Stable Nanocomposite Based on PEGylated and Silver Nanoparticles Loaded Graphene Oxide for Long-Term Antibacterial Activity

Functionalized zeolite regulates bone metabolic microenvironment

The regulation of bone metabolic microenvironment imbalances in diseases such as osteoporosis, bone defects, infections, and tumors remains a significant challenge in orthopedics. Therefore, it has become urgent to develop biomaterials with effective bone metabolic microenvironmental regulatory functions. Zeolites, as advanced biomedical materials, possess distinctive physicochemical properties such as multi-level pore structures, adjustable frameworks, easily modifiable surfaces, and excellent adsorption capabilities. These advantageous characteristics give zeolites broad application prospects in regulating the bone metabolic microenvironment. Therefore, this paper first classifies zeolites used to regulate the bone metabolic microenvironment based on their topological structures and compositional frameworks. Subsequently, it provides a detailed description of modification strategies for zeolite materials aimed at regulating this microenvironment. Next, a comprehensive summary was provided on the preparation strategies for zeolite materials aimed at regulating the bone metabolic microenvironment. Additionally, the paper focuses on the specific applications of zeolite materials in conditions of bone metabolic imbalance, such as osteoporosis, bone defects, orthopedic infections, and bone tumors, highlighting their potential in enhancing osteogenic microenvironments, controlling infections, and treating bone tumors. Finally, it outlines the prospects and challenges associated with the application of zeolites in regulating the bone metabolic microenvironment. This review comprehensively summarizes zeolites used for bone metabolic regulation, aiming to provide guidance for future research and application development.

Antibacterial and safe chitosan-graphene hydrogel films: a promising nanotherapeutic for Staphylococcus aureus wound infections

Pathogenic bacterial growth at wound sites, particularly Staphylococcus aureus, poses a serious threat during trauma. Delayed treatment can lead to increased inflammation and severe tissue damage. In this study, a chitosan cross-linked polycationic peptide-conjugated graphene-silver (CGrAP) nanocomposite hydrogel film was developed as an antibacterial wound dressing to treat S. aureus infections. The CGrAP hydrogel was synthesized via a Schiff-base reaction between the ε-poly-L-lysine functionalized graphene-silver nanocomposite and chitosan, and then cast into a film. Its antibacterial action is due to electrostatic interactions and ROS generation, finally disrupting the bacterial cells. In vivo studies on Wistar rat model demonstrated superior bacterial eradication and wound healing compared to antibiotic treatment. The CGrAP hydrogel also showed excellent physicochemical properties, including porosity, water uptake and cytocompatibility with L929 fibroblast cells along with no skin irritation or acute dermal toxicity. These results suggest that, CGrAP nanocomposite hydrogel films have strong potential for antibacterial wound dressing development in chronic wound care.

Spider Silk-Inspired Hyaluronic Acid-Based Hydrogels with Superior Self-Healing Capability and Enhanced Strength

Hyaluronic acid hydrogels are promising materials for diverse applications, yet their potential is hampered by limitations such as low self-healing efficiency and insufficient mechanical strength. Inspired by the heterogeneous structures of spider silk, we introduce a novel dual dynamically crosslinked network hydrogel. This hydrogel comprises an acylhydrazone-crosslinked network, utilizing aldehyde hyaluronic acid (AHA) and 3,3'-dithiobis (propionohydrazide) (DTP) as a first network, and a secondary network formed by hydrogen bonds-crosslinked network between tannic acid (TA) and silk fibroin (SF) with β-sheet formation. The hydrogel exhibits exceptional self-healing ability due to the dynamic and reversible nature of Schiff base bonds, disulfide bonds, and hydrogen bonds, achieving complete healing within 5 minutes. Additionally, the spider silk-inspired heterogeneous structures enhance mechanical properties. Furthermore, the incorporation of TA provides enhances adhesion, as well as remarkable antibacterial and antioxidant properties. This innovative hyaluronic acid-based hydrogel, inspired by spider silk, offers a promising avenue to fortify both the mechanical strength and self-healing capabilities of hydrogels, thus expanding opportunities for applications in tissue engineering and biomedicine.

Self-template impregnated silver nanoparticles in coordination polymer gel: photocatalytic CO2 reduction, CO2 fixation, and antibacterial activity

CO2 fixation and light-assisted conversion of CO2 in the presence of water into fuels and feedstocks are clean and sustainable techniques to alleviate the energy crisis and global climate change. In this regard, herein, a waterborne multifunctional metal-organic coordination polymer gel (Ag@GMP) was prepared from silver nitrate and guanosine 5'-monophosphate. Electron microscopy exhibits that Ag@GMP has a flower-like structure, which is composed of vertically grown sheets, and corresponding high magnification images display the presence of silver nanoparticles on the vertically grown sheets. Ag@GMP demonstrates remarkable photocatalytic performance, achieving a CO2 conversion rate of 18.6 μmol g-1 with approximately 85% selectivity towards CO at ambient temperature without using sacrificial agents. In situ diffuse reflectance infrared Fourier transform spectroscopy was employed to elucidate the proposed mechanism for photocatalytic CO2 reduction. Additionally, Ag@GMP exhibits significant catalytic activity in the fixation of CO2 with epoxides, leading to the formation of valuable chemicals under atmospheric pressure. Ag@GMP demonstrated efficient antibacterial activity against both Gram-negative and Gram-positive bacteria. The highest zone of inhibition was observed against S. aureus MTCC 3160 (15.83 ± 1.1 mm), and for E. coli, P. aeruginosa PAO1, and B. subtilis, it was found to be 12.66 ± 0.9, 14.33 ± 0.8 and 12.8 ± 0.8 mm, respectively.

Nanotechnology: An avenue for combating fish parasites in aquaculture system

The intensification of aquaculture in recent years has led to the rise of infectious fish diseases caused by bacteria, viruses, and parasites. Parasitic diseases, in particular, are widespread and have significant economic impacts globally. Protozoan parasites like Ichthyophthirius multifiliis and Trichodina sp., myxozoans (cnidarians), monogeneans like Dactylogyrus sp. and Gyrodactylus sp., and crustacean parasites like Argulus sp. and Lernaea cyprinacea primarily cause these diseases. Despite advancements and new technologies aimed at understanding and treating these diseases, parasites remain a major health challenge in aquaculture. Traditional antiparasitic agents face limitations, including drug resistance and negative effects on non-target organisms. Recently, nanotechnology has emerged as a novel approach in aquaculture medicine, enabling the development of effective nanoparticles against pathogenic microbes. Silver nanoparticles (AgNPs) are particularly notable for their strong antimicrobial and antiparasitic properties due to their broad mechanisms of action. Although Argulus is a highly destructive crustacean parasite that financially burdens fish farmers, applying nanoparticles to manage this infection in aquaculture is still underexplored. Therefore, this review explores recent efforts to combat parasitic diseases with AgNPs and investigates their potential parasiticidal mechanisms of action, proposing them as a novel tool that could improve the management and control of argulosis diseases. The article underscores the benefits and challenges of this technology, emphasizing its significance in fostering improved health management for sustainable aquaculture.

