Real-time fluorescence dynamics in one-step synthesis of gold nanoclusters coupling with peptide motifs

The molecule-like electronic structure endows gold nanoclusters (AuNCs) a most intriguing property, fluorescence, thereby AuNCs offer a great potential for biomedical applications. Recent efforts to improve the fluorescence of AuNCs mainly focus on tailoring size, structure and chemical environments. Herein, with the help of molecular dynamics simulation, we designed tyrosine-containing peptide motifs as the reducing agents, protecting ligands to synthesis P (peptide)-AuNCs in one-step reaction, which was developed to real-time monitor the fluorescence evolution of P-AuNCs. P-AuNCs with a quantum yield of ∼ 18 % were synthesized and further demonstrated for multiple biomedical applications, such as sensing of temperature (10-55 ℃) and metal ions (with a limit of detection of 5 nM for Hg2+), as well as cell labeling and imaging. With the excellent biocompatibility, wide spectral range and potential capacity for bio-recognition, this study provides a useful one-step synthesis strategy for screening out peptide motifs to real-time modulate the optical properties of peptide-containing hybrid nanomaterials.

Role of Small Moiety of a Large Ligand: Tyrosine Templated Copper Nanoclusters

To explore the underlying formation mechanism of luminescent metal nanoclusters (NCs) using a small moiety such as amino acids (outside the milieu of a protein environment) as templates, herein we report blue-emitting copper nanoclusters (CuNCs) using l-tyrosine (l-Tyr) as a capping agent as well as a reducing agent. We also demonstrate the effect of an in situ fibrillation of Tyr on the luminescence and structural properties of NCs. Fluorescence studies along with microscopic imaging revealed the rapid formation of a dityrosine (di-Tyr) moiety in an alkaline medium followed by an aggregated "Tamarix dioica leaf"-like fibrillar pattern along with CuNCs. Our present investigation delineates the role played by π-π interactions in the formation of the fibrillar structures. We substantiated the fundamentals of using a small molecule of a large ligand that can serve as a template and also show how these NCs once formed destroy the fibrils of di-Tyr as a function of time.

Gold Nanocluster Extracellular Vesicle Supraparticles: Self-Assembled Nanostructures for Three-Dimensional Uptake Visualization

Extracellular vesicles (EVs) are secreted by the vast majority of cells and are being intensively studied due to their emerging involvement in a variety of cellular communication processes. However, the study of their cellular uptake and fate has been hampered by difficulty in imaging EVs against the cellular background. Here, we show that EVs combined with hydrophobic gold nanoclusters (AuNCs) can self-assemble into supraparticles, offering an excellent labeling strategy for high-resolution electron microscopic imaging in vitro. We have tracked and visualized the reuptake of breast cancer cell-derived EV AuNC supraparticles into their parent cells, from early endocytosis to lysosomal degradation, using focused ion beam-scanning electron microscopy (FIB-SEM). The presence of gold within the EVs and lysosomes was confirmed via DF-STEM EDX analysis of lift-out sections. The demonstrated formation of AuNC EV supraparticles will facilitate future applications in EV imaging as well as the EV-assisted cellular delivery of AuNCs.

Biocompatible gold nanoclusters: synthetic strategies and biomedical prospects

The latest advances concerning ultra-small gold nanoparticles (≤2 nm) commonly known as gold nanoclusters (AuNCs) are reviewed and discussed in the context of biological and biomedical applications (labeling, delivery, imaging and therapy). A great diversity of synthetic methods has been developed and optimized aiming to improve the chemical structures and physicochemical properties of the resulting AuNCs. The main synthetic approaches were surveyed with emphasis on methods leading to water-soluble AuNCs since aqueous solutions are the preferred media for biological applications. The most representative and recent experimental results are discussed in relationship to their potential for biomedical applications.

In situ aqueous synthesis of genetically engineered polypeptide-capped Ag2S quantum dots for second near-infrared fluorescence/photoacoustic imaging and photothermal therapy

Ag₂S quantum dots have received extensive attention as theranostic agents for second near-infrared (NIR-II) fluorescence and photoacoustic dual-mode imaging, and photothermal therapy. However, it is still greatly challenging to synthesize Ag₂S quantum dots using aqueous synthesis. In this study, genetically engineered polypeptide-capped Ag₂S quantum dots were successfully synthesized. Three cysteines were integrated to the C-terminal and N-terminal of RGDPC₁₀A to enhance the stability and brightness of the synthesized Ag₂S quantum dots. The RGDPC₁₀A-capped Ag₂S quantum dots exhibited excellent stability, outstanding resistance to photobleaching, and a superior quantum yield of up to 3.78% in the NIR-II biological window. The in vitro and in vivo results showed that the RGDPC₁₀A-capped Ag₂S quantum dots possessed typical NIR-II fluorescence, photoacoustic imaging, and photothermal therapeutic effectiveness against tumors. Moreover, the results of toxicity assays suggested that the RGDPC₁₀A-capped Ag₂S quantum dots have negligible long-term toxicity. These findings open up the possibility for synthesizing theranostic agents by using this aqueous method.

Peptide-Au Clusters Induced Tumor Cells Apoptosis via Targeting Glutathione Peroxidase-1: The Molecular Dynamics Assisted Experimental Studies

The original motivation of the article is to give a systematic investigation on the protocol of combining computer simulation and accurate synthesis of serial peptide protected gold clusters for potent tumor targeting therapy. Glutathione peroxidase-1 (GPx-1) is a crucial antioxidant selenoenzyme that regulates cellular redox level, thus becomes a potential target in cancer treatment. We firstly utilize molecular dynamic (MD) simulation to rationally design and screen serial peptide-Au cluster compounds with special peptide sequences and precise gold atoms, which can recognize and bind specific domain of GPx-1 with high affinity. The theoretical simulations were further verified by the following peptide-Au clusters synthesis and GPx-1 activity suppression studies in buffer and cells, respectively. Further cytological experiments corroborated that peptide-Au clusters are promising nanoparticles inducing tumor cells apoptosis by suppressing GPx-1 activity and increasing higher cellular reactive oxygen species level to initiate tumor cell apoptosis through intrinsic mitochondrial pathway.

Enzymatic polymerization of poly(thymine) for the synthesis of copper nanoparticles with tunable size and their application in enzyme sensing

A bottom-up strategy was developed for the enzyme mediated synthesis of Cu nanoparticles, which showed good sensing performance.