Inactivation of Bacillus anthracis spores by single-walled carbon nanotubes coupled with oxidizing antimicrobial chemicals

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.

Instructive analysis of engineered carbon materials for potential application in water and wastewater treatment

Water remediation is an essential component for sustainable development. Increasing population and rapid industrialization have contributed to the deterioration of water resources. In particular, effluents from chemical, pharmaceutical, petroleum industries, and anthropogenic activities have led to severe ecological degradation. Many of these detrimental pollutants are highly toxic even at low concentrations, acting as carcinogens and inflicting severe long-lasting effects on human health. This review underscores the potential applications of engineered carbon-based materials for effective wastewater treatment. It focuses on the performance as well as efficiency of activated carbon, graphene nanomaterial, and carbon nanotubes, both with and without chemical functionalization. Plausible mechanisms of action between the chemically functionalized adsorbent and pollutants are also discussed. Based on the keywords from the literature published in the recent five years, a statistical practicality-vs-applicability analysis of these three materials is also provided. The review will provide a deep understanding of the physical or chemical interactions of the wastewater pollutants with carbon materials.

Nanoparticle composite TPNT1 is effective against SARS-CoV-2 and influenza viruses

A metal nanoparticle composite, namely TPNT1, which contains Au-NP (1 ppm), Ag-NP (5 ppm), ZnO-NP (60 ppm) and ClO2 (42.5 ppm) in aqueous solution was prepared and characterized by spectroscopy, transmission electron microscopy, dynamic light scattering analysis and potentiometric titration. Based on the in vitro cell-based assay, TPNT1 inhibited six major clades of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with effective concentration within the range to be used as food additives. TPNT1 was shown to block viral entry by inhibiting the binding of SARS-CoV-2 spike proteins to the angiotensin-converting enzyme 2 (ACE2) receptor and to interfere with the syncytium formation. In addition, TPNT1 also effectively reduced the cytopathic effects induced by human (H1N1) and avian (H5N1) influenza viruses, including the wild-type and oseltamivir-resistant virus isolates. Together with previously demonstrated efficacy as antimicrobials, TPNT1 can block viral entry and inhibit or prevent viral infection to provide prophylactic effects against both SARS-CoV-2 and opportunistic infections.

Review of Decontamination Techniques for the Inactivation of Bacillus anthracis and Other Spore-Forming Bacteria Associated with Building or Outdoor Materials

Since the intentional release of Bacillus anthracis spores through the U.S. Postal Service in the fall of 2001, research and development related to decontamination for this biological agent have increased substantially. This review synthesizes the advances made relative to B. anthracis spore decontamination science and technology since approximately 2002, referencing the open scientific literature and publicly available, well-documented scientific reports. In the process of conducting this review, scientific knowledge gaps have also been identified. This review focuses primarily on techniques that are commercially available and that could potentially be used in the large-scale decontamination of buildings and other structures, as well as outdoor environments. Since 2002, the body of scientific data related to decontamination and microbial sterilization has grown substantially, especially in terms of quantifying decontamination efficacy as a function of several factors. Specifically, progress has been made in understanding how decontaminant chemistry, the materials the microorganisms are associated with, environmental factors, and microbiological methods quantitatively impact spore inactivation. While advancement has been made in the past 15 years to further the state of the science in the inactivation of bacterial spores in a decontamination scenario, further research is warranted to close the scientific gaps that remain.

Carbon nanotubes as antimicrobial agents for water disinfection and pathogen control

Waterborne diseases significantly affect human health and are responsible for high mortality rates worldwide. Antibiotics have been known for decades for treatment of bacterial strains and their overuse and irrational applications are causing increasing bacteria resistance. Therefore, there is a strong need to find alternative ways for efficient water disinfection and microbial control. Carbon nanotubes (CNTs) have demonstrated strong antimicrobial properties due to their remarkable structure. This paper reviews the antimicrobial properties of CNTs, discusses diverse mechanisms of action against microorganisms as well as their applicability for water disinfection and microbial control. Safety concerns, challenges of CNTs as antimicrobial agents and future opportunities for their application in the water remediation process are also highlighted.

Nano/micromotors for security/defense applications. A review

The new capabilities of man-made micro/nanomotors open up considerable opportunities for diverse security and defense applications. This review highlights new micromotor-based strategies for enhanced security monitoring and detoxification of chemical and biological warfare agents (CBWA). The movement of receptor-functionalized nanomotors offers great potential for sensing and isolating target bio-threats from complex samples. New mobile reactive materials based on zeolite or activated carbon offer considerable promise for the accelerated removal of chemical warfare agents. A wide range of proof-of-concept motor-based approaches, including the detection and destruction of anthrax spores, 'on-off' nerve-agent detection or effective neutralization of chemical warfare agents have thus been demonstrated. The propulsion of micromotors and their corresponding bubble tails impart significant mixing that greatly accelerates such detoxification processes. These nanomotors will thus empower sensing and destruction where stirring large quantities of decontaminating reagents and controlled mechanical agitation are impossible or undesired. New technological breakthroughs and greater sophistication of micro/nanoscale machines will lead to rapid translation of the micromotor research activity into practical defense applications, addressing the escalating threat of CBWA.

