Mechanism of inhibition of graphene oxide/zinc oxide nanocomposite against wound infection causing pathogens

Carbon-based metal oxide nanocomposites for water treatment by photocatalytic processes

The increasing contamination of water by emerging contaminants and the need for more efficient and sustainable treatment methods have prompted the exploration of advanced materials and technologies, with a particular focus on photocatalysis. Carbon-based metal oxide nanocomposites are a promising solution for the treatment of polluted water. This paper aims to review the current state of research on the application of these nanocomposites as photocatalysts for complete water treatment, describing breakthroughs in contaminant removal from 2019 through 2024 and milestones in water disinfection from 2016 through 2024. It includes discussion on the utilization of nanocomposites of Metal Oxides (MOs) with carbon materials to improve photocatalytic efficiency and addresses the advantages and drawbacks of these materials, including electron-hole recombination and agglomeration. The review focuses on the photocatalytic mechanisms of these nanocomposites and highlights the importance of heterostructures formed between metal oxides and carbon materials (e.g., graphene, carbon nanotubes, and carbon quantum dots), which enhance light absorption and hydroxyl radical generation, thereby increasing the efficiency of pollutant degradation and water disinfection. The review describes the properties of different MOs (n-type and p-type), exploring synergies between MOs and carbon materials and discussing the benefits and challenges of their application in wastewater treatment and pathogen inactivation. The review ends with a scientometric analysis of research trends in this field.

Antimicrobial activity and nanoremediation of heavy metals using biosynthesized CS/GO/ZnO nanocomposite by Bacillus subtilis ATCC 6633 alone or immobilized in a macroporous cryogel

BACKGROUND

The world society is still suffering greatly from waterborne infections, with developing countries bearing most of the morbidity and death burden, especially concerning young children. Moreover, microbial resistance is one of the most prevalent global problems that extends the need for self-medication and the healing period, or it may be linked to treatment failure that results in further hospitalization, higher healthcare expenses, and higher mortality rates. Thus, innovative synthesis of new antimicrobial materials is required to preserve the environment and enhance human health.

RESULTS

The present study highlighted a simple and cost-effective approach to biosynthesize a chitosan/graphene oxide/zinc oxide nanocomposite (CS/GO/ZnO) alone and immobilized in a macroporous cryogel as a new antimicrobial agent. Bacillus subtilis ATCC 6633 was used as a safe and efficient bio-nano-factory during biosynthesis. The formation of CS/GO/ZnO was confirmed and characterized using different analyses including ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), selective area diffraction pattern (SADP), Zeta analyses, scanning electron microscope (SEM) and transmission electron microscopy (TEM). GO combined with ZnO NPs successfully and displayed an adsorption peak at 358 nm. The XRD results showed the crystalline composition of the loaded ZnO NPs on GO sheets. FTIR spectrum confirmed the presence of proteins during the synthesis which act as stabilizing and capping agents. The nanocomposite has a high negative surface charge (-32.8 ± 5.7 mV) which increases its stability. SEM and TEM showing the size of biosynthesized ZnO-NPs was in the range of 40-50 nm. The CS/GO/ZnO alone or immobilized in cryogel revealed good antimicrobial activities against B. cereus ATCC 14,579, Escherichia coli ATCC 25,922, and Candida albicans ATCC 10,231 in a dose-dependent manner. The CS/GO/ZnO cryogel revealed higher antimicrobial activity than GO/ZnO nanocomposite and standard antibiotics (amoxicillin and miconazole) with inhibition zones averages of 24.33 ± 0.12, 15.67 ± 0.03, and 17.5 ± 0.49 mm, respectively. The MIC values of the prepared nanocomposite against B. cereus, E. coli, and C. albicans were 80, 80, and 90 µg/ml compared to standard drugs (90, 120 and 150 µg/ml, respectively). According to the TEM ultrastructure studies of nanocomposite-treated microbes, treated cells had severe deformities and morphological alterations compared to the untreated cells including cell wall distortion, the separation between the cell wall and plasma membrane, vacuoles formation moreover complete cell lyses were also noted. In the cytotoxicity test of CS/GO/ZnO alone and its cryogel, there was a significant reduction (p˂0.05) in cell viability of WI-38 normal lung cell line after the concentration of 209 and 164 µg/ml, respectively. It showed the low toxic effect of the nanocomposite and its cryogel on the WI-38 line which implies its safety. In addition, water treatment with the CS/GO/ZnO cryogel decreased turbidity (0.58 NTU), total coliform (2 CFU/100 ml), fecal coliform (1 CFU/100 ml), fecal Streptococcus (2 CFU/100 ml), and heterotrophic plate counts (53 CFU/1 ml) not only in comparison with the chlorine-treated samples (1.69 NTU, 4 CFU/100 ml, 6 CFU/100 ml, 57 CFU/100 ml, and 140 CFU/1 ml, respectively) but also with the raw water samples (6.9 NTU, 10800 CFU/100 ml, 660 CFU/100 ml, 800 CFU/100 ml, and 4400 CFU/1 ml, respectively). Moreover, cryogel significantly decreased the concentration of different heavy metals, especially cobalt compared to chlorine (0.004 ppm, 0.002 ppm, and 0.001 ppm for raw water, chlorine-treated, and cryogel-treated groups, respectively) which helped in the reduction of their toxic effects.

