonly associated with the signif icant 1055 of underlying tissue and bone without recovery of the full function allowed by the original cartilage. The prosthesis is also 1S a foreign body which may become an irritating presence in the tissues. Other long-term problems associated with the pPr~~nPnt foreign body can include infection, erosion and instability .
The lack of a truly compatible, functional prosthesis 20 subjects individuals who have lost noses or ears due to burns or trauma to additional surgery involving carving a piece of cartilage out of a piece of lower rib to approximate the nPcP~sAry contours and insert the cartilage piece into a pocket of skin in the area where the nose or 2s ear is missing.
In the past, bone has been replaced using actual segments of sterilized bone or bone powder or porous surgical steel seeded with bone cells which were then implanted. In most cases, repair to injuries was made 30 surgically. Patients suffering from degeneration of cartilage had only pain killers and anti-infl; tuLies for relief.
Until recently, the growth of new cartilage from either transplantation or autologous or allogeneic 35 cartilage has been largely llnc~l~ rP~ful. Consider the example of a lesion extending through the cartilage into the bone within the hip joint. Picture the lesion in the wossl3lls7 21 qa253 P~U~ 9 l shape of a triangle with its base running parallel to the articular cavity, extending entirely through the hyaline cartilage of the head of the femur, and ending at the apex of the lesion, a full inch (2 . 54 cm) into the head of the 5 femur bone. Presently, there is a need to successfully insert an implant device consisting of a macrostructure and a microstructure for containing and transporting cartilage cells and bone cells together with supporting nutrients, growth factors and morphogen6, which will assure survival o and proper future differentiation of these cells after transplantation into the recipient tissue defect.
Presently, cartilage cells, called chondrocytes, when implanted along with bone cells, can degenerate into more bone cells because hyaline cartilage is an avascular 15 tissue and must be protected from intimate contact with sources of high oxygen tension such as blood. Bone cells, in contrast, require high oxygen levels and blood.
Most recently, two different approaches to treating articular lesions have been advanced. One approach such 20 as disclosed in U.S. Patent No. 5,041,138 is coating bioderesorbable polymer fibers of a structure with chemotactic ground substances. No detached microstructure is used . The other approach such as disclosed in U. s .
Patent 5,133,755 uses chemotactic ground substances as a 2s microstructure located in voids of a macrostructure and carried by and separate from the biodegradable polymer forming the macrostructure. Thus, the final spatial relationship of these chemotactic ground substances with respect to the bioresorbable polymeric structure is very 30 different in U.S. Patent No. 5,041,138 from that taught in U.S. Patent No. 5,133,755.
The fundamental distinction between these two approaches presents three different design and engineering consequences. First, the relationship of the chemotactic 35 ground substance with the bioresorbable polymeric structure differs between the two approaches. Second, the location of biologic modifiers carried by the device with respect _ . .

wo95/31157 21 93253 r~ ng to the device's constituent materials differs. Third, the initial location of the pa~en- lly",c,l cells differs.
Both approaches employ a bioresorbable polymeric structure and use chemotactic ground substances. However, S three differences between the two approaches are as f ollows .
I. Relatilln~hir of Chemotactic Ground Substances with the Bioresorbable Polymeric Structure.
The design and engineering consequence of coating the polymer fibers with a chemotactic ground substance is that both materials become fused together to form a single unit from structural and spatial points of view. The 6paces between the f ibers of the polymer structure remain devoid of any material until after the cell culture substances are added.
In contrast, the microstructure approach uses chemotactic ground substances as well as other materials, separate and distinct from the biuL~:svLbable polymeric macrostructure. The microstructure resides within the 20 void spaces of the macrostructure and only occasionally juxtaposes the macrostructure. Additionally, the micro-structure approach uses polysaccharides and chemotactic ground substances spacially separate from the macro-6tructure polymer and forms an identifiable microstructure, 25 separate and distinct from the macrostructure polymer.
The design and engineering advantage to having a6eparate and distinct miuLu:~LLu- LULe capable of carrying other biological active agents can be appreciated in the medical treatment of articular cartilage. RGD att~ L
30 moiety of fibronect~n is a desirable substance for attaching chondrocytes cells to the lesion. However, RGD attachment moiety of fibronectin is not, by itself, capable of forming a microstructure of velour in the microstructure approach. Instead, RGD is blended with 35 a mi~:Lo~LLuuLuL~ material prior to illVe~ i L within macrostructure interstices and is ultimately carried by the microstructure velour.

WO95f31SS'f r~ o~los II . Location of Biologic Modif iers Carried by a Device with Respect to the Device's Constituent ~aterials.
Coating only the polymer structure with chemotactic ground substances necessarily means that the location of 5 the chemotactic ground substance is only f ound on the bioresorbable polymeric structure f ibers . The micro-structure approach uses the microstructure to carry biologic modifiers such as growth factors, morphogens, drugs, etc. The coating approach can only carry biologic lo modifiers with the biodegradable polymeric structure.
III. Initial Location of the Parenchymal Cell.
Because the coating approach attaches the chemotactic ground substance6 to the surfaces of the structure polymer and has no microstructure resident in the void volume of 15 the device, the coating approach precludes the possibility of establishing a network of extracellular matrix material, specifically a microstructure, within the spaces between the fibers of the polymer :~LLU~:LUL~ once the device is fully saturated with cell culture medium. The coating 20 approach pr~ etr~rm;nF~I that any cells introduced via culture medium will be immediately attracted to the surface of the ~LLU~:LUL~ polymer and attach thereto by virtue of the chemotactic ground substances on the polymer ' s surf aces .
The consequence of conf ining chemotactic ground substances to only the surfaces of the polymeric ~LLU~:LULC:
places severe restrictions on the number of cells that can be A~ ted by the coated device. These restrictions on cell capacity are enforced by two limiting factors:
30 1) a 5everely limited quantity of chemotactic ground substance that can be incorporated within the device; and 2) a surface area available for cell att 1~ L that is limited by the surface area supplied by the structure polymer .
In contrast to the coating approach, the microstructure approach, by locating chemotactic ground substances in the void spaces of the device, makes available the entire void Wo95/311S7 21 90253 r~l"~ r~log volume of the device to a~ te their chemotactic ground substance microstructure.
In so far as it relates to a biologic cell trap for controlled growth and guided tissue regeneration, recent s years have increased know~edge concerning biolPgical r--hAn;! involved in the restoration of periodontal defects which has led to a method of treatment known as Guided Tissue Regeneration. This concept is based on the theory of space maintenance for the periodontal bone 10 defect under treatment. Soft tissue is removed from the defect and a barrier is placed between the surrounding soft tissue and the periodontal defect (void) in alveolar bone. The barrier prevents soft tissue from returning to the defect (void) while allowing the slower growing bone 1S sufficient time to fill the void and reestablish att~ L with the tooth. These barriers can be broken down into two major groups: 1) Bioresorbable/Bioerodable;
~nd 2) Non-Bioresorbable/Bioerodable. Those barriers which are not bioresorbable (polytetrafluorethylene, 20 titanium, etc. ) must be removed by a second surgery resulting in additional surgical trauma and risk of damage to newly ~eJelle~ ,,ted bone by ~ i ~e of its collateral circulation. Those barriers which are bioresorbable have one of two drawbacks. They are either solid, in which 25 case they prevent interstitial fluid exchange, or they are permeable and allow rapid penetration of soft tlssue through the device. Thus, a unique design is needed in order to limit or prevent tissue penetration while still allowing for free exchange of interstitial fluid.
U.S. Patent Nos. 4,181,983 and 4,186,444 define porous biuL~su~l,able polymer devices. These devices, designed to treat tissue deficiencies, are comprised of a bioresorbable polymer fabricated in architecture resembling cancellous bone, allowing for rapid and 35 complete penetration of soft and hard tissue through the devices. U.S. Patent No. 3,902,497 meets the general description of U.S. Patent Nos. 4,181,983 and 4,186,444 _ _ , .. .. _ .. _ _ . _ . .. .. .

