Influence of surface coating on the intracellular behaviour of gold nanoparticles: a fluorescence correlation spectroscopy study

Abstract

In the biomedical applications of nanoparticles (NPs), the proper choice of surface chemistry is a crucial aspect in their design. The nature of the coating can heavily impact the interaction of NPs with biomolecules, affect the state of aggregation, and ultimately determine their biological fate. As such, protein corona formation and the aggregation behaviour of gold NPs (Au NPs) are studied here. Au NPs are prepared with four distinct surface functionalisations, namely mercaptosuccinic acid (MSA), N-4-thiobutyroil glucosamine, HS-PEG and HS-alkyl-PEG. Corona formation, aggregation, and the intracellular behaviour of the Au NPs are then investigated by means of Fluorescence Correlation Spectroscopy (FCS) in cell culture media and in live cells. To evaluate the state of aggregation and the formation of a protein corona, the Au NPs are incubated in cell media and the diffusion coefficient is determined via FCS. The in vitro behaviour is compared with the level of aggregation of the NPs in cells. Diffusion times of the NPs are estimated at different positions in the cell after a one hour incubation period. It is found that the majority of MSA and glucose-Au NPs are present inside the cell as slowly diffusing species with diffusion times (τ) greater than 6000 μs (hydrodynamic diameter >250 nm). PEGylated Au NPs adsorb a small amount of protein and manifest low agglomeration both in media and in living cells. In particular, the HS-alkyl-PEG coating shows an excellent correlation between lower protein adsorption, 4-fold lower compared to the MSA coated NPs, and limited intracellular aggregation. In the case of single HS-alkyl-PEG coated NPs, it is found that typical intracellular τ values range from 500 to 1500 μs, indicating that these particles display reduced aggregation in the intracellular environment.

<p>Effects of PEGylation on capture of dextran-coated magnetic nanoparticles in microcirculation</p>

“…PEG coating reduces adhesion of polystyrene spheres to endothelial monolayer under physiological shear in vitro 39. In addition, PEG modulates the intracellular behavior of nanoparticles, probably due to protein adsorption 45. We recently demonstrated that PEGylation of dextran-coated MNPs may alter particle properties in circulation 46.…”

Influence of size and surface capping on photoluminescence and cytotoxicity of gold nanoparticles

“…Functionalization of the NP surface with species containing bio-active terminal groups, such as amino or carboxylic groups, allows for a subsequent linking with relevant biomolecules (Albanese et al 2012 ; Miao et al 2018 ). NP functionalization can also contribute to avoiding aggregation and unspecific cellular uptake, minimizing accumulation in organs and/or phagocyte activation, thus maintaining a prolonged circulation time (Nel et al 2009 ; Silvestri et al 2017 ; Sperling and Parak 2010 ; Verma and Stellacci 2010 ). For biomedical applications, surface functionalization is a common strategy not only to subsequently promote cross-linking between NPs and specific biological species but also to minimize their cytotoxicity and unspecific binding.…”

“…Both capping agents contain a thiol group to be linked to the NP surface, as well as an amino terminal group (in the case of CYS) or both amino and carboxylic groups (in the case of GSH), that remain free to be cross-linked with other biomolecules, as we have previously shown (Beato-Lopez et al 2017 ). Thus, starting from different synthetic routes, we obtain NPs with different capping, size, and homogeneity (Albanese et al 2012 ; Chithrani et al 2006 ; Li et al 2018 ; Silvestri et al 2017 ; Verma and Stellacci 2010 ).…”

Click-based thiol-ene photografting of COOH groups to SiO2 nanoparticles: Strategies comparison

“…protein corona formation). [52] In this context, PRTEA on vinyl-SiO2 nanoparticles avoids the formation of agglomerates during surface modification, a phenomenon typically found when dealing with aminated surfaces.…”