Carbon Nanomaterials as Antibacterial Colloids

Synthesizing Carbon Quantum Dots via Hydrothermal Reaction to Produce Efficient Antibacterial and Antibiofilm Nanomaterials

This study aimed to synthesize antibacterial carbon quantum dots (SP-CDs) from polyethyleneimine and spermidine via hydrothermal reaction. It was revealed that SP-CDs, with small size (7.18 nm) and high positive charge (+31.15 mV), had good fluorescence properties and lots of amino groups on their surfaces. The inhibition effect of SP-CDs on Staphylococcus aureus was better than that towards Escherichia coli, and the SP-CDs also had an inhibitory effect on multi-drug-resistant E. coli. The mechanism of SP-CDs shows that the SP-CDs were adsorbed on the surface of the negatively charged cell membrane through electrostatic interaction. SP-CDs can cause changes in membrane permeability, resulting in a shift of the cell membrane from order to disorder and the decomposition of chemical components, followed by the leakage of cell contents, resulting in bacterial death. SP-CDs can also significantly inhibit biofilm formation, destroy mature biofilms and reduce the number of living cells. Moreover, SP-CDs had negligible antimicrobial resistance even after 18 generations of treatment. This study proves that SP-CDs effectively inhibit the proliferation of foodborne pathogens, providing new feasibility for the application of carbon-based nanomaterials in the food industry.

Changes in the Bacterial Communities of Biocomposites with Different Flame Retardants

In today's world, the use of environmentally friendly materials is strongly encouraged. These materials derive from primary raw materials of plant origin, like fibrous hemp, flax, and bamboo, or recycled materials, such as textiles or residual paper, making them suitable for the growth of microorganisms. Here, we investigate changes in bacterial communities in biocomposites made of hemp shives, corn starch, and either expandable graphite or a Flovan compound as flame retardants. Using Next Generation Sequencing (NGS), we found that after 12 months of incubation at 22 °C with a relative humidity of 65%, Proteobacteria accounted for >99.7% of the microbiome in composites with either flame retardant. By contrast, in the absence of flame retardants, the abundance of Proteobacteria decreased to 32.1%, while Bacteroidetes (36.6%), Actinobacteria (8.4%), and Saccharobacteria (TM7, 14.51%) appeared. Using the increasing concentrations of either expandable graphite or a Flovan compound in an LB medium, we were able to achieve up to a 5-log reduction in the viability of Bacillus subtilis, Pseudomonas aeruginosa, representatives of the Bacillus and Pseudomonas genera, the abundance of which varied in the biocomposites tested. Our results demonstrate that flame retardants act on both Gram-positive and Gram-negative bacteria and suggest that their antimicrobial activities also have to be tested when producing new compounds.

Evaluation of the Toxic Activity of the Graphene Oxide in the Ex Vivo Model of Human PBMC Infection with Mycobacterium tuberculosis

Graphene Oxide has been proposed as a potential adjuvant to develop improved anti-TB treatment, thanks to its activity in entrapping mycobacteria in the extracellular compartment limiting their entry in macrophages. Indeed, when administered together with linezolid, Graphene Oxide significantly enhanced bacterial killing due to the increased production of Reactive Oxygen Species. In this work, we evaluated Graphene Oxide toxicity and its anti-mycobacterial activity on human peripheral blood mononuclear cells. Our data show that Graphene Oxide, different to what is observed in macrophages, does not support the clearance of Mycobacterium tuberculosis in human immune primary cells, probably due to the toxic effects of the nano-material on monocytes and CD4+ lymphocytes, which we measured by cytometry. These findings highlight the need to test GO and other carbon-based nanomaterials in relevant in vitro models to assess the cytotoxic activity while measuring antimicrobial potential.

Antibacterial Effect of Carbon Nanomaterials: Nanotubes, Carbon Nanofibers, Nanodiamonds, and Onion-like Carbon

The increasing resistance of bacteria and fungi to antibiotics is one of the health threats facing humanity. Of great importance is the development of new antibacterial agents or alternative approaches to reduce bacterial resistance to available antibacterial drugs. Due to the complexity of their properties, carbon nanomaterials (CNMs) may be of interest for a number of biomedical applications. One of the problems in studying the action of CNMs on microorganisms is the lack of universally standardized methods and criteria for assessing antibacterial and antifungal activity. In this work, using a unified methodology, a comparative study of the antimicrobial properties of the CNM systemic kit against common opportunistic microorganisms, namely Escherichia coli and Staphylococcus aureus, was carried out. Multiwalled carbon nanotubes (MWNTs), catalytic filamentous carbon with different orientations of graphene blocks (coaxial-conical and stacked, CFC), ionic carbon (OLC), and ultrafine explosive nanodiamonds (NDs) were used as a system set of CNMs. The highest antimicrobial activity was shown by NDs, both types of CFCs, and carboxylated hydrophilic MWCNTs. The SEM results point out the difference between the mechanisms of action of UDD and CFC nanotubes.

Functional Nanomaterials in Biomedicine: Current Uses and Potential Applications

Nanomaterials, that is, materials made up of individual units between 1 and 100 nanometers, have lately involved a lot of attention since they offer a lot of potential in many fields, including pharmacy and biomedicine, owed to their exceptional physicochemical properties arising from their high surface area and nanoscale size. Smart engineering of nanostructures through appropriate surface or bulk functionalization endows them with multifunctional capabilities, opening up new possibilities in the biomedical field such as biosensing, drug delivery, imaging, medical implants, cancer treatment and tissue engineering. This article highlights up-to-date research in nanomaterials functionalization for biomedical applications. A summary of the different types of nanomaterials and the surface functionalization strategies is provided. Besides, the use of nanomaterials in diagnostic imaging, drug/gene delivery, regenerative medicine, cancer treatment and medical implants is reviewed. Finally, conclusions and future perspectives are provided.

Progress in Antiviral Fullerene Research

Unlike traditional small molecule drugs, fullerene is an all-carbon nanomolecule with a spherical cage structure. Fullerene exhibits high levels of antiviral activity, inhibiting virus replication in vitro and in vivo. In this review, we systematically summarize the latest research regarding the different types of fullerenes investigated in antiviral studies. We discuss the unique structural advantage of fullerenes, present diverse modification strategies based on the addition of various functional groups, assess the effect of structural differences on antiviral activity, and describe the possible antiviral mechanism. Finally, we discuss the prospective development of fullerenes as antiviral drugs.

