Method of detecting and/or quantifying an analyte in a biological sample

A method of identifying an analyte molecule in a biological sample, the method comprising the steps of:

• capturing the analyte molecule onto a nano-structured silver SERS surface by means of an analyte molecule-specific aptamer, resulting in a specific aptamer-analyte molecule complex, which has a different pattern of Raman shifts in a SERS spectrum relative to a pattern for the aptamer or the analyte in isolation, the pattern of Raman shifts being unique and reproducible for the specific aptamer-analyte molecule complex, wherein amphiphilic molecules comprising an alkyl thio chain of at least 11 carbon atoms are attached to the silver surface to form a self-assembled monolayer (SAM), the SAM is coated with a layer of oligoethylene glycol molecules, and the analyte molecule-specific aptamer is attached directly to the SAM or attached directly to the silver surface and surrounded by the SAM,
• obtaining SERS spectra at a plurality of different voltages;
• measuring SERS signal intensity and unique pattern of Raman shifts for the specific aptamer-analyte molecule complex, and
• comparing the measured SERS signal intensity and Raman shifts of a SERS spectrum measured for the specific aptamer-analyte molecule complex to a database of reference SERS spectra of aptamer-analyte molecule complexes wherein the database comprises two or more SERS spectra and wherein each SERS spectrum in said database is unique for a different aptamer-analyte molecule complex, thereby identifying the analyte molecule in the aptamer-analyte molecule complex.