Synthesis of silver nanoclusters in colloidal scaffold for biolabeling and antimicrobial applications

Imidazolyl crosslinked chitosan nanogel for nanoconfined synthesis of silver nanocrystallines as antimicrobials

Multi-drug resistant microbes (MDRMs) present a significant threat to human health. Silver nanoparticles possess broad-spectrum antimicrobial properties, but the potential Ag+ ion release and toxicity on primary cells drawback the clinical application. In this study, imidazolylhydrazine was employed to cross-link chitosan into nanogels and subsequently to synthesize nanoconfined silver nanocrystallines. These silver nanocrystallines are predominantly characterized by (111) crystalline facets, featuring a high Ag0 atomic density and an approximate size of 3 nm. these nanocrystallines demonstrated exceptional visible light bactericidal properties, particularly against MDRMs, attributable to a threefold enhancement in reactive oxygen species (ROS) generation efficiency compared to silver nanoparticles. Remarkably, thanks to the nanoconfined domains of the silver nanocrystallines embedded within the nanogel, along with the gel's strong coordination capabilities with Ag through its imidazole, hydrazide, and amino groups, as well as the proton buffering capacity of imidazole, the release of silver ions in the body fluid environment was not significantly observed at any stage of the wound recovery. This ensures exceptional biocompatibility for postoperative wound spraying. The nanoconfined Ag nanocrystalline platform emerges as a novel prospect for wound sterilization.

Silver nanoparticle-functionalized covalent organic frameworks for the inhibition of foodborne pathogenic bacteria and their application in green grape preservation

Foodborne pathogens continue to pose a significant threat to human health. This study aims to enhance the antimicrobial activity of low-dose silver nanoparticles (AgNPs) against foodborne pathogens and use the enhanced AgNPs to preserve green grapes. A chemical delivery carrier for covalent organic frameworks (COFs) impregnated with AgNPs was developed. We investigated the bacteriostatic properties (minimum bacteriostatic concentration, bacteriostatic growth curve), the mechanism of action of the bacteriostatic agent, and the performance of the bacteriostatic film. The bacteriostatic preservation rate of the AgNPs@COFs composite on green grapes was evaluated. The minimum bacteriostatic concentration of the AgNPs@COFs composite was 10 μg/mL, and the bacteriostatic rate varied between 94.01 % and 98.77 %. The developed antibacterial AgNPs@COFs composite has potential applications in food packaging and preservation.

Central Countries' and Brazil's Contributions to Nanotechnology

Abstract:

Nanotechnology is a cornerstone of the scientific advances witnessed over the past few years. Nanotechnology applications are extensively broad, and an overview of the main trends worldwide can give an insight into the most researched areas and gaps to be covered. This document presents an overview of the trend topics of the three leading countries studying in this area, as well as Brazil for comparison. The data mining was made from the Scopus database and analyzed using the VOSviewer and Voyant Tools software. More than 44.000 indexed articles published from 2010 to 2020 revealed that the countries responsible for the highest number of published articles are The United States, China, and India, while Brazil is in the fifteenth position. Thematic global networks revealed that the standing-out research topics are health science, energy, wastewater treatment, and electronics. In a temporal observation, the primary topics of research are: India (2020), which was devoted to facing SARS-COV 2; Brazil (2019), which is developing promising strategies to combat cancer; China (2018), whit research on nanomedicine and triboelectric nanogenerators; the United States (2017) and the Global tendencies (2018) are also related to the development of triboelectric nanogenerators. The collected data are available on GitHub. This study demonstrates the innovative use of data-mining technologies to gain a comprehensive understanding of nanotechnology's contributions and trends and highlights the diverse priorities of nations in this cutting-edge field.

Molybdenum oxide nanotube caps decorated with ultrafine Ag nanoparticles: Synthesis and antimicrobial activity

In the contemporary era, microorganisms, spanning bacteria and viruses, are increasingly acknowledged as emerging contaminants in the environment, presenting significant risks to public health. Nevertheless, conventional methods for disinfecting these microorganisms are often ineffective. Additionally, they come with disadvantages such as high energy usage, negative environmental consequences, increased expenses, and the generation of harmful byproducts. The development of next-generation antifungal and antibacterial agents is dependent on newly synthesized nanomaterials with inherent antimicrobial behavior. In this study, we report an arc-discharge method to synthesize MoOx nanosheets and microbelts, followed by decorating them with ultrafine Ag nanoparticles (NPs). Scanning and transmission electron microscopies show that Ag NPs formation on the Molybdenum oxide nanostructures rolls them into nanotube caps (NTCs), revealing inner and outer diameters of approximately 19.8 nm and 105.5 nm, respectively. Additionally, the Ag NPs are ultrafine, with sizes in the range of 5-8 nm. Results show that the prepared NTCs exhibit dose-dependent sensitivity to both planktonic and biofilm cells of Escherichia coli and Candida albicans. The anti-biofilm activity in terms of biofilm inhibition ranged from 19.7 to 77.2% and 11.3-82.3%, while removal of more than 70% and 90% of preformed biofilms was achieved for E. coli and C. albicans, respectively, showing good potential for antimicrobial coating. Initial MoOx exhibits positive potential, while Ag-decorated Molybdenum oxide NTCs show dual potential effects (positive for Molybdenum oxide NTCs and negative for Ag NPs. Molybdenum oxide NTCs, with their strong positive potential, efficiently attract microbes due to their negatively charged cell surfaces, facilitating the antimicrobial effect of Ag NPs, leading to cell damage and death. These findings suggest that the synthesized NPs could serve as a suitable coating for biomedical applications.