Advances in the Sensing and Treatment of Wound Biofilms

Wound biofilms represent a particularly challenging problem in modern medicine. They are increasingly antibiotic resistant and can prevent the healing of chronic wounds. However, current treatment and diagnostic options are hampered by the complexity of the biofilm environment. In this review, we present new chemical avenues in biofilm sensors and new materials to treat wound biofilms, offering promise for better detection, chemical specificity, and biocompatibility. We briefly discuss existing methods for biofilm detection and focus on novel, sensor-based approaches that show promise for early, accurate detection of biofilm formation on wound sites and that can be translated to point-of-care settings. We then discuss technologies inspired by new materials for efficient biofilm eradication. We focus on ultrasound-induced microbubbles and nanomaterials that can both penetrate the biofilm and simultaneously carry active antimicrobials and discuss the benefits of those approaches in comparison to conventional methods.

Advanced metal and carbon nanostructures for medical, drug delivery and bio-imaging applications

Nanoparticles (NPs) offer great promise for biomedical, environmental, and clinical applications due to their several unique properties as compared to their bulk counterparts. In this review article, we overview various types of metal NPs and magnetic nanoparticles (MNPs) in monolithic form as well as embedded into polymer matrices for specific drug delivery and bio-imaging fields. The second part of this review covers important carbon nanostructures that have gained tremendous attention recently in such medical applications due to their ease of fabrication, excellent biocompatibility, and biodegradability at both cellular and molecular levels for phototherapy, radio-therapeutics, gene-delivery, and biotherapeutics. Furthermore, various applications and challenges involved in the use of NPs as biomaterials are also discussed following the future perspectives of the use of NPs in biomedicine. This review aims to contribute to the applications of different NPs in medicine and healthcare that may open up new avenues to encourage wider research opportunities across various disciplines.

The role of nanoparticles (titanium dioxide, graphene oxide) on the inactivation of co-existing bacteria in the presence and absence of quartz sand

The increased mass production and application of engineered nanomaterials (ENMs) have resulted in the release of nanoparticles (NPs) in the environment, raising uncertainties regarding their environmental impacts. This study examines the effect of graphene oxide (GO) and titanium dioxide (TiO₂) NPs on the inactivation of the three model bacteria originated by mammalians including humans: Escherichia (E.) coli, Enterococcus (E.) faecalis, and Staphylococcus (S.) aureus. A series of dynamic batch experiments were conducted at constant room temperature (22 °C) in order to examine the inactivation of co-existing bacteria by NPs, in the presence and absence of quartz sand. The inactivation experimental data were satisfactorily fitted with a pseudo-first order expression with a time dependent rate coefficient. The inactivation of E. coli and S. aureus was shown to increase in the co-presence of GO or TiO₂ NPs and quartz sand comparing with the presence of GO or TiO₂ NPs alone. For E. faecalis, no clear trend was observed. Moreover, quartz sand was shown to affect inactivation of bacteria by GO and TiO₂ NPs. Among the bacteria examined, the highest inactivation rates were observed for S. aureus.

The Influence of Diamond Nanoparticles on Fibroblast Cell Line L929, Cytotoxicity and Bacteriostaticity of Selected Pathogens

The main problem with using modified allotrophic forms of carbon with nanodiamond particles in the production of food packaging is establishing the boundary between safety, as it affects the human body, and the adequate and effective action of the substances. One vital area of concern is the transmission of pathogens in food into the body. The aim of this study was to evaluate the cytotoxicity and bacteriostatic biological activity of two different modifications of diamond nanoparticles: pure detonation nanodiamond particles (DND) obtained by Danienko and plasma-chemically modified detonation nanodiamond particles obtained by the microwave plasma activated chemical vapor deposition method in a rotary chamber (MDP1) An indirect method was used to evaluate the cytotoxicity effect in accordance with ISO 10993–5. The viability of the L929 fibroblast cell line used as a control was 98.5%, for DND 95.14%, and the lowest level of viability for MDP1 was 88.63%. Escherichia coli and Staphylococcus aureus bacteria were used in bacteriostatic tests and the degree of cytotoxicity of the tested materials was classified as low. The in vitro cytotoxicity results indicate no toxic effect on L929 cells nor any effect on any of the samples tested against the bacterial strains us

Nanomaterials for application in wound Healing: current state-of-the-art and future perspectives

Nanoparticles are the gateway to the new era in drug delivery of biocompatible agents. Several products have emerged from nanomaterials in quest of developing practical wound healing dressings that are nonantigenic, antishear stress, and gas-exchange permeable. Numerous studies have isolated and characterised various wound healing nanomaterials and nanoproducts. The electrospinning of natural and synthetic materials produces fine products that can be mixed with other wound healing medications and herbs. Various produced nanomaterials are highly influential in wound healing experimental models and can be used commercially as well. This article reviewed the current state-of-the-art and briefly specified the future concerns regarding the different systems of nanomaterials in wound healing (i.e., inorganic nanomaterials, organic and hybrid nanomaterials, and nanofibers). This review may be a comprehensive guidance to help health care professionals identify the proper wound healing materials to avoid the usual wound complications.

Antibacterial biomaterials for skin wound dressing

Bacterial infection and the ever-increasing bacterial resistance have imposed severe threat to human health. And bacterial contamination could significantly menace the wound healing process. Considering the sophisticated wound healing process, novel strategies for skin tissue engineering are focused on the integration of bioactive ingredients, antibacterial agents included, into biomaterials with different morphologies to improve cell behaviors and promote wound healing. However, a comprehensive review on anti-bacterial wound dressing to enhance wound healing has not been reported. In this review, various antibacterial biomaterials as wound dressings will be discussed. Different kinds of antibacterial agents, including antibiotics, nanoparticles (metal and metallic oxides, light-induced antibacterial agents), cationic organic agents, and others, and their recent advances are summarized. Biomaterial selection and fabrication of biomaterials with different structures and forms, including films, hydrogel, electrospun nanofibers, sponge, foam and three-dimension (3D) printed scaffold for skin regeneration, are elaborated discussed. Current challenges and the future perspectives are presented in this multidisciplinary field. We envision that this review will provide a general insight to the elegant design and further refinement of wound dressing.

