Label-free Acoustic and Optical Biosensors Playing on Evanescent Waves

摘要

Development of sensitive, reliable, high-throughput, label-free detection techniques is an issue with increasing emphasis because the labeling strategies that most of the microarray applications have employed, such as fluorescent, chemiluminescent and radioactive labeling, have synthetic challenges, multiple label issues and may exhibit interference with the binding sites. Label-free detection techniques monitor biomolecular interactions and simplify the bioassays by eliminating the need for secondary reactants. Especially, biosensors based on evanescent waves often have high sensitivities by recording the changes caused by the molecule interaction near the sensor surface within the evanescent field, and moreover they provide quantitative information for the binding kinetics. In this article, we will describe the similarity of sound waves and electromagnetic waves and review the biosensors to which the two types of label-free techniques are related. The theoretical and technical outlines behind the sensing principles, such as the evanescent waves scattering, interference, resonance and tunnel effects, will be summarized. The physical mechanisms to modulate waves by microano structures, which localize the waves, amplify the signaloise ratio and increase Q factor for high sensitivity and high resolution, will also be discussed. Moreover, the promising acousto-optic sensing mechanism and the possibility of multi-parameter decoupling detection will be mentioned. The potential prospects, merits and challenges of these kinds of biosensors are also indicated.