Biomimetic Synthesis of Au-Nps using Cassia fistula Flower Extract and Studies of their Protein Interaction

Gold nanoparticles (Au-Nps) were synthesized by mediating Cassia fistula flower extract (CFFE) as reducing agent in absence and presence of sodium dodecyl sulphate (SDS) for the first time. Surface Plasmon Resonance (SPR) peak at around 550 nm was used for preliminary inference in the development of nanoparticles (Nps). With the increase in [SDS] the λ_SPR rises from 548 to 585 nm but the intensity of absorption decreased from pre to post cmc [SDS]. The Fourier transform infra-red (FTIR) was performed in absence and presence of SDS in order to ascertain the biomimetic reduction by CFFE and explain the bio-reduction of (Au³⁺) ions from the HAuCl₄. For the preliminary size and dispersity of Au-Nps dynamic light scattering (DLS) was performed to observe the shape and crystallite size of Au-Nps,transmission electron microscopy (TEM) was performed which revealed multiple shapes and dispersity in the different conditions under which the synthesis was carried out. The synthesis was kinetically scanned by UV-visible spectroscopy that led to the assumption of pseudo first order kinetics with respect to HAuCl₄ and CFFE reagents. The NPs were characterized with X-ray diffraction (XRD) for crystallinity and crystallite size. The protein interaction studies of Au-Nps with rabbit serum albumin (RSA) in absence and presence of SDS were accomplished by using UV-visible spectroscopy, DLS and fluorescence spectroscopy etc, that confirmed the denaturing and aggregation of the RSA protein in presence of SDS.