Composite MF@Ag-NPs microspheres for label-free quantitative detection of uric acid

A convenient and easy-scalable synthetic strategy to achieve ultrasensitive surface enhanced Raman spectroscopy (SERS) substrates for single particle detection of targeting molecules is reported. Melamine-formaldehyde (MF) microspheres with variable sizes were synthesized and decorated with Ag nanoparticles (NPs) through an in-situ chemical deposition to obtain composite MF@Ag-NPs microspheres. Individual MF@Ag-NPs microspheres were screened under a microscope and used to examine their single particle SERS properties by using four different probe molecules. The experimental results demonstrated that as-prepared SERS substrates displayed a dramatically enhanced SERS activity and sensitivity as well as an extraordinary stability and reproducibility of the SERS signal. Moreover, we also showed a first example of single MF@Ag-NPs microsphere for quantitative trace detection of uric acid (UA) as biomarker based on the label-free strategy, making them a promising candidate as an ideal substrate for applications in fields of biosensor, trace analysis and biomedical diagnostics.