Sonochemically fabricated microelectrode arrays for biosensors

Immobilized Enzymes in Biosensor Applications

Enzyme-based biosensing devices have been extensively developed over the last few decades, and have proven to be innovative techniques in the qualitative and quantitative analysis of a variety of target substrates over a wide range of applications. Distinct advantages that enzyme-based biosensors provide, such as high sensitivity and specificity, portability, cost-effectiveness, and the possibilities for miniaturization and point-of-care diagnostic testing make them more and more attractive for research focused on clinical analysis, food safety control, or disease monitoring purposes. Therefore, this review article investigates the operating principle of enzymatic biosensors utilizing electrochemical, optical, thermistor, and piezoelectric measurement techniques and their applications in the literature, as well as approaches in improving the use of enzymes for biosensors.

Labeless immunosensor assay for prostate specific antigen with picogram per milliliter limits of detection based upon an ac impedance protocol

This paper describes the development of labeless immunosensors for the prostate cancer marker prostate specific antigen (PSA). Poly(1,2-diaminobenzene) was electrodeposited onto screen-printed carbon electrodes, and this modified surface was sonochemically ablated to form a microelectrode array. Polyaniline was electropolymerized within these pores to form a microarray of conductive polyaniline protrusions. Two methods were utilized to immobilize antibodies for prostate specific antigen (APSA). The first involved entrapment of APSA during electropolymerization of the polyaniline. The second utilized a polyaniline array as a substrate to immobilize a biotinylated APSA using a classical avidin-biotin affinity approach. Microelectrode arrays were interrogated using ac impedance protocols before and following exposure to PSA solutions. Our preliminary results show that concentration/ac response relationships were recorded over very different ranges; sensors fabricated using an affinity approach exhibited detection limits 1000 times lower than those formulated by the entrapment method. This demonstrates that assembly protocols have major effects on immunosensor performance.

Conducting polymers in chemical sensors and arrays

The review covers main applications of conducting polymers in chemical sensors and biosensors. The first part is focused on intrinsic and induced receptor properties of conducting polymers, such as pH sensitivity, sensitivity to inorganic ions and organic molecules as well as sensitivity to gases. Induced receptor properties can be also formed by molecularly imprinted polymerization or by immobilization of biological receptors. Immobilization strategies are reviewed in the second part. The third part is focused on applications of conducting polymers as transducers and includes usual optical (fluorescence, SPR, etc.) and electrical (conductometric, amperometric, potentiometric, etc.) transducing techniques as well as organic chemosensitive semiconductor devices. An assembly of stable sensing structures requires strong binding of conducting polymers to solid supports. These aspects are discussed in the next part. Finally, an application of combinatorial synthesis and high-throughput analysis to the development and optimization of sensing materials is described.