Antibacterial activity of graphene oxide nanosheet against multidrug resistant superbugs isolated from infected patients

Emerging trends and future challenges of advanced 2D nanomaterials for combating bacterial resistance

The number of multi-drug-resistant bacteria has increased over the last few decades, which has caused a detrimental impact on public health worldwide. In resolving antibiotic resistance development among different bacterial communities, new antimicrobial agents and nanoparticle-based strategies need to be designed foreseeing the slow discovery of new functioning antibiotics. Advanced research studies have revealed the significant disinfection potential of two-dimensional nanomaterials (2D NMs) to be severed as effective antibacterial agents due to their unique physicochemical properties. This review covers the current research progress of 2D NMs-based antibacterial strategies based on an inclusive explanation of 2D NMs' impact as antibacterial agents, including a detailed introduction to each possible well-known antibacterial mechanism. The impact of the physicochemical properties of 2D NMs on their antibacterial activities has been deliberated while explaining the toxic effects of 2D NMs and discussing their biomedical significance, dysbiosis, and cellular nanotoxicity. Adding to the challenges, we also discussed the major issues regarding the current quality and availability of nanotoxicity data. However, smart advancements are required to fabricate biocompatible 2D antibacterial NMs and exploit their potential to combat bacterial resistance clinically.

Antimicrobial coatings based on amine-terminated graphene oxide and Nafion with remarkable thermal resistance

We present a novel type of layer-by-layer (LbL) waterborne coating based on Nafion and amine-terminated graphene oxide (GO-NH2) that inhibits the growth of Escherichia coli and Staphylococcus aureus by more than 99% and this performance is not compromised upon extensive thermal annealing at 200 °C. Quartz crystal microbalance (QCM) sensorgrams allow the real time monitoring of the build-up of the LbL assemblies, a process that relies on the strong electrostatic interactions between Nafion (pH = 2.7, ζ = -54.8 mV) and GO-NH2 (pH = 2, ζ = 26.7 mV). Atomic force microscopy (AFM), contact angle and zeta potential measurements were used to characterise the multilayer assemblies. We demonstrate here that Nafion/GO-NH2 advanced coatings can offer drug-free and long-lasting solutions to microbial colonization and can withstand dry heat sterilization, without any decline in their performance.

Ciprofloxacin-, Cefazolin-, and Methicilin-Soaked Graphene Paper as an Antibacterial Medium Suppressing Cell Growth

This paper presents the results of research on the impact of graphene paper on selected bacterial strains. Graphene oxide, from which graphene paper is made, has mainly bacteriostatic properties. Therefore, the main goal of this research was to determine the possibility of using graphene paper as a carrier of a medicinal substance. Studies of the degree of bacterial inhibition were performed on Staphylococcus aureus and Pseudomonas aeruginosa strains. Graphene paper was analyzed not only in the state of delivery but also after the incorporation of the antibiotics ciprofloxacin, cefazolin, and methicillin into its structures. In addition, Fourier-Transform Infrared Spectroscopy, contact angle, and microscopic analysis of bacteria on the surface of the examined graphene paper samples were also performed. Studies have shown that graphene paper with built-in ciprofloxacin had a bactericidal effect on the strains of Staphylococcus aureus and Pseudomonas aeruginosa. In contrast, methicillin, as well as cefazolin, deposited on graphene paper acted mainly locally. Studies have shown that graphene paper can be used as a carrier of selected medicinal substances.

Impact of graphene oxide nanosheets and polymethyl methacrylate on nano/hybrid-based restoration dental filler composites: ultrasound behavior and antibacterial activity

PURPOSE

Graphene-polymer nanocomposites significantly impact dental filler and antibacterial applications. The study aims to overcome some problems dental filers present and improve their properties and antibacterial activity. Synthesis graphene oxide (GO) and poly (methyl methacrylate) (PMMA) were used to reinforce two types of commercial hybrid/nano-dental fillings.

METHODS

Developed acoustic-solution-sonication-casting methods were applied to fabricate the new graphene-polymer-dental filler nanocomposites. The structure, morphology, rheological and mechanical properties, and antibacterial of the newly fabricated filling-PMMA/ GO nanocomposites were investigated.

RESULTS

Fourier transform infrared (FTIR) showed a significant interaction between the filling and the additional materials. The X-ray diffraction (XRD) analysis revealed a considerable change in crystalline behavior. Optical microscope (OM) with field emission scanning electron microscopy (FESEM) pictures demonstrated a substantial change in the morphology of the samples with a homogeneous and fine dispersion of the nanomaterials in the filler matrix. Multi-frequency ultrasound mechanical properties measured the ultrasonic velocity, absorption coefficient, compressibility, bulk modulus, and other mechanical properties that notably enhanced after GO contributed up to 325% of the ultrasonic absorption coefficient compared with hybrid/nano-fillers. Rheological properties were measured as viscosity, absorption coefficient, and specific viscosity, which significantly improved after adding PMMA and incorporating GO up to 57% of the viscosity, compared with hybrid/nano-fillers. The inhibition zone of moth bacteria, such as Enterococcus faecalis and E. staph bacteria, improved after the contribution of GO nanosheets up to 46%.

CONCLUSION

Nanofillers nanocomposites presented better properties and inhabitances zone diameter of antibacterial.

Graphene-Based Composites for Biomedical Applications: Surface Modification for Enhanced Antimicrobial Activity and Biocompatibility

The application of graphene-based materials in medicine has led to significant technological breakthroughs. The remarkable properties of these carbon materials and their potential for functionalization with various molecules and compounds make them highly attractive for numerous medical applications. To enhance their functionality and applicability, extensive research has been conducted on surface modification of graphene (GN) and its derivatives, including modifications with antimicrobials, metals, polymers, and natural compounds. This review aims to discuss recent and relevant studies related to advancements in the formulation of graphene composites, addressing their antimicrobial and/or antibiofilm properties and evaluating their biocompatibility, with a primary focus on their biomedical applications. It was concluded that GN surface modification, particularly with compounds intrinsically active against bacteria (e.g., antimicrobial peptides, silver and copper nanomaterials, and chitosan), has resulted in biomaterials with improved antimicrobial performance. Furthermore, the association of GN materials with non-natural polymers provides composites with increased biocompatibility when interfaced with human tissues, although with slightly lower antimicrobial efficacy. However, it is crucial to highlight that while modified GN materials hold huge potential, their widespread use in the medical field is still undergoing research and development. Comprehensive studies on safety, long-term effects, and stability are essential before their adoption in real-world medical scenarios.

