A novel nanocatalytic SERS detection of trace human chorionic gonadotropin using labeled-free Vitoria blue 4R as molecular probe

In pH 7.4 Na2HPO4-NaH2PO4 buffer solution containing the peptide probes for human chorionic gonadotropin (hCG), silver nanoparticles (AgNPs) were aggregated to big AgNPs clusters that exhibited very weak catalytic effect on the gold nanoparticle reaction of H2O2-HAuCl4. When hCG was present in the peptide probe solution, the AgNPs did not aggregate and it had strong catalytic effect on the gold nanoparticle reaction with a strong resonance Rayleigh scattering (RRS) peak at 370 nm and a strong surface enhanced Raman scattering (SERS) peak at 1615 cm−1 in the presence of molecular probe of Victoria blue 4R (VB4R). With the increase of the hCG concentration, the catalysis enhanced due to the nanocatalyst of AgNPs increasing, and the RRS intensity increased at 370 nm. The increased RRS intensity was linear to the hCG concentration in 0.05-10 ng/mL, with a linear regression equation of ΔI370 nm=409.8 C +294. And the SERS intensity at 1615 cm−1 increased linearly with the hCG concentration in the range of 0.05-20 ng/mL, with a linear regression equation of ΔI1615 cm-1=142 C+134. Based on this, two new methods of nanocatalytic SERS and RRS were proposed for the determination of trace hCG.