Protein-based all-optical sensor device

The integrated optical Mach-Zehnder interferometer is a highly sensitive device, considered a powerful lab-on-a-chip tool for specific detection of various chemical and biochemical reactions. Despite its advantages, there is no commercially available biosensor based on this technique. The main reason is the inherent instability of the device due to slight changes of environmental parameters. In this paper we offer a solution to this problem that enables the optimal adjustment of the working point of the sensor prior to the measurement. The key feature is a control unit made of a thin film of the light-sensitive chromoprotein bacteriorhodopsin deposited on the reference arm of the interferometer. After showing the transfer characteristics of such a device, we demonstrate its applicability to sensing of specific protein–protein interactions. We expect our method to become a rapid and cost-efficient alternative of the commonly used measuring tools in protein research and medical diagnostics.