Guanidinium-Functionalized Carbon Dots: An Efficient Antibacterial Agent against Multidrug-Resistant ESKAPE Pathogens

The rise of multidrug-resistant (MDR) bacteria poses a substantial challenge in clinical settings, particularly with the increasing prevalence of ESKAPE pathogens (E. faecium, S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, and E. coli) as critical MDR bacteria. These ESKAPE pathogens have the capability to undermine antibiotic treatments, leading to a high incidence of drug resistance. However, the development of efficient antibacterial agents against ESKAPE pathogens is still in the bottleneck. Herein, the first example of antibacterial carbon dots against ESKAPE pathogens was reported. Onion powder-based carbon dots were melted with poly(hexamethylene biguanide) hydrochloride (PHMB) to obtain guanidinium-functionalized carbon dots (GCDs), which exhibited satisfactory antibacterial activity against all the tested bacteria, including both Gram-positive and Gram-negative bacteria, and even ESKAPE pathogens. The efficient antibacterial ability of GCDs derives from the rupture of the bacterial cell membrane and elevated ROS levels. Safety assessments revealed that GCDs neither trigger detectable drug resistance nor exhibit any cytotoxic effects. Furthermore, GCDs effectively promoted wound healing without observable adverse reactions of mixed MDR bacteria-infected wounds in rats. The GCDs also showed excellent long-term stability. These findings indicate that GCDs hold promise as an efficient antibacterial agent for the treatment of MDR strain-caused clinical infected-wound healing.

Dialdehyde cellulose nanofibrils/polyquaternium stabilized ultra-fine silver nanoparticles for synergistic antibacterial therapy

Dialdehyde cellulose nanofibrils (DACNF) and Polyquaternium-10 (PQ: chloro-2-hydroxy-3-(trimethylamino) propyl polyethylene glycol cellulose) have become increasingly favored as antibacterial substances due to their advantageous characteristics. DACNF exhibits exceptional mechanical properties and biocompatibility, whereas PQ demonstrates a positive charge that enhances its antibacterial activity. Combined in a DACNF/PQ mixture, they provide an excellent template material for preparing and stabilizing ultra-fine (~ 10.3 nm) silver nanoparticles (AgNPs) at room temperature. Here, the dialdehyde group of DACNF functions as a reducing agent, while the quaternary ammonium of PQ and carboxylate groups of DACNF synergistically helped in-situ generation of AgNPs uniformly. The synthesized nanocomposites, namely PQ@AgNPs, AgNPs@DACNF, and AgNPs@DACNF/PQ, were subjected to comprehensive characterization using various advanced analytical techniques. The films containing AgNPs@DACNF and AgNPs@DACNF/PQ, fabricated via vacuum filtration, exhibited excellent mechanical properties of 9.78 ± 0.21 MPa, and demonstrated superior antibacterial activity against both Escherichia coli and Staphylococcus aureus. Additionally, the silver ion leaching from the prepared composite films was well controlled. The fabricated nanocomposites also effectively inhibited bacterial biofilm formation. It was also found to be highly biocompatible and non-toxic to human skin fibroblast cells. Furthermore, the nanocomposites exhibited enhanced migration of human dermal fibroblasts, suggesting their potential in facilitating wound healing processes.

Antibacterial efficacy of low-dosage silver nanoparticle-sodium alginate-chitosan nanocomposite films against pure and clinical acne strains

The silver nanoparticles-sodium alginate-chitosan (AgNPs-Alg-Chi) nanocomposite film is a compelling material with demonstrated antibacterial efficacy against various pure bacterial strains. However, its potential cytotoxicity at elevated Ag doses warrants investigation. There is a notable dearth of studies assessing its antibacterial effectiveness against clinically relevant bacterial strains, notably Cutibacterium acnes. This study aims to assess the antibacterial efficacy of the low-dose AgNPs-Alg-Chi nanocomposite films on both pure bacterial strains and strains isolated from clinical samples obtained from 65 acne patients. The films were synthesized using green methods, incorporating kumquat (Citrus japonica) extract as a silver ion-reducing agent. The material characterization methods include UV-Vis and FTIR spectroscopies, SEM-EDS, XPS, cell culture, and MTT assay. We successfully fabricated the AgNPs-Alg-Chi nanocomposite films with a low-loading dose of Ag NPs (≤11 μg mL-1, and 37.8 ± 11.5 nm in size). The AgNPs-Alg-Chi nanocomposite film demonstrated comparable antibacterial efficacy to the AgNPs-Chi solution, with MIC values ranging from 3.67 to 5.50 μg mL-1 (p > 0.05) across all strains. Importantly, the AgNPs-Alg-Chi films demonstrated excellent biocompatibility with human keratinocytes (HaCaT cells), maintaining cell viability above 70%. The present AgNPs-Alg-Chi nanocomposite films synthesized by a green approach demonstrated potent antibacterial activity, making them promising for further development into suitable products for human use.

Multifunctional nitrogen-sulfur codoped carbon quantum dots: Determining reduced glutathione, broad-spectrum antibacterial activity, and cell imaging

In this study, nitrogen-sulfur codoped carbon quantum dots (N-S/CQDs) with various functions and properties were synthesized through a one-step method utilizing citric acid and cysteine as reaction substrates. The fluorescence of N-S/CQDs can be specifically quenched by permanganate ion (MnO4 -), and the quenched fluorescence can be recovered by the presence of reduced glutathione (GSH). A fluorescence sensing system based on N-S/CQDs@MnO4 - was developed and successfully applied for the determination of GSH in pharmaceutical preparations. Additionally, N-S/CQDs demonstrated broad-spectrum antibacterial activity, with minimum inhibitory concentrations of 32 μg/ml against Staphylococcus aureus (gram-positive bacterium) and 64 μg/ml against Escherichia coli (gram-negative bacterium). N-S/CQDs also proved effective for cell imaging, exhibiting excellent biocompatibility. These findings underscore the multifunctional characteristics and promising application potential of N-S/CQDs. Furthermore, this study provides a solid foundation for the development of multifunctional carbon quantum dots and the expansion of their applications in various fields.

Sustained-release, antibacterial, adhesive gelatin composite hydrogel with AgNPs double-capped with curdlan derivatives

In this work, carboxymethylated curdlan (CMCD) was utilized as a capping and stabilizing agent for the green synthesis of silver nanoparticles. Subsequently, quaternized curdlan (QCD) was introduced as the second capping layer through electrostatic attraction, leading to the preparation of double-capped silver nanoparticles (AgNPs@CQ). The successful synthesis of silver nanoparticles was characterized using UV-vis, FTIR, XRD, TEM, and DLS. AgNPs@CQ were incorporated into gelatin and a AgNPs@CQ/Gel composite hydrogel was obtained. The incorporation of AgNPs@CQ imparts excellent antibacterial properties to the composite hydrogel, thereby enhancing its antimicrobial efficacy. The presence of double-capping layers significantly retards the release rate of silver, contributing to prolonged antimicrobial activity. The MTT and live/dead fluorescence staining results demonstrate that the gelatin hydrogel incorporating double-capped AgNPs exhibits enhanced cell viability compared to the one incorporating single-capped AgNPs. Additionally, the composite hydrogel exhibits remarkable mechanical strength and adhesive performance. The AgNPs@CQ/Gel composite hydrogel demonstrates a cost-effective and facile preparation, showing significant potential in the field of dressings.