Advances in the Sensing and Treatment of Wound Biofilms

Wound biofilms represent a particularly challenging problem in modern medicine. They are increasingly antibiotic resistant and can prevent the healing of chronic wounds. However, current treatment and diagnostic options are hampered by the complexity of the biofilm environment. In this review, we present new chemical avenues in biofilm sensors and new materials to treat wound biofilms, offering promise for better detection, chemical specificity, and biocompatibility. We briefly discuss existing methods for biofilm detection and focus on novel, sensor‐based approaches that show promise for early, accurate detection of biofilm formation on wound sites and that can be translated to point‐of‐care settings. We then discuss technologies inspired by new materials for efficient biofilm eradication. We focus on ultrasound‐induced microbubbles and nanomaterials that can both penetrate the biofilm and simultaneously carry active antimicrobials and discuss the benefits of those approaches in comparison to conventional methods.

Carbon-Based Coatings in Medical Textiles Surface Functionalisation: An Overview

The COVID-19 pandemic has further highlighted the need for antimicrobial surfaces, especially those used in a healthcare environment. Textiles are the most difficult surfaces to modify since their typical use is in direct human body contact and, consequently, some aspects need to be improved, such as wear time and filtration efficiency, antibacterial and anti-viral capacity, or hydrophobicity. To this end, several techniques can be used for the surface modification of tissues, being magnetron sputtering (MS) one of [hose that have been growing in the last years to meet the antimicrobial objective. The current state of the art available on textile functionalisation techniques, the improvements obtained by using MS, and the potential of diamond-like-carbon (DLC) coatings on fabrics for medical applications will be discussed in this review in order to contribute to a higher knowledge of functionalized textiles themes.

Carbon Nanomaterials Modified Biomimetic Dental Implants for Diabetic Patients

Dental implants are used broadly in dental clinics as the most natural-looking restoration option for replacing missing or highly diseased teeth. However, dental implant failure is a crucial issue for diabetic patients in need of dentition restoration, particularly when a lack of osseointegration and immunoregulatory incompetency occur during the healing phase, resulting in infection and fibrous encapsulation. Bio-inspired or biomimetic materials, which can mimic the characteristics of natural elements, are being investigated for use in the implant industry. This review discusses different biomimetic dental implants in terms of structural changes that enable antibacterial properties, drug delivery, immunomodulation, and osseointegration. We subsequently summarize the modification of dental implants for diabetes patients utilizing carbon nanomaterials, which have been recently found to improve the characteristics of biomimetic dental implants, including through antibacterial and anti-inflammatory capabilities, and by offering drug delivery properties that are essential for the success of dental implants.

Synergistic Antibacterial Potential and Cell Surface Topology Study of Carbon Nanodots and Tetracycline Against E. coli

Increasing drugs and antibiotic resistance against pathogenic bacteria create the necessity to explore novel biocompatible antibacterial materials. This study investigated the antibacterial effect of carbon dot (C-dot) against E. coli and suggested an effective synergistic dose of tetracycline with C-dot, using mathematical modeling of antibacterial data. Colony count and growth curve studies clearly show an enhanced antibacterial activity against E. coli synergistically treated with C-dot and tetracycline, even at a concentration ten times lower than the minimum inhibitory concentration (MIC). The Richards model-fit of growth curve clearly showed an increase in doubling time, reduction in growth rate, and early stationary phase in the synergistic treatment with 42% reduction in the growth rate (μ_m) compared to the control. Morphological studies of E. coli synergistically treated with C-dot + tetracycline showed cell damage and deposition of C-dots on the bacterial cell membrane in scanning electron microscopy imaging. We further validated the topological changes, cell surface roughness, and significant changes in the height profile (ΔZ) with the control and treated E. coli cells viewed under an atomic force microscope. We confirmed that the effective antibacterial doses of C-dot and tetracycline were much lower than the MIC in a synergistic treatment.

Novel Biocompatible with Animal Cells Composite Material Based on Organosilicon Polymers and Fullerenes with Light-Induced Bacteriostatic Properties

A technology for producing a nanocomposite based on the borsiloxane polymer and chemically unmodified fullerenes has been developed. Nanocomposites containing 0.001, 0.01, and 0.1 wt% fullerene molecules have been created. It has been shown that the nanocomposite with any content of fullerene molecules did not lose the main rheological properties of borsiloxane and is capable of structural self-healing. The resulting nanomaterial is capable of generating reactive oxygen species (ROS) such as hydrogen peroxide and hydroxyl radicals in light. The rate of ROS generation increases with an increase in the concentration of fullerene molecules. In the absence of light, the nanocomposite exhibits antioxidant properties. The severity of antioxidant properties is also associated with the concentration of fullerene molecules in the polymer. It has been shown that the nanocomposite upon exposure to visible light leads to the formation of long-lived reactive protein species, and is also the reason for the appearance of such a key biomarker of oxidative stress as 8-oxoguanine in DNA. The intensity of the process increases with an increase in the concentration of fullerene molecules. In the dark, the polymer exhibits weak protective properties. It was found that under the action of light, the nanocomposite exhibits significant bacteriostatic properties, and the severity of these properties depends on the concentration of fullerene molecules. Moreover, it was found that bacterial cells adhere to the surfaces of the nanocomposite, and the nanocomposite can detach bacterial cells not only from the surfaces, but also from wetted substrates. The ability to capture bacterial cells is primarily associated with the properties of the polymer; they are weakly affected by both visible light and fullerene molecules. The nanocomposite is non-toxic to eukaryotic cells, the surface of the nanocomposite is suitable for eukaryotic cells for colonization. Due to the combination of self-healing properties, low cytotoxicity, and the presence of bacteriostatic properties, the nanocomposite can be used as a reusable dry disinfectant, as well as a material used in prosthetics.

