Optical label free biodetection based on the diffraction of light by nanoscale protein gratings

Abstract

In this work, we use a label free biosensing technique based on the diffraction of light by molecular gratings. Molecular gratings are employed as diffractive probe arrays for protein interaction analysis. Indeed, the diffraction efficiency changes in response to analyte binding, due to a shift in line thickness and/or refractive index of the grating. In this perspective, we have developed a scanning instrument, capable of collecting at high speed the diffracted intensity emitted by molecular gratings. Nanogratings composed of anti-GST antibodies lines (500nm width at a pitch of 1μm) were immobilized through Microcontact printing on a PLL-g-dextran coated substrate. By monitoring the diffracted intensity of the anti-GST antibodies gratings, we have detected GST molecules at a concentration of 0.1μM. This biodetection technique appears sensitive to low molecular weight molecules, such as GST (glutathione S-transferase, 26kDa), which is an interesting result in comparison to other label free detection methods.