A novel surface-enhanced Raman scattering-based ratiometric approach for detection of hyaluronidase in urine

A ratiometric surface-enhanced Raman scattering (SERS) based method is described for the determination of the activity of hyaluronidase (HAase). Gold nanorods (AuNRs) were functionalized with 4-thiobenzonitrile (TBN) to act as the Raman reporter (TBN-AuNRs), and 4-thiophenylacetylene-functionalized gold-silver alloy nanoparticles (TPA-AuAgNPs) were used as the reference. Hyaluronic acid (HA) acts as the HAase recognition element. The TBN-modified AuNRs aggregate in the presence of HA due to the strong electrostatic interaction between the positively charged TBN-AuNRs and negatively charged HA. This strongly enhances the Raman signal of TBN at 2220 cm^-1. However, HA has no significant effect on the dispersion of the modified AuAg NPs which are electroneutral. Hence, no change can be seen in the Raman intensity of TPA at 1974 cm^-1. In the presence of HAase, HA is digested into smaller fragments. This results in good dispersion of the TBN-AuNRs and a weaker TBN Raman signal. Hence, the ratio of the Raman peaks at 1974 and 2220 cm^-1 increases. Under the optimized conditions, the ratio changes in the 5-70 U mL^-1 HAase activity range, and the detection limit is 1.7 U mL^-1 (based on the 3σ rule). Moreover, this method has been successfully applied in the determination of the activity of HAase in artificial urine and it is expected to be a new method for the diagnosis of cancer, especially bladder cancer.