Green synthesis and characterization of zinc oxide nanoparticles using carboxylic curdlan and their interaction with bovine serum albumin

Carboxylic curdlan (Cc), as a versatile β-1,3-polyglucuronic acid derivative, was used as both reducing and capping agents for the green synthesis of zinc oxide nanoparticles (ZnO NPs). The as-prepared Cc-ZnO NPs had the hexagonal wurtzite structure with maximum absorption at 370 nm assigned to the intrinsic band-gap absorption. Scanning and transmission electron microscopy (SEM and TEM) images showed that the Cc-ZnO NPs were spherical and agglomerated particles with an average diameter of 58 ± 6 nm. The interaction between Cc-ZnO NPs and bovine serum albumin (BSA) was evaluated using various spectroscopic techniques. The results indicated that the binding between Cc-ZnO NPs and BSA molecules occurred due to static quenching, leading to the formation of a ground state complex. Synchronous fluorescence spectra indicated changes in the microenvironment close to the tryptophan residues; circular dichroism spectra revealed conformational changes in the secondary structure of BSA, which were attributable to electrostatic interactions during the binding process.