Effect of Graphene Oxide and Silver Nanoparticle Hybrid Composite on Acinetobacter baumannii Strains, Regarding Antibiotic Resistance and Prevalence of AMP-C Production

Background and Objectives: Growing antibiotic resistance among bacteria is a global issue that is becoming harder and more expensive to solve. Traditional treatment options are becoming less effective, causing more fatal outcomes of nosocomial infections. Since the development of new antibiotics has stagnated in the last decade, a novel approach is needed. Materials and Methods: Graphene-based materials are being developed and tested for various applications, and the medical field is no exception. We tested 98 clinical A. baumannii strains for antibiotic resistance, AMP-C production and the effectiveness of a graphene oxide and silver nanoparticle hybrid nanocomposite. The disc diffusion method was used to determine antibiotic susceptibility results. Antibiotic discs containing cefotaxime, cloxacillin and clavulanate were used to detect AMP-C production. The effectiveness of the GO-Ag hybrid nanocomposite was determined by counting colony forming units (CFUs) after a suspension of A. baumannii and the GO-Ag hybrid nanocomposite was plated on MH agar and incubated overnight to grow colonies. Results: In our research, we found that A. baumannii strains are resistant to the majority of commonly used antibiotics. Antibiotic resistance levels and AMP-C production can be factors, indicating the better effectiveness of the graphene oxide and silver nanoparticle hybrid nanocomposite. Conclusions: In this study, a GO-Ag hybrid nanocomposite was shown to have the potential to fight even the most problematic bacteria like A. baumannii.

Injectable hydrogel based on silk fibroin/carboxymethyl cellulose/agarose containing polydopamine functionalized graphene oxide with conductivity, hemostasis, antibacterial, and anti-oxidant properties for full-thickness burn healing

Overcoming bacterial infections and promoting wound healing are significant challenges in clinical practice and fundamental research. This study developed a series of enzymatic crosslinking injectable hydrogels based on silk fibroin (SF), carboxymethyl cellulose (CMC), and agarose, with the addition of polydopamine functionalized graphene oxide (GO@PDA) to endow the hydrogel with suitable conductivity and antimicrobial activity. The hydrogels exhibited suitable gelation time, stable mechanical and rheological properties, high water absorbency, and hemostatic properties. Biocompatibility was also confirmed through various assays. After loading the antibiotic vancomycin hydrochloride, the hydrogels showed sustained release and good antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). The fast gelation time and desirable tissue-covering ability of the hydrogels allowed for a good hemostatic effect in a rat liver trauma model. In a rat full-thickness burn wound model, the hydrogels exhibited an excellent treatment effect, leading to significantly enhanced wound closure, collagen deposition, and granulation tissue formation, as well as neovascularization and anti-inflammatory effects. In conclusion, the antibacterial electroactive injectable hydrogel dressing, with its multifunctional properties, significantly promoted the in vivo wound healing process, making it an excellent candidate for full-thickness skin wound healing.

Can Graphene Pave the Way to Successful Periodontal and Dental Prosthetic Treatments? A Narrative Review

Graphene, as a promising material, holds the potential to significantly enhance the field of dental practices. Incorporating graphene into dental materials imparts enhanced strength and durability, while graphene-based nanocomposites offer the prospect of innovative solutions such as antimicrobial dental implants or scaffolds. Ongoing research into graphene-based dental adhesives and composites also suggests their capacity to improve the quality and reliability of dental restorations. This narrative review aims to provide an up-to-date overview of the application of graphene derivatives in the dental domain, with a particular focus on their application in prosthodontics and periodontics. It is important to acknowledge that further research and development are imperative to fully explore the potential of graphene and ensure its safe use in dental practices.

Bactericidal Activity of Graphene Oxide Tests for Selected Microorganisms

The aim of this study was to determine the bactericidal potential of graphene oxide (GO) in contact with four species of bacteria: E. coli, S. mutans, S. aureus and E. faecalis. Bacterial cell suspensions of each species were incubated in a medium containing GO, with incubation times of 5, 10, 30 and 60 min, at final concentrations of 50, 100, 200, 300 and 500 μg/mL. The cytotoxicity of GO was evaluated using live/dead staining. The results were recorded using a BD Accuri C6 flow cytofluorimeter. Obtained data were analyzed using BD CSampler software. A significant bacteria viability reduction was noted in all GO-containing samples. The antibacterial properties of GO were strongly influenced by GO concentration and incubation time. The highest bactericidal activity was observed at concentrations of 300 and 500 μg/mL for all incubation times (5, 10, 30 and 60 min). The highest antimicrobial potential was observed for E. coli: after 60 min, the mortality rate was 94% at 300 µg/mL GO and 96% at 500 µg/mL GO; the lowest was found for S. aureus-49% (300 µg/mL) and 55% (500 µg/mL).

Recent advances and mechanism of antimicrobial efficacy of graphene-based materials: a review

Graphene-based materials have undergone substantial investigation in recent years owing to their wide array of physicochemical characteristics. Employment of these materials in the current state, where infectious illnesses caused by microbes have severely damaged human life, has found widespread application in combating fatal infectious diseases. These materials interact with the physicochemical characteristics of the microbial cell and alter or damage them. The current review is dedicated to molecular mechanisms underlying the antimicrobial property of graphene-based materials. Various physical and chemical mechanisms leading to cell membrane stress, mechanical wrapping, photo-thermal ablation as well as oxidative stress exerting antimicrobial effect have also been thoroughly discussed. Furthermore, an overview of the interactions of these materials with membrane lipids, proteins, and nucleic acids has been provided. A thorough understanding of discussed mechanisms and interactions is essential to develop extremely effective antimicrobial nanomaterial for application as an antimicrobial agent.

