Improving the specificity and stability of label-free optical biosensors

The detection of antigens, bacteria, and viruses for medical diagnostics and environmental monitoring requires the development of highly sensitive and selective biosensors. Conventionally, fluorescent immunoassays have been the primary detection platforms in complex environments, such as serum or whole blood. This technique is particularly successful due to its high specificity to the target molecule and the good signal-to-noise provided by the fluorescent molecule. However, because a dye molecule is required as a read-out mechanism, these approaches are not suitable for real-time, in-line monitoring of biological processes. In contrast, label-free optical sensors, such as those based on optical waveguides and resonant cavity devices, are able to detect the molecule itself, without the use of a secondary fluorescent probe. However, while many of these optical devices are inherently sensitive transducers, detection specificity is equally, if not more, important in many applications. Therefore, it is critical to improve the specificity of detection without degrading the device performance.