Titanium dioxide nanoparticles preferentially bind in subdomains IB, IIA of HSA and minor groove of DNA

Abstract

Titanium dioxide nanoparticles (TiO₂-NPs) interaction with human serum albumin (HSA) and DNA was studied by UV-visible spectroscopy, spectrofluorescence, circular dichroism (CD), and transmission electron microscopy (TEM) to analyze the binding parameters and protein corona formation. TEM revealed protein corona formation on TiO₂-NPs surface due to adsorption of HSA. Intrinsic fluorescence quenching data suggested significant binding of TiO₂-NPs (avg. size 14.0 nm) with HSA. The Stern-Volmer constant (K_sv) was determined to be 7.6 × 10² M^-1 (r² = 0.98), whereas the binding constant (K_a) and number of binding sites (n) were assessed to be 5.82 × 10² M^-1 and 0.97, respectively. Synchronous fluorescence revealed an apparent decrease in fluorescence intensity with a red shift of 2 nm at Δλ = 15 nm and Δλ = 60 nm. UV-visible analysis also provided the binding constant values for TiO₂-NPs-HSA and TiO₂-NPs-DNA complexes as 2.8 × 10² M^-1 and 5.4 × 10³ M^-1. The CD data demonstrated loss in α-helicity of HSA and transformation into β-sheet, suggesting structural alterations by TiO₂-NPs. The docking analysis of TiO₂-NPs with HSA revealed its preferential binding with aromatic and non-aromatic amino acids in subdomain IIA and IB hydrophobic cavity of HSA. Also, the TiO₂-NPs docking revealed the selective binding with A-T bases in minor groove of DNA.

Keywords: Human serum albumin; TiO2-NPs; circular dichroism; docking; fluorescence quenching.