Graphene Nanoribbons: Prospects of Application in Biomedicine and Toxicity

Graphene nanoribbons are a type of graphene characterized by remarkable electrical and mechanical properties. This review considers the prospects for the application of graphene ribbons in biomedicine, taking into account safety aspects. According to the analysis of the recent studies, the topical areas of using graphene nanoribbons include mechanical, chemical, photo- and acoustic sensors, devices for the direct sequencing of biological macromolecules, including DNA, gene and drug delivery vehicles, and tissue engineering. There is evidence of good biocompatibility of graphene nanoribbons with human cell lines, but a number of researchers have revealed toxic effects, including cytotoxicity and genotoxicity. Moreover, the damaging effects of nanoribbons are often higher than those of chemical analogs, for instance, graphene oxide nanoplates. The possible mechanism of toxicity is the ability of graphene nanoribbons to damage the cell membrane mechanically, stimulate reactive oxidative stress (ROS) production, autophagy, and inhibition of proliferation, as well as apoptosis induction, DNA fragmentation, and the formation of chromosomal aberrations. At the same time, the biodegradability of graphene nanoribbons under the environmental factors has been proven. In general, this review allows us to conclude that graphene nanoribbons, as components of high-precision nanodevices and therapeutic agents, have significant potential for biomedical applications; however, additional studies of their safety are needed. Particular emphasis should be placed on the lack of information about the effect of graphene nanoribbons on the organism as a whole obtained from in vivo experiments, as well as about their ecological toxicity, accumulation, migration, and destruction within ecosystems.

An Overview of Antimicrobial Properties of Carbon Nanotubes-Based Nanocomposites

The development of carbon-based nanomaterials has extensively facilitated new discoveries in various fields. Carbon nanotube-based nanocomposites (CNT-based nanocomposites) have lately recognized as promising biomaterials for a wide range of biomedical applications due to their unique electronic, mechanical, and biological properties. Nanocomposite materials such as silver nanoparticles (AgNPs), polymers, biomolecules, enzymes, and peptides have been reported in many studies, possess a broad range of antibacterial activity when incorporated with carbon nanotubes (CNTs). It is crucial to understand the mechanism which governs the antimicrobial activity of these CNT-based nanocomposite materials, including the decoupling individual and synergistic effects on the cells. In this review, the interaction behavior between microorganisms and different types of CNT-based nanocomposites is summarized to understand the respective antimicrobial performance in different conditions. Besides, the current development stage of CNT-based nanocomposite materials, the technical challenges faced, and the exceptional prospect of implementing potential antimicrobial CNT-based nanocomposite materials are also discussed.

Synergistic and On-Demand Release of Ag-AMPs Loaded on Porous Silicon Nanocarriers for Antibacteria and Wound Healing

Due to the abuse of antibiotics, antimicrobial resistance is rapidly emerging and becoming a major global risk for public health. Thus, there is an urgent need for reducing the use of antibiotics, finding novel treatment approaches, and developing controllable release systems. In this work, a dual synergistic antibacterial platform with on-demand release ability based on silver nanoparticles (AgNPs) and antimicrobial peptide (AMP) coloaded porous silicon (PSi) was developed. The combination of AgNPs and AMPs (Tet-213, KRWWKWWRRC) exhibited an excellent synergistic antibacterial effect. As a carrier, porous silicon can efficiently load AgNPs and AMP under mild conditions and give the platform an on-demand release ability and a synergistic release effect. The AgNPs and AMP coloaded porous silicon microparticles (AgNPs-AMP@PSiMPs) exhibited an acid pH and reactive oxygen species (ROS)-stimulated release of silver ions (Ag⁺) and AMPs under bacterial infection conditions because of oxidation and desorption effects. Moreover, the release of the bactericide could be promoted by each other due to the interplay between AgNPs and Tet-213. In vitro antibacterial tests demonstrated that AgNPs-AMP@PSiMPs inherited the intrinsic properties and synergistic antibacterial efficiency of both bactericides. In addition, wound dressing loaded with AgNPs-AMP@PSiMPs showed outstanding in vivo bacteria-killing activity, accelerating wound-healing, and low biotoxicity in aStaphylococcus aureus-infected rat wound model. The present work demonstrated that PSiMPS might be an efficient platform for loading the antibiotic-free bactericide, which could synergistically and on-demand release to fight wound infection and promote wound healing.

Mesoporous carbon nanospheres derived from agro-waste as novel antimicrobial agents against gram-negative bacteria

Porous carbon nanospheres were synthesized from agro-waste garlic peels by a one-pot facile and easy to scale-up pyrolysis method. Surface morphology and structural features of the nanospheres have been studied by field emission scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and Raman spectroscopy. Fourier transform infrared spectroscopy (FTIR) and N₂ adsorption desorption experiments were explored to detect surface functionality, surface area, and porosity. Average particle diameter of the synthesized nanospheres was 31 ± 6.3 nm and zeta potential of - 25.2 mV ± 1.75 mV. Nanoscale carbon was mesoporous in nature with type IV isotherms, mean pore diameter of 15.2 nm, and total pore volume of 0.032 cm³/g. Minimum inhibitory concentration and minimum bactericidal concentration values of carbon nanospheres against Escherichia coli are 480 ± 0.5 μg/ml and 495 ± 0.5 μg/ml, respectively. Synthesized nanospheres exhibited gram-selective antimicrobial action against Escherichia coli probably linked to membrane deformity due to interaction of nanocarbon with the bacterial membrane. Carbon nanospheres resulting from waste to wealth transformation emerged as promising candidates for antibacterial application. Graphical abstract.

