Construing the interactions between MnO2 nanoparticle and bovine serum albumin: insight into the structure and stability of a protein–nanoparticle complex

Abstract

A systematic study of the interaction of bovine serum albumin (BSA) with MnO₂ nanoparticles (NPs) was carried out. MnO₂ nanoparticles were prepared via a low temperature (90 °C) single-step precipitation route in the absence of surfactant/template and characterized using XRD, TEM, FESEM, FTIR, XPS, and Raman spectroscopy. MnO₂ particles were found to have a length of 900 nm and a diameter of 10 nm. The interaction of BSA with NP was investigated using various spectroscopic and biophysical techniques under physiological pH 7.4. MnO₂ effectively quenches the intrinsic fluorescence of BSA through static quenching. The effect of MnO₂ on the conformation of BSA was analyzed using circular dichroism (CD), Fourier transform infrared (FTIR), and Raman spectroscopy, and it was observed that the secondary structure of BSA altered after the interaction with MnO₂. Thermal CD spectroscopy revealed insignificant variation in the melting temperature of BSA upon binding to MnO₂. Additionally, the morphological changes of BSA upon interaction with MnO₂ were characterized using a field emission scanning electron microscope (FESEM). Moreover, the increase in the size of the BSA–MnO₂ complexes was analyzed using dynamic light scattering (DLS). This study shows that the adsorption of BSA on MnO₂ is dependent on the concentration of the protein as well as the NP.