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Systematic elucidation of interactive unfolding and corona formation of bovine serum albumin with cobalt ferrite nanoparticles

Ahmad, Farooq, Zhou, Ying, Ling, Zhaoxing, Xiang, Qingqing, Zhou, Xing
RSC advances 2016 v.6 no.42 pp. 35719-35730
Fourier transform infrared spectroscopy, X-ray diffraction, absorption, adsorption, binding capacity, bovine serum albumin, circular dichroism spectroscopy, coatings, cobalt, enzyme activity, esterases, ferrimagnetic materials, fluorescence, fluorescence emission spectroscopy, heat production, hydrogen bonding, light scattering, magnetism, nanoparticles, protein corona, protein structure, scanning electron microscopy, thermogravimetry, tryptophan, ultraviolet-visible spectroscopy, van der Waals forces, zeta potential
Nanoparticles (NPs) are extensively being used in modern nano-based therapies and nano-protein formulations. The exposures to these comprehensively used NPs lead to changes in protein structure and functionality, hence raising grave health issues. In this study, we thoroughly investigated the interaction and adsorption of bovine serum albumin (BSA) with CoFe₂O₄ NPs by circular dichroism (CD), Fourier transform infrared (FTIR), absorption, and fluorescence spectroscopic techniques, scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The results indicate that CoFe₂O₄ NPs cause fluorescence quenching in BSA by a static quenching mechanism. The negative values of van't Hoff thermodynamic expressions (ΔH, ΔS and ΔG) corroborate the spontaneity and exothermic nature of static quenching. The major contributors of higher binding affinity of CoFe₂O₄ NPs with BSA were van der Waals forces and hydrogen bonding. Furthermore, BSA protein corona formation on CoFe₂O₄ NPs was confirmed by SEM, TGA, DLS and zeta potential studies. TGA, DLS and zeta potential results confirmed the formation of a thick layer of BSA on CoFe₂O₄ NPs with negative boost in zeta potential. This coating of BSA over CoFe₂O₄ NPs leads to a decrease in the magnetic saturation value from 50.4 to 46.2 emu, hence the magnetic character of CoFe₂O₄ NPs. The development of protein corona on CoFe₂O₄ NPs was further estimated by comparing the steady state fluorescence quenching and theoretical data. In addition, FTIR, UV-CD, and UV-visible spectroscopy and three dimensional fluorescence techniques confirmed that CoFe₂O₄ NP binding could induce microenvironment perturbations leading to secondary and tertiary conformation changes in BSA. Furthermore, synchronous fluorescence spectroscopy confirmed the significant changes in microenvironment around tryptophan (Trp) residue caused by CoFe₂O₄ NPs. The denaturing of BSA biochemistry by CoFe₂O₄ NPs was investigated by assaying esterase activity.