A surface enhanced Raman scattering based colloid nanosensor for developing therapeutic drug monitoring.

Competitive reactions, on the surface of plasmonic nanostructures, allow exploiting SERS signals for quantitative Therapeutic Drug Monitoring. As an example, the concentration of Erlotinib, an anti-EGFR small molecule, used for the treatment of non-small cell lung and pancreatic cancer, is determined. The numerous side effects and the variability of patient responses make Erlotinib a good candidate for monitoring. The new SERS based sensor can estimate Erlotinib down to nanomolar concentration and is based on the chemical reaction of the drug and of a competitor SERS reporter on the surface of gold nanostructures. Colloid solutions of naked gold nanoparticles obtained by laser ablation in solution were used for obtaining nanostructures with very efficient hot spots for SERS and with a clean surface for chemistry. Detection of the drug in the nanomolar concentration range is shown to be possible also in spiked plasma samples.