Unprecedented enhancement and preservation of the peroxidase activity of cytochrome- c packaged with ionic liquid-modified gold nanoparticles by offsetting temperature and time stresses.

Inspired by the biocompatibility of ionic liquids and their dexterousness for the preservation of enzyme structure and activity, herein, the interactions of Cyt- c with naked AuNPs and four IL-mediated AuNPs, which were formed by the fabrication of ILs with common cation 1-ethyl-3-methyl-imidazolium (EMIM) and different anions, to obtain AuNP-IL1 [(BF4) -1 anion], AuNP-IL2 [(CH 3 OSO 3 ) -1 anion], AuNP-IL3 [(CH 3 CH 2 OSO 3 ) -1 anion], and (AuNP-IL4) [Cl -1 anion], were studied. Through this work, the peroxidase activity observed in the presence of a lower concentration IL-AuNPs is exceptionally increased (16 fold). IL-AuNPs preferentially counteract the temperature gradient change and long-term solvent preservation effects while persistently maintaining the Cyt- c peroxidase activity without much depreciation. The hydrodynamic diameter (d H ) of the Cyt- c -AuNP system was obtained, which supported the TEM results. Furthermore, to evaluate the effect of Cyt- c interaction with the AuNPs, a Zeta potential analysis was performed. Taken together, the binding of IL-AuNPs with Cyt- c , diameter size analysis, zeta potential, structural integrity evaluation using the DichroWeb software and morphology results suggest the interaction order of the IL-AuNPs to be in a sequence of AuNP-IL2 > AuNP-IL3 > AuNP- IL4 > AuNP-IL1 > Naked AuNPs. Moreover, results indicate that the IL anions play a dominating role in the modulation of interactions between IL-mediated AuNPs and Cyt- c . The study strongly supports the promising character of sulfur-containing IL-mediated AuNPs for Cyt- c immobilization simultaneously opening new avenues for the application of greener and biocompatible nanoparticles with drug delivery and therapeutic applications.