Label-free sensing on microarrays

Abstract

Microarrays of biological molecules such as DNAs,proteins,carbohydrates,and small molecules provide a high-throughput platform for screening tens of thousands of biomolecular interactions simultaneously,facilitating the functional characterization of these biomolecules in areas of genomics,proteomics,glycomics,and cytomics. Routinely,analysis of binding reactions between solution-phased probes and surface-immobilized targets involves some kinds of fluorescence-based detection methods. Even though these methods have advantages of high sensitivity and wide dynamic range,labeling probes and/or targets inevitably changes their innate properties and in turn affects probe-target interactions in often uncharacterized ways. Therefore,in recent years,various label-free sensing technologies have been developed for characterizing biomolecular interactions in microarray format. These biosensors,to a certain extent,take the place of fluorescent methods by providing a comparable sensitivity as well as retaining the conformational and functional integrality of biomolecules to be investigated. More importantly,some of these biosensors are capable of real-time monitoring probe-target interactions,providing the binding affinities of these reactions. Using label-free biosensors in microarrays has become a current trend in developing high-throughput screening platforms for drug discoveries and applications in all areas of "-omics." This article is aimed to provide principles and recent developments in label-free sensing technologies applicable to microarrays,with special attentions being paid to surface plasmon resonance microscopy and oblique-incidence reflectivity difference microscopy.