Graphical abstract

Nanoantibiotic effect of carbon-based nanocomposites: epicentric on graphene, carbon nanotubes and fullerene composites: a review

Carbon in many different forms especially, Graphene, Carbon nanotubes (CNTs), and Fullerene is emerging as an important material in the areas of the biomedical field for various applications. This review comprehensively describes the nano antibiotic effect of carbon-based nanocomposites: epicenter on graphene, carbon nanotubes, and fullerene Composites. It summarises the studies conducted to evaluate their antimicrobial applications as they can disrupt the cell membrane of bacteria resulting in cell death. The initial section gives a glimpse of both "Gram"-positive and negative bacteria, which have been affected by Graphene, CNTs, and Fullerene-based nanocomposites. These bacteria include Staphylococcus Aureus, Bacillus Thuringiensis, Enterococcus faecalis, Enterococcus faecium, Bacillus subtilis, Escherichia coli, Klebseilla pneumoniae, Pseudomonas aeroginosa, Pseudomonas syringae , Shigella flexneri,Candida Albicans, Mucor. Another section is dedicated to the insight of Graphene, and its types such as Graphene Oxide (GO), Reduced graphene oxide (rGO), Graphene Nanoplatelets (GNPs), Graphene Nanoribbons (GNRs), and Graphene Quantum Dots (GQDs). Insight into CNT, including both the types SWCNT and MWCNT, studied, followed by understanding fullerene is also reported. Another section is dedicated to the antibacterial mechanism of Graphene, CNT, and Fullerene-based nanocomposites. Further, an additional section is dedicated to a comprehensive review of the antibacterial characteristics of Graphene, CNT, and nanocomposites based on fullerene. Future perspectives and recommendations have also been highlighted in the last section.

Microspheres with 2D rGO/Alginate Matrix for Unusual Prolonged Release of Cefotaxime

A synergistic interaction between reduced graphene oxide (rGO) and a biodegradable natural polymer, sodium alginate, was developed to create unique microspheres with protruding spiky features at the surface (spiky microspheres) that act as a super encapsulation and sustained release system for the highly effective antibiotic cefotaxime. Three forms of microspheres, namely alginate (Alg), alginate-cefotaxime (Alg-CTX), and alginate-cefotaxime-reduced graphene (Alg-CTX-rGO) composites, were prepared using calcium chloride as a cross-linking agent. The microspheres were characterized using field emission scanning electron microscopy (FESEM), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray diffraction to investigate their pores, roughness, surface morphology, functional groups, phase formation, purity, and structural properties. The membrane diffusion method was employed to determine the release profile of Cefotaxime from the fabricated microspheres. The antibacterial activities of CTX solution, Alg microspheres, Alg-CTX microspheres, and Alg-CTX-rGO microspheres were investigated against gram-negative bacteria (Escherichia coli) using the agar diffusion method on Muller-Hinton agar. The prepared samples exhibited excellent results, suggesting their potential for enhanced antibiotic delivery. The results demonstrated the potential of the microsphere 2D rGO/alginate matrix for enhancing cefotaxime delivery with an unusual, prolonged release profile.

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.

A novel bioactive glass/graphene oxide composite coating for a polyether ether ketone-based dental implant

Polyether ether ketone (PEEK) is a biocompatible material that lacks antimicrobial activity and bioactivity; therefore, is not appropriate for use as a dental implant. To overcome these deficiencies, a novel composite coating of bioactive glass and graphene oxide was prepared. PEEK discs were polished, cleaned, and the surface treated with sulfuric acid for 15 min. The composite coating consisted of bioactive glass produced by the sol-gel route and doped with 0.75 wt% graphene oxide. X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy-energy dispersive spectroscopy analyses were employed to characterize the composite coating, and the coating adhesion strength quantified using a pull-off test. Cytotoxicity was assessed using osteoblast-like cells and gingival fibroblasts. The wettability of the coated and non-coated samples was determined by optical contact angle assessment, and bioactivity was assessed by immersion in simulated body fluid. The results revealed that the bioactive glass/graphene oxide composite coating, approximately 7 μm thick, was transparent, homogenous with few microcracks and microporosities, but adhered strongly and was not cytotoxic to either osteoblast-like cells or gingival fibroblasts. The wettability of the PEEK sample was increased to <20° after coating with the composite, and apatite formation was detectable after 14 days of immersion in simulated body fluid.

Friends against the Foe: Synergistic Photothermal and Photodynamic Therapy against Bacterial Infections

Multidrug-resistant (MDR) bacteria are rapidly emerging, coupled with the failure of current antibiotic therapy; thus, new alternatives for effectively treating infections caused by MDR bacteria are required. Hyperthermia-mediated photothermal therapy (PTT) and reactive oxygen species (ROS)-mediated photodynamic therapy (PDT) have attracted extensive attention as antibacterial therapies owing to advantages such as low invasiveness, low toxicity, and low likelihood of causing bacterial resistance. However, both strategies have notable drawbacks, including the high temperature requirements of PTT and the weak ability of PDT-derived ROS to penetrate target cells. To overcome these limitations, a combination of PTT and PDT has been used against MDR bacteria. In this review, we discuss the unique benefits and limitations of PTT and PDT against MDR bacteria. The mechanisms underlying the synergistic effects of the PTT–PDT combination are also discussed. Furthermore, we introduced advancements in antibacterial methods using nano-based PTT and PDT agents to treat infections caused by MDR bacteria. Finally, we highlight the existing challenges and future perspectives of synergistic PTT–PDT combination therapy against infections caused by MDR bacteria. We believe that this review will encourage synergistic PTT- and PDT-based antibacterial research and can be referenced for future clinical applications.