CONCLUSION

This study provides an effective, promising, safe, and alternative nanocomposite to treat different human and animal pathogenic microbes that might be used in different environmental, industrial, and medical applications.

Synergistic effects of thermally reduced graphene oxide/zinc oxide composite material on microbial infection for wound healing applications

Infections originating from pathogenic microorganisms can significantly impede the natural wound-healing process. To address this obstacle, innovative bio-active nanomaterials have been developed to enhance antibacterial capabilities. This study focuses on the preparation of nanocomposites from thermally reduced graphene oxide and zinc oxide (TRGO/ZnO). The hydrothermal method was employed to synthesize these nanocomposites, and their physicochemical properties were comprehensively characterized using X-ray diffraction analysis (XRD), High-resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared (FT-IR), Raman spectroscopy, UV-vis, and field-emission scanning electron microscopy (FE-SEM) techniques. Subsequently, the potential of TRGO/ZnO nanocomposites as bio-active materials against wound infection-causing bacteria, including Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, was evaluated. Furthermore, the investigated samples show disrupted bacterial biofilm formation. A reactive oxygen species (ROS) assay was conducted to investigate the mechanism of nanocomposite inhibition against bacteria and for further in-vivo determination of antimicrobial activity. The MTT assay was performed to ensure the safety and biocompatibility of nanocomposite. The results suggest that TRGO/ZnO nanocomposites have the potential to serve as effective bio-active nanomaterials for combating pathogenic microorganisms present in wounds.

In vitro long-term antibacterial performance and mechanism of Zn-doped micro-arc oxidation coatings

Micro-arc oxidation (MAO) coatings containing 2.86 wt%, 5.83 wt% and 8.81 wt% Zn (Zn-2.86 wt%, Zn-5.83 wt% and Zn-8.81 wt%) were separately fabricated on Ti6Al4V alloys using EDTA-ZnNa2 electrolytes. In vitro antibacterial examination exhibits that the antibacterial rates of Zn-2.86 wt%, Zn-5.83 wt% and Zn-8.81 wt% against Staphylococcus aureus (S. aureus) are 76.0 %, 100.0 % and 99.2 %, respectively. Reactive oxygen species (ROS) level of MAO samples is significantly higher than that of the untreated Ti6Al4V. Zn-containing coatings especially Zn-5.83 wt% induces the strongest oxidative stress on S. aureus due to relatively high released Zn2+ concentration. Moreover, qPCR analysis shows that MAO samples inhibit the icaADBC transcription and result in the down-regulation of PIA production, thereby mitigating biofilm formation. After immersion in simulated body fluid (SBF) for 3, 8 and 14 d, the antibacterial rate of Zn-5.83 wt% is 84.7 %, 63.2 % and 12.5 % respectively, and ROS level of MAO samples is also significantly higher than that of the untreated Ti6Al4V even after 14 d of immersion, suggesting that the antibacterial performance of MAO samples can last a relatively long immersion period and exhibit large application potential in orthopedic clinic.

