United States Patent 
Yoshioka et al.
 BIOSENSOR UTILIZING ENZYME AND A METHOD FOR PRODUCING THE SAME
 Inventors: Toshibiko Yoshioka, Osaka; Shiro Nankai, Hirakata, both of Japan
 Assignee: Matsushita Electric Industrial Co., Ltd., Osaka, Japan
 Appl. No.: 845,073
 Filed: Mar. 2,1992
 Foreign Application Priority Data
Mar. 4, 1991 [JP] Japan 3-37259
Mar. 4, 1991 [JP] Japan 3-37261
Sep. 2, 1991 [JP] Japan 3-221402
Jan. 14, 1992 [JP] Japan 4-04592
 Int. CI.* G01N 27/26
 U.S. a 204/403; 204/412;
204/416; 204/153.12  Field of Search 204/403, 412, 416, 153.12
 References Cited
U.S. PATENT DOCUMENTS
4,897,173 1/1990 Nankai et al 204/403
5,120,420 6/1992 Nankai et al 204/403
FOREIGN PATENT DOCUMENTS
0359831 3/1990 European Pat. Off. .
0400918 12/1990 European Pat. Off. .
[ii] Patent Number: 5,192,415  Date of Patent: Mar. 9, 1993
1114747 5/1989 Japan .
9109139 6/1991 PCT Int'l Appl. .
Primary Examiner—John Niebling
Assistant Examiner—Bruce F. Bell
Attorney, Agent, or Firm—Panitch, Schwarze, Jacobs &
The biosensor of the present invention quantifies a substrate contained in a sample liquid by reducing electron acceptors using electron generated in a reaction of the substrate to enzyme and then by measuring the reduced amount of the electron acceptors electrochemically. The biosensor has an electrical insulating substrate, an electrode system including at least a working electrode and a counter electrode, a reaction layer including the enzyme provided on the electrode system and a hydrogen ion concentration control layer, and the reaction layer is in contact with the electrode system. According to the present invention, the hydrogen ion concentration in the sample liquid can be made most appropriate in accordance with the type of the enzyme contained in the reaction layer, without the adjustment of the hydrogen ion concentration in the sample liquid beforehand. Thus, the specific substrate contained in the sample liquid can be easily quantified with accuracy and speed.
13 Claims, 7 Drawing Sheets