One-pot facile synthesis of hexagonal Bi2Te3 nanosheets and its novel nanocomposites: Characterization, anticancer, antibacterial, and antioxidant activities

Bismuth Telluride (Bi₂Te₃) layered structure results in extraordinary features in diagnostic and therapeutic applications. However, Bi₂Te₃ synthesis with reliable stability and biocompatibility in biological systems was the major challenge that limited its biological application. Herein, reduced graphene oxide (RGO) or graphitic carbon nitride (CN) nanosheets were incorporated into Bi₂Te₃ matrix to improve exfoliation. Bi₂Te₃ nanoparticles (NPs) and its novel nanocomposites (NCs): CN@Bi₂Te₃ and CN-RGO@Bi₂Te₃ were solvothermally synthesized, physiochemically characterized and assessed for their anticancer, antioxidant, and antibacterial activities. X-ray diffraction depicted Bi₂Te₃ rhombohedral lattice structure. Fourier-transform infrared and Raman spectra confirmed NC formation. Scanning and transmission electron microscopy revealed 13 nm thickness and 400-600 nm diameter of hexagonal, binary, and ternary nanosheets of Bi₂Te₃-NPs/NCs. Energy dispersive X-ray Spectroscopy revealed the presence of Bi, Te, and carbon atoms in the tested NPs with negatively charged surfaces as depicted by zeta sizer. CN-RGO@Bi₂Te₃-NC displayed the smallest nanodiameter (359.7 nm) with the highest Brunauer-Emmett-Teller surface area and antiproliferative activity against MCF-7, HepG2 and Caco-2. Bi₂Te₃-NPs had the greatest scavenging activity (96.13 ± 0.4%) compared to the NCs. The NPs inhibitory activity was greater against Gram-negative bacteria than that of Gram-positive bacteria. Integration of RGO and CN with Bi₂Te₃-NPs enhanced their physicochemical properties and therapeutic activities giving rise to their promising capacity for future biomedical applications.

Biofilms in Chronic Wound Infections: Innovative Antimicrobial Approaches Using the In Vitro Lubbock Chronic Wound Biofilm Model

Chronic wounds have harmful effects on both patients and healthcare systems. Wound chronicity is attributed to an impaired healing process due to several host and local factors that affect healing pathways. The resulting ulcers contain a wide variety of microorganisms that are mostly resistant to antimicrobials and possess the ability to form mono/poly-microbial biofilms. The search for new, effective and safe compounds to handle chronic wounds has come a long way throughout the history of medicine, which has included several studies and trials of conventional treatments. Treatments focus on fighting the microbial colonization that develops in the wound by multidrug resistant pathogens. The development of molecular medicine, especially in antibacterial agents, needs an in vitro model similar to the in vivo chronic wound environment to evaluate the efficacy of antimicrobial agents. The Lubbock chronic wound biofilm (LCWB) model is an in vitro model developed to mimic the pathogen colonization and the biofilm formation of a real chronic wound, and it is suitable to screen the antibacterial activity of innovative compounds. In this review, we focused on the characteristics of chronic wound biofilms and the contribution of the LCWB model both to the study of wound poly-microbial biofilms and as a model for novel treatment strategies.

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.

Silver nanoparticles loaded graphene-poly-vinylpyrrolidone composites as an effective recyclable antimicrobial agent

Silver nanoparticles (AgNPs) are often used as antibacterial agents. Here, graphene-silver nanoparticles (G-Ag) and graphene-silver nanoparticles poly-vinylpyrrolidone (G-AgPVPy) were prepared by chemical reduction and in-situ polymerization of vinylpyrrolidone (VPy). The prepared G-Ag and G-AgPVPy composites were characterized using various techniques. The size of the AgNPs on the graphene surface in the prepared G-Ag and G-AgPVPy composites was measured as ∼20 nm. The graphene sheets size in the G-Ag and G-AgPVPy composites were measured as 6.0-2.0 μm and 4.0-0.10 μm, respectively, which are much smaller than graphene sheets in graphite powder (GP) (10.0-3.0 μm). The physicochemical analysis confirmed the formation of G-Ag and G-AgPVPy composites and even the distribution of AgNPs and PVPy on the graphene sheets. The synthesized composites (G-AgPVPy, G-Ag) exhibited a broad-spectrum antibacterial potential against both Gram-negative and Gram-positive bacteria. The lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were calculated as >40 μg/mL using G-Ag and GP, while G-AgPVPy showed as 10 μg/mL against Staphylococcus aureus. Among GP, G-Ag, and G-AgPVPy, G-AgPVPy disturbs the cell permeability, damages the cell walls, and causes cell death efficiently. Also, G-AgPVPy was delivered as a significant reusable antibacterial potential candidate. The MIC value (10 μg/mL) did not change up to six subsequent MIC analysis cycles.

Synthesis and characterization of Ag2O, CoFe2O4, GO, and their ternary composite for antibacterial activity

Currently, nanomaterials with exceptional antibacterial activity have become an emerging domain in research. The optimization of nanomaterials against infection causing agents is the next step in dealing with the present-day problem of antibiotics. In this research work, Ag₂O, CoFe₂O₄, and Ag₂O/CoFe₂O₄/rGO are prepared by chemical methods. Ag₂O was prepared by co-precipitation method, while solvothermal technique was utilized for the synthesis of CoFe₂O₄. The ternary nanocomposite was synthesized by a simple in situ reduction using a two-step approach. The structural and morphological properties were studied by UV-Vis spectroscopy, X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (SEM), dynamic light scattering (DLS), and Fourier-transform infrared spectroscopy (FTIR). From the X-ray diffraction analysis, the crystallite size is found to be 14 nm, 5 nm, and 6 nm for Ag₂O, CoFe₂O₄, and Ag₂O/CoFe₂O₄/rGO respectively. The synthesized nanomaterials were investigated for antibacterial activities against gram-positive strain Staphylococcus aureus (S. aureus) and gram-negative strain Escherichia coli (E. coli) using Agar well diffusion method. Ag₂O and CoFe₂O₄ showed zones of inhibition (ZOI) of 13 mm and 11 mm against gram positive bacteria while 12 mm against gram negative bacteria respectively, while ternary nanocomposite showed 14 mm and 13 mm of ZOI. The antibacterial activity of nanomaterials showed a gradual increment with an increase in the concentration of the materials. Ag₂O, CoFe₂O₄, and Ag₂O/CoFe₂O₄/rGO showed minimum inhibitory concentration (MIC) values of 4.5, 6.5, and 4.5 μg/mL for S. aureus and 6.5, 7.2, and 4.8 μg/mL for E. coli respectively. Minimum bactericidal concentrations were found to be same as the MIC values. Additionally, a time-kill curve analysis was performed and for ternary nanocomposite; the killing response was most effective as the complete killing was achieved at 3 h of incubation at 3-MIC (9.75 μg/mL). These results demonstrate that all the nanomaterials, as a kind of antibacterial material, have a great potential for a wide range of biomedical applications.

