Surface-Enhanced Raman Spectroscopy Detection of Hyaluronic Acid: A Potential Biomarker for Osteoarthritis

摘要

A novel application of surface-enhanced Raman spectroscopy (SERS) for in-vitro osteoarthritis (OA) biomarker detection is described. Hyaluronic acid (HA) is a potential OA biomarker and synovial fluid levels of HA have been correlated with progression of joint space narrowing. However, current immunoassay and chromatographic methods used to identify HA in synovial fluid specimens are cumbersome and often require sophisticated instrumentation. Raman spectroscopy may be an alternative to these analytical methods, providing rapid identification of HA using characteristic Raman biomarker bands. Yet, previous reports of normal (unenhanced) Raman spectroscopy for HA are in aqueous solutions exceed 1000X in-vivo concentrations because HA is a weakly scattering polysaccharide. In contrast, SERS could improve the detection limits of HA to below the clinical range and we present, to our best knowledge, the first surface-enhanced Raman spectra of HA. Moreover, the recent commercial availability of gold-coated SERS substrates has enabled rapid the SERS detection of this biomarker at physiological concentrations. Preliminary results show that HA can be readily observed at low concentrations in aqueous solutions and in synthetic models of biofluids, such as artificial rnsynovial fluid, that contain HA at low concentrations. These complex biofluids often contain proteins that will compete with HA for the SERS-active sites, and the resulting spectra are dominated by protein Raman bands. To overcome this problem, we use a simple and validated protein precipitation protocol to artificial synovial fluid prior to deposition onto the SERS substrate. We show that HA can be readily detected in these biofluids at clinically useful levels after protein precipitation.