OPTICAL BIOSENSORS FOR LABEL-FREE DETECTION OF BIOMOLECULAR INTERACTIONS

Biosensors are important tools in fields of biophysics, biochemistry, and biomedical engineering because they provide a platform for the detection of various analytes. Currently, fluorescence-based detection methods have been routinely used for their high sensitivity and diverse selections of labeling agents. However, tagging extra molecules (such as dyes) on to one of the binding pair might change the intrinsic binding affinity of that reaction. To do away with this drawback, label-free biosensors based on optical techniques have drawn more and more attention recently because they are non invasive to the biomolecules under investigation. This article reviews some modern optical biosensors including surface plasmon resonance, oblique-incidence reflectivity difference, interferometry, resonant cavity, and resonant waveguide grating. Some of these techniques have already been commercialized for biological applications. While surface plasmon resonance is the most sensitive and commonly used method, oblique-incidence reflectivity difference provides comparable sensitivity with additional advantages in throughput as well as compatibility. It is believed that in the future, optical techniques will still lead the way in the development of label-free biosensors for biological applications.