wo 95~31157 2 1 9 ~3 2 5 3 P~J~U.,, r~lO9 1 and will also allow complete soft tissue penetration in a short period of time.
U.S. Patent No. 4,442,655 teaches a fibrin matrix formed in an aqueous solution which, once placed in 5 mammalian tissue, will collapse and afford no barrier function to soft tissue invasion.
U.S. Patent Nos. 4,563,489; 4,596,574; and 4,609,551, although different from U.S. Patent Nos. 4,181,483 and 4,186,444, are designed to accomplish the same goal;
10 repair tissue def iciencies and create a continuous, uninterrupted mend. This is also the goal of U. S.
Patent No. 5,041,138, in which the device is of branching bi(,Lescll,able sutures.
None of the aforementioned devices, however, is 15 designed to operate as a cell trap or barrier. Each encourages rapid ingrowth of tissue which will escape the device and invade the def ect void .
STlMMARV AND DTTATTFn DES~ N OF THE INVENl~ION
The anatomically specif ic device i8 a living 20 prosthesis or implant for transport and for in vivo culturing of tissue cells in a diverse tissue lesion.
The entire macrostructure of this device is composed of a bioresorbable polymer.
The anatomically specific device integrates a 25 macrostructure, microstructure, free precursor cells cultured in vitro or from tissue, and biologically active agents, such as associated growth factors, morphogens, drugs and therapeutic agents.
The anatomically specific device in the ~nho~l;t L
30 designed for treating a cartilage and bone lesion has two main regions: a cartilage region and a sl~h~-hnn~lral bone region.
The cartilage region has a macro~L~ U~:LUL_ composed of two distinct zones. The tangential zone of the 35 cartilage region has intimate contact with synovial fluid.
The radial zone located between the tangential zone and WO 95131157 2 1 9 0 2 5 ~ r~ ' 0~109 ,--the 6l]hrhnn~lral bone region and comprising about 70% to 90% of the cartilage region is distinguished by vertically oriented plates which are ~enestrated by multiple voids.
The radial zone of the cartilage region is intimately S bound to the macrostructure of the subchondral region at an interface surface.
The microstructure material of the cartilage region in the most preferred form is alginate or hyaluronan.
Alginate, also known as alginic acid, is used for the o transport of both in vitro and in vivo cultured cells and the estAhli~l -nt of an in vivo cell culture system within the device. Alginic acid, though having no chemotactic properties, is especially suitable for use in a device for treating articular cartilage defects because it acilitates the culturing and transport of llu.l-~Lo-yLes.
The structure and the strategic location of the alginate mi~:L UD LL UL LUL ~ inside the macrostructure provides the opportunity to segregate microstructure material from the s~lhch~m-lral bone region. The alginate microstructure 20 has a primary function of delivering chondrocytes only to the cartilage region of the device by sequestering the chu~,dLu.yLe cell population with the in vitro cell culture medium in its alginate gel . The mi- L L :. LL UL LUL ~: has a secnn~lAry function of presenting enough chu~,-lLu-yLes to 25 the 511hrhnn~1ral bone region immediately adjacent to the cartilage regions to establish a competent osteo-chondral bond .
The selective concentration gradient of microstructure material may be selectively varied within certain regions 30 of the macrostructure void to affect different biologic characteristics critical to different tissue requirements.
The microstructure of a single device may be . - ~ J
of multiple different materials, some without chemotactic properties, in different regions of macrostructure void 35 6pace ~ r~n~l; n~ upon varying tissue and biologic characteristics and reSIuirements.

W09S/31157 21 90253 r~"u~-r~lo9 g The s~lhrhnn~ral bone region of the anatomically specif ic device includes a macrostructure _ - secl of a biologically acceptable, bioresorbable polymer arranged as a one piece porous body with ~enclosed randomly sized, S randomly positioned and randomly shaped interconnecting - voids, each void communicating with all the others, and communicating with substantially the entire exterior of the body" (quoted portion from U.S. Patent No. 4,186,448).
Polylactic acid (PLA), fabricated in the 3-D architecture 10 of inteL . i cationg voids described above is the polymer currently used to f orm the macrostructure . Other members of the hydroxy acid group of ~ ~- can also be used as can any bioresorbable polymer if fabricated into a similar architecture .
The gross, or macro, structure of the invention fulfills three major functions for chc,ll~Log~llesis and osteogenesis:
1) restoration of - -n;c~l architectural and structural ~ nre; 2 ) provides biologically acceptable and mechanically stable surface ~,L~ul ~ule suitable for 20 genesis, growth and development of new non-calcified and calcified tissue; and 3) functions as a carrier for other constituents of the invention which do not have mechanical and structural competence.
The microstructure of the implant device is -s ~ ' 2s of various polysaccharides which, in a preferred form, is alginate but can also be hyaluronic acid (abbreviated by HY). Interstices of the polylactic acid macrostructure of the body member are invested with the microstructure substance in the form of a velour having the same 30 architecture of interconnecting voids as described for the macrostructure, but on a microscopic scale. Functions of the chemotactic ground substance microstructure ( i . e . HY) are listed as: 1) attraction of fluid blood throughout the device; 2) chemotaxis for mesenchymal cell migration 35 and aggregation; 3) carrier for osteoinductive and chondro-inductive agent(s); 4) generation and maintenance of an electro-negative wound environment; and 5 ) agglutination Wos5/31157 ` ` r~ J.. c~1os o~ other connective tissue substances with each other and with itself. Other eYamples of chemotactic ground substances are fibronectin and, especially for the reconstruction of articular cartilage, an RGD attR- hr L
s moiety of f ibronectin.
The osteoinductive agent, bone ~hogt!netic protein, ha6 the capacity to induce primitive mesenchymal cells to differentiate into bone forming cells. Another osteogenic ~gent, bone derived growth factor, stimulates activity of l0 more mature mesenchymal cells to form new bone tissue.
Other biologically active agents which can be utilized, especially for the ~cù~ Lu- l iOn of articular cartilage, include transforming growth factor ~ (beta) and basic fibroblastic growth factor.
In a further aspect of the present invention, the anat~ ;CA1 ly specific implant device acts as a transport device of ~La- UL~UL cells harvested for the production of connective tissue. The device with its secured precursor cells can be press f it into the site of lesion repair.
20 In a preferred aspect of the present invention, the micro-~I_Lu,:Lu~ ~ velour (i.e. hyaluronan or alginate in the most preferred form) treated with an RGD atta~ t moiety of fibronectin facilitates the att~1 L of free, precursor cells to be carried ~o the lesion repair site.
2s Significant advantages and features of the present invention include:
l. The arrangement of fenestrated polymer strands of the tangential region produces a network of inter-communicating void spaces which have a horizontal 30 orientation with respect to void spaces of the radial zone, thus making this construction anatomically specific for articular cartilage tissue.
2. The cartilage region's radial zone provides void spaces in horizontal planes which peneLLc.te the vertically 35 orientated polymer sheets and create intt:L. ; cations between the vertically positioned void spaces.

wo 95131157 ~ PCT/lJS9~/06109 3. The radial zone of the cartilage region at the interface surface with the sllh~h~nflral bone region provides a honeycomb pattern of pores with an uninterrupted space - communicating from the interface surface, through the S radial and tangential zones, to the pores which ultimately the synovial fluid.

4. The hydrophobic barrier creates a strategic zone without interrupting the continuity of the ma~:Lo~Lu~ ~ULe:
polymer of the sl~hrhon~lral bone region and further without lo introducing any chemical change in the macrostructure polymer .

5. The mi~:L~LU~:~UL~ is strategically located within one, or multiple, discrete locales of the macrostructure void network while other locales of the macrostructure 1S void network remain devoid of microstructure material.

6. The concentration gradients of microstructure material are selectively varied within certain regions of maC:L~Lu- ~UL~ voids to affect different biologic characteristics critical to di~ferent tissue requirements.

7. A microstructure is provided to a single anatomically specific device having a composition of multiple different materials in different regions of ma~;Loa~Lu~ ~UL~ voids according to the varying tis6ue and biologic characteristic requirements.
2s 8. The use of a microstructure within a macrostructure provides multiple locations for L 'n~UL ~ of one or more types of biologic modifier cargo:
1) onto the surface of the macrostructure;
2 ) ~ L ~ d between the macrostructure and the mi-,:LO:~LUI;--ULC:;
3 ) onto the surf ace of the microstructure;
4) inside the microstructure; and/or 5 ) within the hydration domains of the microstructure and yet detached from the polysaccharide of the microstructure as well as detached from the polymer of the ma~:L;I:,--LU--:LULt:.

WO95/311~7 21 90253 I ",,~r log 9. rrhe three-dimensional configuration of the cell i6 preserved.
10. The entire 6urface area of each cell i6 pre6erved in optimum condition for interaction with the micro-S structure and its cargo of biologically active agents.
11. Each cell is coated with microstructure materialwhich, in the case of hyaluronic acid, is - -sed of a high percentage of naturally occurring extrAcP~ r matrix .
12. Free cells are maintained in a semi-fluid environment so that the cells can move to establish multiple regions of optimum cell density.
13. The cells are maintained in close proximity to high concentrations of free, solubilized and unattached 15 biologically active agents.
14. A transport for biologically active agents is provided .
15. A transport for osteoinductive/osteogenic and/or chondroinductive/cho~drogenic agents, as well as other 20 therapeutic substances ( i . e. living cells appropriate for the tissue under treatment, cell nutrient media, varieties of growth factors, morphogens and other biologically active protein6) are provided.
16. An electronegative environment is created which 2s is conducive to ostPogPn~qis/ch~--dL ~J~PC; ~ .
17. The need for more surgery to remove the device is eliminated since it is biuL~:suLbable in its entirety.
18. A transport for precursor repair cells to lesion repair sites is created.
19. The attachment of free, precursor cells to the device and to the repair site is facilitated.
Objects of the present invention include:
1. Joins bioresorbable polymers of different architectures and chemical prof iles into a single unit 35 whose composite architectures are specifically ordered to duplicate the aLLc.ny~ -~ts of parenchymal cells and stromal tissue of the tissue or organ under treatment and _ _ _ _ _ _ . . , . . , . . , _ . . . _ _ . .. .. _ _ ~ WO95~3ll57 21 90253 ~ r~los whose constituent polymers are specifically synthesized to possess chemical profiles appropriate for their particular locations within the whole. This object of the invention - is expressed in the example of a device for treatment of 5 articular cartilage defects in the most preferred form.
The cartilage region architecture is j oined to the 5llhrhnnrlral bone region (cancellous bone) architecture to form a bioresorbable polymer implant having an anatomically specif ic architecture f or articular lo cartilage.
2. Strategically positions microstructure material in that specific portion of the complete device to perform the particular unique functions required by the particular tissues being treated.
3. Segregates microstructure material within the anatomically specif ic device according to the special biologic functions of a particular implant.
4. Delivers chv~ldLvL:y~es only to the cartilage region of the device and supports their life functions in 20 the cartilage dePect by sequestering the chondrocyte cell population together with the in vitro cell culture medium in its miC:LU~LLU~LULe (alginate) gel.
5. Presents enough chondrocytes to the suh~hnn~lral bone region immediately adjacent to the cartilage region 25 50 as to assure that a ~ nt osteo-chondral bond is established between the newly developed cartilage and the newly developed bone.
6. Provides a bioresorbable structure to carry and to support cell attachment enhancing material such as a 30 chemotactic ground substance which is in the form of a f ilamentous velour having incomplete, interconnecting intersticies .
7. Generates electronegative potentials by maintaining an alginate or HY-f luid phase and PLA
35 structural phase interface, as well as by the electronegative chemical PLV~Je~ Ly of alginate or HY
alone .