Active Carbon-Based Nanomaterials in Food Packaging

Carbon-based nanomaterials (CBN) are currently used in many biomedical applications. The research includes optimization of single grain size and conglomerates of pure detonated nanodiamond (DND), modified nanodiamond particles and graphene oxide (GO) in order to compare their bactericidal activity against food pathogens. Measurement of grain size and zeta potential was performed using the Dynamic Light Scattering (DLS) method. Surface morphology was evaluated using a Scanning Electron Microscope (SEM) and confocal microscope. X-ray diffraction (XRD) was performed in order to confirm the crystallographic structure of detonation nanodiamond particles. Bacteriostatic tests were performed by evaluating the inhibition zone of pathogens in the presence of carbon based nanomaterials. Raman spectroscopy showed differences between the content of the diamond and graphite phases in diamond nanoparticles. Fluorescence microscopy and adenosine-5′-triphosphate (ATP) determination methods were used to assess the bactericidal of bioactive polymers obtained by modification of food wrapping film using various carbon-based nanomaterials. The results indicate differences in the sizes of individual grains and conglomerates of carbon nanomaterials within the same carbon allotropes depending on surface modification. The bactericidal properties depend on the allotropic form of carbon and the type of surface modification. Depending on the grain size of carbon-based materials, surface modification, the content of the diamond and graphite phases, surface of carbon-based nanomaterials film formation shows more or less intense bactericidal properties and differentiated adhesion of bacterial biofilms to food films modified with carbon nanostructures.

Antimicrobial and anti-adhesive properties of carbon nanotube-based surfaces for medical applications: a systematic review

Although high-performance carbon materials are widely used in surface engineering, with emphasis on carbon nanotubes (CNTs), the application of CNT nanocomposites on medical surfaces is poorly documented. In this study, we aimed to evaluate the antimicrobial and anti-adhesive properties of CNT-based surfaces. For this purpose, a PRISMA-oriented systematic review was conducted based on predefined criteria and 59 studies were selected for the qualitative analysis. Results from the analyzed studies suggest that surfaces containing modified CNTs, and specially CNTs conjugated with different polymers, exhibited strong antimicrobial and anti-adhesive activities. These composites seem to preserve the CNT toxicity to microorganisms and promote CNT-cell interactions, as well as to protect them from nonspecific protein adsorption. However, CNTs cannot yet compete with the conventional strategies to fight biofilms as their toxicity profile on the human body has not been thoroughly addressed. This review can be helpful for the development of new engineered medical surfaces.

Review on Carbon Nanotube Varieties for Healthcare Application: Effect of Preparation Methods and Mechanism Insight

Many potential uses of carbon nanotubes (CNT) in various sectors have created an urge to assess their diverse range of properties pertaining to various applications like catalysis, biosensor, and antimicrobial activity. Increasing studies on the biosensor and antibacterial activity of CNT have prompted tremendous interest in the utilization of the carbon-based nanostructured material as an alternative to currently existing antibiotics. However, the study of bactericidal aspects of this nanomaterial is relatively new and hence the deeper understanding of the various physicochemical characteristics and antimicrobial nature of CNT is extremely wanted. This review covers the effect of framework substitution and explains the understanding of membrane disintegration and oxidative stresses upon nanomaterials for antimicrobial activity. The present article has also reviewed effect of preparation nanoparticle deposition and framework modification on carbon nanotube structure. The recent research on graphene-modified nanomaterials for biosensor applications related to healthcare/clinical applications have also been discussed. Major physicochemical contributing factors such as size, functionalization, high surface area, and aggregation features of CNT assisting in the bacterial killing have nicely been outlined. Hence, the present review explains the supporting information related with Single and multi-walled carbon nanotube and summarized the advantages of functionalized carbon nanotube/graphene-based nanostructured carbon-based materials towards protection and reduction of bacterial/viral infections in the healthcare sector.

Porphyrin–Nanodiamond Hybrid Materials—Active, Stable and Reusable Cyclohexene Oxidation Catalysts

The quest for active, yet “green” non-toxic catalysts is a continuous challenge. In this work, covalently linked hybrid porphyrin–nanodiamonds were prepared via ipso nitro substitution reaction and characterized by X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy, infrared spectroscopy (IR) and thermogravimetry-differential scanning calorimetry (TG-DSC). The amine-functionalized nanodiamonds (ND@NH2) and 2-nitro-5,10,15,20-tetra(4-trifluoromethylphenyl)porphyrin covalently linked to nanodiamonds (ND@βNH-TPPpCF3) were tested using Allium cepa as a plant model, and showed neither phytotoxicity nor cytotoxicity. The hybrid nanodiamond–copper(II)–porphyrin material ND@βNH-TPPpCF3-Cu(II) was also evaluated as a reusable catalyst in cyclohexene allylic oxidation, and displayed a remarkable turnover number (TON) value of ≈265,000, using O2 as green oxidant, in the total absence of sacrificial additives, which is the highest activity ever reported for said allylic oxidation. Additionally, ND@βNH-TPPpCF3-Cu(II) could be easily separated from the reaction mixture by centrifugation, and reused in three consecutive catalytic cycles without major loss of activity.

Cytotoxicity Effects of Water-Soluble Multi-Walled Carbon Nanotubes Decorated with Quaternized Hyperbranched Poly(ethyleneimine) Derivatives on Autotrophic and Heterotrophic Gram-Negative Bacteria

Oxidized multi-walled carbon nanotubes (oxCNTs) were functionalized by a simple non-covalent modification procedure using quaternized hyperbranched poly(ethyleneimine) derivatives (QPEIs), with various quaternization degrees. Structural characterization of these hybrids using a variety of techniques, revealed the successful and homogenous anchoring of QPEIs on the oxCNTs' surface. Moreover, these hybrids efficiently dispersed in aqueous media, forming dispersions with excellent aqueous stability for over 12 months. Their cytotoxicity effect was investigated on two types of gram(-) bacteria, an autotrophic (cyanobacterium Synechococcus sp. PCC 7942) and a heterotrophic (bacterium Escherichia coli). An enhanced, dose-dependent antibacterial and anti-cyanobacterial activity against both tested organisms was observed, increasing with the quaternization degree. Remarkably, in the photosynthetic bacteria it was shown that the hybrid materials affect their photosynthetic apparatus by selective inhibition of the Photosystem-I electron transport activity. Cytotoxicity studies on a human prostate carcinoma DU145 cell line and 3T3 mouse fibroblasts revealed that all hybrids exhibit high cytocompatibility in the concentration range, in which they also exhibit both high antibacterial and anti-cyanobacterial activity. Thus, QPEI-functionalized oxCNTs can be very attractive candidates as antibacterial and anti-cyanobacterial agents that can be used for potential applications in the disinfection industry, as well as for the control of harmful cyanobacterial blooms.