Fabrication of poly (lactic-co-glycolic acid)/gelatin electro spun nanofiber patch containing CaCO3/SiO2 nanocomposite and quercetin for accelerated diabetic wound healing

An open wound or sore on the bottom of the foot caused by diabetes is known as a diabetic foot ulcer. Preventive measures are essential, including consistent foot care and glycemic management. The dangers associated with diabetic foot ulcers can be reduced via early identification and timely treatment. The risk of foot ulcers and limb amputation increases with age and duration of diabetes. Quercetin contains anti-inflammatory and antioxidant properties. Furthermore, the calcium carbonate/silica (CaCO3/SiO2) nanocomposite has a good anti-inflammatory property due to the presence of calcium, which will aid in wound healing. As a result, combining quercetin (plant based anti-inflammatory drug) and CaCO3/SiO2 nanocomposite will boost the wound healing rate. We have synthesized CaCO3/SiO2 nanocomposite in sol-gel method and characterized using XRD, FTIR and TEM. Cell line tests and the MTT assay revealed that the PLGA/gelatin/CaCO3/SiO2/quercetin patch enhanced the proliferation of cells. Its anti-bacterial efficacy against four major bacterial strains often found in wound locations, as well as its water retention, make it an ideal material for diabetic wound healing. In-vivo trials confirms the enhanced diabetic wound healing potential of the patch.

Exploring the bioactivity of reduced graphene oxide and TiO2 nanocomposite for the regenerative medicinal applications

Millions of people globally suffer from issues related to chronic wounds due to infection, burn, obesity, and diabetes. Nanocomposite with antibacterial and anti-inflammatory properties is a promising material to promote wound healing. This investigation primarily aims to synthesize reduced graphene oxide and titanium dioxide (rGO@TiO2) nanocomposite for wound healing applications. The rGO@TiO2 nanocomposite was synthesized by the one-step hydrothermal technique, and the physicochemical characterization of synthesized nanocomposite was performed by X-ray diffraction, Fourier transforms infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, and dynamic light scattering. Further, the nanocomposite antibacterial, cytotoxicity, and wound-healing properties were analyzed by disc diffusion method, MTT assay, and in vitro scratch assay, respectively. Based on the TEM images, the average particle size of TiO2 nanoparticles was around 9.26 ± 1.83 nm. The characteristics peak of Ti-O-Ti bonds was observed between 500 and 850 cm-1 in the Fourier transforms infrared spectrum. The Raman spectrum of graphene oxide (GO) was obtained for bands D and G at 1354 cm-1 and at 1593 cm-1, respectively. This GO peak intensity was reduced in rGO, revealing the oxygen functional group reduction. Moreover, the rGO@TiO2 nanocomposite exhibited dose-dependent antibacterial properties against the positive and negative bacterium. The cytotoxicity for 5-100 µg/mL of rGO@TiO2 nanocomposite was above the half-maximal inhibitory concentration value. The in vitro scratch assay for rGO@TiO2 indicates that the nanocomposite promotes cell proliferation and migration. The nanocomposite recovered the wound within 48 h. The rGO@TiO2 nanocomposite shows potential materials for wound healing applications.

Antimicrobial efficacy of Mentha piperata-derived biogenic zinc oxide nanoparticles against UTI-resistant pathogens

