Direct potentiometric immunoelectrodes

Electrochemical biochips for protein analysis

Proteins bear important functions for most life processes. It is estimated that the human proteome comprises more than 250,000 proteins. Over the last years, highly sophisticated and powerful instruments have been developed that allow their detection and characterization with great precision and sensitivity. However, these instruments need well-equipped laboratories and a well-trained staff. For the determination of proteins in a hospital, in a doctor's office, or at home, low-budget protein analysis methods are needed that are easy to perform. In addition, for a proteomic approach, highly parallel measurements with small sample sizes are required. Biochips are considered as promising tools for such applications. The following chapter describes electrochemical biochips for protein analysis that use antibodies or aptamers as recognition elements.

The construction and characterization of an amperometric immunosensor for the thyroid hormone (+)-3,3',5,5'-tetraiodo-L-thyronine (L-T4)

A novel amperometric immunosensor, based on graphite paste (graphite powder and paraffin oil), has been constructed for the assay of L-T4. The graphite paste is impregnated with mouse monoclonal anti-(+)-3,3',5,5'-tetraiodo-L-thyronine (anti-L-T4). The immunosensor can be reliably used for the assay of L-T4 in thyroid and in drugs, using chronoamperometry technique, at ppt up to ppb concentration levels. The potential used for L-T4 assay was +450 mV vs. Ag/AgCl electrode. The surface of the immunosensor can be regenerated by simply polishing, obtaining fresh immunocomposite ready to be used in a new assay.

Immunosensors: electrochemical sensing and other engineering approaches

This article overviews the engineering approaches and the recent trends in the development of alternative immunoassay systems. A brief description of the main principles and limitations of conventional immunoassay is given. Immunosensing approaches overcoming these limitations are discussed. Alternatives to traditional immunoassay systems are discussed in terms of the enhancement of immunointeraction processes and in terms of the various detection principles. Applications of flow-injection techniques to the development of immunosensing systems are presented. Immunosensors are categorized based on the detection principle employed, as immunoelectrodes (electrochemical immunosensors), piezoelectric immunosensors, or as sensors based on optical detection of the immunointeraction. The discussion focuses on electrochemical immunosensors. In conclusion, the engineering issues involved in immunosensor development are outlined and trends towards practical applications are discussed.