Macro-Size Regenerated Cellulose Fibre Embedded with Graphene Oxide with Antibacterial Properties

Macro-size regenerated cellulose fibres (RCFs) with embedded graphene oxide (GO) were fabricated by dissolving cellulose in a pre-cooled sodium hydroxide (NaOH)/urea solution and regenerated in sulphuric acid (H₂SO₄) coagulant. Initially, GO was found to disperse well in the cellulose solution due to intercalation with the cellulose; however, this cellulose-GO intercalation was disturbed during the regeneration process, causing agglomeration of GO in the RCF mixture. Agglomerated GO was confirmed at a higher GO content under a Dino-Lite microscope. The crystallinity index (CrI) and thermal properties of the RCFs increased with increasing GO loadings, up to 2 wt.%, and reduced thereafter. Cellulose-GO intercalation was observed at lower GO concentrations, which enhanced the crystallinity and thermal properties of the RCF-GO composite. It was shown that the GO exhibited antibacterial properties in the RCF-GO composite, with the highest bacterial inhibition against E. coli and S. aureus.

Antimicrobial Activity of Graphene Oxide Contributes to Alteration of Key Stress-Related and Membrane Bound Proteins

Introduction

Antibacterial activity of graphene oxide (GO) has been extensively studied, wherein penetration of the bacterial cell membrane and oxidative stress are considered to play a major role in the bactericidal activity of GO. However, the specific mechanism responsible for the antibacterial activity of GO remains largely unknown. Hence, the goal of this study was to explore the mode of action of GO, via an in-depth proteomic analysis of the targeted bacteria.

Methods

Staphylococcus aureus was grown in the presence of GO and samples were collected at different growth phases to examine the cell viability and to analyze the changes in protein expression. Antimicrobial efficiency of GO was tested by assessing bacterial viability, live/dead staining and scanning electron microscopy. The intracellular reactive oxygen species (ROS) induced by GO treatment were examined by fluorescence microscopy. Label-free quantitative proteomics analysis was performed to examine the differentially regulated proteins in S. aureus after GO treatment.

Results

GO treatment was observed to reduce S. aureus viability, from 50 ± 17% after 4 h, to 93 ± 2% after 24 h. The live/dead staining confirmed this progressive antimicrobial effect of GO. SEM images revealed the wrapping of bacterial cells and their morphological disruption by means of pore formation due to GO insertion. GO treatment was observed to generate intracellular ROS, correlating to the loss of cell viability. The proteomics analysis revealed alteration in the expression of cell membrane, oxidative stress response, general stress response, and virulence-associated proteins in GO-treated bacterial cells. The time-dependent bactericidal activity of GO correlated with a higher number of differentially regulated proteins involved in the above.-mentioned processes.

Conclusion

The obtained results suggest that the time-dependent bactericidal effect of GO is attributed to its wrapping/trapping ability, ROS production and due to physical disruption of the cell membrane.

Combined effects of copper oxide and nickel oxide coated chitosan nanoparticles adsorbed to styrofoam resin beads on hydrothermal vent bacteria

Microplastics are potential carriers of harmful contaminants but their combined effects are largely unknown. It needs intensive monitoring in order to achieve a better understanding of metal-oxide nanoparticles and their dispersion via microplastics such as styrofoam in the aquatic environment. In the present study, an effort was made to provide a preferable perception about the toxic effects of engineered nanoparticles (NPs), namely, copper oxide (CuO NPs), nickel oxide (NiO NPs), copper oxide/chitosan (CuO/CS NPs) and nickel oxide/chitosan (NiO/CS NPs). Characterizations of synthesized NPs included their morphology (SEM and EDX), functional groups (FT-IR) and crystallinity (XRD). Their combined toxic effect after adsorption to styrofoam (SF) was monitored using the hydrothermal vent bacterium Jeotgalicoccus huakuii as a model. This was done by determining MIC (minimum inhibitory concentration) through a resazurin assay measuring ELISA, growth, biofilm inhibition and making a live and dead assay. Results revealed that at high concentrations (60 mg/10 mL) of CuO, CuO/CS NPs and 60 mg of SF adsorbed CuO and CuO/CS NPs inhibited the growth of J. huakuii. However, NPs rather than SF inhibited the growth of bacteria. The toxicity of NPs adsorbed on plain SF was found to be less compared to NPs alone. This study revealed new dimensions regarding the positive impacts of SF at low concentrations. Synthesized NPs applied separately were found to affect the growth of bacteria substantially more than if coated to SF resin beads.

Graphene Oxide (GO): A Promising Nanomaterial against Infectious Diseases Caused by Multidrug-Resistant Bacteria

Infectious diseases are major threat due to it being the main cause of enormous morbidity and mortality in the world. Multidrug-resistant (MDR) bacteria put an additional burden of infection leading to inferior treatment by the antibiotics of the latest generations. The emergence and spread of MDR bacteria (so-called “superbugs”), due to mutations in the bacteria and overuse of antibiotics, should be considered a serious concern. Recently, the rapid advancement of nanoscience and nanotechnology has produced several antimicrobial nanoparticles. It has been suggested that nanoparticles rely on very different mechanisms of antibacterial activity when compared to antibiotics. Graphene-based nanomaterials are fast emerging as “two-dimensional wonder materials” due to their unique structure and excellent mechanical, optical and electrical properties and have been exploited in electronics and other fields. Emerging trends show that their exceptional properties can be exploited for biomedical applications, especially in drug delivery and tissue engineering. Moreover, graphene derivatives were found to have in vitro antibacterial properties. In the recent years, there have been many studies demonstrating the antibacterial effects of GO on various types of bacteria. In this review article, we will be focusing on the aforementioned studies, focusing on the mechanisms, difference between the studies, limitations and future directions.