Misuse of antibiotics leads to the worldwide spread of antibiotic resistance, which motivates scientists to create new antibiotics. The recurring UTI due to antibiotics-resistant microorganism's challenges scientists globally. The biogenic nanoparticles have the potential to meet the escalating requirements of novel antimicrobial agents. The green synthesis of nanoparticles (NPs) gained more attention due to their reliable applications against resistant microbes. The current study evaluates the biogenic ZnO NPs of Mentha piperata extract against resistant pathogens of urinary tract infections by agar well diffusion assay. The biogenic ZnO NPs revealed comparatively maximum inhibition in comparison to synthetic antibiotics against two bacterial strains (Proteus mirabilis, Pseudomonas aeruginosa) and a fungal strain (Candida albicans).The synthesized biogenic ZnO NPs alone revealed maximum activities than the combination of plant extract (PE) and ZnO NPs, and PE alone. The physiochemical features of ZnO NPs characterized through UV-Vis spectroscopy, FTIR, XRD, SEM, and EDX. The UV-Vis spectroscopy revealed 281.85 nm wavelengths; the XRD pattern revealed the crystalline structure of ZnO NPs. The FTIR analysis revealed the presence of carboxylic and nitro groups, which could be attributed to plant extract. SEM analysis revealed spherical hollow symmetry due to electrostatic forces. The analysis via EDX confirmed the presence of Zn and oxygen in the sample. The physiochemical features of synthesized ZnO NPs provide pivotal information such as quality and effectiveness. The current study revealed excellent dose-dependent antimicrobial activity against the pathogenic isolates from UTI-resistant patients. The higher concentration of ZnONPs interacts with the cell membrane which triggers oxidative burst. They may bind with the enzymes and proteins and brings epigenetic alteration which leads to membrane disruption or cell death.

A selective analysis of sulfamethoxazole - Trimethoprim in tablet formulations using graphene oxide-zinc oxide quantum dots based nanocomposite modified glassy carbon electrode

In this study, simultaneous analysis on electrochemical detection of SMX and TMP in tablet formulation has been made using graphene oxide (GO) and ZnO QDs (GO-ZnO QDs) based nanocomposite modified glassy carbon electrode (GCE). The functional group presence was observed using FTIR study. The electrochemical characterization for GO, ZnO QDs and GO-ZnO QDs was studied using cyclic voltammetry using [Fe(CN)₆]^3- medium. In order to estimate the electrochemical redox behavior of SMX and TMP from tablet, the developed electrodes GO/GCE, ZnO QDs/GCE and GO-ZnO QDs/GCE are initially tested for electrochemical activity towards the SMX tablet in BR pH 7 medium. Later their electrochemical sensing has been monitored using square wave voltammetry (SWV). On observing the characteristic behavior of developed electrodes, GO/GCE exhibited detection potential of +0.48 V for SMX and +1.37 V for TMP whereas, ZnO QDs/GCE with +0.78V for SMX and for TMP 1.01 V respectively. Similarly, for GO-ZnO QDs/GCE, its 0.45 V for SMX and 1.11 V for TMP are observed using cyclic voltammetry. The obtained potential results on detecting SMX and TMP are in good agreement with previous results. Under optimized conditions, the response has been monitored with linear concentration range 50 μg/L to 300 μg/L for GO/GCE, ZnO QDs/GCE and GO-ZnO QDs/GCE in SMX tablet formulations. Their detection limits for the individual detection using GO-ZnO/GCE for SMX and TMP are found to be 0.252 ng/L and 19.10 μg/L and for GO/GCE it was 0.252 pg/L and 2.059 ng/L respectively. It was observed that ZnO QDs/GCE could not provide the electrochemical sensing towards SMX and TMP which may be due to the ZnO QPs can act as a blocking layer impeding the electron transfer process. Thus, the sensor performance lead to promising biomedical applications in real-time monitoring on evaluating selective analysis with SMX and TMP in tablet formulations.

Metal-Polymer Nanocomposites: A Promising Approach to Antibacterial Materials

There has been a new approach in the development of antibacterials in order to enhance the antibacterial potential. The nanoparticles are tagged on to the surface of other metals or metal oxides and polymers to achieve nanocomposites. These have shown significant antibacterial properties when compared to nanoparticles. In this article we explore the antibacterial potentials of metal-based and metal-polymer-based nanocomposites, various techniques which are involved in the synthesis of the metal-polymer, nanocomposites, mechanisms of action, and their advantages, disadvantages, and applications.