Emergence of nanomaterials as potential immobilization supports for whole cell biocatalysts and cell toxicity effects

The traditional approach of fermentation by a free cell system has limitations of low productivity and product separation that need to be addressed for production enhancement and cost effectiveness. One of potential methods to solve the problems is cell immobilization. Microbial cell immobilization allows more efficient up-scaling by reducing the nonproductive growth phase, improving product yield and simplifying product separation. Furthermore, the emergence of nanomaterials such as carbon nanotubes, graphene, and metal-based nanomaterials with excellent functional properties provides novel supports for cell immobilization. Nanomaterials have catalytic properties that can provide specific binding site with targeted cells. However, the toxicity of nanomaterials towards cells has hampered its application as it affects the biological system of the cells, which cannot be neglected in any way. This gray area in immobilization is an important concern that needs to be addressed and understood by researchers. This review paper discusses an overview of nanomaterials used for cell immobilization with special focus on its toxicological challenges and how by understanding physicochemical properties of nanomaterials could influence the toxicity and biocompatibility of the cells.

Antimicrobial Mechanisms and Effectiveness of Graphene and Graphene-Functionalized Biomaterials. A Scope Review

Bacterial infections represent nowadays the major reason of biomaterials implant failure, however, most of the available implantable materials do not hold antimicrobial properties, thus requiring antibiotic therapy once the infection occurs. The fast raising of antibiotic-resistant pathogens is making this approach as not more effective, leading to the only solution of device removal and causing devastating consequences for patients. Accordingly, there is a large research about alternative strategies based on the employment of materials holding intrinsic antibacterial properties in order to prevent infections. Between these new strategies, new technologies involving the use of carbon-based materials such as carbon nanotubes, fullerene, graphene and diamond-like carbon shown very promising results. In particular, graphene- and graphene-derived materials (GMs) demonstrated a broad range antibacterial activity toward bacteria, fungi and viruses. These antibacterial activities are attributed mainly to the direct physicochemical interaction between GMs and bacteria that cause a deadly deterioration of cellular components, principally proteins, lipids, and nucleic acids. In fact, GMs hold a high affinity to the membrane proteoglycans where they accumulate leading to membrane damages; similarly, after internalization they can interact with bacteria RNA/DNA hydrogen groups interrupting the replicative stage. Moreover, GMs can indirectly determine bacterial death by activating the inflammatory cascade due to active species generation after entering in the physiological environment. On the opposite, despite these bacteria-targeted activities, GMs have been successfully employed as pro-regenerative materials to favor tissue healing for different tissue engineering purposes. Taken into account these GMs biological properties, this review aims at explaining the antibacterial mechanisms underlying graphene as a promising material applicable in biomedical devices.

Elucidation of Antimicrobial Activity of Non-Covalently Dispersed Carbon Nanotubes

Microorganisms have begun to develop resistance because of inappropriate and extensive use of antibiotics in the hospital setting. Therefore, it seems to be necessary to find a way to tackle these pathogens by developing new and effective antimicrobial agents. Carbon nanotubes (CNTs) have attracted growing attention because of their remarkable mechanical strength, electrical properties, and chemical and thermal stability for their potential applications in the field of biomedical as therapeutic and diagnostic nanotools. However, the impact of carbon nanotubes on microbial growth has not been fully investigated. The primary purpose of this research study is to investigate the antimicrobial activity of CNTs, particularly double-walled and multi-walled nanotubes on representative pathogenic strains such as Gram-positive bacteria Staphylococcus aureus, Gram-negative bacteria Pseudomonas aeruginosa, Klebsiella pneumoniae, and fungal strain Candida albicans. The dispersion ability of CNT types (double-walled and multi-walled) treated with a surfactant such as sodium dodecyl-benzenesulfonate (SDBS) and their impact on the microbial growth inhibition were also examined. A stock concentration 0.2 mg/mL of both double-walled and multi-walled CNTs was prepared homogenized by dispersing in surfactant solution by using probe sonication. UV-vis absorbance, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) were used for the characterization of CNTs dispersed in the surfactant solution to study the interaction between molecules of surfactant and CNTs. Later, scanning electron microscopy (SEM) was used to investigate how CNTs interact with the microbial cells. The antimicrobial activity was determined by analyzing optical density growth curves and viable cell count. This study revealed that microbial growth inhibited by non-covalently dispersed CNTs was both depend on the concentration and treatment time. In conclusion, the binding of surfactant molecules to the surface of CNTs increases its ability to disperse in aqueous solution. Non-covalent method of CNTs dispersion preserved their structure and increased microbial growth inhibition as a result. Multi-walled CNTs exhibited higher antimicrobial activity compared to double-walled CNTs against selected pathogens.

Extrusion of Polymer Nanocomposites with Graphene and Graphene Derivative Nanofillers: An Overview of Recent Developments

This review is focused on the recent developments of nanocomposite materials that combine a thermoplastic matrix with different forms of graphene or graphene oxide nanofillers. In all cases, the manufacturing method of the composite materials has been melt-processing, in particular, twin-screw extrusion, which can then be followed by injection molding. The advantages of this processing route with respect to other alternative methods will be highlighted. The results point to an increasing interest in biodegradable matrices such as polylactic acid (PLA) and graphene oxide or reduced graphene oxide, rather than graphene. The reasons for this will also be discussed.

Carbon Dots for Bacterial Detection and Antibacterial Applications-A Minireview

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The prevention and treatment of various infections caused by microbes through antibiotics are becoming less effective due to antimicrobial resistance. Researches are focused on antimicrobial nanomaterials to inhibit bacterial growth and destroy the cells, to replace conventional antibiotics. Recently, carbon dots (C-Dots) become attractive candidates for a wide range of applications, including the detection and treatment of pathogens. In addition to low toxicity, ease of synthesis and functionalization, and high biocompatibility, C-Dots show excellent optical properties such as multi-emission, high brightness, and photostability. C-Dots have shown great potential in various fields, such as biosensing, nanomedicine, photo-catalysis, and bioimaging. This review focuses on the origin and synthesis of various C-Dots with special emphasis on bacterial detection, the antibacterial effect of CDots, and their mechanism.