Graphene Oxide (GO) Materials-Applications and Toxicity on Living Organisms and Environment

Graphene-based materials have attracted much attention due to their fascinating properties such as hydrophilicity, high dispersion in aqueous media, robust size, high biocompatibility, and surface functionalization ability due to the presence of functional groups and interactions with biomolecules such as proteins and nucleic acid. Modified methods were developed for safe, direct, inexpensive, and eco-friendly synthesis. However, toxicity to the environment and animal health has been reported, raising concerns about their utilization. This review focuses primarily on the synthesis methods of graphene-based materials already developed and the unique properties that make them so interesting for different applications. Different applications are presented and discussed with particular emphasis on biological fields. Furthermore, antimicrobial potential and the factors that affect this activity are reviewed. Finally, questions related to toxicity to the environment and living organisms are revised by highlighting factors that may interfere with it.

Synthesis of Cu(OH)2 nanowires modified by Fe3O4@SiO2 nanocomposite via green and innovative method with antibacterial activity and investigation of magnetic behaviours

In this study, green synthesis of modified Cu(OH)₂ nanowires by Fe₃O₄@SiO₂ core-shell nanospheres was easily performed via chemical reduction. In other words, the direct coating of Cu(OH)₂ on Fe₃O₄@SiO₂ was successfully realized without the extra complicated procedures. Various concentrations of synthesized nanocomposites were tested on pathogenic and nosocomial bacteria. In this study, the structural information and characterization of Fe₃O₄@SiO₂/Cu(OH)₂ nanowires (FSCNWs) were obtained using FE-SEM, FT-IR, EDX and X-ray diffraction. This nanocomposite can effectively kill important infectious bacteria, including Staphylococcus aureus, Escherichia coli, Staphylococcus saprophyticus, Pseudomonas aeruginosa and Klebsiella pneumoniae. Studies have shown that FSCNW nanocomposites affect common antibiotic-resistant bacteria. This result confirms the function of FSCNW as an effective, beneficial and environmentally friendly antibacterial agent that can used in a wide range of applications in medicine. FSCNWs can be separated conveniently from bacteria-containing solutions using a magnet. Compared with nanocomposites based on other metals such as silver and gold, the use of FSCNWs in water treatment has been recommended because of the precursor of copper for its low price and less toxicity. In addition to its special properties such as mild reaction conditions, green synthesis methods, admissible magnetic properties, easy separation, high antibacterial activity and beneficial efficiency.

Genotoxicity of Graphene-Based Materials

Graphene-based materials (GBMs) are a broad family of novel carbon-based nanomaterials with many nanotechnology applications. The increasing market of GBMs raises concerns on their possible impact on human health. Here, we review the existing literature on the genotoxic potential of GBMs over the last ten years. A total of 50 articles including in vitro, in vivo, in silico, and human biomonitoring studies were selected. Graphene oxides were the most analyzed materials, followed by reduced graphene oxides. Most of the evaluations were performed in vitro using the comet assay (detecting DNA damage). The micronucleus assay (detecting chromosome damage) was the most used validated assay, whereas only two publications reported results on mammalian gene mutations. The same material was rarely assessed with more than one assay. Despite inhalation being the main exposure route in occupational settings, only one in vivo study used intratracheal instillation, and another one reported human biomonitoring data. Based on the studies, some GBMs have the potential to induce genetic damage, although the type of damage depends on the material. The broad variability of GBMs, cellular systems and methods used in the studies precludes the identification of physico-chemical properties that could drive the genotoxicity response to GBMs.

Diospyros malabarica Fruit Extract Derived Silver Nanoparticles: A Biocompatible Antibacterial Agent

Biogenic silver nanoparticles demonstrate excellent antibacterial activity against a broad range of bacteria. Herein, aqueous biogenic silver nanoparticles (Aq@bAgNPs) and ethanolic biogenic silver nanoparticles (Et@bAgNPs) were synthesized using aqueous as well as ethanolic extracts of Diospyros malabarica fruit, respectively. The as-prepared biogenic silver nanoparticles (bAgNPs) were characterized using UV-Vis, FTIR as well as energy dispersive X-ray (EDS) spectroscopy, electron microscopy, dynamic light scattering spectroscopy (DLS), and zetasizer. The zeta potentials of Aq@bAgNPs and Et@bAgNPs were −9.8 ± 2.6, and −12.2 ± 1.9 mV, respectively. The antibacterial activity of bAgNPs was investigated against seven bacterial strains (i.e., pathogenic and nonpathogenic) and Et@bAgNPs exhibited the highest antibacterial propensity (i.e., 20 nm in diameter) against Bacillus subtillis through disk diffusion assay. The trypan blue dye exclusion assay also confirmed the antibacterial propensity of as-prepared bAgNPs. Furthermore, both Aq@bAgNPs and Et@bAgNPs oxidize bacterial membrane fatty acids and generate lipid peroxides which eventually form complexes with thiobarbituric acid (i.e., malondialdehyde-thiobarbituric acid adduct) to bring about bacterial death. Both the nanoparticles demonstrated good hemocompatibility against human as well as rat red blood cells (RBCs). In addition, they exhibited excellent biocompatibility in vivo in terms of rat liver (i.e., serum ALT, AST, and γ-GT) and kidneys (i.e., serum creatinine) function biomarkers.

Functionalized graphene oxide nanosheets with folic acid and silk fibroin as a novel nanobiocomposite for biomedical applications

In this paper, a novel graphene oxide-folic acid/silk fibroin (GO-FA/SF) nanobiocomposite scaffold was designed and fabricated using affordable and non-toxic materials. The GO was synthesized using the hummer method, covalently functionalized with FA, and then easily conjugated with extracted SF via the freeze-drying process. For characterization of the scaffold, several techniques were employed: Fourier-transform infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), and thermogravimetric analysis (TGA). The cell viability method, hemolysis, and anti-biofilm assays were performed, exploring the biological capability of the nanobiocomposite. The cell viability percentages were 96.67, 96.35 and 97.23% for 24, 48, and 72 h, respectively, and its hemolytic effect was less than 10%. In addition, it was shown that this nanobiocomposite prevents the formation of Pseudomonas aeruginosa biofilm and has antibacterial activity.

