文摘
Surface enhanced infrared absorption spectroscopy (SEIRAS) with attenuated total reflection (ATR) configuration has been used to determine bovine serum albumin (BSA) protein adsorbed onto bare gold nanoparticles (AuNPs). The AuNPs forming the SEIRA-active substrate were directly synthesized inside the ATR liquid cell taking advantage of stainless steel assisted synthesis via the walls composing the ATR compartment. The formation of the AuNPs can be directly monitored via the enhancement of the corresponding water absorption features. The absorbance of BSA at the AuNPs deposited onto the Si ATR waveguide is significantly enhanced when compared to bare Si, thereby improving the sensitivity of detection. Apparently, the presence of the AuNPs layer at the ATR waveguide surface at the measured conditions does not affect the secondary structure of the protein. Measurements were performed in water and confirmed in deuterium oxide, which significantly reduces the strongly absorbing mid-infrared background of water in the spectral regime of interest. The limits of detection achieved for BSA protein analysis in water and deuterium oxide media are 1.93 and 4.15 mg·L−1, respectively, and the precisions at a 250 mg·L−1 concentration are 11.9% and 8.1%, respectively.