Carbon nanotubes as antimicrobial agents for water disinfection and pathogen control

Effect of Human Adenovirus Type 35 Concentration on Its Inactivation and Sorption on Titanium Dioxide Nanoparticles

Removal of pathogenic viruses from water resources is critically important for sanitation and public health. Nanotechnology is a promising technology for virus inactivation. In this paper, the effects of titanium dioxide (TiO2) anatase nanoparticles (NPs) on human adenovirus type 35 (HAdV-35) removal under static and dynamic (with agitation) batch conditions were comprehensively studied. Batch experiments were performed at room temperature (25 °C) with and without ambient light using three different initial virus concentrations. The virus inactivation experimental data were satisfactorily fitted with a pseudo-first-order expression with a time-dependent rate coefficient. The experimental results demonstrated that HAdV-35 sorption onto TiO2 NPs was favored with agitation under both ambient light and dark conditions. However, no distinct relationships between virus initial concentration and removal efficiency could be established from the experimental data.

Nano-microflora Interaction Inducing Pulmonary Inflammation by Pyroptosis

Antimicrobial nanomaterials frequently induce inflammatory reactions within lung tissues and prompt apoptosis in lung cells, yielding a paradox due to the inherent anti-inflammatory character of apoptosis. This paradox accentuates the elusive nature of the signaling cascade underlying nanoparticle (NP)-induced pulmonary inflammation. In this study, we unveil the pivotal role of nano-microflora interactions, serving as the crucial instigator in the signaling axis of NP-induced lung inflammation. Employing pulmonary microflora-deficient mice, we provide compelling evidence that a representative antimicrobial nanomaterial, silver (Ag) NPs, triggers substantial motility impairment, disrupts quorum sensing, and incites DNA leakage from pulmonary microflora. Subsequently, the liberated DNA molecules recruit caspase-1, precipitating the release of proinflammatory cytokines and activating N-terminal gasdermin D (GSDMD) to initiate pyroptosis in macrophages. This pyroptotic cascade culminates in the emergence of severe pulmonary inflammation. Our exploration establishes a comprehensive mechanistic axis that interlinks the antimicrobial activity of Ag NPs, perturbations in pulmonary microflora, bacterial DNA release, macrophage pyroptosis, and consequent lung inflammation, which helps to gain an in-depth understanding of the toxic effects triggered by environmental NPs.

Accelerating wound healing: Unveiling synergistic effects of P25/SWCNT/Ag and P25/rGO/Ag nanocomposites within PRP-gelatin scaffold, highlighting the synergistic antimicrobial activity

Wound healing is a multifaceted biological process requiring innovative strategies to enhance efficiency and counter infections. In this groundbreaking study, we investigate the regenerative potential of platelet-rich plasma (PRP) integrated into a gelatin (GLT) scaffold along with nanocomposites of titanium dioxide (TiO2) (P25)/single-walled carbon nanotubes (SWCNTs)/Ag and P25/reduced graphene oxide (rGO)/Ag. Incorporating these advanced materials into the PRP/GLT delivery system aims to optimize the controlled release of growth factors (GFs) and leverage the exceptional properties of nanomaterials for enhanced tissue repair and wound healing outcomes. Antioxidant activity assessment using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity reveals the superior performance of P25/SWCNTs/Ag compared to P25/rGO/Ag. Their synergistic effects are evaluated in conjunction with antibacterial and antifungal antibiotics. Furthermore, the wound healing potential of P25/SWCNTs/Ag and P25/rGO/Ag, combined with PRP/GLT, is examined. Notably, both nanocomposites exhibit promising synergistic effects with gentamicin and fluconazole against pathogenic strains. Significantly, the inclusion of non-activated PRP substantially augments the wound healing efficacy of P25/SWCNTs/Ag on days 3 (p < 0.01) and 15 (p < 0.05). These findings pave the way for advanced wound dressing and therapeutic interventions, capitalizing on the synergistic effects of PRP and nanomaterials, thus ultimately benefiting patients and advancing regenerative medicine.