21 9~253 8. Creates biophysical conditions and environment such that exogenous electric signals can be applied to the implant device to produce a synergistic effect with the endogenous currents generated by alginate or HY/PLA
5 surface interactions and the intrinsic electronegativity of the microstructure.

9. Provides a unique juxtaposition of polylactate, alginate/hyaluronic acid and chemical osteoinductive/
osteogenic and/or chondroinductive/chondrogenic agents.

10. Juxtaposes cell attachment enhancing material such as a chemotactic ground substance with a biodegradable polymer of either fiolid, open cell meshwork form, or in either form or both forms.
ll. Provides a biodegradable structure to transport 5 and to support precursor repair cells for repair sites.
12. Creates conditions and environments for facilitating the attachment of free, precursor cells for carriage to the repair site.
BRIEF ~ESCRIPTION OF THE DRAWTNGS
Figure 1 is a top view of the macrostructure and architecture of the tangential zone of the cartilage region with no microstructure alginate shown;
Figure 2 is a top view of a cartilage region of a t~gential zone as in Figure 1 invested with alginate 2s microstructure;
Figure 3 is an enlarged view of Figure 1;
Figure 4 is an enlarged view of Figure 2;
Figure 5 is a cross-sectional view through the entire device without any microstructure;
Figure 6 is a cross-sectional view through the entire device invested with alginate microstructure;
Figure 7 is a cross-sectional view through the entire device showing a hydrophobic barrier;
Figure 8 is a cross-sectional view of the radial zone 35 of the cartilage region at the interface surface;
~4E~DED SHEET

~ - 21 90253 Figure 9 is a cross-sectional view of the radial zone of cartilage region at the interface surface with alginate invested into the interstices;
Figure 10 is a cross-sectional view of a periodontal s barrier according to the preferred teachings of the present invention;
Figure 11 is a view of the surface of the periodontal barrier of Figure 10 which interfaces with the mucoperiosteum; and Figure 12 is a view of the surface of the periodontal barrier of Figure 10 which interfaces with the bone void.
DESCRIPTION OF ~HE PREFERRED
ANATOMICALLY SPECIFIC DEVICE E~BODTM~NT
A device and method according to the pref erred 15 teachings of the present invention is disclosed for treating r~ n bone and cartilage def iciencies, defects, voids and conformational discontinuities produced by congential disformities, osseous and/or soft tissue pathology, tramatic injuries, accidential and/or surgical, 20 and functional atrophy. The primary purpose of the anatomically specific implant device of the preferred form ~MEt~DED SIIEET

~ wo gS/31157 2 1 9 0 2 5 3 of the present invention is to provide the means by which chondrocytes and their attendant synthesis products, principally collagen type II, cultured in vitro, can be transported into an articular cartilage defect and be 5 safely established therein.
Specif ically, the anat~ i r~ l l y specif ic device according to the preferred t~rh;n~C of the present invention consists of two main parts, the cartilage region and the 5llhrh~n~1ral bone region joined at an interface 10 surface. Each of the cartilage and the sllhrhnn-lral bone regions of the device includes a macrostructure composed of a bioresorbable polymer either as h~ , - polymers or combinations of two or more co-polymers from groups of, for example, poly talpha-hydroxy acids), such as polylactic acid or polyglycolic acid or their co-polymers, polyanhydrides, polydepsipeptides, or polyorthoester.
Devices fabricated for prototypes of animal studies to-date have been fabricated from the homopolymer D,D-L,L-polylactic acid.
The bioresorbable polymer in the sllhrh~n~ral bone region in the most preferred form is in the architecture of cancellous bone such as of the type described in U. S .
Patent Nos. 4,186,448 and 5,133,755 which are hereby in~ UL~OLClted herein by reference.
The cartilage region comprises 10% to 30% of the anatomically specif ic device and contains a tangential zone and a radial zone each having an architecturally distinct pattern. The radial zone is located int~ te or between the tangential zone and the sllhrh~ 9ral bone 30 region. The tangential zone is approximately 100 micro-meters thick in a vertical direction and has intimate contact with the synovial fluid. Hereinafter, vertical refers to an orientation situated at right angles to the interface of the cartilage tissue with subchondral bone 3~ or in other words an orientation at right angles to the interface surface between the cartilage and El~hrh-~n~lral bone regions of the device. This tangential zone is ~ WO95131157 21 90253 P~ 109 formed by major polymer strands which run parallel to each other and are arranged in a horizontal plane forming horizontal h~nnPl ~ approximately 100 to 120 micrometers - wide in a horizontal direction. Hereinafter, horizontal 5 refers to an orientation situated parallel to the interface of cartilage tissue with sllhl hnntlral bone or in other words an orientation parallel to the interface surface between the cartilage and sl~hch~n~lral bone regions of the device. The rh~nnPl ~ formed by the major polymer lo strands are separated from each other by a network of minor polymer strands. These minor polymer strands are also arranged in a horizontal plane, join the major polymer strands at approximately right angles, and are approximately 650 micrometers in length in a horizontal lS direction. All polymer strands of the tangential zone are fenestrated by multiple void spaces. The arrangement of fenestrated polymer strands ~L~dUCeS a network of int~L. i cating void spaces which have a horizontal orientation with respect to the void spaces of the radial 20 zone.
The radial zone comprises 70% to 90% of the cartilage region. The radial zone i5 ~ ,- ed of vertically arranged, thin sheets of polymer which are fenestrated by multiple void spaces oriented in both horizontal and 2s vertical planes. The vertically oriented void spaces of the radial zone extend, uninterrupted, from the interface surface of the cartilage and sllhrh~n~lral bone regions to the tangential zone. Void spaces in the horizontal plane penetrate the vertically oriented polymer sheets and 30 create int~L- i cations between the vertically positioned void spaces.
The radial zone at the interface surface reveals the vertically oriented void spaces of the radial zone in cross section. The pattern of the radial zone at the 35 interface surface formed may be described as a ho~ y.
pattern ~ obed of discrete pores. The majority of discrete pores measure approximately 200 to 250 micrometers W095131157 21 90253 P~ 109 in feret diameter. These pore~ are generally circular.
Some pores are partially ocrl ~ od by a thin polymer membrane. Through these pores, there i5 uninterrupted void space communication from the interface surface 5 through the radial and tangential zones to the void spaces of the tangential zone which access synovial fluid.
The architecture of the cartilage region may be formed utilizing estAhl; ~hF~d techniques widely practiced by those skilled in the art of bioresorbable polymers. These methods include injection molding, vacuum foaming, spinning hollow filaments, solvent eYaporation, soluble particulate leaching or combinations thereof. For some methods, plasticizers may be required to reduce the glass transition temperature to low enough levels so that 15 polymer flow will occur without tl~ ition.
For the devices which were fabricated for use in a rabbit ' s knee, the cartilage region was limited to a thit~kn~ of about l,000 micrometers plus or minus 200 micrometers. In a human, the cartilage region can be 20 increased to a maximum of about 3 . o mm in thickness, specif ically 3, 000 micrometers .
The macrostructure polymer of the cartilage region is joined or bound to the ma-Lu~-~u~:Lu~: polymer of the 5~h ~ l, al bone region by a proce6s such as heat fusion 2s which does not involve the use of solvents or ~ h~
reactions between the two poiymer segments. The resulting union between the t~o architectural regions is very strong and can withstand any h~n~ll in~ required to package the device as well as any forces delivered to it as a result 30 of the implantation to~hniq~ without distorting the device's internal architecture of void spaces.
Alginate is the microstructure material most preferred in the cartilage region f or the transport of in vitro and in vivo cultured cells and for the establ i ! L of an in 35 vivo cell culture system within a bioresorbable implant.
Alginate is especially suitable for use in an anatomically specific device for treating articular cartilage defects ~ WO 9S131157 2 1 9 ~ 2 5 3 r~l~u~ Of]og because alginate has no known angiogenic properties and has been used s~ cP~fully by others to culture and transport chondrocytes.
- Alginate is a polysaccharide derived from Phaeophyceae s also known as brown seawood. The most common source of alginate is the species Macrocystis pyrifera, the giant kelp, which grows along the coasts of North and South America, New Zealand, Australia and Africa. Other poly-saccharides, such as agar and carrageenan, extracted from 10 various types of red algae, as well as hyaluronan, also make suitable microstructure materials for bioresorbable systems designed to ~L~ UVL L and culture chondrocytes.
Alginate is a polysaccharide polymer - osed of repeating units of D-mannuronic acid, repeating units of 15 L-guluronic acid or alternating D-mannuronic acid and L-guluronic acid residues. The exact composition of a given alginate sample depends on the sllhspeci~c of kelp (Macrocystis pyrifera) from which it was derived.
The most preferred form of the present invention 20 employs a ref ined sodium alginate called Keltone-HV .
Another pref erred embodiment of the micro6tructure material is calcium cross-linked alginate or any other alginic acid preparation which provides a hydrocolloid gel of alginic acid suitable for the cell tLCl~ JUL ~ and 2s culturing tissue at hand.
In former constructs such as U.S. Patent 5,133,755, the preferred microstructure was hyaluronan which is synonymous with hyaluronic acid, hyaluronate, HA and HY.
The hyaluronan was distributed uniformly throughout the 30 internal void volume of the device. According to the teachings of the present invention, an option is provided of selecting whether or not the microstructure should be dispersed throughout all the void spaces dPrPnrlin~ on whether the arrangement is bPnPfici~l to the tissues 35 being treated. The present invention permits incomplete dispersal as desired or complete dispersal throughout the entire void volume of the device but expressing . . ~

