Biosensor-Based Detection Methods

The application of biosensors for pathogen detection from food samples is challenging because of fhe complex nature of food matrices, which 

---

Further progress of ECL probes immobilization methods should result in new robust, stable, reproducible ECL sensors. Especially, the use of electrochemilumi-nescent polymers may prove to be useful in this respect. There are also good prospects for ECL to be used as detection in miniaturized analytical systems particularly with a large increase in the applications of ECL immunoassay because high sensitivity, low detection limit, and good selectivity. One can believe that miniaturized biosensors based on ECL technology will induce a revolution in clinical analysis because of short analysis time, low consumption of reactants, and ease of automation. 

Several techniques have been developed for the determination of purine and pyrimidine derivatives in food sample and in particular for hypoxanthine quantification biosensors (220-223) and electrochemical methods making use of immobilized enzyme electrode (224 -227), electrochemical enzymatic-based HA methods (228,229), enzyme reaction with fluorimetric detection (230), radioimmunoassay (231), colorimetric methods (232), capillary electrophoresis (233), and TLC (234). Many HPLC methods have also been developed and are reported in Table 4 (235-247) the most recent ones are described next. 

In this part we will describe recent achievements in the development of biosensors based on DNA/RNA aptamers. These biosensors are usually prepared by immobilization of aptamer onto a solid support by various methods using chemisorption (aptamer is modified by thiol group) or by avidin-biotin technology (aptamer is modified by biotin) or by covalent attachment of amino group-labeled aptamer to a surface of self-assembly monolayer of 11-mercaptoundecanoic acid (11-MUA). Apart from the method of aptamer immobilization, the biosensors differ in the signal generation. To date, most extensively studied were the biosensors based on optical methods (fluorescence, SPR) and acoustic sensors based mostly on thickness shear mode (TSM) method. However, recently several investigators reported electrochemical sensors based on enzyme-labeled aptamers, electrochemical indicators and impedance spectroscopy methods of detection. 

The development of electrochemical genosensors and immunosen-sors based on labelling with NPs has registered an important growth, principally for clinical and environmental applications. The electrochemical detection of NP labels in affinity biosensors using stripping methods allows the detailed study of DNA hybridisation as well as immunoreactions with interest in genosensor or immunosensor applications. 

Nucleic acid biosensors based on optical modes of detection represent another common approach for generating analytical signals based on nucleic acid hybridization. The methods discussed herein are based on methods that are suitable for the study of materials on surfaces. There are a number of different optical methods that have been described, with the most common being attenuated total reflectance (ATR), total internal reflection fluorescence (TIRF) and surface plasmon resonance (SPR) [15]. All of these methods work... 

Pazos, M.I, Alfonso, A., Vieytes, M., Yasumoto, T, and Botana, L. 2004. Resonant mirror biosensor detection method based on yessotoxin-phosphodiesterase interactions. Analytical Biochemestry 335, 112—118. 

---