Abstract
The formation and growth of gold nanoparticles (AuNPs) were investigated in pH 7 buffer solution of bovine serum albumin (BSA) at room temperature. The processes were monitored by UV-Vis, circular dichroism, Raman and electron paramagnetic resonance (EPR) spectroscopies. TEM microscopy and dynamic light scattering (DLS) measurements were used to evidence changes in particle size during nanoparticle formation and growth. The formation of AuNPs at pH 7 in the absence of BSA was not observed, which proves that the albumin is involved in the first step of Au(III) reduction. Changes in the EPR spectral features of two spin probes, CAT16 and DIS3, with affinity for BSA and AuNPs, respectively, allowed us to monitor the particle growth and to demonstrate the protective role of BSA for AuNPs. The size of AuNPs formed in BSA solution increases slowly with time, resulting in nanoparticles of different morphologies, as revealed by TEM. Raman spectra of BSA indicate the interaction of albumin with AuNPs through sulfur-containing amino acid residues. This study shows that albumins act as both reducing agents and protective corona of AuNPs.
Highlights
The research focused on the synthesis and properties of gold nanoparticles (AuNPs) has expanded into the advanced fields of nanomedicine and nanotechnologies [1,2,3,4]
Results and Discussion reduction of Au(III) in the system containing bovine serum albumin (BSA) is due to the presence of specific amino acids in the protein chain, namely 35 threonine and 32 serine units that bear hydroxyl groups [20,21]
The gold (III) reduction and the growth of gold nanoparticles are processes accompanied by conformational changes in the BSA
Summary
The research focused on the synthesis and properties of gold nanoparticles (AuNPs) has expanded into the advanced fields of nanomedicine and nanotechnologies [1,2,3,4]. The interactions of AuNPs with biomolecules found in biofluids are relevant for medicinal applications like imaging, sensing, drug and gene delivery, and in photothermal therapy. AuNPs are usually stabilized in different solutions by layers of small organic molecules. Amino or hydroxyl groups bind to the surface of AuNPs through chemical or physical interactions [5]. A nontoxic and relevant species for biological systems, represents both a reducing agent and a stabilization agent for AuNPs in water [6]. Albumin can bind spontaneously to citrate-protected AuNPs [7,8,9,10] and the resulting nanosystems are of interest for multicomponent drug system applications
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