WO95t31157 f~ 1 q 0253 r~ .f;ff.~fs ~

concentration gradients of microstructure material as a means of controlling transplanted cell population numbers within the device's internal domains.
The microstructure approach can carry biologic s modifiers with 1) the biodegradable polymeric macro-structure, 2) the microstructure protein, or 3) the microstructure polysaccharide.
This multiple-carrying capacity provides for five different types of locations within the device for o loading biologic modifiers: 1) joined at the polymeric maL:L ~f~ ~L U~:~UL e interior surf ace; 2 ) j oined to the chemotactic ground substance at the microstructure's exterior surface; 3~ located between the biodegradable polymer and the chemotactic ground substance; 4) carried 5 within the chemotactic ground substance in the microstructure interior; and 5) entrapped within the hydration domains of the hyaluronic acid or alginic acid microstructure yet detached from the hyaluronan/alginate polysaccharide .
At the fifth location, the biologic modifier(s) are ULc:d by the hydration domains of the polysaccharide microstructure while the biologic modif iers are still dissolved in their original water solution. The biologically active agent (s) is attached to the hyaluronic 25 acid or illginic acid mi-;L~ff~-LU~ -UL~ but is not in physical contact with the polysaccharide, since it is still dissolved in water which, in turn, is entrapped within the hydration domains of the hyaluronan. This method of delivering biologically active cargo to a tissue defect 30 i5 impossible with the coating approach of U. 5 . Patent No. 5,041,138.
A dry f ilamentous velour of chemotactic ground substance, 6pecifically RGD attachment moiety of fibro-nectin carried by hyaluronic acid or alginic acid velour, 35 can be established within the void spaces of the device.
Upon saturation with water, water-based cell culture media or f luid blood, the dry velour of chemotactic ground W095131157 21 9~253 r~ slog substance is dissolved into a highly viscous gel which maintains the chemotactic ground substance as a network of dissolved polysaccharide strands, still suspended within - the void volume of the polymeric macrostructure.
If the cell culture media is a f luid which saturates the device and creates the gel, then those cells s~ rPnt1Pcl in the culture medium will be temporarily trapped within the gel due to the gel viscosity. The degree of gel viscosity and the length of time the gel maintains significantly high viscosities are detprminpc~ by 1) the initial molecular weight of the microstructure; 2) the microstructure in vivo rate of degradation; 3) the 2Ivailability of interstitial fluid to dilute re-~;n;ng mi~LU:~LU- LUL~ and remove microstructure degradation 15 products from the region; and 4) the initial .;c~.ce..L,~tion of microstructure originally placed within the macro-structure ( s ) interstices .
Temporarily restraining transported parenchymal cells by means of microstructure gel gives the cells time to 20 execute two critical biologic processes . The f irst biologic process is the union with the microstructure via direct interaction between the mi-;Lu~LLu~;LuLe and the plasma membrane CD44H receptor of the cells as well as union with the RGD attachment moiety of f ibronectin which 2s may be incorporated with the mi~:lo-LLu~_LuL~:. The second biological process involves bonding with any other biologic modifiers which may be also inuuL~uLclted with the microstructure or dissolved in water trapped by hydration domains of mif~LU~LLU- ~ULe polysaccharide.
After approximately 12-to-72 hours in vivo, the microstructure gel has been reduced in viscosity to such an extent that its contents of the microstructure, which now has a reduced molecular weight, together with the surviving cell population attached to the microstructure 35 directly or via RGD attachment moiety of fibronectin, are WO95/31157 21 9~253 -22- r~l/u.,~1!6109 compelled to rest upon the structural surf aces supplied by the macrostructure polymer.
The volume of space once occupied by the microstructure gel is now occupied by the interstitial f luid and increased S numbers of paIe~ lylllal cells generated by mitosis of the transplanted parent cells. In the articular cartilage regeneration of the most preferred form, it is desired to protect the transplanted cells from access to fluid blood and collateral circulation. Therefore, blood products lO will not be f ound in the void spaces of the cartilage region. In other tissue ~ eLCltiOn situations, however, it is desirable to attract fluid blood into the device's interstices as quickly as possible. In these situations, therefore, fibrin (i.e. blood clot), endothelial budding 15 and granulation tissue advancing within the device interstices from sources of viable collateral circulation will be substances ~ound within the internal void spaces of the device along with the other materials noted above.
The device interaction with cell receptors is an 20 i JL ~dll- advantage to the microstructure approach for achieving cell transfer. The biologic processes of cell transfer involved in U.S. Patent No. 5,133,755 are all mediated by the interaction of various proteins and polysaccharides with specif ic receptors located in the 25 plasma membrane or "cell wall" of subject cells. These specif ic receptors are also ~ - ~cd of protein .
Transplanted cells attach to the microstructure and to the RGD att~ ~ moiety of fibronectin supported by the microstructure via interactions of the transplanted 30 cell specific protein receptors located in their cell piasma membranes with the specif ic amino acid sequences or amine groups of the microstructure complex. For example, there are interactions between the transported cell receptors and the RGD attachment moiety. Another example 35 is the direct interaction of a transported cell membrane receptor such as CD44H and hyaluronan miuLu:~Lu~:LuL~:.