A Comprehensive Review of Silver and Gold Nanoparticles as Effective Antibacterial Agents

The increasing threat from antibiotic-resistant bacteria has necessitated the development of novel methods to counter bacterial infections. In this context, the application of metallic nanoparticles (NPs), especially gold (Au) and silver (Ag), has emerged as a promising strategy due to their remarkable antibacterial properties. This review examines research published between 2006 and 2023, focusing on leading journals in nanotechnology, materials science, and biomedical research. The primary applications explored are the efficacy of Ag and Au NPs as antibacterial agents, their synthesis methods, morphological properties, and mechanisms of action. An extensive review of the literature on NPs synthesis, morphology, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and effectiveness against various Gram(+/-) bacteria confirms the antibacterial efficacy of Au and Ag NPs. The synthesis methods and characteristics of NPs, such as size, shape, and surface charge, are crucial in determining their antibacterial activity, as these factors influence their interactions with bacterial cells. Furthermore, this review underscores the urgent necessity of standardizing synthesis techniques, MICs, and reporting protocols to enhance the comparability and reproducibility of future studies. Standardization is essential for ensuring the reliability of research findings and accelerating the clinical application of NP-based antimicrobial approaches. This review aims to propel NP-based antimicrobial strategies by elucidating the properties that enhance the antibacterial activity of Ag and Au NPs. By highlighting their inhibitory effects against various bacterial strains and relatively low cytotoxicity, this work positions Ag and Au NPs as promising materials for developing antibacterial agents, making a significant contribution to global efforts to combat antibiotic-resistant pathogens.

Evaluation of Zn-Cd-Sn-S nanostructures for in vitro pyrene degradation and antimicrobial activity

The present work describes the fabrication of the quaternary Zn-Cd-Sn-S nanostructure and its use in photocatalytic remediation of the biological contaminant pyrene from water resources. Nanostructures fabricated were characterized by XRD, UV-DRS, FTIR, DLS, EDX, and SEM. In addition, an agar well diffusion test was conducted to determine the antimicrobial activity. Zn-Cd-Sn-S (ZCSS) nanostructures were evaluated for their photocatalytic degrading potential by using pyrene as a model pollutant and evaluating the effects of parameters like initial pyrene concentration, nanocatalyst dosage, solution pH, and light sources during batch adsorption. Nanostructures had a size of 16.74 nm according to the XRD analysis. With a 300 min time interval, ZCSS nanostructures achieved the highest removal rate of 86.3%. Pyrene degradation metabolites were identified using GC-MS analysis of the degraded samples. A Freundlich isothermal (R2 0.9) and pseudo-first-order (R2 0.952) reaction kinetic path best fit the adsorption results for pyrene by the fabricated ZCSS nanostructure, based on the adsorption and kinetic studies. Zn-Cd-Sn-S exhibited the highest antibacterial activity against Staphylococcusaureus (22.4 mM). Due to the combined synergistic actions of the constituent metals, this quaternary nanostructure exhibited exceptional photocatalytic activity. To our est knowledge, the ZCSS nanostructure was made and used to remove pyrene by photocatalysis and fight microbes. Ultimately, the ZCSS nanostructure was found to be an effective photocatalyst for eradicating pathogenic microbes from water.

Synthesis, characterisation and in vitro anticancer activity of conjugated protease inhibitor-silver nanoparticles (AgNPs-PI) against human breast MCF-7 and prostate PC-3 cancer cell lines

The conjugated silver nanoparticles using biomolecules have attracted great attention of researchers because physical dimensions and surface chemistry play important roles in toxicity and biocompatibility of AgNPs. Hence, in the current study, synthesis of bio-conjugated AgNPs with protein protease inhibitor (PI) isolated from Streptomyces spp. is reported. UV-visible spectra of PI and AgNPs showed stronger peaks at 280 and 405 nm, confirming the synthesis of conjugated AgNPs-PI. TEM and SEM images of AgNPs-PI showed spherical-shaped nanoparticles with a slight increase in particle size and thin amorphous layer around the surface of silver nanomaterial. Circular dichroism, FT-IR and fluorescence spectral studies confirmed AgNPs-PI conjugation. Conjugated AgNPs-PI showed excellent anticancer potential than AgNPs and protease inhibitor separately on human breast MCF-7 and prostate PC-3 cell lines. The findings revealed that surface modification of AgNPs with protein protease inhibitor stabilised the nanomaterial and increased its anticancer activity.

Bactericidal Effect and Cytotoxicity of Graphene Oxide/Silver Nanocomposites

To tackle the proliferation of pathogenic microorganisms without relying on antibiotics, innovative materials boasting antimicrobial properties have been engineered. This study focuses on the development of graphene oxide/silver (GO/Ag) nanocomposites, derived from partially reduced graphene oxide adorned with silver nanoparticles. Various nanocomposites with different amounts of silver (GO/Ag-1, GO/Ag-2, GO/Ag-3, and GO/Ag-4) were synthesized, and their antibacterial efficacy was systematically studied. The silver nanoparticles were uniformly deposited on the partially reduced graphene oxide surface, exhibiting spherical morphologies with an average size of 25 nm. The nanocomposites displayed potent antibacterial properties against both gram-positive bacteria (S. aureus and B. subtilis) and gram-negative bacteria (E. coli and S. enterica) as confirmed by minimum inhibition concentration (MIC) studies and time-dependent experiments. The optimal MIC for Gram-positive bacteria was 62.5 μg/mL and for Gram-negative bacteria was 125 μg/mL for the GO/Ag nanocomposites. Bacterial cells that encountered the nanocomposite films exhibited significantly greater inhibitory effects compared to those exposed to conventional antibacterial materials. Furthermore, the cytotoxicity of these nanocomposites was assessed using human epithelial cells (HEC), revealing that GO/Ag-1 and GO/Ag-2 exhibited lower toxicity levels toward HEC and remained compatible even at higher dilution rates. This study underscores the potential of GO/Ag-based nanocomposites as versatile materials for antibacterial applications, particularly as biocompatible wound dressings, offering promising prospects for wound healing and infection control.

Tailoring functional two-dimensional nanohybrids: A comprehensive approach for enhancing photocatalytic remediation

Photocatalysis is gaining prominence as a viable alternative to conventional biohazard treatment technologies. Two-dimensional (2D) nanomaterials have become crucial for fabricating novel photocatalysts due to their nanosheet architectures, large surface areas, and remarkable physicochemical properties. Furthermore, a variety of applications are possible with 2D nanomaterials, either in combination with other functional nanoparticles or by utilizing their inherent properties. Henceforth, the review commences its exploration into the synthesis of these materials, delving into their inherent properties and assessing their biocompatibility. Subsequently, an overview of mechanisms involved in the photocatalytic degradation of pollutants and the processes related to antimicrobial action is presented. As an integral part of our review, we conduct a systematic analysis of existing challenges and various types of 2D nanohybrid materials tailored for applications in the photocatalytic degradation of contaminants and the inactivation of pathogens through photocatalysis. This investigation will aid to contribute to the formulation of decision-making criteria and design principles for the next generation of 2D nanohybrid materials. Additionally, it is crucial to emphasize that further research is imperative for advancing our understanding of 2D nanohybrid materials.

