Fabrication of a miniature CMOS-based optical biosensor.

This work presents a novel, miniature optical biosensor by immobilizing horseradish peroxidase (HRP) or the HRP/glucose oxidase (GOx) coupled enzyme pair on a CMOS photosensing chip with a detection area of 0.5 mm x 0.5 mm. A highly transparent TEOS/PDMS Ormosil is used to encapsulate and immobilize enzymes on the surface of the photosensor. Interestingly, HRP-catalyzed luminol luminescence can be detected in real time on optical H(2)O(2) and glucose biosensors. The minimum reaction volume of the developed optical biosensors is 10 microL. Both optical H(2)O(2) and glucose biosensors have an optimal operation temperature and pH of 20-25 degrees C and pH 8.4, respectively. The linear dynamic range of optical H(2)O(2) and glucose biosensors is 0.05-20 mM H(2)O(2) and 0.5-20 mM glucose, respectively. The miniature optical glucose biosensor also exhibits good reproducibility with a relative standard deviation of 4.3%. Additionally, ascorbic acid and uric acid, two major interfering substances in the serum during electrochemical analysis, cause only slight interference with the fabricated optical glucose biosensor. In conclusion, the CMOS-photodiode-based optical biosensors proposed herein have many advantages, such as a short detection time, a small sample volume requirement, high reproducibility and wide dynamic range.

Application of SiO2-poly(dimethylsiloxane) hybrid material in the fabrication of amperometric biosensor.

Silica xerogel was widely used in the development of biosensors by coupling the desired biological components to various transducers. Unfortunately, the application of xerogels is limited due to their poor mechanical properties and poor structural maintenance of entrapped biomaterials. In this study, the availability of poly(dimethylsiloxane) (PDMS)-modified silica sol-gel (TEOS/PDMS Ormosil) glass in the immobilization of enzymes and its application in the fabrication of amperometric biosensor was investigated. We demonstrated that most of activity of encapsulated horseradish peroxidase can be preserved in PDMS-modified SiO2 glass compared with conventional silica xerogel. The synthesized monoliths exhibited high transparency and crack-free. The enzyme electrode based on glucose oxidase encapsulated TEOS/PDMS Ormosil glass on Pd electrode was fabricated and characterized electrochemically. The characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The biosensor exhibited a series of good properties: high sensitivity (1.63 microA mM(-1) analyte), short response time and high reproducibility. The results indicate that TEOS/PDMS Ormosil glass has great potential to the immobilization of biomaterials as well as the fabrication of biosensors.