W095/31157 21 90253 r~l,u~ ~ los Still another example is the interaction of the transported cell membrane receptor and alginate microstructure.
By directly attaching transplanted cells to the tbree-- dimensional microstructure immediately after the cells 5 have been exposed to the transport device, the following results are obtained until the microstructure~s viscosity is reduced below a critical level: 1) preserves the three-dimensional conf iguration of the cell; 2 ) preserves the entire surface area of each cell in optimum condition for 0 interaction with the mi~:Lo~LL~-- LuLæ and its cargo of biologically active agents; 3 ) coats each cell with microstructure material which, in the case of hyaluronan, _ - s~5 a high percentage of naturally occurring extracellular matrix; 4) maintains the cells, free, in a 15 semi-f luid environment so that they can move in order to establish multiple regions of optimum cell density; 5) maintains the cells in a close proximity to high col~ce~lLr ~Itions of free, solubilized and unattached biologically active agents; and 6) maintains the cargo of 20 biologically active, therapeutic proteins carried in the hydration domains of the microstructure polysaccharide with their three-dimensional configurations undisturbed, thus optimizing their biologic activities.
In cell transplantation, the use of only a chemotactic 25 ground substance coated on a polymeric structure can help many transplanted cells survive. However, as a result of being attached to the unyielding macrostructure surfaces, transplanted cells 50 attached may have distorted three-dimensional conf igurations and their plasma membranes may 30 have a reduced surface area available for interaction with biologically active agents.
The present invention departs f rom prior practice by strategically positioning the microstructure material in that specific portion of the device which performs 35 particular functions unique to the mature anatomy being regenerated in that vicinity. Such segregation of microstructure material within the device is based on WO95B1157 21 90253 P~ r~los the need to endow one portion of the device with special biologic functions that must be isolated from the L~ in(~Pr of the implanted device.
In a more preferred ~ L of the present S invention, the microstructure has a primary purpose to deliver chondrocytes only to the cartilage region of the device and support their life function in the mammal's cartilage defect by sequestering the chondrocyte cell population together with the in vitro cell culture medium 10 within its alginate gel. The mi~:ro~Llu-;-uLt has a secon~Ary purpose to present enough chondrocytes to the sllhrhon~ral bone region immediately adjacent to the cartilage region to insure that a ~ _~Pnt osteo-chondral bond is estAhl i RhPd between the newly developed cartilage and the newly developed bone.
Within the inventive concept of the present invention is the establ icl ~ of variations in the c:ullc~:"LL~tion of microstructure within the void space network of the macrostructure in order to assure that the therapeutic 20 elements brought from in vitro culture are present within the f inal device in greatest quantity where they are most needed. Examples of biologically active agents, also known as therapeutic elements and brought in from in vitro culture are cell populations, growth f actors, morphogens, 2s other therapeutic agents, drugs, etc. Such variations in concentration can be a~ hPd by varying oullc~llLL~tions of mioLu~LLu~:LuLe solutions prior to investment into macrostructure voids of the device or regions thereof be f ore j o in ing .
In the more preferred ~ ir-nt of the present invention, the alginate velour is present in highest concentration within the tangential zone of the cartilage region and the immediately adjacent locales of the radial zone. The concentration of alginate microstructure 35 declines from the point of highest cu.lc~l1LL~tion toward the interface of the radial zone with the sllhrh-~nrlral bone region. Microstructure alginate velour is present in the -- _ _ _ _ , _ _ _ _ _ _ _ _ _ _ _ _ _ .. . .. . .. _ WO 95/31157 2 ~ q 0 2 5 3 P~IJ~' _ rflO9 least c~ LL~Lion in the 500 to 800 micrometer thick space of the s~lhrhonAral bone region.
Within the inventive concept of the present invention is the placing of two or more microstructure materials at s strategic locations within the 6ame biore60rbable implant to perform multiple and varied biologic function6 6egregated to 6pecif ic anatomic locale6 of the implant device. For example, a large ostoorh-~n~lral defect would require hyaluronan velour for microstructure in the 10 sllh~h~ n~lral region intended for 06tennooy~neci ~. In contrast, alginate velour would be more appropriate microstructure material for the cartilage region of the device intended for cho..dL~Ileogenesis. The placement of different micro6tructure material can be accomplished by 5 inve6ting the micro6tructure material into the region6 before they are joined, by inve6ting the device or region6 thereof before joining from a fir6t surface with a desired volume of microstructure material less than the total void volume of the macrostructure and then investing from the 20 opposite surface with a volume of a different micro-structure material equal to the balance of void volume of the macrostructure.
Except for the critical location at the interface between the cartilage region, the polymer of the 25 8llhrhrTl~lral bone region is hydrophilic by virtue of being treated with a wetting agent such as set f orth in U . S .
Patent No. 4,186,448. Beginning at about 500 to 800 micrometers from the interface surface and extending to the interface surface, the macrostructure polymer of the 30 6~hr~h~n~1ral bone region ha6 been rendered hydrophobic 6uch a6 by treating the entire device or the ~llhrhr~n~lral bone region with a surfactant and then inactivating the 6urfactant on the hydrophobic barrier 6urface6 or by not treating the barrier surfaces with a 6urfactant while the 35 rr-o;n;n~ portion6 are treated. Likewi6e, a hydrophobic barrier may be created within a device of 6imple ( i . e .
6ingle) or complex (i.e. multiple) internal architecture6 Wo95/31157 2~ 90253 1 "~ log by means other than selective treatment of certain polymer regions with a surf actant . For example, a separate fibrillar construct of bioresorbable polymer may be fabricated devoid of surfactant and may be interspersed s between two segment6 of a device whose polymers have been rendered hydrophilic.
Water-based fluids, 6pecifically fluid blood, brought to this locale by capillary action through hydrophilic polymer of the 5llh- ht7n-'ral bone region closest to lO sl~hrh~7n~7~ral bone, are prohibited from traveling further toward the cartilage region by the hydrophobic polymer of the s--'~ 1..~..,1, c-l bone region in this vicinity. The interstices of the 1Iydrophobic fibrillar membrane would eventually A~ te cell growth, but the immediate 5 ef f ect of such a membrane would be to prevent passage of water-based f luids across its boundaries .
The hydrophobic barrier is a signif icant advance and development of devices intended for use in u 1.u-ldLu.,eoy~llesis because hyaline cartilage, specifically the articular 20 cartilage of joints, is an avascular tissue and must be protected from intimate contact with sources of high oxygen tension such as blood. When the recipient cartilage tissue defect is prepared to receive the implant, it is nr~c~81;,7ry to continue the defect into the underlying s~lh-hl~n~'ral 25 bone, called the cancellous bone, to assure that there will be a new bone formed beneath the cartilage region which will produce a competent bond with the newly developing cartilage.
Such tissue preparation engages the rich collateral 30 circulation of subchondral cancellous bone and its associated bone marrow. If the cultured chondrocytes and specif ically the cartilage cells come into cQntact with t~le fluid blood produced by this source of collateral circulation, they will fail to maintain their chondrocyte 35 phenotype.
It is essential that the majority of cultured chondrocytes be protected from intimate contact with W095J31157 21 9a253 I~l/U~ O9 collateral circulation so that they will ret~ t:~-cir chondrocyte phenotype and contin-le to prod11c,~ co] ] ~gc11 Type II in the architectural pa~tern dictate~ y t:1~c ~ C~-o-structure polymer of the cartilaqe reqion. ~ y(1ro1,~1o1~ic s- barrier of tbe preferred form of the prescnl: i ~1v~
described above achieves this objective.
It can then be appreciated that the anatorl1ically specific bioresorbable device according to the teachin~s of the present lnvention has a fabricated macrostructure closely rPs~ n~ the mature tissues which are to be regenerated by the completed implant. Further, the anatomlcally specific bioresorbable device of the present invention integrates the macrostructure, microstructure, cells cultured in vitro, culture medium and a~sociated growth factors, morphogens, drugs and other i:herapeutic agents .
According to the prcferred tP~ h 1 n~C of the present invention, the anat: 1rA1ly specific bioresol-bable device according to the preferred teachlngs of the ~ esent ~o invention can be utilized as a transport sys1:cm for chondrocytes, growth factors, morphogens and ot11er biologically active agents, in treatment of ~rticular cartilage defects. In particular and in the preferred form, suitable source tissue is harvested and t]le cells 25 are cultured using standard chondrocyte culturing methods, ~with the specific cell type in the most preferred form ~being articular cartllage chondrocyte. The cartilage ~defect ls surgically prepared by removing diseased or damaged cartilage to create a cartllage and subchondral 30 bone defect, with the defect extending approximately o . 5 cm to l . O cm into subchondral cancellous bone. With the device and defect having generally the same shape, the -dQvlce is inserted into the tissue defect suc11 as by press fitting. A volume of in vitro cell culture suspension is 35 measured out by a microliter syringe which generally matches exactly the void volume of the cartilage region W095/31157 2 1 9 0253 ~ 09 macrostructure lnvested by the microstructure and is injected onto the outer surface of the tangential zone of :the cartilage region and which will ultimal~ely be in contact with synovial fluid . The ~ oint anatomy can then s be replaced in proper position and the wound can be closed .
Although the preferrcd form relates to the transport and in vivo culturing of chondrocytes, it should be noted that the teachings of the pre5ent invention, and the ~Iseful o devices fabricated as a result thereof, are intended to transport, and sustain in life, any cell type havinq therapeutic value to animals and plants. I~x~mples of other cells of therapeutic value other than chondrocytes are: islets of T.An~rhAns which produce insulin, liver 1S parenchymal cells which have the capacity to regenerate liver tissue, and tumor cells used to stimulate the immune system against a certain tumor type.
A functionally specific device and method according to the pref erred teachings of the present invention are 20 further disclosed for facilitating healing of voids in tissue by which cellular penetration can be delayed, limited or prevented while simultaneously controllin~ and directing cellular growth within the interstices of the device, promoting cell attachment to structural elements 2s of the device and allowing turnover of intersl~itial f].uid carrying nutrients to, and waste products from, the cells, whether they are conf ined within the d~vice or are external to it. These characteristics are us~f~ll to llea].
tissues which are in intimate contact with another tissu~
30 wherein this intimate contact must be delaye~l, limit~d or prevented while cellular growth is occurrin~ GUch as in a variety of medical applications including, b-lt not limited to, artificial burn grafts or dressings, dec~lbitus ulcer dressings, orbital floor implants, cleft pal].et dressings, 3s oral antral c l;cAtion dressings, cranial defect dressings, controls of internal hemorrhage, vein and Artery repair devices, artificial organ matrixes for Wo 95131157 2 1 9 0 2 ~j 3 P~l/L -log 1 regeneration of liver, kidney and pancreas, organ repair matrixes, muscle repair matrixes, bone and cartilage regeneration, delivery of drugs and other biologic modifiers, and periodontal barriers and membranes.
5 Essentially the device of the present invention will be valuable for any healing tis6ue which is in intimate contact with another tissue wherein this intimate contact must be delayed, limited or prevented while cellular growth is occurring, and ~ULIIUVt:~ of interstitial fluid lo carrying nutrientg to, and waste products away from the cells both conf ined within and external to the device is required. Additionally, the device of the present invention may be located external to the tissue being repaired to prevent undamaged tis6ue from interfering with 15 the healing tis5ue. The above medical applications will be obvious to those skilled in the art with the following descriptions of Pmho~;- L~ according to the preferred te~h;n~c of the present invention.
The biological cell trap pmho~; Ls described herein 20 may appear complex and varied, but can all be quickly brought into focus with the analogy of an architectural interrelationship of oU2~ straws. Each straw forms an elongated chamber having a diameter and a length no less than two times the ~ P~. The elongated chambers 25 can be randomly placed in the structure by the analogy of dumping a plurality of straws into a box creating a tangle of elongated rh: ' a or can be organized into very elaborate designs such as being layered. The elongated chambers can be of different diameters and lengths 30 including lengths which run the entire th;o~nP~ length, and/or width of the ~Lu- Lu~a. The elongated rhi t, can be straight or curved. ûther shaped chambers which are not elongated such as cubes, spheres, cones, irregulars, etc. may be intPrm;YPd at various 35 ~ ce~LL~ILions with the elongated rhi~nnPl ,:
The presence of elongated chambers or rhi~nnP1~ in the internal three-dimensional architecture of the ~,LLU~:LULa _ _ . . . .