Development of Optical Differential Sensing Based on Nanomaterials for Biological Analysis

The discrimination and recognition of biological targets, such as proteins, cells, and bacteria, are of utmost importance in various fields of biological research and production. These include areas like biological medicine, clinical diagnosis, and microbiology analysis. In order to efficiently and cost-effectively identify a specific target from a wide range of possibilities, researchers have developed a technique called differential sensing. Unlike traditional "lock-and-key" sensors that rely on specific interactions between receptors and analytes, differential sensing makes use of cross-reactive receptors. These sensors offer less specificity but can cross-react with a wide range of analytes to produce a large amount of data. Many pattern recognition strategies have been developed and have shown promising results in identifying complex analytes. To create advanced sensor arrays for higher analysis efficiency and larger recognizing range, various nanomaterials have been utilized as sensing probes. These nanomaterials possess distinct molecular affinities, optical/electrical properties, and biological compatibility, and are conveniently functionalized. In this review, our focus is on recently reported optical sensor arrays that utilize nanomaterials to discriminate bioanalytes, including proteins, cells, and bacteria.

Bioinspired silver nanoparticle-based nanocomposites for effective control of plant pathogens: A review

Plant pathogens, including bacteria, fungi, and viruses, pose significant challenges to the farming community due to their extensive diversity, the rapidly evolving phenomenon of multi-drug resistance (MDR), and the limited availability of effective control measures. Amid mounting global pressure, particularly from the World Health Organization, to limit the use of antibiotics in agriculture and livestock management, there is increasing consideration of engineered nanomaterials (ENMs) as promising alternatives for antimicrobial applications. Studies focusing on the application of ENMs in the fight against MDR pathogens are receiving increasing attention, driven by significant losses in agriculture and critical knowledge gaps in this crucial field. In this review, we explore the potential contributions of silver nanoparticles (AgNPs) and their nanocomposites in combating plant diseases, within the emerging interdisciplinary arena of nano-phytopathology. AgNPs and their nanocomposites are increasingly acknowledged as promising countermeasures against plant pathogens, owing to their unique physicochemical characteristics and inherent antimicrobial properties. This review explores recent advancements in engineered nanocomposites, highlights their diverse mechanisms for pathogen control, and draws attention to their potential in antibacterial, antifungal, and antiviral applications. In the discussion, we briefly address three crucial dimensions of combating plant pathogens: green synthesis approaches, toxicity-environmental concerns, and factors influencing antimicrobial efficacy. Finally, we outline recent advancements, existing challenges, and prospects in scholarly research to facilitate the integration of nanotechnology across interdisciplinary fields for more effective treatment and prevention of plant diseases.

The therapeutic efficacy of silver loaded rhenium disulfide nanoparticles as a photothermal agent for cancer eradication

Cancer is a life-threatening disease when it is diagnosed at a late stage or treatment procedures fail. Inhibiting cancer cells in the tumor environment is a significant challenge for anticancer therapy. The photothermal effects of nanomaterials are being studied as a new cancer treatment. In this work, rhenium disulfide (ReS2) nanosheets were made by liquid exfoliation with gum arabic (GA) and coated with silver nanoparticles (AgNPs) to produce reactive oxygen species that destroy cancer cells. The synthesized AgNP-GA-ReS2 NPs were characterized using UV, DLS, SEM, TEM, and photothermal studies. According to the DLS findings, the NPs were about 216 nm in size and had a zeta potential of 76 mV. The TEM and SEM analyses revealed that the GA-ReS2 formed single-layered nanosheets on which the AgNPs were distributed. The photothermal effects of the AgNP-GA-ReS2 NPs at 50 μg/mL were tested with an 808 nm laser at 1.2 W cm-2, and they reached 55.8 °C after 5 min of laser irradiation. MBA-MB-231 cells were used to test the cytotoxicity of the newly designed AgNP-GA-ReS2 NPs with and without laser irradiation for 5 min. At 50 μg/mL, the AgNP-GA-ReS2 showed cytotoxicity, which was confirmed with calcein and EtBr staining. The DCFH-DA and flow cytometry analyses demonstrated that AgNP-GA-ReS2 nanosheets under NIR irradiation generated ROS with high anticancer activity, in addition to the photothermal effects.

A high-efficient antibacterial and biocompatible polyurethane film with Ag@rGO nanostructures prepared by microwave-assisted method: Physicochemical and dermal wound healing evaluation

Wound infections are a significant issue that can hinder the wound healing process. One way to address this problem is by enhancing the antibacterial activity of wound dressings. Accordingly, this work focuses on developing a castor-oil-based antibacterial polyurethane nanocomposite film impregnated with silver nanoparticles (AgNPs) decorated on the surface of reduced graphene oxide (rGO) nanostructures (Ag@rGO). To this aim, rGOs act as a platform to stabilize AgNPs and improve their bioavailability and dispersion quality within the PU film. The microwave-assisted synthesis of Ag@rGO nanohybrids was proved by FTIR, XRD, TGA, FE-SEM, EDS, and TEM analyses. Compared to PU/GO, the effect of Ag@rGO nanohybrids on thermo-mechanical features, morphology, antibacterial activity, cytocompatibility, and in vivo wound healing was assessed. SEM photomicrographs revealed the enhanced dispersion of Ag@rGO nanohybrids compared to GO nanosheets. Besides, according to XRD results, PU/Ag@rGO nanocomposite film demonstrated higher microphase mixing, which could be due to the finely dispersed Ag@rGO nanostructures interrupting the hydrogen bonding interactions in the hard segments. Moreover, PU/Ag@rGO nanocomposite showed excellent antibacterial behavior with completely killing E. coli and S. aureus bacteria. In vitro and in vivo wound healing studies displayed PU/Ag@rGO film effectively stimulated fibroblast cells proliferation, migration and re-epithelialization. However, the prepared antibacterial PU/Ag@rGO nanocomposite film has the potential to be used as a biomaterial for dermal wound healing applications.

Polyethylene glycol modified graphene oxide-silver nanoparticles nanocomposite as a novel antibacterial material with high stability and activity

Inorganic antibacterial nanomaterials play an increasingly important role in addressing the growing threat of drug-resistant bacteria. Graphene oxide-silver nanoparticles composite (GO-AgNPs), as a kind of inorganic nanomaterials, have excellent antibacterial properties, showing promising potential in biomedical field. However, GO-AgNPs are terribly prone to sedimentation due to aggregation in physiological solutions, along with its non-environmental issues during the synthesis process, seriously limits the antibacterial application of GO-AgNPs in the biomedical field. To solve this problem, herein, polyethylene glycol-graphene oxide-silver nanoparticles composite (GO-AgNPs-PEG) were prepared by modifying GO-AgNPs with polyethylene glycol to enhance their dispersion stability in physiological solutions. In addition, GO-AgNPs-PEG were prepared with using the natural product gallic acid as a reductant and stabilizer, exhibiting the characteristic of environmentally friendly. Meanwhile, the dispersion stability and antibacterial activity of GO-AgNPs-PEG were characterized by various technical methods, it was found that GO-AgNPs-PEG can be stably dispersed in a variety of physiological solutions (e.g., physiological saline, phosphate buffer solution, Luria-Bertani medium, Murashige and Skoog medium) for more than one week. Moreover, the antibacterial properties of GO-AgNPs-PEG in physiological solutions were significantly better than those of GO-AgNPs. Furthermore, it was discovered that the antibacterial mechanism of GO-AgNPs-PEG was probably associated to destroying the integrity of bacterial cell walls and membranes. The findings in this work can provide new ideas and references for the development of new inorganic antibacterial nanomaterials with stable dispersion in physiological solutions.

