UV imaging of biochips based on resonant grating

Abstract

International audienceIn the frame of biological threat, security systems require label free biochips for rapid detection. Biosensors enable to detect biological interactions, between probes localized at the surface of a chip, and targets present in the sample solution. Here, we present an optical transduction, enabling 2D imaging, and consequently parallel detection of several reactions. It is based on the absorption of biological molecules in the UV domain. Thus, it is based on an intrinsic property of biological molecules and does not require any labelling of the biological molecules. DNA and proteins absorb UV light at 260 and 280 nm respectively. Sensitivity is a major requirement of biosensing devices. Configurations leading to enhancement of the interaction between light and biological molecules are of interest. For a better sensitivity, resonant grating structures are then studied. They enable to confine the electric field close to the biological layer. Imaging of resonant grating is not largely studied, even for visible wavelengths, but it results in good sensitivity. The protein used in this study is the methionyl-tRNA synthetase. Its absorption is representative of protein absorption, and it can then serve as a model for immunological detection. The best experimental contrast due to a monolayer of proteins is 40%. With data processing currently employed for biochip imaging: average on several acquisitions and on all the pixels imaging the biological spots, the device is able to detect a surface density of proteins in the 10 pg/mm range. © (2010) COPYRIGHT SPIE--The International Society for Optical Engineerin