WO 95/311S7 2 1 9 ~ 2 5 3 30 ~ D~ --of the device of the present invention provides three functions. The first is structural support; the cylindrical shape being one of the ~,I Lul,~e~l_ known in engineering. The second function provides a network or 5 conduit system accessing the entire device through which nutrients can be introduced and waste products removed.
Finally the elongated chambers provide large flattened surface areas for cell attachment.
The original use of elongated rhAr~ ~ or rhAnnP 1 R
within the device of the present invention traps cells and controls their growth by a unique method. Central to the function of the device is the f act that cells in contact with large flat 6urface areas of biologically acceptable materials quickly attach and deposit an extracellular 15 matrix. This cellular activity rapidly occludes pACCA~PR
through the device effectively trapping cells within the device and preventing other cells from entering the device.
The combination of the bioresorbable device and attached cells creates a living tissue barrier. Over the lifetime 20 of the device, all of the chambers will be filled, creating a tissue mass rPcpmhl i nrJ the shape of the device implanted .
The properties of the device of the present invention can be PnhAnred or modif ied through simple manipulations 25 of the architecture and the addition of additives. The architecture of the device of the present invention may be formed u1-;1;7in~ methods of injection molding, vacuum foaming, spinning hollow filaments, solvent evaporation, or a combination thereof.
Mn~li fications to structure: The creation of a device where the elongated chambers are intersected by other elongated chambers will create sudden directional changes within the device which can be used to control the development of more aggressive growing tissues such as 3~ f ibrous connective tissue . Further control can be achieved by layering or increasing the th i rknP~s of the device. Addition of other chambers, at various .. . . . .. _ . . _ .... _ _ _ . _ . . ...

W09S131157 3~ 2 ~ 9~2~3 p~ "". ~ og 1 eoncentrations, which are not elongated provides increased control over the growth of cells and tissues.
M~; fie~ions to the s~rfa~e: Modifieations of the device such as partitions whieh partially or completely seal a surface of the device can be used to limit or prevent acces6 to collateral circulation as well a6 eontrol the loeation and numbers of cells whieh have aecess to the eentral domains of the device. Meshes or weave6 can be used f or size exclusion of cells or to lo create more 6urfaee area for platelet fracture before entrance to the deviee.
ContrQlled use of a s~rfaetAnt: Addition of physiologically acceptable surfactants to porou6 hydrophobic bioresorbable polymers facilitates complete 15 saturation by body f luid6 . Example6 of surfactant6 include ananionic, cationic, amphoteric and nonionic surfactants. ~riethanolamine dodecylben2yl 6ulfonate in a ~o..~ Lcltion of 1% by mass has provided excellent results for instantaneous device saturation while le6ser amounts 20 can be utili2ed for slower, delayed saturation and delayed cellular migration. Additionally, a device containing a layer or portion of polymer which has not been exposed to a surfactant adjacent to a layer or portion which has, can be used to further enhance the trapping ability of the 25 invention when in contact with aggressively growing cells by creating a breathable hydrophobic barrier.
Another novel use of surfactant in a bioresorbable porous device is for providing delayed saturation of hydrophobic layers. Increasing the amount or concentra-30 tion of 6urfactant in the hydrophilic layers or portionsso that a suf f icient concentration can be liberated by inter6titial fluid facilitates penetration of the fluid into the hydrophobic layer. The depth of penetration is ~ rpntlpnt on the mass of the hydrophobic layer as it 35 relate6 to the concentration of surf actant within the hydrophilic layer and av~ hility of inter6titial fluid.
Specifically, a porous D,D-L,L-polylactic acid device with _,,,,, _ _ _ _ _ _ _ Wo 95/31157 2 1 q 0 2 5 3 ~ 109 a layer or portion of mass containing 1. 5% triethanolamine dodecylbenzyl sulfonate exposed to fetal bovine serum will draw the f etal bovine serum into the device to liberate a sufficient quantity of surfactant to facilitate in~uL uul ,ltion or penetration of the f etal bovine serum into a layer or portion of mass which has not been exposed to or contain triethanolamine dodecylbenzyl sulfonate within 5 minutes when the f low of f luid is directed towards the hydrophobic layer.
0 This time may be increased or decreased by several methods including, but not limited to, having a quantity of surfactant within the hydrophobic layer which is just insufficient to impart hydrophilicity, increasing or decreasing the sluantity of surfactant in the hydrophilic 15 layer, coating of the surfactant on the polymer surface allowing it to be liberated in a shorter period of time, or any combination of the above. Thus, the device of the present invention may use a pPrl--nPnt, temporary, or size reducing hydrophobic barrier based on surfactant 20 liberation.
Controlled use gf a ~lasticizer: When required, plasticizers, in a mass not to exceed 50% of the mass of the entire device, can be incorporated into the device to provide flexibility. This addition may be nPcP~s~ry when 2s the bioresorbable polymer utilized does not provide suf f icient f lexibility to the device or the molecular weight of the material is so low as to result in a brittle device.
An additional novel use of a plasticizer in a porous 30 biuL~suLbable polymer is for temporary flexibility. A
plasticizer such as triethyl citrate, which is extractable in body fluids, is used to conform the device, during implantation into the tissue to be healed and regenerated.
The plasticizer is leached out of the device leaving it 35 less flexible and relatively rigid. Other citric acid esters are water extractable, specifically those with molecular weights less than 402 daltons.

w095131~57 33 21 9~253 r~ r~09 .
9ther additives: Biologically active agents such as physiologically acceptable drugs, biological modifiers, proteins, hormones, and antigens and mixtures thereof may also be utilized with the device of the present invention 5 by either incorporating the additives within the bioresorbable mass or attaching them to the surfaces of the bioresorbable mass. These substances may be used to enhance the primary purpose of the device or may use the device of the present invention to achieve a secondary lo purpose.
It can be realized that like the surfactant, the plasticizers and/or other additives can be ; ~-!1 llA~A in portions of the device while other portions of the device of the present invention can be substantially free of the 15 plasticizer and/or other additives.
Q~ OLOGI~'AT~ ~'T~'T.T. TT~AP EMRODIMT~'NT OF THE INVT'NTION
The preferred ~omho~ of the invention is in the form of a device fo~ use as a periodontal barrier utilized in restorative surgeries. In particular, the device is 20 formed of a biocompatible material including bioerodable materials and polymer materials and bioresorbable materials and polymer materials such as a polymerized alpha-hydroxy acid. In the most preferred form, D,D-L,L-polylactic acid is fabricated, in the presence of 0.5% triethanolamine 2s dodecylbenzyl sulfonate by mass, into sheets ranging from 350 to 500 microns in thickness. As best seen in Figure 24, the body of the device is -sefl of multiple elongated rh: ` :, which are intersected by other elongated chambers resulting in sudden directional changes 30 which delay penetration of aggressive growing f ibroblasts until sufficient quantities of new bone have formed to fill the deficiency. The surface of the device at the interface with the mucoperiosteum as best seen in Figure 25 is composed of a tightly woven mesh of D,L-polylactic 35 acid. The surface of the device in contact with the bone void as best seen in Figure 26 has 20-35% of the elongated wog~ll~7 2 1 90253 34 P~ 109 chambers sealed off with solid partitions. This device, when placed over baboon periodontal defects and contacting the tissue to be healed and regenerated, is invaded by fibroblasts at a rate of 20% per month delaying contact 5 with the healing bone void for 5 months.
Thus since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which f orms have been indicated, the embodiments lo described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the ~rppnrl~d claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims (102)

1. Device for regenerating at least first and second, juxtaposed tissues having different histologic patterns including a first region having an internal three-dimensional architecture, and a second region having an internal three-dimensional architecture, with the first and second regions being integrally connected together at an interface surface, with the regions being formed of a bioresorbable polymer characterized in that the internal three-dimensional architecture of the first region approximates the histologic pattern of the first tissue and the internal three-dimensional architecture of the second region approximates the histologic pattern of the second tissue, so that regeneration is anatomically specific.

2. The anatomically specific device of claim 1 wherein each of the first and second regions include a macrostructure defining void spaces, with the device further comprising, in combination: at least a first material for enhancing the attachment of cells to the three-dimensional architecture in the void spaces of at least one of the first and second regions.

3. The anatomically specific device of claim 2 wherein the cell attachment enhancing material is present at varying concentrations in the regions.

