Immobilization of glucose oxidase with polyurethane on carbon support

Glucose oxidase (GOD) has been immobilized by physical entrapment on polyurethane PU-6 matrix. It has been found that the enzyme acquires greater thermal stability on immobilization. Oxygen acts as a co-substrate for the redox reaction. However, maintaining oxygen concentration constant throughout the experiment is a difficult task. To overcome this we have coimmobilized ferrocene, which can act as an electron acceptor. 31P NMR results indicate that ferrocene is located in the close proximity of the active site of GOD. Moreover, simultaneous use of mediators such as ferricyanide, phenazine methosulphate or flavine mononucleotide have been found to facilitate electron transfer. Platinum, apart from being an expensive metal, is likely to exhibit adverse toxic effects during prolonged 'in-vivo' applications. Electrodes prepared using carbon in the place of platinum, show comparably good response. This opens a new possibility for making cheaper and biocompatible sensors

Synthesis and LB film formation of fatty acid- fad complex

Flavin adenine dinucleotide can exist in two oxidation states. Switching from one state to the other can be achieved chemically or electrically. The flavin undergoes reduction reversibly by two one electron steps or one two electron step, changing the chemistry of the enediamine subfunction of the isoalloxazine moiety. The adenine moiety is not involved in the catalysis, but helps in anchoring the coenzyme at the active site. The hydrophilicity of FAD has been changed by chemically attaching hydrocarbon chains to the noncatalytic adenine moiety. The modified coenzyme has been verified to retain the electro chemical, optical and the biochemical properties. The amphiphilic molecules can form monolayers at the air-water interface. A film of desired thickness can be formed on a solid support by means of monomolecular deposition using LB film technique. The characterization of the film has been done using spectrophotometric and electrochemical methods

Clinical evaluation of the FreeStyle Precision Pro system

AbstractBackgroundA new version of international standard (ISO 15197) and CLSI Guideline (POCT12) with more stringent accuracy criteria are near publication. We evaluated the glucose test performance of the FreeStyle Precision Pro system, a new blood glucose monitoring system (BGMS) designed to enhance accuracy for point-of-care testing (POCT).MethodsPrecision, interference and system accuracy with 503 blood samples from capillary, venous and arterial sources were evaluated in a multicenter study. Study results were analyzed and presented in accordance with the specifications and recommendations of the final draft ISO 15197 and the new POCT12.ResultsThe FreeStyle Precision Pro system demonstrated acceptable precision (CV <5%), no interference across a hematocrit range of 15–65%, and, except for xylose, no interference from 24 of 25 potentially interfering substances. It also met all accuracy criteria specified in the final draft ISO 15197 and POCT12, with 97.3–98.9% of the individual results of various blood sample types agreeing within ±12mg/dl of the laboratory analyzer values at glucose concentrations <100mg/dl and within ±12.5% of the laboratory analyzer values at glucose concentrations ≥100mg/dl.ConclusionsThe FreeStyle Precision Pro system met the tighter accuracy requirements, providing a means for enhancing accuracy for point-of-care blood glucose monitoring

Conducting polymers in the fabrication of efficient biosensors

561-564Fabrication of efficient biosensors for industrial and medical applications is a challenging problem. Several polymers have been used for interfacing a biological component to the electrode surface in order to attain higher performance efficiency and faster electron transfer processes between the enzyme and the electrode. In this mini review, some of the successful matrices used in biosensor fabrication have been discussed

Glucose oxidase immobilized electrode for potentiometric estimation of glucose

Glucose oxidase has been immobilized onto a thin platinum strip, by co-crosslinking with bovine serum albumin and glutaraldehyde. The retention of redox characteristics of glucose oxidase has been verified by cyclic voltammetry. The activity of the immobilized enzyme reduces to a quarter of its value when the enzyme is in solution but improves when coimmobilized with 1 m urea. The potentiometric response builds up and remains stable after 100 s. It is sensitive to the thickness of the immobilizing matrix, pH and temperature. An improvement in the performance of the electrode has been achieved by coimmobilizing 2 m urea and metal ions such as Mg2+ and Mn2+. The presence of Cu has been proved to be detrimental. The electrode has been calibrated in the 0.1-5.0 mM glucose concentration range. It gives a stable response for more than 50 independent assays and can be stored for 60 days without significant loss of function