Matrix entrapment of glucose oxidase by gamma irradiation

High performance conducting polymer nanofiber biosensors for detection of biomolecules

Sensitive detection and selective determination of the physiologically important chemicals involved in brain function have drawn much attention for the diagnosis and treatment of brain diseases and neurological disorders. This paper reports a novel method for fabrication of enzyme entrapped-conducting polymer nanofibers that offer higher sensitivity and increased lifetime compared to glucose sensors that are based on conducting polymer films.

Methods for reducing biosensor membrane biofouling

The deleterious effect that biofouling has on sensor stability is a serious impediment to the development of long term implanted biosensors. This paper reviews the surface modification strategies currently employed to minimize membrane biofouling of in vivo sensors. Nine sensor modifications are discussed herein: hydrogels, phospholipid-based biomimicry, flow-based systems, Nafion, surfactants, naturally derived materials, covalent attachments, diamond-like carbons, and topology.

Biotechnological developments in Turkey

Turkey is a country not usually associated with industrial biotechnology. However, when current research potential in universities and other R & D centers and particularly contributions made to the international literature since the mid-1980s are taken into account, high-quality international-level work is now commonplace, especially in areas such as industrial microbiology, enzyme technology, biomaterials and biological wastewater treatment. Work in plant biotechnology is at a relatively early stage, but is expected to become a rapidly developing force in the near future. The present article documents current potential in Turkey, based on significant publications produced during the last 8 years.

Covalently immobilized enzymes on biocompatible polymers for amperometric sensor applications

Glucose oxidase or choline oxidase were covalently immobilized on the surface of 2-hydroxyethyl and glycidyl methacrylate copolymer membranes. The polymerization was induced by gamma irradiation at low temperature. The enzyme modified polymers were applied on Clark-type or platinum electrodes to form amperometric sensors based on the electrochemical measurements of oxygen or hydrogen peroxide. Glucose and choline content in standard solutions were measured and linear calibration curves were determined. The sensors studied showed a response time of less than 2 min and the observed linear ranges were increased with respect to usual biosensors owing to the diffusion-limiting effects of the membranes used. The influence of the copolymer composition on the electrochemical response and on the retained enzyme activity were explored for verifying the optimum analytical performance. The immobilized enzyme membranes stored in suitable buffers were very stable and showed a decrease up to 20% in the electrode response after 3 months of constant use.

Glucose sensors based on enzyme immobilization onto biocompatible membranes obtained by radiation-induced polymerization

Amperometric glucose biosensors based on glucose oxidase immobilized onto poly(2-hydroxyethylmethacrylate) membranes obtained by gamma radiation-induced polymerization were constructed. In a three-electrode configuration, smooth or platinized platinum electrodes with different shapes were used, in order to detect the amount of hydrogen peroxide produced in the glucose oxidation. A saturated calomel electrode and a platinum foil were used as a reference and counterelectrode, respectively. The biocompatible obtained sensors were characterized as regards the temperature effect, the response, and lifetime. The determination of glucose in standard solutions was carried out, and linear calibration curves were obtained. Depending on the electrode configuration, the sensor had a response time of 1-4 min, and the measuring range extended from 5 x 10(-5) to 4 x 10(-3) M.

Glucose oxidase sandwiched between pHEMA layers: a continuous flow reactor application

Glucose oxidase was entrapped between poly(2-hydroxyethyl methacrylate) membranes and conditions were optimized for high enzyme activity and high levels of entrapment. Highest entrapment was with a 78 microns thick coat. A continuous flow membrane reactor was designed and used. The reaction was first order with respect to glucose and to oxygen. Vmax values for the native and immobilized enzymes were 0.182 and 0.133 mM/min. The Km's for native and immobilized enzymes were 6.2 and 16.9 mM, respectively. At high substrate concentrations enzyme poisoning was detected. Both pH and temperature profiles moved to higher values upon immobilization. The enzyme retained 80% of its activity for at least 3 months in dry form.