Elucidating the interaction of L-cysteine-capped selenium nanoparticles and human serum albumin: spectroscopic and thermodynamic analysis

Selenium (Se) nanoparticles (NPs) have attracted significant interest in biological and biomedical applications due to their therapeutic efficacy. For any in vivo clinical trials the in vitro molecular interactions between Se NPs and human serum albumin (HSA) are very significant and hence systematically investigated in this article using spectroscopic and calorimetric techniques. The NPs were prepared by a simple one-pot method using L-cysteine as a capping agent and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, FTIR, HRTEM, and UV-Vis absorption spectroscopy. The synthesized Se NPs are in the monoclinic phase with an average size of 60 nm. The intrinsic fluorescence of HSA is quenched when complexed with Cy-Se NPs and the static quenching is confirmed from fluorescence lifetime measurements. The thermodynamic parameters associated with the complexation were evaluated using the Van't Hoff equation. The distance between HSA and the Se NPs was obtained from fluorescence resonance energy transfer theory. The CD spectra revealed a change in the microenvironment and the conformation of HSA due to the addition of Se NPs. The current investigations will pave the way for designing Se-based materials for medical applications including drug delivery and imaging.