Interaction of Graphene Oxide Nanoparticles with Human Mononuclear Cells in the Cell-IQ System

The interaction of graphene oxide nanoparticles with human peripheral blood mononuclear cells was studied using the Cell-IQ continuous monitoring system for living cells. We used graphene oxide nanoparticles of various sizes coated with linear or branched polyethylene glycol (PEG) in concentrations of 5 and 25 μg/ml. After 24-h incubation with graphene oxide nanoparticles, the increase in the number of peripheral blood mononuclear cells at visualization points decreased; nanoparticles coated with branched PEG more markedly suppressed cell growth in culture. In the presence of graphene oxide nanoparticles, peripheral blood mononuclear cells retained high viability in culture after daily monitoring in the Cell-IQ system. The studied nanoparticles were engulfed by monocytes and the type of PEGylation had no effect on this process. Thus, graphene oxide nanoparticles reduced the increase in peripheral blood mononuclear cell mass during dynamic observation in the Cell-IQ system without reducing their viability.

Graphene in nanomedicine: A review on nano-bio factors and antibacterial activity

Graphene-based nanomaterials possess potent antibacterial activity and have engrossed immense interest among researchers as an active armour against pathogenic microbes. A comprehensive perception of the antibacterial activity of these nanomaterials is critical to the fabrication of highly effective antimicrobial nanomaterials, which results in highly efficient and enhanced activity. These materials owing to their antimicrobial activity are utilized as nanomedicine against various pathogenic microbes. The present article reviews the antimicrobial activity of graphene and its analogs such as graphene oxide, reduced graphene oxide as well as metal, metal oxide and polymeric composites. The review draws emphasis on the effect of various nano-bio factors on the antibacterial capability. It also provides an insight into the antibacterial properties of these materials along with a brief discussion on the discrepancies in their activities as evidenced by the scientific communities. In this way, the review is expected to shed light on future research and development in graphene-based nanomedicine.

Controllability, antiproliferative activity, Ag+ release, and flow behavior of silver nanoparticles deposited onto cellulose nanocrystals

Silver nanoparticles (AgNPs)/carboxylated cellulose nanocrystals (Ag-cCNC) from Eucalyptus pulp were prepared using a three-step process. The cCNC were synthesized by oxidation of CNC from Eucalyptus pulp with ammonium persulfate, followed by a hydrothermal reaction to form Ag-cCNC. The Ag-cCNC was then characterized with respect to Ag⁺ release, flow behavior, and anticancer activity for potential applications in biomedicine and drug delivery. AgNPs with particle sizes in the range of 16.25 ± 7.83 to 21.84 ± 7.21 nm were uniformly embedded on the surface of the cCNC. The Ag-cCNC exhibited a slow and controllable release of Ag⁺ at a rate of 0.02 % per day for 28 days. Ag⁺ release was best described by the Korsmeyer-Peppas model based on non-Fickian diffusion. The Ag-cCNC at 200 μg/mL exerted antiproliferative activity in MCF-7 human breast cancer cells with 1.01 % ± 0.35 % cell viability and was non-toxic against normal Vero cells with 90 % viability. In contrast, the chemotherapeutic drug melphalan exhibited cytotoxic effects against both MCF-7 and Vero cells. The Ag-cCNC samples showed shear thinning properties with a pseudoplastic fluid behavior, indicating that Ag-cCNCs are suitable for drug delivery by injection.

Gallium Metal-Organic Nanoparticles with Albumin-Stabilized and Loaded Graphene for Enhanced Delivery to HCT116 Cells

Background

Gallium (III) metal-organic complexes have been shown to have the ability to inhibit tumor growth, but the poor water solubility of many of the complexes precludes further application. The use of materials with high biocompatibility as drug delivery carriers for metal-organic complexes to enhance the bioavailability of the drug is a feasible approach.

Methods

Here, we modified the ligands of gallium 8-hydroxyquinolinate complex with good clinical anticancer activity by replacing the 8-hydroxyquinoline ligands with 5-bromo-8-hydroxyquinoline (HBrQ), and the resulting Ga(III) + HBrQ complex had poor water solubility. Two biocompatible materials, bovine serum albumin (BSA) and graphene oxide (GO), were used to synthesize the corresponding Ga(III) + HBrQ complex nanoparticles (NPs) BSA/Ga/HBrQ NPs and GO/Ga/HBrQ NPs in different ways to enhance the drug delivery of the metal complex.

Results

Both of BSA/Ga/HBrQ NPs and GO/Ga/HBrQ NPs can maintain stable existence in different solution states. In vitro cytotoxicity test showed that two nanomedicines had excellent anti-proliferation effect on HCT116 cells, which shown higher level of intracellular ROS and apoptosis ratio than that of cisplatin and oxaliplatin. In addition, the superior emissive properties of BSA/Ga/HBrQ NPs and GO/Ga/HBrQ NPs allow their use for in vivo imaging showing highly effective therapy in HCT116 tumor-bearing mouse models.

Conclusion

The use of biocompatible materials for the preparation of NPs against poorly biocompatible metal-organic complexes to construct drug delivery systems is a promising strategy that can further improve drug delivery and therapeutic efficacy.

Enhanced Antibacterial Effect on Zirconia Implant Abutment by Silver Linear-Beam Ion Implantation

Peri-implant lesions, such as peri-implant mucositis and peri-implantitis, are bacterial-derived diseases that happen around dental implants, compromising the long-term stability and esthetics of implant restoration. Here, we report a surface-modification method on zirconia implant abutment using silver linear-beam ion implantation to reduce the bacterial growth around the implant site, thereby decreasing the prevalence of peri-implant lesions. The surface characteristics of zirconia after ion implantation was evaluated using energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and a contact-angle device. The antibacterial properties of implanted zirconia were evaluated using Streptococcus mutans and Porphyromonas gingivalis. The biocompatibility of the material surface was evaluated using human gingival fibroblasts. Our study shows that the zirconia surface was successfully modified with silver nanoparticles by using the ion-implantation method. The surface modification remained stable, and the silver-ion elution was below 1 ppm after one-month of storage. The modified surface can effectively eliminate bacterial growth, while the normal gingiva's cell growth is not interfered with. The results of the study demonstrate that a silver-ion-implanted zirconia surface possesses good antibacterial properties and good biocompatibility. The surface modification using silver-ion implantation is a promising method for future usage.

