LONG-FUNCTIONING BETA-D-GLUCOSE AND L-LAC TATE BIOSENSORS FOR CONTINUOUS FLOW-THROUGH MEASUREMENTS FOR FOULING-RESISTANT AND SELECTIVITY-OPTIMIZED SERUM-ANALYSIS AND HAEMOANALYSIS

Bioelectrochemical membrane-electrodes for O-2-sensitive enzymatic flo w-through analysis of beta-D-glucose and L-lactate are described. The enzyme-membranes of the biosensors consist of glucose-oxidase or lacta te-oxidase molecules cross-linked with glutardialdehyde between two di alysis membranes. The accuracy of the biosensors is demonstrated by el ectroanalysis of diluted control serum and compared with redox-mediato r-free H2O2 detection and photometric methods. Continuous haemoanalysi s of uncoagulated blood was carried out, using an intermediate carrier stream with additive systems. Tangential streaming to the miniaturize d dialysis chamber with a circular channel minimizes blockage of the p ores of the dialysis membrane by erythrocytes, leukocytes or protein. An oxygenator pump for the exchange of gases between the buffered solu tion of the intermediate carrier and the surrounding atmosphere guaran tees a constant oxygen partial pressure within the carrier stream. The pulsations produced by the oxygenator pump are dampened by a miniatur e pressure balance chamber with an unsignificant dead space volume for protecting the enzyme membrane of the sensor. Glutardialdehyde inhibi ts growth of microorganisms and any resulting oxygen consumption, so t hat even in protein-containing measuring solutions enzyme electrodes c an be used without interference from microbial contamination. The bioe lectrochemical measuring system can therefore also be employed for the electroanalysis of fermentation solutions. For continuous flow-throug h measurements, it is necessary to change the glucose-oxidase membrane s after 100-150 days, and the lactate-oxidase membranes after 3-6 week s.