A disposable biosensor for urea determination in blood based on an ammonium-sensitive transducer.

Disclosed are bioanodes comprising a quaternary ammonium treated Nation® polymer membrane and a dehydrogenase incorporated within the treated Nation® polymer. The dehydrogenase catalyzes the oxidation of an organic fuel and reduces an adenine dinucleotide. The ion conducting polymer membrane lies juxtaposed to a polymethylene green redox polymer membrane, which serves to electro-oxidize the reduced adenine dinucleotide. The bioanode is used in a fuel cell to produce high power densities.

Enzyme immobilization for use in biofuel cells and sensors

Disclosed is an improved biofuel cell having a cathode comprising a dual function membrane, which contains an oxygen oxidoreductase enzyme immobilized within a buffered compartment of the membrane and an electron transport mediator which transfers electrons from an electron conducting electrode to the redox reaction catalyzed by the oxygen oxidoreductase enzyme. The improved biofuel cell also has an anode that contains an oxidoreductase enzyme that uses an organic fuel, such as alcohol, as a substrate. An electric current can flow between the anode and the cathode.

Immobilized enzymes in biocathodes

The last decade has seen not only an enormous growth in the number of hemodialysis patients but also a concomitant growth in the number of hemodialysis machines produced every year by fewer companies than 10 years ago. Because the risk of accidents increases with the number of different machines in the field, standard organizations and government authorities worldwide have issued standards and laws that regulate the design of hemodialysis machines. Both effects have slowed the development of new concepts and the effective use of modern technology in hemodialysis machines. The extracorporeal circuit has remained unchanged for more than twenty years. Bicarbonate dialysis with single patient machines and volumetric ultrafiltration control which were developed in the late 70s took more than 10 years to be generally accepted. Cost pressure has been an effective driving force for the introduction of new technology. High-efficiency dialysis was introduced in order to reduce treatment time. Underdialysis of many patients was the result because in many cases the shortening of the treatment time was not sufficiently compensated for by the increased efficacy of the dialysis process

Hemodialysis machines and monitors

Microfluidic biofuel cells comprising a bioanode and/or a biocathode are formed using microfluidic principles and soft lithography. The enzymes utilized in the redox reactions at the bioanode and/or the biocathode are stabilized in a micellar or inverted micellar structure. The biofuel cell is used to produce high power densities.

Microfluidic biofuel cell

An ion-selective electroanalyzer for bio-electrochemically controlled hemodialysis will be described. The bedside analysers are solid-contact flow-through electrodes based on tubular carrier-PVC-membranes for potassium, sodium, calcium and chloride. This multi-measurement system with series-connected biosensors in modular construction is provided with a chemosensor for pH measurements. Besides the technical aspects of the apparatus, the quantitative electrode characteristics and the fundamental basis for the application of ion activities in clinical analytic measurement will be described.

[Ion-selective electro-analyser with tubular solid contact flow-through sensors for continuous bioelectrochemically controlled hemodialysis of K+, Na+, Ca2+, Cl- and pH].

Up to now calcium-selective electrodes with carrier-PVC-membranes have shown a need for correction during their application in controlling the process at an artificial kidney, for the presence of acetate anions leads to immense differences of measurements because of the anion interference On the basis of experimental research the membrane characteristics could be changed in such a way that there is no need to correct the measurements when the electrodes are used during bicarbonate haemodialyses with 2 mmol/1 acetate This was achieved by optimizing the ratio of the concentration of synthetic, electrically neutral carrier and lipophilic anion and by using plasticizer effects A special membrane was developed in the same way for an application in dialysis solutions with 35 mmol/l acetate

Minimization of the acetate interference of calcium-selective carrier-PVC-membrane electrodes for process-controlled haemodialysis

Bioelectrochemical membrane-electrodes for O2-sensitive enzymatic flow-through analysis of beta-D-glucose and L-lactate are described. The enzyme-membranes of the biosensors consist of glucose-oxidase or lactate-oxidase molecules cross-linked with glutardialdehyde between two dialysis membranes. The accuracy of the biosensors is demonstrated by electroanalysis of diluted control serum and compared with redox-mediator-free H2O2 detection and photometric methods. Continuous haemoanalysis of uncoagulated blood was carried out, using an intermediate carrier stream with additive systems. Tangential streaming to the miniaturized dialysis chamber with a circular channel minimizes blockage of the pores of the dialysis membrane by erythrocytes, leukocytes or protein. An oxygenator pump for the exchange of gases between the buffered solution of the intermediate carrier and the surrounding atmosphere guarantees a constant oxygen partial pressure within the carrier stream. The pulsations produced by the oxygenator pump are dampened by a miniature pressure balance chamber with an unsignificant dead space volume for protecting the enzyme membrane of the sensor. Glutardialdehyde inhibits growth of microorganisms and any resulting oxygen consumption, so that even in protein-containing measuring solutions enzyme electrodes can be used without interference from microbial contamination. The bioelectrochemical measuring system can therefore also be employed for the electroanalysis of fermentation solutions. For continuous flow-through measurements, it is necessary to change the glucose-oxidase membranes after 100-150 days, and the lactate-oxidase membranes after 3-6 weeks.

