Preferential binding to zinc oxide nanoparticle interface inhibits lysozyme fibrillation and cytotoxicity

The aim of present investigation is to explore the effect of zinc oxide nanoparticles (ZnONP, 30 nm) interface on conformational dynamics and stability of lysozyme, at pH 7.4 and pH 9.0. Lysozyme adopts partially disordered conformation at pH 9.0, which adopts fibril morphology in presence of sodium dodecyl sulfate (SDS), compared to the conformation adopted at pH 7.4. However, the presence of ZnONP interface renders partially disordered lysozyme relatively regular and non-amyloidogenic conformation, and enhances the functional efficacy of lysozyme at pH 9.0. Additionally, the thermograms reveal a non-cooperative unfolding of the pH 9.0 lysozyme conformation, which accompanied with intermediate conformations that increased with increase in the interface concentration. The binding thermodynamics indicate that at pH 9.0, lysozyme conformation preferentially binds to ZnONP interface than SDS interface. The preferential binding is attributed for the resulting anti-fibrillation propensity of ZnONP interface. The data, altogether, suggest that the presence of ZnONP interface resulted in conformational rearrangements in the partially disordered lysozyme at pH 9.0 causing accumulation of non-amyloidogenic and functionally active intermediates, thus shielding the lysozyme from SDS induced fibrillation and cytotoxicity.