Surface-Enhanced Raman Spectroscopy for Evaluation of Antibacterial Activity of the N-Heterocyclic Carbene Selenium Complex and Its Ligand Against Pathogenic Bacterial Strains Using Multivariate Data Analysis Techniques

Surface-enhanced Raman spectroscopy has been employed to analyze the antibacterial potential of an N-heterocyclic carbene selenium complex (NHC Se complex), its ligand, and commercial derivative ornidazole. Surface-enhanced Raman spectroscopy (SERS) is an analytical method that enhances Raman signals through the interaction of molecules with nanostructured metallic surfaces. Two pathogenic bacteria, including gram positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia Coli (E. coli), were used to characterize the antibacterial activity of the complex and ligand. After the application of selenium complex and its ligand, notable spectral changes were observed in mean SERS spectra of both bacteria treated with these antibacterial agents. SERS spectral features of bacterial cell metabolites at 657 cm-1, 728 cm-1, 1091 cm-1 and 1462 cm-1 decreased after treatment by the complex and its ligand. However, the intensity of features at 1410 cm-1 and 1226 cm-1 were enhanced after the application of complex and its ligand. SERS was an efficient tool in demonstrating the trend of the spectral data of bacteria treated with different concentrations of antibiotics. Three multivariate data analysis techniques, including principal component analysis (PCA), partial least square discriminant analysis (PLS-DA) and partial least square regression (PLSR), discriminated the spectra of those treated and untreated with the antibacterial agents.