Photocatalytic nanoparticles - From membrane interactions to antimicrobial and antiviral effects

As a result of increasing resistance among pathogens against antibiotics and anti-viral therapeutics, nanomaterials are attracting current interest as antimicrobial agents. Such materials offer triggered functionalities to combat challenging infections, based on either direct membrane action, effects of released ions, thermal shock induced by either light or magnetic fields, or oxidative photocatalysis. In the present overview, we focus on photocatalytic antimicrobial effects, in which light exposure triggers generation of reactive oxygen species. These, in turn, cause oxidative damage to key components in bacteria and viruses, including lipid membranes, lipopolysaccharides, proteins, and DNA/RNA. While an increasing body of studies demonstrate that potent antimicrobial effects can be achieved by photocatalytic nanomaterials, understanding of the mechanistic foundation underlying such effects is still in its infancy. Addressing this, we here provide an overview of the current understanding of the interaction of photocatalytic nanomaterials with pathogen membranes and membrane components, and how this translates into antibacterial and antiviral effects.

Metal/metal oxide nanocomposites for bactericidal effect: A review

Many microbial species causing infectious disease all over the world became a social burden and creating threat among community. These microbes possess long lifetime, enhancing mortality and morbidity rate in affected organisms. In this condition, the treatment was ineffective and more chances of spreading of infection into other organisms. Hence, it is necessary to initiate infection control efforts and prevention activities against multidrug resistant microbes, to reduce the death rate of people. Seriously concerning towards this problem progress was shown in developing significant drugs with least side effects. Emergence of nanoparticles and its novelty showed effective role in targeting and destructing microbes well. Further, many research works have shown nanocomposites developed from nanoparticles coupled with other nanoparticles, polymers, carbon material acted as an exotic substance against microbes causing severe loss. However, metal and metal oxide nanocomposites have gained interest due to its small size and enhancing the surface contact with bacteria, producing damage to it. The bactericidal mechanism of metal and metal oxide nanocomposites involve in the production of reactive oxygen species which includes superoxide radical anions, hydrogen peroxide anions and hydrogen peroxide which interact with the cell wall of bacteria causing damage to the cell membrane in turn inhibiting the further growth of cell with leakage of internal cellular components, leading to death of bacteria. This review provides the detailed view on antibacterial activity of metal and metal oxide nanocomposite which possessed novelty due to its physiochemical changes.

Photo induced mechanistic activity of GO/Zn(Cu)O nanocomposite against infectious pathogens: Potential application in wound healing

Treating infection causing microorganisms is one of the major challenges in wound healing. These may gain resistance due to the overuse of conventional antibiotics. A promising technique is antimicrobial photodynamic therapy (aPDT) used to selectively cause damage to infectious pathogenic cells via generation of reactive oxygen species (ROS). We report on biocompatable nanomaterials that can serve as potential photosensitizers for aPDT. GO/Zn(Cu)O nanocomposite was synthesized by co-precipitation method. Graphene Oxide (GO) is known for its high surface to volume ratio, excellent surface functionality and enhanced antimicrobial property. ZnO nanoparticle induces the generation of reactive oxygen species (ROS) under light irradiation and it leads to recombination of electron-hole pair. Nanocomposites of GO and Cu doped ZnO increases visible light absorption and enhances the photocatalytic property. It generates more ROS and increases the bacterial inhibition. GO/Zn(Cu)O nanocomposite was tested against Staphylococcus aureus (S. aureus), Enterococcus faecium (E. faecium), Escherichia coli (E. coli), Salmonella typhi (S. typhi), Shigella flexneri (S. flexneri) and Pseudomonas aeruginosa (P. aeruginosa) by well diffusion method, growth curve, colony count, biofilm formation under both dark and visible light condition. Reactive Oxygen Species assay (ROS), Lactate dehydrogenase leakage (LDH) assay, Protein estimation assay and membrane integrity study proves the mechanism of inhibition of bacteria. Inhibition kinetics shows the sensitivity between bacteria and GO/Zn(Cu)O nanocomposite.

