Understanding Conformational Changes in Human Serum Albumin and Its Interactions with Gold Nanorods: Do Flexible Regions Play a Role in Corona Formation?

Abstract

The importance of protein−nanoparticle (NP) conjugates for biomedical applications has seen an exponential growth in the past few years. The protein corona formation on NPs with human serum albumin (HSA), being the most abundant protein in blood serum, has become one of the most studied protein analyses under NP−protein interactions as HSA is readily adsorbed on the surface of the NPs. Understanding the fate of the NPs in physiological media along with the change in biological responses due to the formation of the protein corona thus becomes important. We analyzed the HSA protein corona formation on gold nanorods (AuNRs) through different spectroscopic studies in addition to the effects of change in the protein concentration on the protein−NP interactions. Different imaging techniques such as high-resolution transmission electron microscopy, field emission scanning electron microscopy, and atomic force microscopy were used to determine the morphology and the dimensions of the nanorods and the protein−nanorod conjugates. Fourier-transform infrared data showed a reduction in the α-helix content and an increase in β-sheet content for the HSA−AuNR conjugate compared to the native protein. A decrease in steady-state fluorescence intensity occurred with instant addition of AuNR to HSA showing better and efficient quenching of Trp fluorescence for the lower concentration of protein. Time-correlated single photon counting results showed greater energy transfer efficiency and faster decay rate for higher concentrations of proteins. The circular dichroism study gives insight into the secondary structural changes due to unfolding, and a greater change was observed for lower concentrations of protein due to a thermodynamically stable protein corona formation. Surface-enhanced Raman spectroscopy (SERS) indicated the presence of aromatic residues such as Phe, Tyr, and Cys that appear to be close to the surface of the AuNRs in addition to hydrophobic interactions between AuNR and the protein. The disordered and flexible regions mapped onto HSA (PDB: 1AO6), predicted by the intrinsically disordered region predictors, point toward the interactions of similar residues with the nanorods observed from SERS and fluorescence studies. These studies could provide a clearer understanding of the interactions between HSA and AuNRs for possible biological applications.

Immunogenic Potential and Therapeutic Efficacy of Multi‐Epitope Encapsulated Silk Fibroin Nanoparticles against Pseudomonas aeruginosa‐Mediated Urinary Tract Infections

“…In our study, in some cases, alum was found to be more effective than SFNPs, which could be due to the formation of antigen depots that gradually release antigen [25] or due to the impact of nanoparticles encapsulation (SFNPs) on protein conformation. [26,27] In addition, the previous studies have reported enhanced antibody responses with alum, [13,28] whereas our study showed a significant Th1 response that can be due to the presence of immunodominant T-cell epitopes in the designed multi-epitope protein.…”

pH-Responsible Doxorubicin-Loaded Fe3O4@CaCO3 Nanocomposites for Cancer Treatment

“…On entering biological fluids, the surface of the nanomaterials is quickly coated with biomolecules forming a bioinspired coating [ 94 ]. Serum or cellular proteins can form strongly and weakly adsorbed protein coating, known as “hard and soft nanoparticle corona,” respectively [ 94 ].…”

“…On entering biological fluids, the surface of the nanomaterials is quickly coated with biomolecules forming a bioinspired coating [ 94 ]. Serum or cellular proteins can form strongly and weakly adsorbed protein coating, known as “hard and soft nanoparticle corona,” respectively [ 94 ]. For instance, the protein corona produces stealth-like properties, improving biodistribution, biocompatibility, cellular interaction, and the recognition of nanoparticles by immune cells [ 95 , 96 , 97 , 98 ].…”

How Does pH Affect the Adsorption of Human Serum Protein in the Presence of Hydrophobic and Hydrophilic Nanoparticles at Air–Water and Lipid–Water Interfaces?

“…Human serum albumin (HSA) is the most abundant blood serum protein in mammals and plays a vital role in transportation of essential molecules such as drug, metals, and fatty acids. − It was observed that the conformation and structure of albumin were easily altered depending upon the surface chemistry of the NPs. ,− For instance, Melby et al reported that the initial surface coating of NPs can influence their interactions with the cell membrane by affecting the assembly of proteins . This finding highlights the importance of understanding how the surface properties of NPs affect their interaction with the HSA protein.…”