Activation of Ibuprofen via Ultrasonic Complexation with Silver in N-Doped Oxidized Graphene Nanoparticles for Microwave Chemotherapy of Cervix Tumor Tissues

An ultrasonic method (20 kHz) is introduced to activate pristine ibuprofen organic molecular crystals via complexation with silver in nitrogen-doped oxidized graphene nanoplatforms (∼50 nm). Ultrasonic complexation occurs in a single-step procedure through the binding of the carboxylic groups with Ag and H-bond formation, involving noncovalent π_C=C → π_C=C* transitions in the altered phenyl ring and π_PY → π_CO* in ibuprofen occurring between the phenyl ring and C-O bonds as a result of interaction with hydroxyl radicals. The ibuprofen-silver complex in ≪NrGO≫ exhibits a ∼42 times higher acceleration rate than free ibuprofen of the charge transfer between hexacyanoferrate and thiosulfate ions. The increased acceleration rate can be caused by electron injection/ejection at the interface of the ≪Ag-NrGO≫ nanoplatform and formation of intermediate species (Fe(CN)₅(CNSO₃)^x- with x = 4 or 5 and AgHS₂O₃) at the excess of produced H⁺ ions. Important for microwave chemotherapy, ibuprofen-silver complexes in the ≪NrGO≫ nanoplatform can produce H⁺ ions at ∼12.5 times higher rate at the applied voltage range from 0.53 to 0.60 V. ≪Ibu-Ag-NrGO≫ NPs develop ∼10⁵ order higher changes of the electric field strength intensity than free ibuprofen in the microwave absorption range of 100-1000 MHz as revealed from the theoretical modeling of a cervix tumor tissue.

Covalent Organic Frameworks (COFs) as Multi-Target Multifunctional Frameworks

Covalent organic frameworks (COFs), synthesized from organic monomers, are porous crystalline polymers. Monomers get attached through strong covalent bonds to form 2D and 3D structures. The adjustable pore size, high stability (chemical and thermal), and metal-free nature of COFs make their applications wider. This review article briefly elaborates the synthesis, types, and applications (catalysis, environmental Remediation, sensors) of COFs. Furthermore, the applications of COFs as biomaterials are comprehensively discussed. There are several reported COFs having good results in anti-cancer and anti-bacterial treatments. At the end, some newly reported COFs having anti-viral and wound healing properties are also discussed.

Enhanced and sustained pesticidal activity of a graphene-based pesticide delivery system against the diamondback moth Plutella xylostella

BACKGROUND

Traditional abamectin (Abm) formulations have several shortcomings, such as low water solubility, burst release behavior, poor photostability, and short persistence periods, which decrease their pesticidal activity and the risks they pose to the environment. Nanomaterial-based pesticide delivery systems (PDSs) provide new strategies for the efficient and safe application of pesticides. Here, we developed Abm-loaded graphene oxide (Abm/GO) as a PDS for the sustained release of Abm, which shows enhanced control efficacy against Plutella xylostella.

RESULTS

The hydrophobic Abm molecule was effectively loaded on GO nanocarrier by a physisorption method, which formed a uniform and stable Abm/GO nanoformulation. GO possesses high adsorption capacity and can effectively load Abm. The Abm/GO nanoformulation shows enhanced water dispersion stability and can remain stable during a 2-year storage period in contrast to the water-insoluble Abm. In addition, the Abm/GO nanoformulation exhibits sustained pesticide release behavior and possesses significantly improved anti-ultraviolet properties. Thus, the Abm/GO nanoformulation shows superior pesticidal activity compared with Abm. Abm/GO showed negligible toxicity to maize seedlings, and its GO nanocarrier can reduce the cytotoxicity of Abm to A549 cells.

CONCLUSION

GO-based PDSs can effectively overcome the disadvantages of traditional pesticides, such as their insolubility, burst release behavior, instability, and short persistence period. GO shows much future promise in agriculture in light of its industrialization potential. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Antimicrobial Activity of Graphene-Based Nanocomposites: Synthesis, Characterization, and Their Applications for Human Welfare

Graphene (GN)-related nanomaterials such as graphene oxide, reduced graphene oxide, quantum dots, etc., and their composites have attracted significant interest owing to their efficient antimicrobial properties and thus newer GN-based composites are being readily developed, characterized, and explored for clinical applications by scientists worldwide. The GN offers excellent surface properties, i.e., a large surface area, pH sensitivity, and significant biocompatibility with the biological system. In recent years, GN has found applications in tissue engineering owing to its impressive stiffness, mechanical strength, electrical conductivity, and the ability to innovate in two-dimensional (2D) and three-dimensional (3D) design. It also offers a photothermic effect that potentiates the targeted killing of cells via physicochemical interactions. It is generally synthesized by physical and chemical methods and is characterized by modern and sophisticated analytical techniques such as NMR, Raman spectroscopy, electron microscopy, etc. A lot of reports show the successful conjugation of GN with existing repurposed drugs, which improves their therapeutic efficacy against many microbial infections and also its potential application in drug delivery. Thus, in this review, the antimicrobial potentialities of GN-based nanomaterials, their synthesis, and their toxicities in biological systems are discussed.

Recent Advances in the Development of Lipid-, Metal-, Carbon-, and Polymer-Based Nanomaterials for Antibacterial Applications

Infections caused by multidrug-resistant (MDR) bacteria are becoming a serious threat to public health worldwide. With an ever-reducing pipeline of last-resort drugs further complicating the current dire situation arising due to antibiotic resistance, there has never been a greater urgency to attempt to discover potential new antibiotics. The use of nanotechnology, encompassing a broad range of organic and inorganic nanomaterials, offers promising solutions. Organic nanomaterials, including lipid-, polymer-, and carbon-based nanomaterials, have inherent antibacterial activity or can act as nanocarriers in delivering antibacterial agents. Nanocarriers, owing to the protection and enhanced bioavailability of the encapsulated drugs, have the ability to enable an increased concentration of a drug to be delivered to an infected site and reduce the associated toxicity elsewhere. On the other hand, inorganic metal-based nanomaterials exhibit multivalent antibacterial mechanisms that combat MDR bacteria effectively and reduce the occurrence of bacterial resistance. These nanomaterials have great potential for the prevention and treatment of MDR bacterial infection. Recent advances in the field of nanotechnology are enabling researchers to utilize nanomaterial building blocks in intriguing ways to create multi-functional nanocomposite materials. These nanocomposite materials, formed by lipid-, polymer-, carbon-, and metal-based nanomaterial building blocks, have opened a new avenue for researchers due to the unprecedented physiochemical properties and enhanced antibacterial activities being observed when compared to their mono-constituent parts. This review covers the latest advances of nanotechnologies used in the design and development of nano- and nanocomposite materials to fight MDR bacteria with different purposes. Our aim is to discuss and summarize these recently established nanomaterials and the respective nanocomposites, their current application, and challenges for use in applications treating MDR bacteria. In addition, we discuss the prospects for antimicrobial nanomaterials and look forward to further develop these materials, emphasizing their potential for clinical translation.

Compare the physicochemical and biological properties of engineered polymer-functionalized silver nanoparticles against Porphyromonas gingivalis

Background

Some polymer-functionalized AgNPs (P-AgNPs) have been developed to optimize the biological properties of AgNPs. However, there are no studies in the literature comparing the differences in physicochemical and biological properties of AgNPs caused by various polymer-functionalizations and providing evidence for the selection of polymers to optimize AgNPs.

Methods

Two AgNPs with similar nano-size and opposite surface charges were synthesized and functionalized by seven polymers. Their physicochemical properties were evaluated by UV-Visible absorption, dynamic light scattering, transmission electron microscopy and inductively coupled plasma optical emission spectroscopy. Their biological properties against Porphyromonas gingivalis and human gingival fibroblast were investigated by MIC determination, time-dependent antibacterial assay, antibiofilm activity and cell viability assay. Silver diamine fluoride, AgNO3 and metronidazole were used as positive controls.

