The interaction between gold nanoparticles (GNPs) and bovine haemoglobin (BHb) was studied by ultraviolet-visible (UV-Vis) absorption, circular dichroism (CD) and fluorescence spectroscopic techniques. The UV-Vis absorption spectrum demonstrated that there was interaction between GNPs and BHb, but no direct interaction between GNPs and haem groups of BHb. The fluorescence data revealed that GNPs effectively quenched the intrinsic fluorescence of BHb via static quenching. The binding of GNPs to BHb occurred at a single site. The binding process was a spontaneous molecular interaction procedure, in which hydrophobic force and hydrogen bonds played a major role. The alternations of protein secondary structure in the presence of GNPs were also determined by CD spectroscopy. This work is helpful to understand the interaction mechanism of GNPs with haemoglobin, which can guide the applications of GNPs in biomedicine.
Most of the synthesising methods of gold nanoplates reported to date rely heavily on the use of chemical reducing agents such as N, N-dimethylformamide, sodium borohydride or other organic compounds. All of these chemicals are highly reactive and may pose potential biological risks. A simple, convenient and economical route for the mass synthesis of single-crystalline, micro-sized, polygonal gold nanoplates using chitosan as a reducing/capping agent is reported. The nanoplates possess well-defined shapes with sharp edges confirmed by scanning electron microscopy. The gold nanoplates are single crystals bound primarily by (1 1 1) lattice planes, as revealed by both selected area electron diffraction and powder X-ray diffraction. These large gold nanoplates had strong absorption in the near-infrared region. The concentration and molecular weight of chitosan are important factors for the morphology and size control of the final product. This facile approach may be extended to the synthesis of some other metal nanostructures.
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