Peptide-gold nanocluster synthesis and intracellular Hg2+ sensing

Luminescence Fingerprint of Intracellular NIR-II Gold Nanocluster Transformation: Implications for Sensing and Imaging

Gold nanoclusters emitting in the second biological window (NIR-II-AuNCs) have gained significant interest for their potential in deep-tissue bioimaging and biosensing applications due to the partial transparency and reduced autofluorescence of tissues in this spectral range. However, the limited understanding of how the biological environment affects their luminescent properties might hinder their use in bioimaging and biosensing. In this study, we investigated the emission properties of NIR-II-AuNCs when interacting and internalizing into live cells including macrophages, fibroblasts, and cancer cell lines, revealing substantial alterations in their luminescence. A systematic comparison between control and in vitro experiments concluded that the disruption of surface ligands is the main factor responsible for these alterations. NIR-II-AuNCs within cellular environments may also be influenced by other interactions, including aggregation or complexation with proteins. Furthermore, we also corroborated these spectroscopic modifications at the in vivo level, providing additional evidence of the environmental sensitivity of NIR-II-AuNCs. The results obtained in this study contribute to a deeper understanding of the luminescence mechanisms of NIR-II-AuNCs in biological environments in cells and in living tissues and are crucial for their optimization as reliable tools in biological environment for in vitro and in vivo imaging and diagnostics.

Empowering hydrophobic anticancer drugs by ultrashort peptides: General Co-assembly strategy for improved solubility, targeted efficacy, and clinical application

The current state of drug delivery systems allows for the resolution of specific issues like inadequate solubility, limited targeting capabilities, and complex preparation processes, requiring tailored designs for different drugs. Yet, the major challenge in clinical application lies in surmounting these obstacles with a universal carrier that is effective for a variety of anticancer drugs. Herein, with the help of computer simulation, we rationally design ultrashort peptides GY and CCYRGD, which can co-assemble with hydrophobic anticancer drugs into nanoparticles with enhanced solubility, targeting ability and anticancer efficacy. Taking 7-ethyl-10-hydroxy camptothecin (SN38) as a model anticancer drug, the co-assembled SN38-GY-CCYRGD nanoparticles significantly enhance the water solubility of SN38 by more than three orders of magnitude. The as-prepared nanoparticles can effectively kill cancer cells, e.g., human small cell lung cancer (A549) cells with a notable cell mortality rate of 71%. Mice experimental results demonstrate the nanoparticles' efficient targeting capability, marked reducing the toxicity to normal tissues while improving antitumor efficacy. This work presents a novel drug delivery method, integrating effective, targeted, and safe strategies into a comprehensive carrier system, designed for the administration of hydrophobic anticancer drugs.

Loading of AuNCs with AIE effect onto cerium-based MOFs to boost fluorescence for sensitive detection of Hg2. Talanta 2024;273:125843. [PMID: 38492285 DOI: 10.1016/j.talanta.2024.125843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Ligand-protected gold nanoclusters (AuNCs) have become promising nanomaterials in fluorescence (FL) methods for mercury ions (Hg2+) monitoring, but low FL efficiency hinders their widespread application. Herein, AuNCs/cerium-based metal-organic frameworks (AuNCs/Ce-MOFs) were prepared by loading 6-aza-2-thiothymine-protected AuNCs (ATT-AuNCs) with aggregation-induced emission (AIE) effect on the surface of Ce-MOFs by electrostatic attraction. This strategy improved the FL intensity of AuNCs through two aspects: (i) the AIE effect of ATT-AuNCs and (ii) the confinement effect of Ce-MOFs, which improved the restriction of intramolecular motion (RIM) of ATT-AuNCs. In addition, Ce-MOFs could adsorb and aggregate Hg2+ during detection, which might increase the local concentration. Therefore, based on the high FL signal of AuNCs/Ce-MOFs and enriched Hg2+, sensitive detection of Hg2+ could be achieved. More importantly, the strong specific recognition between AuNCs and Hg2+ could guarantee selectivity. The developed FL sensor exhibited superior detection performances with a wide linear range of 0.2-500 ng mL-1 and a low detection limit of 0.067 ng mL-1. Furthermore, the FL sensor used for sensitive and selective detection of Hg2+ in real samples, and the results agreed well with the standard method. In summary, this work proposed an effective and generalized strategy for improving the FL efficiency of AuNCs, which would greatly facilitate their application in pollutant monitoring.

