Study on the binding of colloidal zinc oxide nanoparticles with bovine serum albumin

The interaction between colloidal zinc oxide (ZnO) nanoparticles and bovine serum albumin (BSA) was studied by using absorption, fluorescence, Fourier transform infrared, synchronous and time resolved fluorescence spectroscopic measurements. The apparent association constant has been deduced (Kapp = 1.1 × 104 M−1) from the absorption spectral changes of BSA–colloidal ZnO nanoparticles using Benesi–Hildebrand equation. Addition of colloidal ZnO nanoparticles effectively quenched the intrinsic fluorescence of BSA. The number of binding sites (n = 1.06) and apparent binding constant (K = 2.5 × 104 M−1) were calculated by relevant fluorescence data. Based on Forster’s non-radiation energy transfer theory, distance between the donor (BSA) and acceptor (ZnO) (r0 = 2.88 nm) as well as the critical energy transfer distance (R0 = 2.49 nm) has also been calculated. The interaction between colloidal ZnO and BSA occurs through static quenching mechanism. The effect of colloidal ZnO nanoparticles on the conformation of BSA has been analyzed by means of UV–visible absorption spectra and synchronous fluorescence spectra.