Protein-activated transformation of silver nanoparticles into blue and red-emitting nanoclusters

Apoptosis and cell cycle arrest of bone marrow cells by green-synthesized silver but not albumin nanoparticles

Metallic nanoparticles (NPs) made by traditional means have a deleterious effect on bone marrow (BM) cells. Alternatively, green-synthesized NPs are cost-effective, ecofriendly, and may be less toxic. Also, albumin is a biocompatible blood protein involved in several physiological processes, employed in drug delivery without posing adverse effects, and is thought to be ideal NPs or coating for reducing the metallic NP's toxicity. We prepared albumin NPs (AlbNPs), biosynthesized silver NPs (AgNPs) using the metabolite of the Escherichia coli D8 strain and coated them with albumin (Ag/AlbNPs). These NPs were characterized and intraperitoneally administered to rats to compare their effect on rat BM cells. The flow cytometry results revealed that AgNPs significantly reduced viability, increased apoptosis, downregulated the antiapoptotic Bcl2 gene expression, and upregulated the apoptotic genes Bax and p53 in BM cells, while treatment with AlbNPs maintained these parameters. Principally, AgNPs caused significant DNA fragmentation, since all parameters observed by the comet assay (tail length, tail DNA content, tail moment, and olive moment) were significantly higher in AgNP-treated groups than in control and AlbNP-treated groups. Investigation of the cell cycle revealed that treatment with AgNP, but not AlbNPs, downregulated the expression of the regulatory genes Cdk2, Cdk4, and the cyclins A1 (Ccna1) and D1 (Ccnd1), which resulted in the arrest of the progression of the cell cycle at GO/G1, as demonstrated by flow cytometry. Coating AgNPs with albumin increased their size, and decreased their intracellular concentration, resulting in reduced apoptosis and cell cycle arrest. However, these results for the Ag/AlbNP-treated group were still not comparable to those treated with pure AlbNPs. In conclusion, in contrast to AlbNPs, green AgNPs are toxic to bone marrow cells. Their coating with albumin, however, reduces this toxicity. To avoid this metal NP toxicity, it is recommended to use compatible degradable NPs instead of metal NPs for medication delivery to BM.

Biofabrication of GO-Ag nanocomposite using Cucumis callosus (kachri) fruits: Enhanced antibacterial properties and green synthesis approach

This study presents a novel, environmentally sustainable method for the synthesis of graphene oxide (GO) sheets decorated uniformly with silver nanoparticles (Ag NPs) ranging in size from 4 to 34 nm. The reduction of AgNO3 is achieved using an extract derived from Cucumis callosus fruit, which serves as a dual-function stabilizing and reducing agent. Cucumis callosus, belonging to the Cucurbitaceae family and native to regions such as India, South America, Thailand, Africa, and Egypt, is recognized for its substantial nutritional and medicinal value, encompassing antioxidant, antidiabetic, anticancer, and anti-inflammatory properties. In this study, we explore the utilization of Cucumis callosus extract for the first time in synthesizing Ag NPs, employing a green synthesis approach to produce GO-Ag nanocomposites. Comprehensive characterization techniques confirm the structural integrity and quality of the synthesized nanocomposites. The antibacterial efficacy of the green-synthesized Ag-decorated GO nanocomposites was evaluated using the disk diffusion method against Bacillus subtilis (Gram-positive) and Escherichia coli (Gram-negative) bacteria at varying dosages. The nanocomposites demonstrated dose-dependent antibacterial activity against both bacterial strains, with a notably heightened effect observed against Gram-negative bacteria. These findings underscore the potential of Cucumis callosus as a promising candidate for the sustainable preparation of GO-Ag nanocomposites with enhanced antibacterial properties, suitable for various biomedical and environmental applications. RESEARCH HIGHLIGHTS: This work presents a simple, environmentally free, and cost-effective green synthesis method to decorate uniformly small (4-34 nm) spherical Ag NPs on the GO sheets. Ag NPs were produced by reducing AgNO3 using Cucumis callosus fruit extract as a stabilizing and reducing agent. The nanocomposites show dosage-dependent antibacterial activities against both Gram-positive and Gram-negative bacteria, but the antibacterial effect is higher against the Gram-negative bacteria. Synthesis of these nanocomposites via the green route using an herbal plant/fruit like Cucumis callosus will benefit the medical industry.

Selective synthesis of fluorescent metal nanoclusters over metal nanoparticles

Metal nanoparticles and nanoclusters are pivotal in nanomaterial science, each offering unique properties for diverse applications. Nanoclusters, typically smaller than 2 nm, exhibit distinct optical and electronic characteristics due to quantum confinement, resulting in fluorescence emission. In contrast, metal nanoparticles, sized between 2 and 100 nm, exhibit absorption spectra. Both are synthesized by reducing metal precursors in the presence of a suitable stabilizing agent. While nanoparticles have been the historical research focus, recent attention has shifted to nanoclusters for their exceptional properties and their synthesis has evolved significantly over the past few decades. This review discusses the selective synthesis of nanoclusters over nanoparticles, emphasizing the role of various factors such as ligand concentration (metal-to-ligand ratio), reducing agents, pH, reaction time and temperature, solvents, and assistant reagents. Higher ligand concentrations stabilize smaller nanoclusters by preventing aggregation, while lower concentrations lead to larger nanoparticles. Stronger reducing agents produce smaller, more uniform particles, whereas weaker reducing agents yield larger ones. pH affects nanocluster size and emission properties. Solvents and assistant reagents influence reaction kinetics and material properties. Temperature and reaction time also play critical roles in controlling nanocluster size and properties. These insights guide the optimized synthesis of metal nanoclusters, for their specific applications.

