Interaction of Ionic Liquid with Silver Nanoparticles: Potential Application in Induced Structural Changes of Globular Proteins

Silver nanoparticles (AgNPs) show immense application potential in many fields including biomedical sciences owing to their advanced antimicrobial property (antibacterial, antifungal and anti-inflammatory). Ionic liquids (ILs) known as designer solvents with a melting point below 100 degrees C are a new class of compounds with exclusive properties and great chemical variety. Since the past decade, ILs are vastly used in interdisciplinary research including the synthesis and stabilization of metal nanoparticles. In the present work, we have studied the interaction between IL 1-butyl-3-methylimidazolium octylsulfate [Bmim] [OS] and AgNPs using a simple and sensitive UV-visible spectroscopic method via the response obtained from the surface plasmon resonance (SPR) band of AgNPs. The analysis of the SPR band at the 400-425 nm range and the Fourier transform infrared (FT-IR) spectral results show a transfer of N-H stretching frequency from 3367 to 3228 cm(-1), which clearly suggests the formation of nanoparticles. FT-IR spectroscopy is systematically applied to explore information about the intermolecular interactions taking place within AgNPs-[Bmim] [OS] micellar solutions. The critical micelle concentration (CMC) of [Bmim] [OS] is determined using conductivity and UV-visible spectroscopy, and the size of micellar aggregates is obtained using dynamic light scattering (DLS) technique. Further, the above system is also utilized to consider the structural modify of human serum albumin (HSA) and bovine serum albumin (BSA). UV-vis, fluorescence, FT-IR, H-1 nuclear magnetic resonance and DLS spectroscopic investigations reveal some interesting outcomes. It is observed that modification in the structures of both the globular proteins HSA and BSA takes place within the system, thus indicating significant IL-protein binding. Further, it is noticed that HSA shows more binding affinity toward [Bmim] [OS] than compared to BSA.