Optical express monitoring of Internalin B, a protein of the pathogenic bacterium Listeria monocytogenes, using SERS-active silver-decorated silicon nanowires

Surface-enhanced Raman Scattering (SERS) is a powerful vibrational optical spectroscopy method that allows highly sensitive detection of molecules at very low concentrations of matter by amplifying the electromagnetic fields created by excitation of localized surface plasmons on the surface of noble metal nanostructures. In the presented work a method of manufacturing composite nanostructures of silicon nanowires decorated with silver (AgSiNWs) has been developed. The SERS activity of AgSiNWs for protein detection was investigated using human serum albumin as an example. For the first time, the possibility of rapid diagnosis of internalin B (InlB) protein of pathogenic bacteria Listeria monocytogenes by SERS using the obtained nanostructures was shown. In the spectra of InlB adsorbed on AgSiNWs at different concentrations, distinct peaks corresponding to Raman scattering on protein molecules are observed. Based on the experimental data obtained, the detection limit of InlB was calculated to be 4.8 $\cdot$ 10$^{-9}$ M. The results presented in this work demonstrate the high potential of the obtained composite nanostructures for the diagnosis of various proteins by SERS.