Nanoparticles as potential new generation broad spectrum antimicrobial agents

The rapid emergence of antimicrobial resistant strains to conventional antimicrobial agents has complicated and prolonged infection treatment and increased mortality risk globally. Furthermore, some of the conventional antimicrobial agents are unable to cross certain cell membranes thus, restricting treatment of intracellular pathogens. Therefore, the disease-causing-organisms tend to persist in these cells. However, the emergence of nanoparticle (NP) technology has come with the promising broad spectrum NP-antimicrobial agents due to their vast physiochemical and functionalization properties. In fact, NP-antimicrobial agents are able to unlock the restrictions experienced by conventional antimicrobial agents. This review discusses the status quo of NP-antimicrobial agents as potent broad spectrum antimicrobial agents, sterilization and wound healing agents, and sustained inhibitors of intracellular pathogens. Indeed, the perspective of developing potent NP-antimicrobial agents that carry multiple-functionality will revolutionize clinical medicine and play a significant role in alleviating disease burden.

Micromotors to capture and destroy anthrax simulant spores

Towards addressing the need for detecting and eliminating biothreats, we describe a micromotor-based approach for screening, capturing, isolating and destroying anthrax simulant spores in a simple and rapid manner with minimal sample processing. The B. globilli antibody-functionalized micromotors can recognize, capture and transport B. globigii spores in environmental matrices, while showing non-interactions with excess of non-target bacteria. Efficient destruction of the anthrax simulant spores is demonstrated via the micromotor-induced mixing of a mild oxidizing solution. The new micromotor-based approach paves a way to dynamic multifunctional systems that rapidly recognize, isolate, capture and destroy biological threats.

Inhibitory effects of single-walled carbon nanotubes on biofilm formation from Bacillus anthracis spores

This study reports the inhibitory effect of single walled carbon nanotubes (SWCNTs) on biofilm formation from Bacillus anthracis spores. Although the presence of 50 to 100 μg ml(-1) of SWCNTs in the suspension increased spore attachment in the wells of 96-well plates, the presence of 200 μg ml(-1) of SWCNTs in the germination solution decreased the germination percentage of the attached spores by 93.14%, completely inhibiting subsequent biofilm formation. The inhibition kinetics of 50 μg ml(-1) SWCNTs on biofilm formation showed that this concentration inhibited biofilm formation by 81.2% after incubation for 48 h. SWCNT treatment in the earlier stages of biofilm formation was more effective compared to treatment at later stages. Mature biofilms were highly resistant to SWCNT treatment.

Investigation of gelatin/multi-walled carbon nanotube nanocomposite films as packaging materials

Gelatin composite films were prepared from gelatin solutions (10% w/v) containing multi-walled carbon nanotubes (MWCNT, 0.5, 1, 1.5, and 2% w/w gelatin) as nanofiller. The water solubility, water swelling, water uptake, water vapor permeability (WVP), mechanical, and antibacterial properties of the films were examined. Water solubility, water swelling, water uptake, and WVP for gelatin films were 45 ± 1%, 821 ± 42%, 45 ± 1.1%, and 0.4 ± 0.022 g mm/m² kPa h, respectively. Incorporation of MWCNT caused a significant decrease in water solubility, water swelling, water uptake, and WVP. Gelatin/MWCNT films containing 1–1.5% MWCNT showed the lowest water vapor transmission. Tensile strength, elongation at break, and Young's modulus for gelatin films were 13.4 ± 1.2 MPa, 95 ± 5%, and 45.4 ± 7 MPa, respectively. Incorporation of MWCNT caused a significant increase in tensile strength and decrease in the elongation at break. The largest mechanical strength was found at 1.5% MWCNT. All gelatin/MWCNT films showed significant antibacterial activities against both gram-positive and gram-negative bacteria. Our results suggest that the gelatin/MWCNT composites films could be used as a very attractive alternative to traditional materials for different biomedical and food applications.

Dual effects of single-walled carbon nanotubes coupled with near-infrared radiation on Bacillus anthracis spores: inactivates spores and stimulates the germination of surviving spores

BACKGROUND

Bacillus anthracis is a pathogen that causes life-threatening disease--anthrax. B. anthracis spores are highly resistant to extreme temperatures and harsh chemicals. Inactivation of B. anthracis spores is important to ensure the environmental safety and public health. The 2001 bioterrorism attack involving anthrax spores has brought acute public attention and triggered extensive research on inactivation of B. anthracis spores. Single-walled carbon nanotubes (SWCNTs) as a class of emerging nanomaterial have been reported as a strong antimicrobial agent. In addition, continuous near infrared (NIR) radiation on SWCNTs induces excessive local heating which can enhance SWCNTs' antimicrobial effect. In this study, we investigated the effects of SWCNTs coupled with NIR treatment on Bacillus anthracis spores.

RESULTS AND DISCUSSION

The results showed that the treatment of 10 μg/mL SWCNTs coupled with 20 min NIR significantly improved the antimicrobial effect by doubling the percentage of viable spore number reduction compared with SWCNTs alone treatment (88% vs. 42%). At the same time, SWCNTs-NIR treatment activated the germination of surviving spores and their dipicolinic acid (DPA) release during germination. The results suggested the dual effect of SWCNTs-NIR treatment on B. anthracis spores: enhanced the sporicidal effect and stimulated the germination of surviving spores. Molecular level examination showed that SWCNTs-NIR increased the expression levels (>2-fold) in 3 out of 6 germination related genes tested in this study, which was correlated to the activated germination and DPA release. SWCNTs-NIR treatment either induced or inhibited the expression of 3 regulatory genes detected in this study. When the NIR treatment time was 5 or 25 min, there were 3 out of 7 virulence related genes that showed significant decrease on expression levels (>2 fold decrease).

CONCLUSIONS

The results of this study demonstrated the dual effect of SWCNTs-NIR treatment on B. anthracis spores, which enhanced the sporicidal effect and stimulated the germination of surviving spores. SWCNTs-NIR treatment also altered the expression of germination, regulatory, and virulence-related genes in B. anthracis.