Insights into the exciton- tryptophan coupling and corona formation of the serum albumin with cerium oxide nanoparticle along with temperature dependent denaturation and unfolding of protein.

In this report, the coupling of the excitonic peak of the grown semiconducting cerium oxide (CeO2) NPs ( ~350 nm) with tryptophan (~278 nm) along with biophysical study of interaction have been studied through UV-Vis, photoluminescence, and CD spectroscopy, TCSPC, DLS, and HRTEM, AFM imaging. The interaction of small sizes CeO2 NPs with serum albumin protein (SAP) showed formation of ground state complex with association constant (k) varied from 8.7x103 (μM)-1 to 4.8x103 (μM)-1. The kinetics of the interaction study showed that the initial corona formation binding time was ~9 min, and the binding induced albumin reorganization time was ~248.5 min and unfolding was much prominent than binding. Dynamic quenching was found to be the major mechanism for albumin, with an exothermic nature observed during the interaction study across the temperature range from room temperature to human body temperature (298-312 K). The energy transfer efficiency varied from ~75.9% to ~87.4% with temperature. The visualized images of HRTEM and AFM showed formation of albumin corona and protein fibrillation. At body temperature the probability of soft corona formation was more prominent than room temperature. The hydrodynamic sizes of the nano-protein corona were changes from 33.5 nm to 80.5 nm and ultrafast life time of the corona changes from 6.1 ns to 4.05 ns with increment of temperature. The change in the ratio of β strand to α-helix of the SAP has been occurred from ~15% to ~26.03% with change in the corona temperature from 298 K to 312 K.