The roles of templates consisting of amino acids in the synthesis and application of gold nanoclusters

Gold nanoclusters (AuNCs) with low toxicity, high photostability, and facile synthesis have attracted great attention. The ligand is of great significance in stabilizing AuNCs and regulating their properties. Ligands consisting of amino acids (proteins and peptides) are an ideal template for synthesizing applicative AuNCs due to their inherent bioactivity, biocompatibility, and accessibility. In this review, we summarize the correlation of the template consisting of amino acids with the properties of AuNCs by analyzing different peptide sequences. The selection of amino acids can regulate the fluorescence excitation/emission and intensity, size, cell uptake, and light absorption. By analyzing the role played by AuNCs stabilized by proteins and peptides in the application, universal rules and detailed performances of sensors, antibacterial agents, therapeutic reagents, and light absorbers are reviewed. This review can guide the template design and application of AuNCs when selecting proteins and peptides as ligands.

Optical nanosensors based on noble metal nanoclusters for detecting food contaminants: A review

Food contaminants present a significant threat to public health. In response to escalating global concerns regarding food safety, there is a growing demand for straightforward, rapid, and sensitive detection technologies. Noble metal nanoclusters (NMNCs) have garnered considerable attention due to their superior attributes compared to other optical materials. These attributes include high catalytic activity, excellent biocompatibility, and outstanding photoluminescence properties. These features render NMNCs promising candidates for crafting nanosensors for food contaminant detection, offering the potential for the development of uncomplicated, swift, sensitive, user-friendly, and cost-effective detection approaches. This review investigates optical nanosensors based on NMNCs, including the synthesis methodologies of NMNCs, sensing strategies, and their applications in detecting food contaminants. Furthermore, it involves a comparative assessment of the applications of NMNCs in optical sensing and their performance. Ultimately, this paper imparts fresh perspectives on the forthcoming challenges. Hitherto, optical (particularly fluorescent) nanosensors founded on NMNCs have demonstrated exceptional sensing capabilities in the realm of food contaminant detection. To enhance sensing performance, future research should prioritize atomically precise NMNCs synthesis, augmentation of catalytic activity and optical properties, development of high-throughput and multimode sensing, integration of NMNCs with microfluidic devices, and the optimization of NMNCs storage, shelf life, and transportation conditions.

A methionine biomolecule-modified chromenylium-cyanine fluorescent probe for the analysis of Hg2+ in the environment and living cells

The objective of the study is, for the first time, to construct a new near infrared (NIR) fluorophore, spectrophotometric, colorimetric, ratiometric, and turn-on probe (CSME) based on chromenylium cyanine platform decorated with methionine biomolecule to provide an efficient solution for critical shortcoming to be encountered for analysis of hazardous Hg²⁺ in environment and living cell. The CSME structure and its interaction with Hg²⁺ ion were evaluated by NMR, FTIR, MS, UV-Vis and fluorescence methods as well as Density Functional Theory (DFT) calculations. The none fluorescence CSME having spirolactam ring only interacted with Hg²⁺ in aqueous solution including competing ions. This interaction caused the fluorescence CSME with opened spirolactam form which exhibited spectral and colorimetric changes in the NIR region. The probe based on UV-Vis and fluorescence techniques respond in 90 s, has wide linear ranges (for UV-Vis: 6.29 × 10^-8 - 1.86 × 10^-4 M; for fluorescence: 9.49 × 10^-9 - 1.13 × 10^-5 M), and has a lower Limit of Detection (LOD) value (for fluorescence: 4.93 × 10^-9 M, 0.99 ng/mL) than the value predicted by the US Environmental Protection Agency (EPA) organization. Hg²⁺ analysis was performed in drinking and tap water with low Relative Standard Deviation (RSD) values and high recovery. Smartphone and living cell applications were successfully performed for colorimetric sensing Hg²⁺ in real samples and 3T3 cells, respectively.