Carbon Nanostructures As Antibacterials and Active Food-Packaging Materials: A Review

In this article, we discuss carbon nanoparticles for application as antibacterials and food-packaging materials. The use of petroleum-derived products, synthetic materials, ceramics, wax, etc. in the food-packaging industry emits polluted gas and wastewater, which leads to environmental pollution. To overcome the problems faced by the industry to preserve and package food, carbon nanomaterials may be good alternatives to enhance the shelf life of food without affecting the nutrients. Carbon atoms bond with each other in diverse ways to form many allotropes, resulting in a variety of carbon nanomaterials (CNMs). CNMs include zero-dimensional carbon dots, graphene quantum dots, 1-dimensional carbon nanotubes, 2-dimensional pristine graphene, graphene oxide, reduced graphene oxide, and other derivatives of graphene. Most of the carbon-based nanomaterials are synthesized through a green process that is widely used in the field of food science and technology, and they are used mostly as antibacterial agents and as a biofiller in the development of active food-packaging materials. Carbon nanomaterials (CNMs), viz., carbon dots, graphene, activated carbon-based nanocomposites, carbon nanotubes, etc., are found to be environmentally benign and better materials for food packaging. With antibacterial efficiency, they support food preservation and other applications as well. Thus, carbon nanostructures are found to be applicable as superior materials for food preservation and packaging in modern industry.

Fluorine-18 Fluorodeoxyglucose Isolation Using Graphene Oxide for Alternative Radiopharmaceutical Spillage Decontamination in PET Scan

Radiopharmaceuticals (RPC) used for diagnostic and therapeutic purposes in nuclear medicine may contaminate surface areas due to spillage during its preparation or accident during RPC transfer from laboratory to the treatment room. Fluorine-18 Fluorodeoxyglucose (18F-FDG) is the most common RPC for positron emission tomography (PET) scan in nuclear medicine due to its ideal annihilation converted energy at 511 keV and short half-life at 109.8 min. Ineffective medical waste management of 18F-FDG may pose a risk to the environment or cause unnecessary radiation doses to the personnel and public. Depending on the incident rate of these events, simple decontamination methods such as the use of chemicals and swabs might not be cost-effective and sustainable in the environment. This study aims to propose an alternative method to decontaminate 18F-FDG by using graphene oxide (GO). GO was synthesised using the Hummers method while the physical morphology was analysed using a field emission scanning electron microscope (FESEM). 18F-FDG adsorption efficiency rate using GO nanolayers was analysed based on the kinetic study of the GO:18F-FDG mixtures. The chemical adsorbability of the material was analysed via UV–vis spectrophotometer to interlink the microstructures of GO with the sorption affinity interaction. Resultantly, the adsorption rate was effective at a slow decay rate and the optical adsorption of GO with 18F-FDG was dominated by the π → π* plasmon peak, which was near 230 nm. By elucidating the underlining GO special features, an alternative technique to isolate 18F-FDG for the decontamination process was successfully proven.

Bone morphogenetic protein (BMP)-modified graphene oxide-reinforced polycaprolactone-gelatin nanofiber scaffolds for application in bone tissue engineering

In this study, blend nanofibrous scaffolds were electrospun from polycaprolactone/gelatin (PCL/Gel) blend solutions reinforced by bone morphogenetic protein (BMP)-modified graphene oxide (GO). SEM results showed that uniform and bead-less nanofibers with 270 nm average diameter were obtained from electrospun of PCL/Gel blend solutions. Tensile strength test and contact angle measurement demonstrated that addition of PCL led to higher mechanical and physical properties of the resulting nanofibers. The addition of PCL as well as GO in the blend supports the suitable mechanical strength in the body media. The loading of BMP-modified graphene in the Gel/PCL structure caused the formation of nanofibrous substrate with great resemblance to bone tissue. Gel/PCL-G hybrid nanofibers revealed good biocompatibility in the presence of human osteosarcoma cells, and no trace of cellular toxicity was observed. The cells grown on the scaffolds exhibited a spindle-like and broad morphology and almost uniformly covered the entire nanofiber scaffold. Gel/PCL nanofibers reinforced by graphene oxide-immobilized bone morphogenetic protein was prepared as a promising safe and biocompatible nanofiber with high antibacterial activity for bone tissue engineering.

Nanotechnology as a Novel Approach in Combating Microbes Providing an Alternative to Antibiotics

The emergence of infectious diseases promises to be one of the leading mortality factors in the healthcare sector. Although several drugs are available on the market, newly found microorganisms carrying multidrug resistance (MDR) against which existing drugs cannot function effectively, giving rise to escalated antibiotic dosage therapies and the need to develop novel drugs, which require time, money, and manpower. Thus, the exploitation of antimicrobials has led to the production of MDR bacteria, and their prevalence and growth are a major concern. Novel approaches to prevent antimicrobial drug resistance are in practice. Nanotechnology-based innovation provides physicians and patients the opportunity to overcome the crisis of drug resistance. Nanoparticles have promising potential in the healthcare sector. Recently, nanoparticles have been designed to address pathogenic microorganisms. A multitude of processes that can vary with various traits, including size, morphology, electrical charge, and surface coatings, allow researchers to develop novel composite antimicrobial substances for use in different applications performing antimicrobial activities. The antimicrobial activity of inorganic and carbon-based nanoparticles can be applied to various research, medical, and industrial uses in the future and offer a solution to the crisis of antimicrobial resistance to traditional approaches. Metal-based nanoparticles have also been extensively studied for many biomedical applications. In addition to reduced size and selectivity for bacteria, metal-based nanoparticles have proven effective against pathogens listed as a priority, according to the World Health Organization (WHO). Moreover, antimicrobial studies of nanoparticles were carried out not only in vitro but in vivo as well in order to investigate their efficacy. In addition, nanomaterials provide numerous opportunities for infection prevention, diagnosis, treatment, and biofilm control. This study emphasizes the antimicrobial effects of nanoparticles and contrasts nanoparticles' with antibiotics' role in the fight against pathogenic microorganisms. Future prospects revolve around developing new strategies and products to prevent, control, and treat microbial infections in humans and other animals, including viral infections seen in the current pandemic scenarios.