Multi-Walled Carbon Nanotubes (MWCNTs) Activate Apoptotic Pathway Through ER Stress: Does Surface Chemistry Matter?

PURPOSE

Physicochemical properties play a crucial role in determining the toxicity of multi-walled carbon nanotubes (MWCNTs). Recently we found that MWCNTs with longer length and smaller diameters could induce toxicity to human umbilical vein endothelial cells (HUVECs) through the activation of endoplasmic reticulum (ER) stress. In this study, we further investigated the possible contribution of hydroxylation and carboxylation to the cytotoxicity of MWCNTs.

METHODS

The HUVECs were exposed to pristine (code XFM19), hydroxylated (code XFM20; content of hydroxyl groups 1.76 wt%) and carboxylated (code XFM21; content of carboxyl groups 1.23 wt%) MWCNTs, respectively. Then, the internalization, cytotoxicity, oxidative stress and activation of apoptosis-ER stress pathway were measured.

RESULTS

In consequence, all types of MWCNTs could be internalized into the HUVECs, and the cellular viability was significantly reduced to a similar level. Moreover, the MWCNTs increased intracellular reactive oxygen species (ROS) and decreased glutathione (GSH) to similar levels, indicating their capacity of inducing oxidative stress. The Western blot results showed that all types of MWCNTs reduced BCL-2 and increased caspase-3, caspase-8, cleaved caspase-3 and cleaved caspase-8. The expression of ER stress gene DNA damage-inducible transcript 3 (DDIT3) and protein level of chop were only significantly induced by XFM20 and XFM21, whereas protein level of p-chop was promoted by XFM19 and XFM21. In addition, the pro-survival gene XBP-1s was significantly down-regulated by all types of MWCNTs.

CONCLUSION

These results suggested that MWCNTs could induce cytotoxicity to HUVECs via the induction of oxidative stress and apoptosis-ER stress, whereas a low degree of hydroxylation or carboxylation did not affect the toxicity of MWCNTs to HUVECs.

Antibacterial Carbon-Based Nanomaterials

The emergence and global spread of bacterial resistance to currently available antibiotics underscore the urgent need for new alternative antibacterial agents. Recent studies on the application of nanomaterials as antibacterial agents have demonstrated their great potential for management of infectious diseases. Among these antibacterial nanomaterials, carbon-based nanomaterials (CNMs) have attracted much attention due to their unique physicochemical properties and relatively higher biosafety. Here, a comprehensive review of the recent research progress on antibacterial CNMs is provided, starting with a brief description of the different kinds of CNMs with respect to their physicochemical characteristics. Then, a detailed introduction to the various mechanisms underlying antibacterial activity in these materials is given, including physical/mechanical damage, oxidative stress, photothermal/photocatalytic effect, lipid extraction, inhibition of bacterial metabolism, isolation by wrapping, and the synergistic effect when CNMs are used in combination with other antibacterial materials, followed by a summary of the influence of the physicochemical properties of CNMs on their antibacterial activity. Finally, the current challenges and an outlook for the development of more effective and safer antibacterial CNMs are discussed.

The effect of water hardness on the toxicity of graphene oxide to bacteria in synthetic surface waters

Graphene oxide (GO), used in a wide variety of applications, is increasingly being introduced into aquatic environments; this situation calls for research on GO toxicity to assess its environmental risks. In this study, the toxic effect of GO to E.coli was studied before and after its aggregation equilibrium in the synthetic surface waters (the soft water, moderately hard water, and hard water) to reveal the effects of GO aggregation and solution hardness. The cytotoxicity of GO increased with increasing solution hardness while decreased after GO aggregation. The 3 h 50% inhibitory concentration (IC₅₀) values of dispersed GO in the soft water, moderately hard water, and hard water were 12.2 ± 2.2, 8.5 ± 1.5, and 4.0 ± 1.0 mg/L, respectively. After 24 h shaking (aggregation equilibrium) in the synthetic surface waters, the dispersed GO aggregated and the 3 h IC₅₀ values of GO aggregates in the three synthetic waters were 40.3 ± 6.9, 15.9 ±  2.2, and 7.5 ± 1.5 mg/L, respectively. The dispersed GO sheets wrapped E. coli cells and cut the cell membrane, resulting in the disruption of cell membrane and the cell inactivation. With increasing water hardness, the heteroaggregation between GO sheets/aggregates and E. coli cells was enhanced, resulting in the increase of toxic effect. The GO aggregates could also entrap E.coli cells while exhibited limited effect on cell membrane disruption without sharp edges, thereby causing the lower toxic effect compared with the dispersed GO sheets. These outcomes shed new light on the assessment of ecological effects of GO.

New insight into the aggregation of graphene oxide in synthetic surface water: Carbonate nanoparticle formation on graphene oxide

Graphene oxide (GO), used in a wide variety of applications, is increasingly being introduced into aquatic environments; this situation calls for research on GO aggregation and sedimentation to regulate the environmental behaviors and risks. Many studies have investigated the aggregation and the mechanism of GO in water with a single background salt (monosalt system); however, this may not reflect real water environments where multiple salts coexist (multisalt system). A typical synthetic surface water (soft water) with representative multisalts was therefore used to study the aggregation and sedimentation of GO. The GO concentration-dependent aggregation (low concentration aggregation, high concentration stability) was observed in the soft water, and this concentration-dependent aggregation is opposite to the aggregation in monosalt systems (NaCl or CaCl₂ solutions). The presence of GO sheets induced the formation of amorphous CaMg(CO₃)₂ nanoparticles on the GO surfaces in the soft water, and the formed nanoparticles promoted the aggregation and sedimentation of low concentrations of GO through bridging action. Neutral and alkaline conditions were favorable for the formation of CaMg(CO₃)₂ nanoparticles and the induced GO aggregation. These findings show a new mechanism of GO aggregation in environmentally relevant waters and help us to better evaluate the environmental fate of GO.