Environmental behavior of silver nanomaterials in aquatic environments: An updated review

The increasing applications of silver nanomaterials (nano-Ag) and their inevitable release posed great potential risks to aquatic organisms and ecosystems. Considerable attention has been attracted on their behaviors and transformations, which were critically important for their subsequent biological toxicities and ecological effects. Therefore, the summary of the recent efforts on the environmental behavior of nano-Ag would be beneficial for understanding the environmental fate and accurate risk assessment. This review summarized the studies on various physical, chemical and biological transformations of nano-Ag, meanwhile, the influencing factors (including the intrinsic properties and environmental conditions) and related mechanisms were highlighted. Surface structure and facets of nano-Ag, abiotic conditions and natural freeze-thaw cycle processes could affect the transformations of nano-Ag under different environmental scenarios (including freshwater, seawater and wastewater). The interactions with co-present components, such as chemicals and other particles, impacted the multiple processes of nano-Ag. Besides, the contradictory effects and mechanisms by several environmental factors were summarized. Lastly, the key knowledge gaps and some aspects that deserve further investigation were also addressed. Therefore, the current review aimed to provide an overall analysis of transformation processes of nano-Ag, which will provide more available information and pave the way for the future research areas.

Two-photon fluorescence probe for quantification of cyclosporine

A novel ratiometric fluorescent sensor was fabricated for the fast and facile determination of cyclosporine A (CsA). Due to the narrow therapeutic index of CsA, its desired therapeutic effects are evident within a limited range of blood concentration, indicating the fundamental role of therapeutic drug monitoring in CsA pharmacological response. In this study, a two-photon fluorescence probe based on the zeolitic imidazolate framework (ZIF-8) and norepinephrine-capped silver nanoparticles (AgNPs@NE) was employed for the quantification of the CsA in human plasma samples. In the presence of CsA, the fluorescent emission intensity of ZIF-8-AgNPs@NE was quenched. Under the optimum conditions, the proposed probe determines CsA in plasma samples in two linear ranges of 0.01 to 0.5 μg mL^-1 and 0.5 to 10 μg mL^-1. The developed probe demonstrates the advantages of a facile and fast platform with limit of detection as low as 0.007 μg mL^-1. At last, this method was applied to find CsA concentration in four patients receiving oral CsA regimen which indicates it as a promising method for on-site detection applications.

In Situ Microscopic Studies on the Interaction of Multi-Principal Element Nanoparticles and Bacteria

Multi-principal element nanoparticles are an emerging class of materials with potential applications in medicine and biology. However, it is not known how such nanoparticles interact with bacteria at nanoscale. In the present work, we evaluated the interaction of multi-principal elemental alloy (FeNiCu) nanoparticles with Escherichia coli (E. coli) bacteria using the in situ graphene liquid cell (GLC) scanning transmission electron microscopy (STEM) approach. The imaging revealed the details of bacteria wall damage in the vicinity of nanoparticles. The chemical mappings of S, P, O, N, C, and Cl elements confirmed the cytoplasmic leakage of the bacteria. Our results show that there is selective release of metal ions from the nanoparticles. The release of copper ions was much higher than that for nickel while the iron release was the lowest. In addition, the binding affinity of bacterial cell membrane protein functional groups with Cu, Ni, and Fe cations is found to be the driving force behind the selective metal cations' release from the multi-principal element nanoparticles. The protein functional groups driven dissolution of multielement nanoparticles was evaluated using the density functional theory (DFT) computational method, which confirmed that the energy required to remove Cu atoms from the nanoparticle surface was the least in comparison with those for Ni and Fe atoms. The DFT results support the experimental data, indicating that the energy to dissolve metal atoms exposed to oxidation and/or the to presence of oxygen atoms at the surface of the nanoparticle catalyzes metal removal from the multielement nanoparticle. The study shows the potential of compositional design of multi-principal element nanoparticles for the controlled release of metal ions to develop antibacterial strategies. In addition, GLC-STEM is a promising approach for understanding the nanoscale interaction of metallic nanoparticles with biological structures.

