Plasmonic spot-on Raman sensor for biomolecules

In an attempt to produce a SERS-active and low cost sensor for label free detection of trace amounts and small volumes of biomolecule samples, silver nanowires with high aspect ratio were implemented in a flow-through self assembly process on hydrophobic PTFE membrane. This bottom up assembly was followed by spot arrays design and fabrication through laser patterning of the silver nanostructured surface, leading to the formation of circular spots of defined size aimed at both concentrating microliter volumes of aqueous solution droplets and enhancing the Raman signal of micromolar amounts of biomolecules. The spot arrays so produced were efficiently tested as SERS sensors via direct detection, i.e. by direct measurement of the analyte molecular Raman fingerprint, with several proteins and biomarkers of neurodegenerative diseases and they showed excellent reproducibility and sensitivity. The specificity of the detection system is intrinsic in the Raman spectroscopic signal, which enables a structural characterization of the biomolecules while a rapid and effective detection is perfomed. The silver spot arrays can also represent a versatile label free SERS platform for indirect biomolecular detection, thanks to the simple and easy functionalization of the silver spots by thiolated small molecules and receptors.