pH activated colloidal Nanospheres: A viable sensing platform for the Therapeutic Drug Monitoring of the anticancer Drug 6-Mercaptopurine

A SERS colloidal solution of gold nanoparticles is proposed as a sensing platform potentially suitable for the Therapeutic Drug Monitoring of the anticancer drug 6-mercaptopurine. The as-synthesized nanospheres were fully characterized in terms of morphological features, plasmonic properties and SERS activity. Modifying the pH of the colloidal solution toward acidic values allowed us to improve considerably the platform sensitivity. A kinetic analysis performed at different analyte concentrations revealed the occurrence of adsorption/aggregation processes which induced a time-dependent SERS response. This dependence, causing unreliable quantitative analysis, was accounted for by a normalizing procedure based on the enhanced elastic scattering signal. After normalization for hot-spot concentration, a 1 - 15 mu M linearity range was identified, within which the quantitative analysis is accurate and reproducible. The working range of the present assaying platform is suitable for clinical applications.