Recent advances of Au@Ag core-shell SERS-based biosensors

The methodological advancements in surface-enhanced Raman scattering (SERS) technique with nanoscale materials based on noble metals, Au, Ag, and their bimetallic alloy Au-Ag, has enabled the highly efficient sensing of chemical and biological molecules at very low concentration values. By employing the innovative various type of Au, Ag nanoparticles and especially, high efficiency Au@Ag alloy nanomaterials as substrate in SERS based biosensors have revolutionized the detection of biological components including; proteins, antigens antibodies complex, circulating tumor cells, DNA, and RNA (miRNA), etc. This review is about SERS-based Au/Ag bimetallic biosensors and their Raman enhanced activity by focusing on different factors related to them. The emphasis of this research is to describe the recent developments in this field and conceptual advancements behind them. Furthermore, in this article we apex the understanding of impact by variation in basic features like effects of size, shape varying lengths, thickness of core-shell and their influence of large-scale magnitude and morphology. Moreover, the detailed information about recent biological applications based on these core-shell noble metals, importantly detection of receptor binding domain (RBD) protein of COVID-19 is provided.

One-Step Synthesis of Peptide-Gold Nanoclusters with Tunable Fluorescence and Enhanced Gene Delivery Efficiency

In this study, peptide-gold nanoclusters with tunable fluorescence were prepared by a simple "one-pot" method, which were used for gene localization and delivery in vivo to achieve efficient intracellular colocalization, uptake, and transfection. The efficiency of pDNA transfection was up to 70.6%, and there was no obvious cytotoxicity. This study proves that the simple-composition and bio-friendly peptide-gold nanoclusters are promising gene delivery carriers and can provide a powerful theoretical and experimental basis for the application of peptide-metal nanocomplexes in gene delivery and other biomedicine fields.

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.

A novel polypeptide-modified fluorescent gold nanoclusters for copper ion detection

Biomolecule-functionalized fluorescent gold nanocluster (AuNCs) have attracted a lot of attention due to good biocompatibility, stable physicochemical properties and considerable cost advantages. Inappropriate concentration of Cu²⁺ may cause a variety of diseases. In this study, AuNCs were synthesized in alkaline aqueous solution using bovine serum albumin (BSA) as a template. And then, the peptide CCYWDAHRDY was coupled to AuNCs. Furthermore, the fluorescence of synthesized CCYWDAHRDY-AuNCs response to Cu²⁺ was evaluated. As the results shown that the CCYWDAHRDY-AuNCs can sensitively detect Cu²⁺. After adding Cu²⁺ to the probe system, the fluorescence of the CCYWDAHRDY-AuNCs was quenched. The detection conditions were at pH 6 and 30 °C for 10 min, the linear relationship between Cu²⁺ concentration and fluorescence intensity were good in the range of 0.1 ~ 4.2 μmol/L. The regression equation was y = − 105.9x + 693.68, the linear correlation coefficient is 0.997, and the minimum detection limit was 52 nmol/L.

Gold nanoclusters: An ultrasmall platform for multifaceted applications

Gold nanoclusters (Au NCs) with a core size below 2 nm form an exciting class of functional nano-materials with characteristic physical and chemical properties. The properties of Au NCs are more prominent and extremely different from their bulk counterparts. The synthesis of Au NCs is generally assisted by template or ligand, which impart excellent cluster stability and high quantum yield. The tunable and sensitive physicochemical properties of Au NCs open horizons for their advanced applications in various interdisciplinary fields. In this review, we briefly summarize the solution phase synthesis and origin of the characteristic properties of Au NCs. A vast review of recent research work introducing biosensors based on Au NCs has been presented along with their specifications and detection limits. This review also highlights recent progress in the use of Au NCs as bio-imaging probe, enzyme mimic, temperature sensing probe and catalysts. A speculation on present challenges and certain future prospects have also been provided to enlighten the path for advancement of multifaceted applications of Au NCs.

Synthesis of Exosome-Based Fluorescent Gold Nanoclusters for Cellular Imaging Applications

In recent years, fluorescent metal nanoclusters have been used to develop bioimaging and sensing technology. Notably, protein-templated fluorescent gold nanoclusters (AuNCs) are attracting interest due to their excellent fluorescence properties and biocompatibility. Herein, we used an exosome template to synthesize AuNCs in an eco-friendly manner that required neither harsh conditions nor toxic chemicals. Specifically, we used a neutral (pH 7) and alkaline (pH 11.5) pH to synthesize two different exosome-based AuNCs (exo-AuNCs) with independent blue and red emission. Using field-emission scanning electron microscopy, energy dispersive X-ray microanalysis, nanoparticle tracking analysis, and X-ray photoelectron spectroscopy, we demonstrated that AuNCs were successfully formed in the exosomes. Red-emitting exo-AuNCs were found to have a larger Stokes shift and a stronger fluorescence intensity than the blue-emitting exo-AuNCs. Both exo-AuNCs were compatible with MCF-7 (human breast cancer), HeLa (human cervical cancer), and HT29 (human colon cancer) cells, although blue-emitting exo-AuNCs were cytotoxic at high concentrations (≥5 mg/mL). Red-emitting exo-AuNCs successfully stained the nucleus and were compatible with membrane-staining dyes. This is the first study to use exosomes to synthesize fluorescent nanomaterials for cellular imaging applications. As exosomes are naturally produced via secretion from almost all types of cell, the proposed method could serve as a strategy for low-cost production of versatile nanomaterials.