4. The anatomically specific device of claim 2 or 3 further comprising, in combination: a second material for enhancing the attachment of cells to the three-dimensional architecture in the void spaces of the second region with the first region being substantially free of the second cell attachment enhancing material, with the first cell attachment enhancing material located in the void spaces of the first region and the second region being substantially free of the first cell attachment enhancing material.

5. The bioresorbable device of any claim 2-4 wherein the first material dissolves into a highly viscous gel suspended within the three-dimensional architecture.

6. The bioresorbable device of claim 5 further comprising, in combination: a cell culture media in the form of a fluid, with the cell culture media including suspended cells, with the cell culture media dissolving the first material into the highly viscous gel for trapping the suspended cells in the highly viscous gel.

7. The anatomically specific device of claim 1 wherein the first region is divided into first and second zones having differing three-dimensional patterns, with the second zone located between the first zone and the second region.

8. The anatomically specific device of claim 7 wherein the three-dimensional pattern of the first zone includes a network of intercommunicating voids which have an orientation parallel to the interface surface, and the three-dimensional pattern of the second zone includes a network of inter-communicating voids extending between the first zone and the second region.

9. The anatomically specific device of claim 8 further comprising, in combination: a porous microstructure formed from a material for enhancing the attachment of cells to the three-dimensional architecture and located in the intercommunication voids of the first region and carried by and separate from the bioresorbable polymer forming the first region.

10. The anatomically specific device of claim 9 wherein the cell attachment enhancing material is alginate.

11. The anatomically specific device of claim 10 wherein the first tissue is cartilage and the second tissue is subchondral cancellous bone; and wherein the device further comprises, in combination: RGD attachment moiety of fibronectin carried by the cell attachment enhancing material and within the intercommunicating voids of the first region.

12. The anatomically specific device of claim 11 wherein the second region includes a porous macrostructure including interconnecting voids; and wherein the device includes a material for enhancing the attachment of cells to the three-dimensional architecture located in the interconnecting voids of the porous macrostructure and carried by and separate from the bioresorbable polymer forming the porous macrostructure.

13. The anatomically specific device of claim 12 wherein the cell attachment enhancing material of the porous macrostructure is a chemotactic ground substance in the form of hyaluronic acid.

14. The anatomically specific device of any preceeding claim wherein the first and second regions include intercommunicating voids; and wherein the device further comprises, in combination: at least one hydrophobic barrier within the three-dimensional architecture of at least one of the first and second regions, with the second region outside of the hydrophobic barrier being hydrophilic.

15. The anatomically specific device of claim 14 wherein the first and second regions are formed by a single bioresorb-able polymer, with the single bioresorbable polymer of the first region being hydrophobic and the second region being hydrophilic by treatment with a surfactant.

16. Bioresorbable polymer device for regenerating cartilage tissue interfacing at an interface with subchondral cancellous bone and located between the subchondral cancellous bone and synovial fluid comprising, in combination: a tangential zone including a network of intercommunicating void spaces having an orientation parallel to the interface and in communication with the synovial fluid; and a radial zone located between the tangential zone and the interface, with the radial zone including void spaces extending between and providing communication between the interface and the tangential zone.

17. The bioresorbable device of claim 16 wherein the tangential zone includes channels extending parallel to the interface and formed by major polymer strands running parallel to each other, with the channels separated by a network of minor polymer strands extending parallel to the interface and generally perpendicular to the major polymer strands.

18. The bioresorbable device of claim 17 wherein the radial zone includes thin sheets of the bioresorbable polymer arranged perpendicular to the interface.

19. The bioresorbable device of any claim 16-18 further comprising, in combination: a porous microstructure formed from a material for enhancing the attachment of cells to the three-dimensional architecture and located in the void spaces of at least one of the tangential and radial zones and carried by and separate from the bioresorbable polymer defining the void spaces.

20. The bioresorbable device of claim 18 wherein the cell attachment enhancing material is alginate.

21. The bioresorbable device of claim 20 further comprising, in combination: RGD attachment moiety of fibronectin carried by the cell attachment enhancing material and within the void spaces.

22. The bioresorbable device of claim 19 wherein the cell attachment enhancing material is present at varying concentrations in the zones.

23. The bioresorbable device of claim 19 wherein the first material dissolves into a highly viscous gel suspended within the three-dimensional architecture.

24. The bioresorbable device of claim 23 further comprising, in combination: a cell culture media in the form of a fluid, with the cell culture media including suspended cells, with the cell culture media dissolving the first material into the highly viscous gel for trapping the suspended cells in the highly viscous gel.

25. The bioresorbable device of any claim 16-24 further comprising, in combination: means for protecting the tangential and radial zones from intimate contact with collateral circulation from the subchondral cancellous bone.

26. The bioresorbable device of claim 25 wherein the protecting means comprises a hydrophobic barrier at the interface with the radial zone.

27. Bioresorbable device for facilitating healing of voids in tissue including a structure made from a polymer providing an internal three-dimensional architecture, and a material for enhancing the attachment of cells to the three-dimensional architecture carried by the structure, characterized in the material being at varying concentrations in the three-dimensional architecture.

28. The bioresorbable device of claim 21 wherein the structure includes first and second, spaced surfaces, with the concentration of the cell attachment enhancing material carried by the structure decreasing from the first surface to the second surface.

29. The bioresorbable device of claim 28 wherein the structure is in the form of a porous macrostructure including interconnecting voids; and wherein the cell attachment enhancing material forms a porous microstructure located in the interconnecting voids and carried by and separate from the polymer forming the porous macrostructure.

30. The bioresorbable device of any claim 26-29 wherein the first material dissolves into a highly viscous gel suspended within the three-dimensional architecture.

31. The bioresorbable device of claim 30 further comprising, in combination: a cell culture media in the form of a fluid, with the cell culture media including suspended cells, with the cell culture media dissolving the first material into the highly viscous gel for trapping the suspended cells in the highly viscous gel.

32. Bioresorbable device for facilitating healing of voids in tissue including a structure made from a polymer providing an internal three-dimensional architecture including at least first and second locations, and a first material for enhancing the attachment of cells to the three-dimensional architecture carried by the structure in the first location, characterized in the second location being substantially free of the first cell attachment enhancing material.

33. The bioresorbable device of claim 32 wherein the first material dissolves into a highly viscous gel suspended within the three-dimensional architecture.

34. The bioresorbable device of claim 33 further comprising, in combination: a cell culture media in the form of a fluid, with the cell culture media including suspended cells, with the cell culture media dissolving the first material into the highly viscous gel for trapping the suspended cells in the highly viscous gel.

35. The bioresorbable device of any claim 32-34 further comprising, in combination: a second material for enhancing the attachment of cells to the three-dimensional architecture carried by the structure in the second location, with the first location being substantially free of the second cell attachment enhancing material.

36. The bioresorbable device of claim 35 wherein the first cell attachment enhancing material facilitates osteo-neogenesis and the second cell attachment enhancing material facilitates chondroneogenesis.

37. The bioresorbable device of claim 35 or 36 wherein the first cell attachment enhancing material comprises a chemotactic ground substance in the form of hyaluronic acid and the second cell attachment enhancing material comprises alginate.

38. The bioresorbable device of any claim 35-37 further comprising, in combination: RGD attachment moiety of fibronectin carried by the second cell attachment enhancing material.

39. The bioresorbable device of claim 38 wherein the structure is in the form of a porous macrostructure including interconnecting voids; and wherein the cell attachment enhancing materials form porous microstructures located in the interconnecting voids of the respective locations and carried by and separate from the polymer forming the porous macrostructure.

40. Bioresorbable device for facilitating healing of voids in tissue including a structure made from a polymer providing an internal three-dimensional architecture, characterized in a barrier formed in the three-dimensional architecture for prohibiting water-based fluid from passing therethrough.

41. The bioresorbable device of claim 40 wherein the barrier is hydrophobic and the three-dimensional architecture outside of the barrier is hydrophilic on at least one surface.

42. The bioresorbable device of claim 41 wherein the polymer is hydrophobic and is treated with a surfactant to become hydrophilic.

43. A bioresorbable device for facilitating healing of structural voids in bone, cartilage as well as soft tissue including a macrostructure, made from a bioresorbable polymer, providing structural and mechanical integrity to the void being treated, and a material for enhancing the attachment of cells to the macrostructure and carried by the bioresorbable polymer forming the macrostructure, with the cell attachment enhancing material being alginate characterized in that the macrostructure is porous and provides a porous architecture, with the porous macro-structure including interconnecting voids, with the alginate being formed into a porous microstructure located in the voids and separate from the bioresorbable polymer forming the porous macrostructure.

44. The bioresorbable device of claim 43 wherein the cell attachment enhancing material dissolves into a highly viscous gel suspended within the porous architecture.

45. The bioresorbable device of claim 44 further comprising, in combination: a cell culture media in the form of a fluid, with the cell culture media including suspended cells, with the cell culture media dissolving the cell attachment enhancing material into the highly viscous gel for trapping the suspended cells in the highly viscous gel.