Low-dimensional nanomaterials for antibacterial applications

The excessive use of antibiotics has led to a rise in drug-resistant bacteria. These "superbugs" are continuously emerging and becoming increasingly harder to treat. As a result, new and effective treatment protocols that have minimal risks of generating drug-resistant bacteria are urgently required. Advanced nanomaterials are particularly promising due to their drug loading/releasing capabilities combined with their potential photodynamic/photothermal therapeutic properties. In this review, 0-dimensional, 1-dimensional, 2-dimensional, and 3-dimensional nanomaterial-based systems are comprehensively discussed for bacterial-based diagnostic and treatment applications. Since the use of these platforms as antibacterials is relatively new, this review will provide appropriate insight into their construction and applications. As such, we hope this review will inspire researchers to explore antibacterial-based nanomaterials with the aim of developing systems for clinical applications.

Comparison of the Toxicity of Pristine Graphene and Graphene Oxide, Using Four Biological Models

There are numerous applications of graphene in biomedicine and they can be classified into several main areas: delivery systems, sensors, tissue engineering and biological agents. The growing biomedical field of applications of graphene and its derivates raises questions regarding their toxicity. We will demonstrate an analysis of the toxicity of two forms of graphene using four various biological models: zebrafish (Danio rerio) embryo, duckweed (Lemna minor), human HS-5 cells and bacteria (Staphylococcus aureus). The toxicity of pristine graphene (PG) and graphene oxide (GO) was tested at concentrations of 5, 10, 20, 50 and 100 µg/mL. Higher toxicity was noted after administration of high doses of PG and GO in all tested biological models. Hydrophilic GO shows greater toxicity to biological models living in the entire volume of the culture medium (zebrafish, duckweed, S. aureus). PG showed the highest toxicity to adherent cells growing on the bottom of the culture plates—human HS-5 cells. The differences in toxicity between the tested graphene materials result from their physicochemical properties and the model used. Dose-dependent toxicity has been demonstrated with both forms of graphene.

Nanomaterials and Essential Oils as Candidates for Developing Novel Treatment Options for Bovine Mastitis

Nanomaterials have been used for diagnosis and therapy in the human medical field, while their application in veterinary medicine and animal production is still relatively new. Nanotechnology, however, is a rapidly growing field, offering the possibility of manufacturing new materials at the nanoscale level, with the formidable potential to revolutionize the agri-food sector by offering novel treatment options for prevalent and expensive illnesses such as bovine mastitis. Since current treatments are becoming progressively more ineffective in resistant bacteria, the development of innovative products based on both nanotechnology and phytotherapy may directly address a major global problem, antimicrobial resistance, while providing a sustainable animal health solution that supports the production of safe and high-quality food products. This review summarizes the challenges encountered presently in the treatment of bovine mastitis, emphasizing the possibility of using new-generation nanomaterials (e.g., biological synthesized nanoparticles and graphene) and essential oils, as candidates for developing novel treatment options for bovine mastitis.

Extracellular metabolites of endophytic fungi from Azadirachta indica inhibit multidrug-resistant bacteria and phytopathogens

Aim: To evaluate antimicrobial activity of extracellular metabolites (EMs) of endophytic fungal isolates (EFIs) from Azadirachta indica. Materials & methods: EFIs were identified by internal transcribed spacer (ITS) sequencing. Antimicrobial activity, and minimum inhibitor concentration (MIC) and minimum bactericidal concentration (MBC) were determined using agar diffusion and microdilution method, respectively. Results: Seventeen EFIs were isolated from different organs of A. indica. Eight of them were identified based on ITS sequencing. The EMs of EFIs inhibited the growth of six multidrug-resistant (MDR) bacterial superbugs and three phytopathogenic fungi. The MDR bacterial superbugs are resistant to six commercial antibiotics of different generations but susceptible to EMs of EFIs. The MIC (0.125-1.0 μg/μl), MBC (0.5-4.0 μg/μl) and minimum fungicidal concentration (1.0-4.0 μg/μl) of the EMs from EFIs are lower enough. Conclusion: The EMs of the EFIs have promising antimicrobial activity against MDR bacteria and phytopathogenic fungi.

Graphene oxide-based rechargeable respiratory masks

Respiratory masks having similar standards of 'N95', defined by the US National Institute for Occupational Safety and Health, will be highly sought after, post the current COVID-19 pandemic. Here, such a low-cost (∼$1/mask) mask design having electrostatic rechargeability and filtration efficiency of >95% with a quality factor of ∼20 kPa-1 is demonstrated. This filtration efficacy is for particles of size 300 nm. The tri-layer mask, named PPDFGO tri, contains nylon, modified polypropylene (PPY), and cotton nonwoven fabrics as three layers. The melt-spun PPY, available in a conventional N95 mask, modified with graphene oxide and polyvinylidene fluoride mixture containing paste using a simple solution casting method acts as active filtration layer. The efficacy of this tri-layer system toward triboelectric rechargeability using small mechanical agitations is demonstrated here. These triboelectric nanogenerator (TENG)-assisted membranes have high electrostatic charge retention capacity (∼1 nC/cm2 after 5 days in ambient condition) and high rechargeability even in very humid conditions (>80% RH). A simple but robust permeability measurement set up is also constructed to test these TENG-based membranes, where a flow rate of 30-35 L/min is maintained during the testing. Such a simple modification to the existing mask designs enabling their rechargeability via external mechanical disturbances, with enhanced usability for single use as well as for reuse with decontantamination, will be highly beneficial in the realm of indispensable personal protective equipment.