POF Biosensors Based on Refractive Index and Immunocapture Effect

The combat against tropical diseases is becoming an increasingly important issue in developing countries and they need to rely on readily available and rapid response diagnostic assays. The diagnostic methods for the detection of common pathogens are still time consuming, require laboratories and specialized personnel. To the effective combat of these diseases, the diagnostic needs to be fast, reliable and accurate, not only to the clinical area, but also to immediate detection of contaminants, particularly for water quality, clinical diagnosis or food security. With the development of new technologies, especially in methods based on immunological assays, one expects increased sensitivity, specificity and speed in the detection of important microorganisms for health, veterinary medicine, agriculture and industry. This advance serves as a basis for various other techniques such as the use of biosensors for the detection of pathogens. Optical biosensors offer several advantages when compared with conventional biosensors and some of these advantages are electrical passiveness, long distance sensing and electromagnetic immunity. The objective of this work is to develop three biosensor platforms based on refractive index measurement by the following techniques: surface plasmon resonance, evanescent wave and gold thin film evanescent wave techniques using a plastic optical fiber. We aimed at the best configuration of the optical setup, sensitivity, response time, a simple fabrication method, and a good specificity for Escherichia coli detection.