[Long-functioning beta-D-glucose and L-lactate biosensors for continuous flow-through measurements for "fouling"-resistant and selectivity-optimized serum- and hemoanalysis].

Aufgrund modelltheoretischer Uberlegungen bezuglich der unterschiedlichen Kaliumselektivitat einiger Transportantibiotica aus der Valinomycin-Gruppe ist zur Erzielung hoher Selektivitaten eine ausreichende Rigiditat der Hohlraumstruktur zu fordern. Daher wurde in Analogie dazu fur die Konzipierung eines hochselektiven Natrium-Sensors ein in seiner Ringflexibilitat eingeschrankter uberbruckter Hemispharand als ionophorer Carrier in eine PVC-Membran inkorporiert. Das natriumselektive Membransystem weist eine Selektivitat gegenuber K− von 460:1 und Li− von 2179:1 (K−1
Na
+−S+) auf. Diese hohe Diskriminierung beider Storionen wurde anderen natriumselektiven Membransystemen gegenubergestellt.

Natrium-Sensor mit ausgeprägter Diskriminierung von Kalium- und Lithium-Ionen auf der Basis einer Carrier-PVC-Membran

Zusammenfassung: Es werden bioelektrochemische Membranelektroden zur O2-sensitiv-enzymatischen Durchflusanalyse von s-D-Glucose und L-Lactat beschrieben. Die Enzymmembranen der Biosensoren basieren auf der Quervernetzung von Glucose-Oxidaseoder Lactat-Oxidase-Molekulen durch Glutardialdehyd zwischen zwei Dialysemembranen. Anhand einer Gegenuberstellung zur redoxmediatorfreien H2O2-Detektion und im Vergleich zu photometrischen Bestimmungsmethoden wird ihre Verlaslichkeit in der Elektroanalytik verdunnter Seren durch die Vermessung von Richtigkeitskontrollseren demonstriert. Die kontinuierliche Hamoanalytik im ungerinnbaren Blut erfolgt nach dem Prinzip der Zwischentrageranalyse auf der Basis von Additivsystemen. Die tangentiale Anstromung des Miniatur-Dialysators mit zirkularer Kanalfuhrung minimiert eine Porenverlegung der Dialysemembran durch Erythrocyten, Leukocyten oder Proteine. Eine Oxigenatorpumpe zum Gasaustausch zwischen der gepufferten Tragerlosung und der umgebenden Atmosphare ist der Garant fur einen konstanten Sauerstoffpartialdruck im Carrierstrom. Die durch die Oxigenatorpumpe erzeugten Pulsationen werden durch eine miniaturisierte Druckausgleichskammer mit vernachlassigbarem Totraumvolumen fur die Enzymmembran des Sensors gedampft. Glutardialdehyd wirkt als Hemmstoff fur mikrobielles Wachstum im Kanalsystem und beugt damit einer unerwunschten Sauerstoffzehrung durch Mikroorganismen vor, so das auch in proteinhaltigen Mesmedien eine „fouling-resistente Applikation der Etizymelektroden ermoglicht wird. Daher kann das bioelektrochemische Messystem auch in anderen Medien wie Fermentationslosungen zur Elektroanalytik eingesetzt werden. Bei kontinuierlichem Durchflusbetrieb wurde ein Wechsel der Glucose^Oxidase-Membranen nach 100 bis 150 Tagen und der Lactat-Oxidase-Membranen nach 3 bis 6 Wochen vorgenommen.

/pdf/langlebige-s-d-glucose-und-l-lactat-biosensoren-fur-2q24axz4t3.pdf

Langlebige ß-D-Glucose- und L-Lactat-Biosensoren für kontinuierliche Durchflußmessungen zur „fouling”-resistenten und selektivitätsoptimierten Serum- und Hämoanalytik

K. Herna

Papers

[Ion-selective electro-analyser with tubular solid contact flow-through sensors for continuous bioelectrochemically controlled hemodialysis of K+, Na+, Ca2+, Cl- and pH].

Minimization of the acetate interference of calcium-selective carrier-PVC-membrane electrodes for process-controlled haemodialysis

[Long-functioning beta-D-glucose and L-lactate biosensors for continuous flow-through measurements for "fouling"-resistant and selectivity-optimized serum- and hemoanalysis].

Natrium-Sensor mit ausgeprägter Diskriminierung von Kalium- und Lithium-Ionen auf der Basis einer Carrier-PVC-Membran

Langlebige ß-D-Glucose- und L-Lactat-Biosensoren für kontinuierliche Durchflußmessungen zur „fouling”-resistenten und selektivitätsoptimierten Serum- und Hämoanalytik