Facile Preparation of Cationic Gold Nanoparticle-Bioconjugates for Cell Penetration and Nuclear Targeting

Abstract

The present work faces the rising demand of cationic particles of different sizes for biological applications, especially in gene therapies and nanotoxicology studies. A simple phase-transfer methodology has been developed for the functionalization of gold nanoparticles (Au NPs) with a variety of ligands, both cationic and anionic in aqueous solution, employing different nanocrystal sizes with narrow size distributions. Successful functionalization has been demonstrated by UV-vis spectroscopy, DLS, ζ-potential, and FTIR spectroscopy characterization of the particles before and after the phase transfer. The intracellular uptake of the differently charged Au NPs functionalized with peptidic biomolecules was investigated with human fibroblasts (1BR3G) by ICP-MS analysis of the digested cells and confocal fluorescence microscopy, which showed increased internalization of the cationic bioconjugates. Nuclear targeting could be observed by TEM, suggesting that the cationic peptidic biomolecule is acting as a nuclear localization signal.

One-Pot Synthesis of Cationic Gold Nanoparticles by Differential Reduction

“…This is particular important in biological scenarios, where surface interactions [23] ultimately determine the formation of the protein corona [24,25], the intracellular uptake and localization of the NPs [26], and in turn, their biological functions [27]. Although their relevance, the production of cationic Au NP is still limited [28], due in part to the difficulties in obtaining cationic particles from citrate-stabilized Au NPs upon surface ligand exchange [29].…”

“…Thus, the direct displacement of the negative citrate by positively charged molecules causes multiple electrostatic bridging, leading to irreversible agglomeration of the conjugates [29]. Alternatively, most direct synthetic approaches involves the reduction of an aqueous solution of Au 3+ precursor in the presence of cationic ligands [26,[30][31][32], or following minor modifications of the well-known Brust-Schiffrin two-phase methodology [10,33], which is generally limited to Au NPs of very small sizes (from 1.5 to 6 nm).…”

Energetic stabilities of thiolated pyrimidines on gold nanoparticles investigated by Raman spectroscopy and density functional theory calculations

“…Nuclear targeted delivery has attracted a great deal of attention when it comes to curing cancers [15]. Nanoparticles have been reported to enter the nuclear parts in cells after proper modification by penetrating the nuclear membrane [17][18][19][20][21]. Considering that the molecules are pyrimidine base analogs, it would be interesting to investigate whether these can enter into the nuclear membrane.…”

“…Nanoparticles have been reported to enter the nuclear parts of cells [16]. Modified gold nanoparticles (AuNPs) appear to penetrate the nuclear membrane [17][18][19][20][21]. Moreover, SERS has been used to estimate the presence of adsorbed drugs on AuNPs [22].…”

SERS in Cells: from Concepts to Practical Applications

“…Inductively coupled plasma mass spectrometry (ICP-MS) is a well-established method to determine the metal content per cell [79,80]. Inorganic nanoparticles can be quantified by elemental analysis, in particular by ICP-MS or ICP-AES (inductively coupled plasma atomic emission spectroscopy) upon extraction or after digestion of the cell suspension [64,81,82]. Gschwind et al and Franze et al coupled a droplet on demand sample introduction system to an ICP-MS for the direct analysis of nanoparticles with particles sizes below 100 nm [83,84].…”