Enhanced Colloidal Stability of Various Gold Nanostructures Using a Multicoordinating Polymer Coating

Abstract

We describe the effectiveness of a multicoordinating polymer coating to surface functionalize gold nanospheres, nanoshells, and nanorods and promote their steric stabilization in biological media. The polymer ligand synthesized via one-step nucleophilic addition reaction starting with poly­(isobutylene-alt-maleic anhydride) precursor presents multiple lipoic acid groups for strong coordination on metal-rich surfaces and several hydrophilic motifs (e.g., zwitterion groups or short poly­(ethylene glycol) (PEG) chains) to promote water solubilization. We show that nanocrystals ligated with this polymer are compact in size and exhibit excellent long-term colloidal stability over broad conditions. We compare the ability of zwitterion- and PEG-modified polymer ligands to shield the metal surfaces from sodium cyanide digestion, or resist the competitive removal by dithiothreitol (DTT). We find that polymers appended with either hydrophilic motif essentially eliminate DTT competition for surface binding, while nanocrystals capped with the PEGylated coating exhibits substantially better resistance to sodium cyanide digestion compared with zwitterionic coating. Furthermore, we probe the differences between the two coatings in terms of endowing surface charge to the nanocrystals and affecting their Brownian diffusion properties. Additionally, we show that zwitterionic coating is very effective in preventing the formation of protein corona on such nanostructures, a highly valuable result with direct implications in biotechnology.

Zwitterionic polymer ligands: an ideal surface coating to totally suppress protein-nanoparticle corona formation?

“…[16] More recently, other hydrophilic polymers have been proposed as an alternative to PEG such as polysaccharides and polybetaines. The latter belong to the zwitterionic family and have been used as solubilizing ligands for a variety of nanoparticles such as silica [17][18][19][20], gold [21][22][23][24][25][26][27][28][29][30], quantum dots (QDs) [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] , SPION [30,[47][48][49][50][51] and others. [52][53][54][55][56][57][58] Zwitterionic moieties consist of positively (quaternary ammonium in the case of betaines) and negatively charged groups linked by a small carbon chain.…”

Intracellular Delivery of Gold Nanocolloids Promoted by a Chemically Conjugated Anticancer Peptide

“…Such coating also yields nanomaterials with substantially better colloidal stability and reduced nonspecific interactions. 40 , 41 The polymer presents several amines per ligand, which allows for the simultaneous conjugation of multiple peptides and other functionalities to a nanocrystal. We estimate that based on the ligand structure, size of the nanocrystal, and the fraction of PEG–NH 2 blocks inserted in a ligand, there are ∼4000 amines per AuNR and ∼170 amines per AuNP.…”

Screening Small Metabolites from Cells as Multifunctional Coatings Simultaneously Improves Nanomaterial Biocompatibility and Functionality

“…d ‐sorbitol at 1 mg L −1 increased the hydrodynamic diameter of nAg from 119.03 ± 4.96 to 135.73 ± 4.07 nm ( p < 0.05) at 0 h. In contrast, myoinositol at 1 mg L −1 did not increase the hydrodynamic diameters of nAg (Figure a). The increase of diameters of nanomaterials was due to the formation of surface coatings . Therefore, d ‐sorbitol showed a better wrapping effect onto nAg at low concentration (1 mg L −1 ) compared with myoinositol.…”