Antimicrobial Activity of Zinc Oxide Nano/Microparticles and Their Combinations against Pathogenic Microorganisms for Biomedical Applications: From Physicochemical Characteristics to Pharmacological Aspects

Zinc oxide (ZnO) nano/microparticles (NPs/MPs) have been studied as antibiotics to enhance antimicrobial activity against pathogenic bacteria and viruses with or without antibiotic resistance. They have unique physicochemical characteristics that can affect biological and toxicological responses in microorganisms. Metal ion release, particle adsorption, and reactive oxygen species generation are the main mechanisms underlying their antimicrobial action. In this review, we describe the physicochemical characteristics of ZnO NPs/MPs related to biological and toxicological effects and discuss the recent findings of the antimicrobial activity of ZnO NPs/MPs and their combinations with other materials against pathogenic microorganisms. Current biomedical applications of ZnO NPs/MPs and combinations with other materials are also presented. This review will provide the better understanding of ZnO NPs/MPs as antibiotic alternatives and aid in further development of antibiotic agents for industrial and clinical applications.

ZnO nanoparticles as photodegradation agent controlled by morphology and boron doping

ZnO nanoparticles with different morphology and doping possess different atomic planes at their interfaces. This changed their catalytic efficiency during degradation experiments with dyes, significantly dependent also on used dopant concentrations.

Recent Advances in Zinc Oxide Nanostructures with Antimicrobial Activities

This article reviews the recent developments in the synthesis, antibacterial activity, and visible-light photocatalytic bacterial inactivation of nano-zinc oxide. Polycrystalline wurtzite ZnO nanostructures with a hexagonal lattice having different shapes can be synthesized by means of vapor-, liquid-, and solid-phase processing techniques. Among these, ZnO hierarchical nanostructures prepared from the liquid phase route are commonly used for antimicrobial activity. In particular, plant extract-mediated biosynthesis is a single step process for preparing nano-ZnO without using surfactants and toxic chemicals. The phytochemical molecules of natural plant extracts are attractive agents for reducing and stabilizing zinc ions of zinc salt precursors to form green ZnO nanostructures. The peel extracts of certain citrus fruits like grapefruits, lemons and oranges, acting as excellent chelating agents for zinc ions. Furthermore, phytochemicals of the plant extracts capped on ZnO nanomaterials are very effective for killing various bacterial strains, leading to low minimum inhibitory concentration (MIC) values. Bioactive phytocompounds from green ZnO also inhibit hemolysis of Staphylococcus aureus infected red blood cells and inflammatory activity of mammalian immune system. In general, three mechanisms have been adopted to explain bactericidal activity of ZnO nanomaterials, including direct contact killing, reactive oxygen species (ROS) production, and released zinc ion inactivation. These toxic effects lead to the destruction of bacterial membrane, denaturation of enzyme, inhibition of cellular respiration and deoxyribonucleic acid replication, causing leakage of the cytoplasmic content and eventual cell death. Meanwhile, antimicrobial activity of doped and modified ZnO nanomaterials under visible light can be attributed to photogeneration of ROS on their surfaces. Thus particular attention is paid to the design and synthesis of visible light-activated ZnO photocatalysts with antibacterial properties.

Recent advancement in biomedical applications on the surface of two-dimensional materials: from biosensing to tissue engineering

As biosensors and biomedical devices have become increasingly important to everyday diagnostics and monitoring, there are tremendous, and constant efforts towards developing and improving the reliability and versatility of such technology. As they offer high surface area-to-volume ratios and a diverse range of properties, from electronic to optical, two dimensional (2D) materials have proven to be very promising candidates for biological applications and technologies. Due to the dimensionality, 2D materials facilitate many interfacial phenomena that have shown to significantly improve the performance of biosensors, while recent advances in synthesis techniques and surface engineering methods also enable the realization of future biomedical devices. This short review aims to highlight the influence of 2D material surfaces and the properties that arise due to their 2D structure. Using recent (within the last few years) examples of biosensors and biomedical applications, we emphasize the important role of 2D materials in advancing developments and research for biosensing and healthcare.

The biosynthesis of a graphene oxide-based zinc oxide nanocomposite using Dalbergia latifolia leaf extract and its biological applications

ZnO/GO nanocomposites were synthesized and their antibacterial activities assessed against various pathogens. They are potential antibacterial materials and significant anticancer activity against the MCF-7 breast cancer cell line compared to the A549 lung cancer cell line.