Results

Comparative analysis found that there were no significant differences between P-AgNPs and AgNPs in nano-size and in surface charge. Raman spectroscopy analysis provided evidence about the attachment of polymers on AgNPs. For antibacterial property, among the negatively charged AgNPs, only polyvinylpyrrolidone (PVP)-functionalized AgNPs-1 showed a significant lower MIC value than AgNPs-1 (0.79 vs. 4.72 μg/ml). Among the positively charged AgNPs, the MIC values of all P-AgNPs (0.34–4.37 μg/ml) were lower than that of AgNPs-2 (13.89 μg/ml), especially PVP- and Pluronic127-AgNPs-2 (1.75 and 0.34 μg/ml). For antibiofilm property, PVP-AgNPs-1 (7.86 μg/ml, P = 0.002) and all P-AgNPs-2 (3.42–31.14 μg/ml, P < 0.001) showed great antibiofilm effect against P. gingivalis biofilm at 5* to 10*MIC level. For cytotoxicity, all negatively charged AgNPs and PVP-AgNPs-2 showed no cytotoxicity at MIC level, but significant cytotoxicity was detected at 2.5* to 10*MIC levels.

Conclusion

Among the polymers studied, polymer functionalization does not significantly alter the physical properties of AgNPs, but modifies their surface chemical property. These modifications, especially the functionalization of PVP, contribute to optimize the antibacterial and antibiofilm properties of AgNPs, while not causing cytotoxicity at the MIC level.

Co-spray-dried poly-L-lysine with L-leucine as dry powder inhalations for the treatment of pulmonary infection: Moisture-resistance and desirable aerosolization performance

Poly-L-lysine (PLL) is a promising candidate for the treatment of pulmonary infection with lower occurrence of drug-resistance due to its unique antibacterial mechanisms. Dry powder inhalations (DPIs) are considered as the first choice for formulating PLL to treat pulmonary infection on account of direct delivery and satisfactory stability. However, hygroscopicity of PLL limited its therapeutic effect on pulmonary infection when PLL developed into DPIs. The hygroscopicity caused two obstacles including the low drug deposition in the lower respiratory tract and undesirable aerosolization performance deterioration. In this study, PLL was co-spray-dried with L-leucine (LL) to achieve moisture-resistance and desirable aerosolization performance. The ratio of PLL and LL was optimized to obtain particles with different morphology, hygroscopicity and aerodynamic properties. The obtained PLL DPIs were suitable for inhalation with a corrugated surface formed by hydrophobic LL. The anti-hygroscopicity, aerosolization performance and rheological properties of P2 DPIs were optimal when PLL:LL = 85:15. The DPIs particles were stable after being stored at high relative humidity (60 ± 5%), and their superiority in treating pulmonary infections was also proved by in vitro and in vivo experiments. The established PLL DPIs were proved to be a feasible and desirable approach to treat pulmonary infections.

Self-polishing antifouling coatings based on benzamide derivatives containing capsaicin

In this study, N-hydroxymethylbenzamide was alkylated with various aromatic compounds to obtain five novel benzamide derivatives containing capsaicin (BDCC), and the BDCC were incorporated into coatings as auxiliary agents. The relationships between properties and structures were discussed based on experimental and theoretical results. The theoretical results showed the optimized configurations of BDCC and confirmed that the benzene ring, phenolic hydroxyl, ester and amide groups were active sites. Experimental results indicated that the antimicrobial and antifouling effects of compounds b1, b2 and b3 were better than those of chlorothalonil, their MIC and MBC values were no more than 64 and 512 μg·mL-1, and their test panels were covered only with small amounts of dirt and biofilms; they worked well as green antifouling additives. The experimental and theoretical results showed that BDCC and BDCC antifouling coatings were effective and eco-friendly.

Antibacterial Designs for Implantable Medical Devices: Evolutions and Challenges

The uses of implantable medical devices are safer and more common since sterilization methods and techniques were established a century ago; however, device-associated infections (DAIs) are still frequent and becoming a leading complication as the number of medical device implantations keeps increasing. This urges the world to develop instructive prevention and treatment strategies for DAIs, boosting the studies on the design of antibacterial surfaces. Every year, studies associated with DAIs yield thousands of publications, which here are categorized into four groups, i.e., antibacterial surfaces with long-term efficacy, cell-selective capability, tailored responsiveness, and immune-instructive actions. These innovations are promising in advancing the solution to DAIs; whereas most of these are normally quite preliminary “proof of concept” studies lacking exact clinical scopes. To help identify the flaws of our current antibacterial designs, clinical features of DAIs are highlighted. These include unpredictable onset, site-specific incidence, and possibly involving multiple and resistant pathogenic strains. The key point we delivered is antibacterial designs should meet the specific requirements of the primary functions defined by the “intended use” of an implantable medical device. This review intends to help comprehend the complex relationship between the device, pathogens, and the host, and figure out future directions for improving the quality of antibacterial designs and promoting clinical translations.

Enhanced Antibacterial Activity through Silver Nanoparticles Deposited onto Carboxylated Graphene Oxide Surface

The strong bactericidal action of silver nanoparticles (AgNPs) is usually limited by their degree of aggregation. Deposition of AgNPs onto a graphene oxide (GO) surface to generate GO-Ag hybrids has been shown to be an effective method of controlling these aggregation problems. In this sense, a novel carboxylated graphene oxide–silver nanoparticle (GOCOOH-Ag) material has been synthesized, and their antibacterial and biofilm formation inhibitions have been studied. AgNPs decorating the GOCOOH surface achieved an average size of 6.74 ± 0.25 nm, which was smaller than that of AgNPs deposited onto the GO surface. In addition, better distribution of AgNPs was achieved using carboxylated material. It is important to highlight the main role of the carboxylic groups in the nucleation and growth of the AgNPs that decorate the GO-based material surface. In vitro antibacterial activity and antibiofilm-forming action were tested against Gram-positive (Staphylococcus aureus and Staphylococcus epidermidis) and Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli). Both GO-Ag and GOCOOH-Ag reduced bacterial growth, analyzed by time–kill curves. However, the minimum inhibitory concentration and the minimum bactericidal concentration of GOCOOH-Ag were lower than those of GO-Ag for all strains studied, indicating that GOCOOH-Ag has better antibacterial activity. In addition, both nanomaterials prevent biofilm formation, with a higher reduction of biofilm mass and cell viability in the presence of GOCOOH-Ag. The carboxylation functionalization in GO-based materials can be applied to improve the bactericidal and antibiofilm-forming action of the AgNPs.

