BSA binding to silica capped gold nanostructures: effect of surface cap and conjugation design on nanostructure–BSA interface

Abstract

This paper presents a detailed and systematic study of amine functionalization of silica coating of gold nanostructures and the electrostatic and covalent binding of the prepared silica capped gold nanostructures to BSA. The involvement of a Tryptophan residue in the hydrophobic pocket of BSA and its interaction with nanostructures was established. Fluorescence studies of tryptophan residues of the protein molecules after conjugation revealed that the method of crosslinking did not bring about major changes to the binding constant (1012 M−1) of BSA to nanostructures. Electrostatic binding indicated a larger number of binding sites (2.56) on the protein. Nanoparticle binding brought about a reduction in the characteristic negative ellipticity of BSA, indicating a change in the helical content. The reduction in the elliptical path of BSA was influenced by both nanoparticle curvature and crosslinker, such as in the case of glutaraldehyde or by the nanoparticle curvature alone as in the case of zero length crosslinker – EDC–NHS. Though not a subject matter of this study, the results obtained in this study could have implications in the design of nanobiomaterials, biosafety concerns and their cellular responses.