Rapid Photoligation of Gold Nanocolloids with Lipoic Acid-Based Ligands

Abstract

An effective and easy to implement ligand exchange strategy is paramount to the design of stable and multifunctional gold and other inorganic nanocolloids. This is also crucial for their use in biology and medicine. In this contribution, we demonstrate that photomediated ligand substitution of gold nanocrystals with a series of lipoic acid-modified ligands yields several advantages, including rapid phase transfer and great long-term colloidal stability. This strategy combines photochemical reduction of the dithiolane group with energetically favorable in situ ligand chemisorption, yielding rapid modification of the surfaces. It requires substantially smaller amounts of excess ligands compared to conventional incubation starting with the oxidized form of the ligands. Complete substitution of the ligands is confirmed by using 1 H NMR and FT-IR spectroscopy. The colloidal properties of the resulting materials have been tested by using a combination of longterm stability in ion-rich media, sodium cyanide digestion, and dithiothreitol competition tests. They show that photoligation preserves the structure and photophysical properties of the various colloids. Mechanistic arguments have been discussed to explain the effectiveness of this ligation strategy. These findings prove the practical benefits of this approach for designing biocompatible gold colloids and bode well for using such materials in a variety of biological assays and photothermal therapy.

Peptidic Sulfhydryl for Interfacing Nanocrystals and Subsequent Sensing of SARS-CoV-2 Protease

“…Importantly, the incorporated thiol bridge [in part (i)] mimics a simple dithiothreitol (DTT) molecule that would favor interparticle interactions due to the high affinity of the thiol to metal surfaces. 41 , 42 The repeating aspartic acid residues improve the peptide performance in aqueous media regardless of the hydrophobicity of the recognition sequence. Overall, this modular design obviates the need for major revisions when targeting other proteases—the specificity of the sensor can be tuned simply by changing the cleavage site.…”

“… 1 , 52 In contrast, most thiol ligand-protected AuNPs were insensitive to DTT aggregation including mercaptopropionic acid (MPA), mercaptopropane sulfonate (MPS), glutathione (GSH), and thiolate PEG oligomers. 42 , 53 Particles functionalized with polymers (i.e., PAA and PSS) have narrow concentration windows (i.e., 5–10 μM) for the DTT-induced visual readout. Thus, subsequent work tested citrate-, TA-, or TCEP-AuNPs with the multivalent peptides.…”

Ultrasmall gold nanorod-polydopamine hybrids for enhanced photoacoustic imaging and photothermal therapy in second near-infrared window

“…Therefore, we replaced CTAB with a methoxy PEG thiol of Mw 2k Da (HS-mPEG) to accommodate stable PDA coating (Figure S3). Using strong Au-thiol bonding formation [44], we successfully exchanged the surfaces of both LGNRs and SGNRs with HS-mPEG, where the zeta potential of LGNRs and SGNRs decreased to 8.3 ± 2.6 mV and 4.6 ± 0.6 mV, respectively (Figure 2g). PEGylated LGNRs and SGNRs carry more negative charges after PDA coating due to the phenolic hydroxyl groups on PDA.…”

A Charge‐Switchable Zwitterionic Peptide for Rapid Detection of SARS‐CoV‐2 Main Protease

“…[8,9] For example, dithiothreitol is a simple molecule to cluster AuNPs due to the strong thiol-togold bond. [10,11,12] Nanoplasmonic sensing based on this covalent bond have been reported for thrombin, trypsin, furin, etc. [10,13] Alternatively, controlled physical factors (e.g., ionic strength, solvent polarity, and ligand hydrophilicity) can also impact colloidal dispersion.…”