Electrocatalytic water treatment using carbon nanotube filters modified with metal oxides

This study examined the electrocatalytic activity of multi-walled carbon nanotube (CNT) filters for remediation of aqueous phenol in a sodium sulfate electrolyte. CNT filters were loaded with antimony-doped tin oxide (Sb-SnO₂; SS) and bismuth- and antimony-codoped tin oxide (Bi-Sb-SnO₂; BSS) via electrosorption at 2 V for 1 h and then assembled into a flow-through batch reactor as anode-cathode couples with perforated titanium foils. The as-synthesized pristine CNT filters were composed of 50-60-nm-thick tubular carbons with smooth surfaces, whereas the tubes composing the SS-CNT and BSS-CNT filters were slightly thicker and bumpy, because they were coated with SS and BSS particles ~50 nm in size. Electrochemical characterization of the samples indicated a positive shift in the onset potential and a decrease in the current magnitude in the modified CNT filters due to passivation and oxidation inhibition of the bare CNT filters. These filters exhibited a similar adsorption capacity for phenol (5-8%), whereas loadings of SS and BSS enhanced the degradation rate of phenol by ~1.5 and 2.1 times, respectively. In particular, the total organic carbon removal performance and mineralization efficiency of the BSS-CNT filters were approximately twice those of the bare CNT filters. The BSS-CNT filters also exhibited an enhanced oxidation of ferrocyanide [Fe^II(CN)₆^4-], which was not adsorbed onto the CNT filters. The enhanced electrocatalytic performance of the modified CNT filters was attributed to an effective generation of OH radicals. The surfaces of the filters were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy.

Graphene Materials in Antimicrobial Nanomedicine: Current Status and Future Perspectives

Graphene materials (GMs), such as graphene, graphene oxide (GO), reduced GO (rGO), and graphene quantum dots (GQDs), are rapidly emerging as a new class of broad-spectrum antimicrobial agents. This report describes their state-of-the-art and potential future covering both fundamental aspects and biomedical applications. First, the current understanding of the antimicrobial mechanisms of GMs is illustrated, and the complex picture of underlying structure-property-activity relationships is sketched. Next, the different modes of utilization of antimicrobial GMs are explained, which include their use as colloidal dispersions, surface coatings, and photothermal/photodynamic therapy agents. Due to their practical relevance, the examples where GMs function as synergistic agents or release platforms for metal ions and/or antibiotic drugs are also discussed. Later, the applicability of GMs in the design of wound dressings, infection-protective coatings, and antibiotic-like formulations ("nanoantibiotics") is assessed. Notably, to support our assessments, the existing clinical applications of conventional carbon materials are also evaluated. Finally, the key hurdles of the field are highlighted, and several possible directions for future investigations are proposed. We hope that the roadmap provided here will encourage researchers to tackle remaining challenges toward clinical translation of promising research findings and help realize the potential of GMs in antimicrobial nanomedicine.

Multiwall Carbon Nanotubes Induce More Pronounced Transcriptomic Responses in Pseudomonas aeruginosa PG201 than Graphene, Exfoliated Boron Nitride, or Carbon Black

Carbonaceous and boron nitride (BN) nanomaterials have similar applications and hydrophobic properties suggesting common release pathways and exposure to bacteria. While high nanomaterial concentrations can be bactericidal or growth-inhibitory, little is known regarding bacterial transcriptional responses to non-growth-inhibitory nanomaterial concentrations. Here, using one strain of Pseudomonas aeruginosa-a clinically and environmentally important bacterial taxon-we analyzed the comparative transcriptomic response to carbonaceous or BN nanomaterials. We show that, at non-growth-inhibitory, equal mass concentrations (10 mg/L), multiwall carbon nanotubes (MWCNTs) induced differential regulation of 111 genes in P. aeruginosa, while graphene, BN, and carbon black caused differential regulation of 44, 26, and 25 genes, respectively. MWCNTs caused the upregulation of genes encoding general stress response (9 genes), sulfur metabolism (15), and transport of small molecules (7) and downregulation of genes encoding flagellar basal-body rod proteins and other virulence-related factors (6), nitrogen metabolism (7), and membrane proteins (12), including a two-component regulatory system CzcS/R. Because two-component systems are associated with antibiotic resistance, the antibiotic susceptibility of P. aeruginosa was tested following MWCNT exposure. In MWCNT-treated cultures, the minimal inhibitory concentrations (MICs) of meropenem and imipenem decreased from 0.06 to 0.03 μg/mL and from 0.25 to 0.125 μg/mL, respectively. Taken together, whole genome analysis indicated that, in the absence of growth inhibition, nanomaterials can alter bacterial physiology and metabolism. For MWCNTs, such alterations may include downregulation of antibiotic resistance pathways, suggesting that pre-exposure to MWCNTs could potentially render bacteria more susceptible to carbapenems which are often the last resort for the globally concerning, highly antibiotic resistant P. aeruginosa.

Toxicity of Pristine and Chemically Functionalized Fullerenes to White Rot Fungus Phanerochaete chrysosporium

Fullerenes are widely produced and applied carbon nanomaterials that require a thorough investigation into their environmental hazards and risks. In this study, we compared the toxicity of pristine fullerene (C60) and carboxylated fullerene (C60-COOH) to white rot fungus Phanerochaete chrysosporium. The influence of fullerene on the weight increase, fibrous structure, ultrastructure, enzyme activity, and decomposition capability of P. chrysosporium was investigated to reflect the potential toxicity of fullerene. C60 did not change the fresh and dry weights of P. chrysosporium but C60-COOH inhibited the weight gain at high concentrations. Both C60 and C60-COOH destroyed the fibrous structure of the mycelia. The ultrastructure of P. chrysosporium was changed by C60-COOH. Pristine C60 did not affect the enzyme activity of the P. chrysosporium culture system while C60-COOH completely blocked the enzyme activity. Consequently, in the liquid culture, P. chrysosporium lost the decomposition activity at high C60-COOH concentrations. The decreased capability in degrading wood was observed for P. chrysosporium exposed to C60-COOH. Our results collectively indicate that chemical functionalization enhanced the toxicity of fullerene to white rot fungi and induced the loss of decomposition activity. The environmental risks of fullerene and its disturbance to the carbon cycle are discussed.