Time-resolved in situ nanoparticle size evolution during magnetron sputtering onto liquids

Despite extensive research since 1996, there are still open questions regarding the primary location of the nucleation process, the growth mechanism of the nanoparticles (NPs), and the influence of the liquid properties on the ultimate size of the NPs for the magnetron sputtering of metals onto liquids. Hence, for the first time to the authors' knowledge, the particle size evolution is in situ and in real-time examined during and after the sputtering of the silver atoms onto silicone oil, i.e., Sputtering onto Liquids (SoL) process. The particle size distribution (PSD) is measured via the Light Extinction Spectroscopy (LES) technique, and the deposition rate and stirring speed effects on the PSDs are analyzed. Based on De Brouckere mean diameters, the size evolution of silver nanoparticles (Ag NPs) over time is monitored. Ag NPs bigger than 20 nm are detected, and the PSDs are shown to be poly-disperse, which is also supported by the ex situ TEM measurements and in situ time-resolved absorption spectra. Moreover, it is shown that aggregation and growth of Ag NPs occur both at the plasma-liquid interface and inside the silicone oil during and after the magnetron sputtering. Despite the same amount of deposited silver, the growth kinetics of Ag NPs in silicone oil vary at different deposition rates. In particular, at higher deposition rates, larger NPs are formed. Stirring is seen to help disaggregate the particle lumps. Faster stirring does not substantially influence the final size but promotes the formation of smaller NPs (<20 nm). Also, low colloidal stability of Ag NPs in silicone oil is observed.

Fluorescent detection of emerging virus based on nanoparticles: From synthesis to application

The spread of COVID-19 has caused huge economic losses and irreversible social impact. Therefore, to successfully prevent the spread of the virus and solve public health problems, it is urgent to develop detection methods with high sensitivity and accuracy. However, existing detection methods are time-consuming, rely on instruments, and require skilled operators, making rapid detection challenging to implement. Biosensors based on fluorescent nanoparticles have attracted interest in the field of detection because of their advantages, such as high sensitivity, low detection limit, and simple result readout. In this review, we systematically describe the synthesis, intrinsic advantages, and applications of organic dye-doped fluorescent nanoparticles, metal nanoclusters, up-conversion particles, quantum dots, carbon dots, and others for virus detection. Furthermore, future research initiatives are highlighted, including green production of fluorescent nanoparticles with high quantum yield, speedy signal reading by integrating with intelligent information, and error reduction by coupling with numerous fluorescent nanoparticles.

Revealing the effects of ligands of silver nanoclusters on the interactions between them and ctDNA: Abstraction to visualization

Silver nanoclusters (AgNCs) have been widely applied in the field of biology, drug therapy and cell imaging in the last decade. In order to study the biosafety of AgNCs, GSH-AgNCs and DHLA-AgNCs were synthesized using glutathione (GSH) and dihydrolipoic acid (DHLA) as ligands, and their interactions with calf thymus DNA (ctDNA) from abstraction to visualization were studied. The results of spectroscopy, viscometry and molecular docking demonstrated that GSH-AgNCs mainly bound to ctDNA in a groove mode, while DHLA-AgNCs were both groove and intercalation binding. Fluorescence experiments suggested that the quenching mechanism of both AgNCs to the emission of ctDNA-probe were both in static mode, and thermodynamic parameters demonstrated that the main forces between GSH-AgNCs and ctDNA were hydrogen bonds and van der Waals forces, while hydrogen bonds and hydrophobic forces contributed to the binding of DHLA-AgNCs to ctDNA. The binding strength demonstrated that DHLA-AgNCs bound to ctDNA more strongly than that of GSH-AgNCs. The results of circular dichroism (CD) spectroscopy reflected small effects of both AgNCs on the structure of ctDNA. This study will support the theoretical foundation for the biosafety of AgNCs and have a guiding significance for the preparation and application of AgNCs.