Copper nanoclusters with/without salicylaldehyde-modulation for multifunctional detection of mercury, cobalt, nitrite and cyanide ions in aqueous solution and bioimaging

The sensitive determination of multiple heavy metal ions and toxic anions is important in biological and environmental fields. Here we report a facile strategy to construct a multifunctional chemosensor for the detection of Hg²⁺, [Formula: see text]Co²⁺, and CN^- in aqueous solution based on the fluorescent copper nanoclusters (Cu NCs). It was interesting to find that salicylaldehyde (SA) could effectively modulate the fluorescence property and sensing behavior of Cu NCs. In the absence of SA, Cu NCs showed 'on-off' fluorescence responses at the addition of Hg²⁺ and [Formula: see text] under different quenching mechanisms. Upon the presence of SA, Cu NCs exhibited a strong intramolecular charge transfer emission at 500 nm, accompanied by the decrease of the initial fluorescence of Cu NCs at 430 nm. This fluorescence on-state of Cu NC-SA at 500 nm was found to be exclusively turned off by Co²⁺ and enhanced by CN^-. Spectroscopy results combined with thermodynamic analysis provided sufficient information to deduce the sensing mechanisms. Finally, the Cu NCs showed high biocompatibility and were able to be used for fluorescence bioimaging in living cells. This study provided a novel and simple strategy to construct the multifunctional chemosensors for bioanalytical applications.

Coassemble dopamine and GHK tripeptide into fluorescent nanoparticles for pH sensing

Fluorescent nanostructures have been widely applied to biomedical researches and clinical diagnosis such as biolabeling/imaging/sensing and have even acted as therapy reagents. Peptide-based fluorescent nanostructures attract recent interest from biomedical researchers. Inspired by the natural existence of GHK-Cu complex with a growth factor-like effect in human blood, here we have developed a novel approach for designing nanosensors through the co-assembling of two kinds of biomolecules. By making best use of both π-π stacking between carbon rings and the easy-oxidation property of an important transmitter molecule, dopamine (DA), we successfully built up a supersensitive and robust fluorescent pH nanosensor by co-assembling oxidized DA (DA_ox ) with a tripeptide GHK. The GHK-DA_ox nanostructures have a quantum yield of 20.82%, which might be the brightest one among all the current co-assembling structures merely through unmodified biomolecules. We envision this approach could open a new avenue for not only hybrid nanostructure construction, but also may inspire the bioengineering of in vivo luminescent probes.

Therapeutic applications of CRISPR/Cas9 in breast cancer and delivery potential of gold nanomaterials

Globally, approximately 1 in 4 cancers in women are diagnosed as breast cancer (BC). Despite significant advances in the diagnosis and therapy BCs, many patients develop metastases or relapses. Hence, novel therapeutic strategies are required, that can selectively and efficiently kill malignant cells. Direct targeting of the genetic and epigenetic aberrations that occur in BC development is a promising strategy to overcome the limitations of current therapies, which target the tumour phenotype. The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas system, composed of only an easily modifiable single guide RNA (sgRNA) sequence bound to a Cas9 nuclease, has revolutionised genome editing due to its simplicity and efficiency compared to earlier systems. CRISPR/Cas9 and its associated catalytically inactivated dCas9 variants facilitate the knockout of overexpressed genes, correction of mutations in inactivated genes, and reprogramming of the epigenetic landscape to impair BC growth. To achieve efficient genome editing in vivo, a vector is required to deliver the components to target cells. Gold nanomaterials, including gold nanoparticles and nanoclusters, display many advantageous characteristics that have facilitated their widespread use in theranostics, as delivery vehicles, and imaging and photothermal agents. This review highlights the therapeutic applications of CRISPR/Cas9 in treating BCs, and briefly describes gold nanomaterials and their potential in CRISPR/Cas9 delivery.