Quantitative analysis of SERS spectra of MnSOD over fluctuated aptamer signals using multivariate statistics

Surface-enhanced Raman scattering (SERS) sensors using specific aptamers often show difficulties in quantitative analysis because the instable aptamer structures show fluctuated background signals. In this communication, we address the quantitative analysis of the SERS spectra of manganese superoxide dismutase (MnSOD) in different concentrations over the signal arisen from its specific aptamer using multivariate statistical analysis. MnSOD is a primary antioxidant enzyme protecting normal tissue against oxidative stress and is known as a cancer biomarker. By applying principal component analysis, SERS spectra were distinguished when MnSOD was present in a specimen even at 10 pm. The relation between SERS spectra and MnSOD concentrations calculated by partial least-squares regression predicted MnSOD concentrations within one order of magnitude. Moreover, statistically obtained spectral correlations reveal that spectral differences did not originate from additional peaks of MnSOD but from the thermodynamic stability of the aptamer structures. These results open new paths for detection and analytical strategies of SERS-based bio-sensors using aptamers.