Spectroscopic characterization and docking studies of ZnO nanoparticle modified with BSA

Nanoparticles (NP) into a biological environment are an interesting topic for diagnosis and therapy in applications for medicine or environment and the knowledge about this interaction is important from the perspective of safe use of nanomaterials. In the current study, we characterized the type of interaction and the orientation of bovine serum albumin (BSA) adsorbed on ZnO nanoparticle surfaces as a function of size, using molecular docking. To probe experimentally different theoretical hypothesis about the interaction, ZnO-NPs were prepared in aqueous solution, and then were bioconjugated with BSA. Transmission electron microscopy (TEM) and Raman spectroscopy confirm the spherical shape of NP and the irreversible adsorption of BSA on NP surface. Raman and Infrared spectroscopy (FTIR) reveal that BSA interaction with ZnO nanoparticle produced a conformational rearrangement into protein, observing changes in Tyr and Trp environment, a minor percentage of α-helix structure and a more extended chain. The fluorescence analysis demonstrated that when BSA concentration higher than 30 μM is used the signal due to the self-oligomerization of protein overlaps with the ZnO nanoparticle emission. The results predicted that the most probable interaction site is near to domain IB and IIA and ionic interactions are the major responsible for the binding. Thermal stability studies reveals that the denaturalization temperature of BSA increase from 57 °C to 65 °C in presence of ZnO NP and their esterase-like activity was improved.