Physicochemical Characteristics of Protein–NP Bioconjugates: The Role of Particle Curvature and Solution Conditions on Human Serum Albumin Conformation and Fibrillogenesis Inhibition

Abstract

Gold nanoparticles (Au NPs) from 5 to 100 nm in size synthesized with HAuCl(4) and sodium citrate were complexed with the plasma protein human serum albumin (HSA). Size, surface charge, and surface plasmon bands of the Au NPs are largely modified by the formation of a protein corona via electrostatic interactions and hydrogen bonding as revealed by thermodynamic data. Negative values of the entropy of binding suggested a restriction in the biomolecule mobility upon adsorption. The structure of the adsorbed protein molecules is slightly affected by the interaction with the metal surface, but this effect is enhanced as the NP curvature decreases. Also, it is observed that the protein molecules adsorbed onto the NP surface are more resistant to complete thermal denaturation than free protein ones as deduced from the increases in the melting temperature of the adsorbed protein. Differences in the conformations of the adsorbed protein molecules onto small (<40 nm) and large NPs were observed on the basis of ζ-potential data and FTIR spectroscopy, also suggesting a better resistance of adsorbed protein molecules to thermal denaturing conditions. We think this enhanced protein stability is responsible for a reduced formation of HSA amyloid-like fibrils in the presence of small Au NPs under HSA fibrillation conditions.

Protein corona: a new approach for nanomedicine design

“…The protein-NP interaction is studied by incubating NPs in protein solutions for a period of time, either a single protein solution such as BSA, fibronectin and IgG, [11][12][13][14] or biological fluid containing multiple proteins such as serum, 15,16 plasma, cytosol, 17 fetal bovine serum (FBS), 18 fetal calf serum, synovial fluid, and cerebrospinal fluid. 19 Protein-NP complexes are then separated from the protein solution via instrumental analysis.…”

“…18 Centrifugation is the typical method to collect NP-protein complex from the interaction media and loosely adsorbed proteins, and sucrose cushion centrifugation allows the separation of complex in a short time (30 sec). 11,12,22,23 The secondary structure of proteins can be evaluated by circular dichroism. However, this method cannot be used for a mixture of proteins due to its spectral complexity.…”

“…11,41,42 It was known that temperature caused significant changes in protein corona pattern of magnetic NPs in the human body temperature, ranging between 37°C and 41°C during exposure to various concentrations of HSA as well as apo-transferrin (apo-Tf). 42 Protein quantity adsorbed on Cu NPs increased when incubation temperature increased from 15°C, 27°C, and 37°C to 42°C.…”

“…• Bigger size, larger degree of protein coverage 8,11,26,118 • Smaller size increases corona thickness and decreases conformational change [119][120][121] • evolution of composition and relative abundance of adsorbed proteins 23,122 NP …”

Nanoparticles in relation to peptide and protein aggregation

“…The fibrillation behavior can be modulated by several factors including hydrophobicity, types of secondary structures, the presence of chaperons, peptide inhibitors, as well as solution properties such as ionic strength, pH, temperature, and so on. 8,9 Thermal denaturation leads to the exposure of hydrophobic residue, which increases hydrophobic attraction that overcomes electrostatic repulsion, and triggers the aggregation of amorphous aggregates. Hill et al 10 found that net attraction causes precipitation, while interaction of repulsive charges causes amyloid formation.…”