46. Method of forming a device for regenerating at least first and second, juxtaposed tissues having different histologic patterns including the steps of: providing a first region having an internal three-dimensional architecture; providing a second region separate from the first region having an internal three-dimensional architecture; and integrally joining the first and second regions together at an interface surface without substantially distorting the three-dimensional architecture of the first and second regions characterized in that the internal three-dimensional architecture of the first region approximates the histologic pattern of the first tissue and the internal three-dimensional architecture of the second region approximates the histologic pattern of the second tissue, so that regeneration is anatomically specific.

47. Method including the step of: providing a structure made from a bioresorbable polymer and having an internal three-dimensional architecture, characterized in the further step of forming a barrier in the three-dimensional architecture for prohibiting water-based fluid from passing therebetween.

48. The method of claim 47 wherein the providing step comprises the steps of: providing the structure formed from the bioresorbable polymer which is hydrophobic, and treating the structure with a surfactant to be hydrophilic; and wherein the forming step comprises the step of inactivating the surfactant in the barrier to render the barrier hydrophobic.

49. Method comprising the steps of: providing a structure made from a bioresorbable polymer and having an internal three-dimensional architecture including at least first and second locations; providing a first material for enhancing the attachment of cells to the three-dimensional architecture; and investing the first location with the first cell attachment enhancing material characterized in that the second location is substantially free of the first cell attachment enhancing material.

50. The method of claim 49 wherein the providing step comprises the steps of: providing the first location;
providing the second location separate from the first location; and joining the first and second locations to form the structure; and wherein the investing step comprises the step of investing the first location with the first cell attachment enhancing material prior to the joining step.

51. The method of claim 49 wherein the structure includes first and second, spaced surfaces, with the first surface located on the first location and the second surface located on the second location; and wherein the investing step comprises investing the first location through the first surface with a volume of the cell attachment enhancing material less than or equal to the volume of cell attachment enhancing material which could be carried by the first location.

52. The method of claim 49 further comprising the steps of: providing a second material for enhancing the attachment of cells to the three-dimensional architecture; and investing the second location with the second cell attachment enhancing material while the first location is substantially free of the second cell attachment enhancing material.

53. The method of claim 49 wherein the first material providing step comprises the step of providing the first material which dissolves into a highly viscous gel suspended within the three-dimensional architecture.

54. The method of claim 53 further comprising the step of providing a cell culture media in the form of a fluid after the first material is invested in the first location, with the cell culture media including suspended cells, with the cell culture media dissolving the first material invested in the first location into the highly viscous gel for trapping the suspended cells in the highly viscous gel.

55. Method including the steps of: providing a structure made from a bioresorbable polymer and having an internal three-dimensional architecture; providing a material for enhancing the attachment of cells to the three-dimensional architecture; and investing the structure with the cell attachment enhancing material characterized in the investing step comprising the step of investing with the attachment enhancing material at varying concentrations in the three-dimensional architecture.

56. Device for facilitating the growth of healing tissue cells in voids in tissue including a structure made from a biocompatible material providing a three-dimensional architecture, characterized in the structure limiting, delaying, or preventing contact of the healing tissue cells with juxtaposed tissue and thereby be functionally specific.

57. The device of claim 56 wherein the three-dimensional architecture is layered within the structure.

58. The device of claim 56 wherein the structure includes at least one surface which is partially or completely sealed by partitions.

59. The device of claim 56 wherein the structure includes at least one surface covered by a mesh.

60. The device of any claim 56-59 wherein at least a first portion of the structure includes a physiologically acceptable surfactant selected from the group consisting of ananionic, cationic, amphoteric and nonionic surfactants.

61. The device of claim 60 wherein the amount of surfactant is present in an amount sufficient to draw fluid into the structure to liberate a quantity of surfactant sufficient to facilitate penetration of the fluid into a second portion of the structure not containing surfactant.

62 . The device of claim 60 wherein the first portion of the structure is adjacent to a second portion of the structure which has not been exposed to a surfactant for creating a breathable hydrophobic barrier.

63. The device of claim 62 wherein the breathable hydrophobic barrier is a size reducing hydrophobic barrier.

64. The device of any claim 56-63 wherein at least a first portion of the structure has incorporated a fluid extractable plasticizer providing temporary flexibility during implantation.

65. The device of claim 64 wherein the plasticizer is contained in the structure in an amount not to exceed 50%
by weight of the entire structure.

66. The device of claim 64 wherein the structure includes a second portion which is substantially free of the plasticizer.

67. A method of healing and tissue regeneration comprising contacting the tissue to be healed and regenerated with the device defined in claim 56.

68. A method as defined in claim 67 wherein the device is implanted into the tissue to be healed and regenerated.

69. A method as defined in claim 67 wherein the device allows tissue integration of the device while delaying total penetration through the device by tissue cells, thereby providing space maintenance and regeneration of tissue forming cells within the device.

70. A method as defined in claim 67 wherein the device is disposed externally to the tissue sought to be repaired to prevent undamaged tissue from interfering with the tissue sought to be repaired.

71. A method as defined in claim 67 wherein cells deposit an extracellular matrix in the device creating a living tissue barrier.

72. A method as defined in claim 71 wherein the extracellular matrix prevents other cells from entering the device.

73. Device for facilitating healing of voids in tissue including a structure made from a biocompatible material providing an internal three-dimensional architecture having a plurality of chambers, with each of the chambers having a diameter and a length, characterized in the chambers being elongated, with the length being no less than two times the diameter of the chamber so the device is functionally specific.

74. The device of claim 73 wherein the structure has a thickness, with the elongated chambers running the entire thickness of the structure.

75. The device of claim 73 wherein the structure has a length and a width, with the elongated chambers running the entire length and width of the structure.

76. The device of claim 75 wherein the enlongated chambers are layered within the structure.

77. The device of claim 73 wherein the elongated chambers are randomly placed within the structure.

78. The device of claim 77 further comprising, in combination: additional chambers which are not elongated and are intermixed with the elongated chambers.

79. The device of claim 73 wherein the structure includes at least one surface which is partially or completely sealed by partitions.

80. The device of claim 73 wherein the structure includes at least one surface covered by a mesh.

81. The device of any claim 73-80 wherein at least a portion of the structure includes a physiologically acceptable surfactant selected from the group consisting of ananionic, cationic, amphoteric and nonionic surfactants.

82. The device of claim 81 wherein the surfactant is triethanolomine dodecylbenzyl sulfonate.

83. The device of claim 81 or 82 wherein the amount of surfactant is present in an amount sufficient to draw fluid into the structure to liberate a quantity of surfactant sufficient to facilitate penetration of the fluid into a portion of the structure not containing surfactant.

84. The device of any claim 73-83 wherein at least a first portion of the structure has incorporated a fluid extractable plasticizer providing temporary flexibility during implantation.

85. The device of claim 84 wherein the plasticizer is contained in the structure in an amount not to exceed 50%
by weight of the entire structure.

86. The device of claim 84 or 85 wherein the plasticizer is triethyl citrate.

87. The device of any claim 84-86 wherein the structure includes a second portion which is substantially free of the plasticizer.

88. The device of any claim 73-87 wherein at least a first portion of the structure includes a biologically active agent.

89. The device of claim 88 wherein the structure includes a second portion which is substantially free of the biologically active agent.

90. The device of claim 88 wherein the biologically active agent is selected from the group consisting of cell populations, a physiologically acceptable drug, a biological modifier, a protein, a hormone, and antigen and mixtures thereof.

91. The device of any claim 73-90 wherein the bio-compatible material is a material selected from the group consisting of bioerodable materials, bioresorbable materials, bioerodable polymer materials, and bioresorbable polymer materials.

92. The device of any claim 73-91 wherein the bio-compatible material is a polymerized alpha-hydroxy acid.

93. The device of claim 92 wherein the polymerized alpha-hydroxy acid is DD, LL-polylactic acid.

94. The device of any claim 73-92 wherein at least some of the elongated chambers communicate with other chambers.

95. The device of any claim 73-94 wherein at least some of the elongated chambers intersect with other chambers.

96. A method of healing and tissue regeneration comprising contacting the tissue to be healed and regenerated with the device defined in claim 73.

97. A method as defined in claim 96 wherein the device is implanted into the tissue to be healed and regenerated.

98. A method as defined in claim 96 or 97 wherein the device allows tissue integration of the device while delaying total penetration through the device by tissue cells, thereby providing space maintenance and regeneration of tissue external to the device and controlled growth of tissue forming cells within the device.

99. A method as defined in claim 96 wherein the device is disposed externally to the tissue sought to be repaired to prevent undamaged tissue from interfering with the tissue sought to be repaired.

100. Bioresorbable device comprising, in combination:
first and second portions; and a physiologically acceptable surfactant engaged with the first portion and the second portion being initially substantially free of the surfactant, with the initial concentration of the surfactant in the first portion being effective to preclude surfactant from being drawn into the second portion, with the initial concentration of the surfactant in the first portion being effective to permit surfactant to be drawn into the second portion when fluid is eventually drawn into the first portion such that the fluid is eventually drawn into the second portion.

101. The device of claim 100 wherein the fluid comprises serum.

102. Bioresorbable device for implantation into a body having body fluids comprising, in combination: a structure made from a biocompatible material; and a fluid extractable plasticizer incorporated in the structure, with the plasticizer permitting the structure to be initially flexible during implantation, with the plasticizer being extractable from the structure by the body fluids after implantation whereby the structure is rendered less flexible.