Fabrication of porous silicon based label-free optical biosensor for heat shock protein 70 detection

Porous silicon (PSi) is an excellent nanostructured material which has been extensively studied for the development of label-free and low-cost optical biosensors. However, the detection of large sized biomolecules is challenging because they clog the pores of PSi and hinder molecular infiltration into the pores. Here, we report the preparation of mesoporous PSi optical biosensor for the label-free sensing of large biomolecule heat shock protein 70 (HSP70). PSi single layer platform was prepared by electrochemical etching and further stabilized by thermal oxidation. PSi was then immobilized with anti-HSP70 antibody via 3-aminopropyltriethoxysilane (APTES)/glutaraldehyde linking chemistry. PSi platform was characterized by fiber optic spectrometer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and contact angle measurements. Porosity and thickness values of PSi platform obtained from spectroscopic liquid infiltration method and SEM were 68% +/- 3% and 2400 +/- 30 nm, respectively. PSi optical biosensor showed sensitive detection of HSP70 in the range of 3000-500000 ng mL(-1) with a limit of detection of 1290 +/- 160 ng mL(-1). The specificity of PSi biosensor was also demonstrated by incubating with immunoglobulin G (IgG) which displayed no binding on the sensor surface.