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.

Plasma-Etched Vertically Aligned CNTs with Enhanced Antibacterial Power

The emergence of multidrug-resistant bacteria represents a growing threat to public health, and it calls for the development of alternative antibacterial approaches not based on antibiotics. Here, we propose vertically aligned carbon nanotubes (VA-CNTs), with a properly designed nanomorphology, as effective platforms to kill bacteria. We show, via a combination of microscopic and spectroscopic techniques, the ability to tailor the topography of VA-CNTs, in a controlled and time-efficient manner, by means of plasma etching processes. Three different varieties of VA-CNTs were investigated, in terms of antibacterial and antibiofilm activity, against Pseudomonas aeruginosa and Staphylococcus aureus: one as-grown variety and two varieties receiving different etching treatments. The highest reduction in cell viability (100% and 97% for P. aeruginosa and S. aureus, respectively) was observed for the VA-CNTs modified using Ar and O₂ as an etching gas, thus identifying the best configuration for a VA-CNT-based surface to inactivate both planktonic and biofilm infections. Additionally, we demonstrate that the powerful antibacterial activity of VA-CNTs is determined by a synergistic effect of both mechanical injuries and ROS production. The possibility of achieving a bacterial inactivation close to 100%, by modulating the physico-chemical features of VA-CNTs, opens up new opportunities for the design of self-cleaning surfaces, preventing the formation of microbial colonies.

Carbon nanotube-based nano-biosensors for detecting heavy metals in the aquatic environment

The identification of harmful metal ions in aquatic environments is a global concern since these contaminants can have serious consequences for plants, animals, humans, and ecosystems. A biosensor is a type of analytical equipment that combines a biological recognition element and a physical transducer to detect biological signals to produce a detectable indication proportionate to the concentration of the samples being analysed. The analyte spreads from the fluid to the biosensor's superficial. The analyte responds precisely and competently with the biosensor's biological component. The physicochemical properties of the transducer surface change as a result of this process. The visual or electric properties of the transducer surface alter as a result of this. The signal that is detected is an electrical signal. With the help of carbon-based nano-biosensors, metals from the aquatic environment can easily be detected, which is much simpler, less time-consuming, and less expensive as well.

Anti-Infective and Toxicity Properties of Carbon Based Materials: Graphene and Functionalized Carbon Nanotubes

Recently, antimicrobial activities of various carbon-based nanomaterials against specific pathogens have become one of the most significant research interests in this field. Carbon nanotubes (CNTs) are promising multidisciplinary nanostructures in biomedicine, drug delivery, genetic engineering, biosensors, and artificial implants. However, the biomedical administration of CNTs is dependent on their solubility, toxicity, and biocompatibility, as well as novel drug-delivery applications through optimization of the drug's loading capacity, cellular absorption, and continuous release within the target cell. The usage of CNTs and Graphene materials as antimicrobial agents and nanocarriers for antibiotics delivery would possibly improve their bioavailability and facilitate better anti-infective therapy. However, it is worth mentioning that CNTs' antimicrobial activity and toxicity are highly dependent on their preparation and synthesis method. Various types of research have confirmed that diameter, length, residual catalyst, metal content, surface coating, electronic structure, and dispersibility would affect CNTs' toxicity toward bacteria and human cells. In this review article, a general study was performed on the antimicrobial properties of carbon-based nanomaterials, as well as their toxicity and applications in confronting different microorganisms. This study could be useful for researchers who are looking for new and effective drug delivery methods in the field of microbial resistance.

