Owing to its high sensitivity, surface-enhanced Raman spectroscopy (SERS) is largely used in biosensing as an efficient optical technique. In this work, we report the elaboration of a novel SERS substrate based aptasensor for ultra-sensitive and selective detection of prostate specific antigen (PSA). The SERS substrate is based on silicon nanowires (SiNWs) as transducer surface coated by silver nanoparticules (AgNPs). The silver nanoparticles have two purposes : a) aptamer immobilization via thiol chemistry and b) Raman signal enhancement. The presence of PSA induces the appearance of amide vibration modes only if the aptamer is present on the surface of SiNWs. The platform is highly sensitive, selective and specific to PSA in a wide range of concentrations from 0.1 to 20 µg.L -1 with a detection limit of 0.1 µg.L -1 , which encompasses the blood serum range of healthy subjects and ill patients. This optical biosensor shows a great stability and it is successfully validated in human blood serum samples showing very good results.

In this work, we combined a hierarchical nano-array effect of silicon nanowires (SiNWs) with a metallic surface of silver nanoparticles (AgNPs) to design a surface-enhanced Raman spectroscopy (SERS) scattering substrate for sensitive detection of Rhodamine 6G (R6G) which is a typical dye for fluorescence probes. The SiNWs were prepared by Metal-Assisted Chemical Etching (MACE) of n-Si (100) wafers. The Doehlert design methodology was used for planning the experiment and analyzing the experimental results. Thanks to this methodology, the R6G SERS response has been optimized by studying the effects of the silver nitrate concentration, silver nitrate and R6G immersion times and their interactions. The immersion time in R6G solution stands out as the most of influential factor on the SERS response.