Ni Nanocrystals Supported on Graphene Oxide: Antibacterial Agents for Synergistic Treatment of Bacterial Infections

The effects of antibiotics on bacterial infections are gradually weakened, leading to the wide development of nanoparticle-based antibacterial agents with unique physical and chemical properties and antibacterial mechanisms different from antibiotics. In this study, we fabricated the uniform and stable graphene oxide (GO)/Ni colloidal nanocrystal cluster (NCNC) nanocomposite by electrostatic self-assembly and investigated its synergistic antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro. The GO/NCNC nanocomposite was shown to possess higher inhibition efficiency than a pure NCNC or GO suspension, with 99.5 and 100% inhibition against S. aureus and E. coli at a 125 μg/mL concentration, respectively. Antibacterial mechanism analysis revealed that (i) NCNCs decorated on GO can further enhance the antibacterial properties of GO by binding and capturing bacteria, (ii) the leaching of Ni²⁺ was detected during the interaction of GO/NCNCs and bacteria, resulting in a decrease in the number of bacteria, and (iii) the GO/NCNC nanocomposite can synergistically destroy the bacterial membrane through physical action and induce the reactive oxygen species generation, so as to further damage the cell membrane and affect ATPase, leakage of intercellular contents, and ultimately bacterial growth inhibition. Meanwhile, cell culture experiments demonstrated no adverse effect of GO/NCNCs on cell growth. These preliminary results indicate the high antibacterial efficiency of the GO/NCNC nanocomposite, suggesting the possibility to develop it into an effective antibacterial agent in the future against bacterial infections.

Insight into the antibacterial resistance of graphdiyne functionalized by silver nanoparticles

OBJECTIVES

Silver nanoparticles (AgNPs) tend to aggregate spontaneously due to larger surface-to-volume ratio, which causes decreased antibacterial activity and even enhanced antimicrobial resistance (AMR). Here, we aim to improve the stability of AgNPs by employing a growth anchor graphdiyne (GDY) to overcome these shortcomings.

MATERIALS AND METHODS

Bacillus subtilis and Escherichia coli were selected to represent gram-positive and gram-negative bacteria, respectively. Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM)-EDS mapping and inductively coupled plasma mass spectrometry (ICP-MS) were carried out to characterize the physiochemical properties of materials. The antimicrobial property was determined by turbidimetry and plate colony-counting methods. The physiology of bacteria was detected by SEM and confocal imaging, such as morphology, reactive oxygen species (ROS) and cell membrane.

RESULTS

We successfully synthesized a hybrid graphdiyne @ silver nanoparticles (GDY@Ag) by an environment-friendly approach without any reductants. The hybrid showed high stability and excellent broad-spectrum antibacterial activity towards both gram-positive and gram-negative bacteria. It killed bacteria through membrane destruction and ROS production. Additionally, GDY@Ag did not induce the development of the bacterial resistance after repeated exposure.

CONCLUSIONS

GDY@Ag composite combats bacteria by synergetic action of GDY and AgNPs. Especially, GDY@Ag can preserve its bacterial susceptibility after repeated exposure compared to antibiotics. Our findings provide an avenue to design innovative antibacterial agents for effective sterilization.

Restoration of antibacterial activity of inactive antibiotics via combined treatment with a cyanographene/Ag nanohybrid

The number of antibiotic-resistant bacterial strains is increasing due to the excessive and inappropriate use of antibiotics, which are therefore becoming ineffective. Here, we report an effective way of enhancing and restoring the antibacterial activity of inactive antibiotics by applying them together with a cyanographene/Ag nanohybrid, a nanomaterial that is applied for the first time for restoring the antibacterial activity of antibiotics. The cyanographene/Ag nanohybrid was synthesized by chemical reduction of a precursor material in which silver cations are coordinated on a cyanographene sheet. The antibacterial efficiency of the combined treatment was evaluated by determining fractional inhibitory concentrations (FIC) for antibiotics with different modes of action (gentamicin, ceftazidime, ciprofloxacin, and colistin) against the strains Escherichia coli, Pseudomonas aeruginosa, and Enterobacter kobei with different resistance mechanisms. Synergistic and partial synergistic effects against multiresistant strains were demonstrated for all of these antibiotics except ciprofloxacin, which exhibited an additive effect. The lowest average FICs equal to 0.29 and 0.39 were obtained for colistin against E. kobei and for gentamicin against E. coli, respectively. More importantly, we have experimentally confirmed for the first time, that interaction between the antibiotic's mode of action and the mechanism of bacterial resistance strongly influenced the combined treatment’s efficacy.

Poly (vinyl alcohol)/chitosan/polyethylene glycol-assembled graphene oxide bio-nanocomposites as a prosperous candidate for biomedical applications and drug/food packaging industry

The graphene oxide (GO) nanoplates and polyethylene glycol-decorated GO (GO-PEG nano-hybrid) were synthesized and characterized by FTIR, Raman, XRD, AFM, FE-SEM-EDAX and MTT assay. Obtained results confirmed the graphite oxidation and also assembly of PEG upon GO plates. The MTT assay indicated that GO-PEG nanohybrid enhanced biocompatibility to cells compared to the GO. The GO-PEG nanohybrid was introduced to the polyvinyl alcohol/chitosan carbohydrate (PVA/CS) blends. The bio-nanocomposite were prepared by simple casting method. The GO-PEG nanohybrids demonstrated a significant role in improving thermal, mechanical and antibacterial properties. Accordingly, bio-nanocomposites containing modified GO (PVA/CS/GO-PEG) exhibited higher glass transition temperature (Tg), Young's modulus, tensile strength, elongation at break and antibacterial properties than nanocomposites containing pure GO (PVA/CS/GO). The biodegradation outcomes indicated that the highest weight loss and degradability is related to the bio-nanocomposite containing modified GO (PVA/CS/GO-PEG), which was also confirmed by FE-SEM micrographs. Therefore, PVA/CS/GO-PEG bio-nanocomposites can be a suitable candidate for biomedical applications (tissue engineering, wound dressing) and food-drug packaging industry.

Quaternized carbon quantum dots with broad-spectrum antibacterial activity for the treatment of wounds infected with mixed bacteria

Bacterial resistance to antibiotics have become one of the most severe threats in global public health, so the development of new-style antimicrobial agents is urgent. In this work, quaternized carbon quantum dots (qCQDs) with broad-spectrum antibacterial activity were synthesized by a simple green "one-pot" method using dimethyl diallyl ammonium chloride and glucose as reaction precursors. The qCQDs displayed satisfactory antibacterial activity against both Gram-positive and gram-negative bacteria. In rat models of wounds infected with mixed bacteria, qCQDs obviously restored the weight of rats, significantly reduced the death of rats from severe infection, and promoted the recovery and healing of infected wounds. Biosafety tests confirmed that qCQDs had no obvious toxic and side effects during the testing stage. The analysis of quantitative proteomics revealed that qCQDs mainly acted on ribosomal proteins in Staphylococcus aureus (Gram-positive bacteria) and significantly down-regulated proteins associated with citrate cycle in Escherichia coli (Gram-negative bacteria). Meanwhile, real-time quantitative PCR confirmed that the variation trend of genes corresponding to the proteins associated with ribosome and citrate cycle was consistent with the proteomic results after treatment of qCQDs, suggesting that qCQDs has a new antibacterial mechanism which is different from the reported carbon quantum dots with antibacterial action. STATEMENT OF SIGNIFICANCE: With the development of the research on carbon quantum dots, the application of carbon quantum dots in the field of medicine has attracted extensive attention. In this paper, quaternized carbon quantum dots (qCQDs) with antimicrobial activity prepared by specific methods were studied, including antimicrobial spectrum, antimicrobial mechanism and in vivo antimicrobial application. The antimicrobial mechanism of qCQDs was studied by proteomics and RT-qRCR, and the different mechanisms of qCQDs against Gram-positive and Gram-negative bacteria were also found. This study provides a research foundation for the application of carbon quantum dots in antimicrobial field, and also expands the application range of carbon quantum dots in medicine field.