Enhanced Pb(II) removal from water using conductive carbonaceous nanomaterials as bacterial scaffolds: An experimental and modelling approach

This study investigated the abilities of electrochemically active bacteria (EAB) as bio-catalysts for Pb(II) bioreduction in an attached growth reactor. Electrically conductive carbon nanofibers (CNF) were used as bacterial scaffolds to facilitate electron transfer between EAB and Pb(II). Our results demonstrated that the CNF attached growth reactor can remove > 80% and > 90% of Pb(II) from solution at 0.5 mg/L and 5.0 mg/L concentrations, respectively, and maintained Pb(II) levels < 0.10 mg/L over repeated Pb(II) dosages dosed at all concentrations. Experimental measurements by SEM-EDX and ICP-OES provided evidence that Pb(II) was reduced to Pb⁰, suggesting that Pb(II) was adsorbed onto CNFs, and subsequently bioreduced. Numerical modelling was used to estimate Pb(II) concentrations along the CNFs via capturing Pb(II)'s diffusive transport, and the removal mechanisms governed by EAB and CNF adsorption. The model simulation results demonstrated that Pb(II) bioreduction was dominant in the reactor and the significance of Monod kinetics, biofilm thickness and Pb(II) dosage concentration on its removal. This study is the first to prove EAB's ability to treat Pb(II) from contaminated waters in an attached growth configuration. The findings here demonstrate that CNFs can boost biological treatment efficacies in wastewater and/or water treatment to meet stringent water guidelines.

Nanostructured Antibiotics and Their Emerging Medicinal Applications: An Overview of Nanoantibiotics

Bacterial strains resistant to antimicrobial treatments, such as antibiotics, have emerged as serious clinical problems, necessitating the development of novel bactericidal materials. Nanostructures with particle sizes ranging from 1 to 100 nanometers have appeared recently as novel antibacterial agents, which are also known as “nanoantibiotics”. Nanomaterials have been shown to exert greater antibacterial effects on Gram-positive and Gram-negative bacteria across several studies. Antibacterial nanofilms for medical implants and restorative matters to prevent bacterial harm and antibacterial vaccinations to control bacterial infections are examples of nanoparticle applications in the biomedical sectors. The development of unique nanostructures, such as nanocrystals and nanostructured materials, is an exciting step in alternative efforts to manage microorganisms because these materials provide disrupted antibacterial effects, including better biocompatibility, as opposed to minor molecular antimicrobial systems, which have short-term functions and are poisonous. Although the mechanism of action of nanoparticles (NPs) is unknown, scientific suggestions include the oxidative-reductive phenomenon, reactive ionic metals, and reactive oxygen species (ROS). Many synchronized gene transformations in the same bacterial cell are essential for antibacterial resistance to emerge; thus, bacterial cells find it difficult to build resistance to nanoparticles. Therefore, nanomaterials are considered as advanced solution tools for the fields of medical science and allied health science. The current review emphasizes the importance of nanoparticles and various nanosized materials as antimicrobial agents based on their size, nature, etc.

Mitigating Antibiotic Resistance Genes in Wastewater by Sequential Treatment with Novel Nanomaterials

Wastewater (WW) has been widely recognized as the major sink of a variety of emerging pathogens (EPs), antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs), which may disseminate and impact wider environments. Improving and maximizing WW treatment efficiency to remove these microbial hazards is fundamentally imperative. Despite a variety of physical, biological and chemical treatment technologies, the efficiency of ARG removal is still far from satisfactory. Within our recently accomplished M-ERA.NET project, novel functionalized nanomaterials, i.e., molecularly imprinted polymer (MIP) films and quaternary ammonium salt (QAS) modified kaolin microparticles, were developed and demonstrated to have significant EP removal effectiveness on both Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB) from WW. As a continuation of this project, we took the further step of exploring their ARG mitigation potential. Strikingly, by applying MIP and QAS functionalized kaolin microparticles in tandem, the ARGs prevalent in wastewater treatment plants (WWTPs), e.g., blaCTXM, ermB and qnrS, can be drastically reduced by 2.7, 3.9 and 4.9 log (copies/100 mL), respectively, whereas sul1, tetO and mecA can be eliminated below their detection limits. In terms of class I integron-integrase I (intI1), a mobile genetic element (MGE) for horizontal gene transfer (HGT), 4.3 log (copies/100 mL) reduction was achieved. Overall, the novel nanomaterials exhibit outstanding performance on attenuating ARGs in WW, being superior to their control references. This finding provides additional merit to the application of developed nanomaterials for WW purification towards ARG elimination, in addition to the proven bactericidal effect.