N-Cholyl d-Penicilamine Micelles Templated Red Light-Emitting Silver Nanoclusters: Fluorometric Sensor for S2- Ions and Bioimaging Application Using Zebrafish Model

Red-light-emitting silver nanoclusters (AgNCs) are recently emerged as a promising nanoprobe in the field of biomedical applications, because of their attractive properties, including brightness, luminescence stability, and better biocompatibility. In this report, we have developed highly water-soluble red-light-emitting AgNCs by using N-cholyl d-penicilamine (NCPA) as a biosurfactant at above the critical micelle concentration (CMC) at room temperature. Moreover, the NCPA was initially synthesized by demonstrating the reaction between cholic acid and d-penicilamine via a simple coupling reaction strategy. The primary and secondary critical micellar concentration (CMC) of NCPA surfactant was measured using pyrene (1 × 10^-6 M) as a fluorescent probe, and the values were found to be 3.18 and 10.6 mM, respectively. Steady-state fluorescence measurements reveal that the prepared AgNCs shows the excitation and emission maxima at 365 and 672 nm, respectively, with a large Stokes shift (307 nm). The average lifetime measurements and quantum yield of the AgNCs were calculated to be 143.43 ns and 16.34%, respectively. Also, the red luminescent NCPA-templated AgNCs was synthesized in various protic and aprotic polar solvents, among which DMF and DMSO exhibit bright emission at longer wavelength as synthesized in aqueous medium. At higher concentration of AgNO₃, bright luminescent and highly stable solid AgNCs was obtained with excitation and emission maxima at 607 and 711 nm, respectively. Furthermore, the synthesized AgNCs has been successfully utilized as a fluorescent probe for selective and sensitive detection of S^2- ions at nanomolar level in water samples, showing its potential applicability for the detection of S^2- ions in drinking, river, and tap water samples. Finally, toxicity and bioimaging studies of NCPA-templated AgNCs was demonstrated using zebrafish as in vivo model, showing no significant toxicity up to 200 μL/mL. The AgNCs-stained embryos exhibited red fluorescence with high intensity, which shows that AgNCs are stable in a living system.

Investigating Chaperone like Activity of Green Silver Nanoparticles: Possible Implications in Drug Development

Protein aggregation and amyloidogenesis have been associated with several neurodegenerative disorders like Alzheimer's, Parkinson's etc. Unfortunately, there are still no proper drugs and no effective treatment available. Due to the unique properties of noble metallic nanoparticles, they have been used in diverse fields of biomedicine like drug designing, drug delivery, tumour targeting, bio-sensing, tissue engineering etc. Small-sized silver nanoparticles have been reported to have anti-biotic, anti-cancer and anti-viral activities apart from their cytotoxic effects. The current study was carried out in a carefully designed in-vitro to observe the anti-amyloidogenic and inhibitory effects of biologically synthesized green silver nanoparticles (B-AgNPs) on human serum albumin (HSA) aggregation taken as a model protein. We have used different biophysical assays like thioflavin T (ThT), 8-Anilino-1-naphthalene-sulphonic acid (ANS), Far-UV CD etc. to analyze protein aggregation and aggregation inhibition in vitro. It has been observed that the synthesized fluorescent B-AgNPs showed inhibitory effects on protein aggregation in a concentration-dependent manner reaching a plateau, after which the effect of aggregation inhibition was significantly declined. We also observed meaningful chaperone-like aggregation-inhibition activities of as-synthesized florescent B-AgNPs in astrocytes.

Recovered fluorescence of the Cd-nanocluster-Hg(II) system based on experimental results and computational methods

Human Serum Albumin, a plasma protein existing in abundance, was selected as a template and reducing agent for the formation of CdNCs due to two factors: its stability and low cost. In the presence of human serum albumin (HSA), a selective and sensitive, low-cost, environmental friendly, and label-free off-on fluorescent sensor was synthesized and characterized for a bioaccumulating and toxic heavy metal, Hg²⁺ and biothiols. HSA - CdNCs can specifically recognize Hg²⁺ through aggregating NCs and causing fluorescence quenching. Subsequently, with increase in the concentration of biothiols, Hg²⁺ was eliminated from the surface of NC, while the fluorescence was restored. The calculated limits of detection (LOD) were 55 pM for Hg(II) and 14 nM for GSH, respectively. The assay was capable of detecting Hg²⁺ ions and GHS at different concentrations in the range of 0.008 to 8530 nM and 7.5-5157 nM, respectively. Furthermore, the appropriate molecular mechanics (MM) as well as quantum mechanical (QM) methods were performed to optimize and the theoretical investigation of the discussed HSA-profile structures and its interactions with the Cd-NCs (one atom of Cd), Hg²⁺ and glutathione (G).

Silver-incorporating peptide and protein supramolecular nanomaterials for biomedical applications

The natural biomolecules of peptides and proteins are able to form elegant metal incorporating supramolecular nanomaterials through multiple weak non-covalent interactions. The use of toxic chemical reagents to fabricate silver nanoparticles poses a danger to apply them in various biomedical applications. Peptide and protein biomolecules have the potential to overcome this barrier by the supramolecular chemistry approach. In this review, we focus on the self-assembly of peptides and proteins to synthesize silver incorporating supramolecular nanoarchitectures, which in turn enhance the biological properties of these silver nanomaterials being used in nanomedicine. This review aims to illustrate the recent developments in amphiphilic peptides, oligopeptides, collagen, bovine serum albumin (BSA), and human serum albumin (HSA) as capping, stabilizing, and reducing agents to form silver incorporating supramolecular nanostructures. Finally, we provide some biomedical applications of silver-incorporating supramolecular nanomaterials along with future perspectives.