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.

SWNTs-PAN/TPU/PANI composite electrospun nanofiber membrane for point-of-use efficient electrochemical disinfection: New strategy of CNT disinfection

Single-walled carbon nanotubes (SWNTs) can be used as 1D electrochemical disinfection material for point-of-use water treatment but are limited by their poor durability and possible cytotoxicity. Immobilizing SWNTs in nanofibers with electrospinning served as slow-release technology develop a novel with a lasting antibacterial and (eco-) toxicological alleviation of SWNTs. Hence, the single-walled carbon nanotubes-polyacrylonitrile/polyurethane/polyaniline (SWNTs-PAN/TPU/PANI, SPTP) composite electrospun nanofiber membrane was successfully fabricated by co-electrospinning process and the electrochemical filtration and disinfection system of point-of-use drinking water treatment is constructed. In the absence of electrolysis, the SPTP filter is effective for complete removal of bacteria by sieving mechanism. Concomitant electrolysis in the course of filtration results in significantly increased inactivation of sieved bacteria. Application of 3.0 V leads to complete (5 log) inactivation of bacteria within 20 min. 5-cycle experiments, membrane flux and shake flask tests prove that composite restrict the excessive release of SWNTs retaining the long-lasting antibacterial properties of SPTP membrane. At 1.0 and 2.0 V, electrolyte concentration and composition is irrelevant to electrochemical inactivation consistent with oxidation of SPTP filter. Bacterial reactive oxygen species (ROSs) also support an oxidation mechanism. At 3.0 V, electrochemical disinfection mainly relies on indirect oxidation.

Removal of bacteriophage f2 in water by Fe/Ni nanoparticles: Optimization of Fe/Ni ratio and influencing factors

Pathogenic viruses in water are seriously harmful to human health and highly resistant to conventional disinfections. As a kind of promising attempts for pollution remediation, Fe-based nanoparticles show excellent performance in removing contaminants. In this study, the Fe/Ni nanoparticles (Fe/Ni NPs) were synthesized using the self-designed device and used for bacteriophage inactivation in water. Scanning electron microscope (SEM) and X-ray diffraction (XRD) showed that the as-prepared Fe/Ni particles were spherical and the average particle size was 93 nm. The synthesized Fe/Ni NPs achieved much higher removal efficiency of bacteriophage f2 than nanoscale zero-valent iron (nZVI), while Ni nanoparticles (Ni NPs) showed no removal effect on the bacteriophage f2. The highest removal efficiency of bacteriophage f2 by Fe/Ni NPs was obtained when the primary ratio of Fe:Ni was 5:1. In addition, the removal efficiency of phage f2 under aerobic condition was significantly higher than that under anaerobic condition with Fe/Ni NPs, and the role of Ni was proved as a catalyst in the system. Besides, the effect of initial pH, initial concentration of bacteriophage f2, particles dose, rotation rate, and temperature on the removal efficiency of bacteriophage f2 were studied. The result showed that the removal efficiency of bacteriophage f2 did not change obviously in the test pH range (5-8), and was positively related with the rotation rate and negatively related with the initial concentration of bacteriophage f2. The particles dose could increase the removal efficiency of phage f2, but the removal efficiency would decrease when the dose was too much due to the aggregation of nanoparticles. The increase of temperature could increase the removal efficiency initially, but decrease the removal efficiency finally due to the accelerated corrosion of iron.