Synthesis of ZnO coated multi-walled carbon nanotubes and their antibacterial activities

Evaluation of antibiofilm activity of metal oxides nanoparticles and carbon nanotubes coated styrofoam on the bacterium Jeotgalicoccus huakuii

The co-existence of metal oxide nanoparticles (MONPs), carbon-based nanomaterials and microplastics (MPs) in the natural environment are expected to be of growing global concern due to their increasing abundance and persistence in the environment worldwide. Knowledge of the interaction of the above compounds particularly under light irradiation in water remains limited. In the present study, the possible individual and combined toxic effects of MONPs, carbon nanotubes (CNTs) through styrofoam (SF) on the environmental bacterium Jeotaglicoccus huakuii were systematically investigated. The fabricated MONPs and CNTs were characterized using the following techniques: FT-IR (functional groups), XRD (crystallinity), SEM, and EDX (topological morphology). The objective of this study was to investigate and identify naturally occurring bacteria capable of mitigating and detoxifying toxic pollutants under adverse conditions. Moreover, the assessment of minimum inhibitory concentration (MIC) was made through an agar well plate method, resazurin (ELISA measurement), growth kinetics and bacterial viability were assessed employing live and dead assay and biofilm combating ability was analyzed using an antibiofilm assay. Further, the biotransformation of f-MWCNTs by J. huakuii was evaluated employing RT-PCR and SEM analysis. The results demonstrated that the toxicity of Pb3O4@f-MWCNTs was comparatively higher than the remaining Pb3O4 NPs and SF coated NPs.. Interestingly, J. huakuii showed resistance against f-MWCNTs at very high concentrations and able to utilize f-MWCNTs as a sole carbon source suggesting J. huakuii as a suitable aquatic bioremediation tool for both MONPs and CNTs transfer via MPs. The results also enhanced our understanding of the affinity of MPs towards MONPs and CNTs under extreme environmental conditions.

A review of microbes mediated biosynthesis of silver nanoparticles and their enhanced antimicrobial activities

In recent decades, biosynthesis of metal and (or) metal oxide nanoparticles using microbes is accepted as one of the most sustainable, cost-effective, robust, and green processes as it does not encompass the usage of largely hazardous chemicals. Accordingly, numerous simple, inexpensive, and environmentally friendly approaches for the biosynthesis of silver nanoparticles (AgNPs) were reported using microbes avoiding conventional (chemical) methods. This comprehensive review detailed an advance made in recent years in the microbes-mediated biosynthesis of AgNPs and evaluation of their antimicrobial activities covering the literature from 2015-till date. It also aimed at elaborating the possible effect of the different phytochemicals, their concentrations, extraction temperature, extraction solvent, pH, reaction time, reaction temperature, and concentration of precursor on the shape, size, and stability of the synthesized AgNPs. In addition, while trying to understand the antimicrobial activities against targeted pathogenic microbes the probable mechanism of the interaction of produced AgNPs with the cell wall of targeted microbes that led to the cell's reputed and death have also been detailed. Lastly, this review detailed the shape and size-dependent antimicrobial activities of the microbes-mediated AgNPs and their enhanced antimicrobial activities by synergetic interaction with known commercially available antibiotic drugs.

Nano Revolution: "Tiny tech, big impact: How nanotechnology is driving SDGs progress"

Nanotechnology has emerged as a powerful tool in addressing global challenges and advancing sustainable development. By manipulating materials at the nanoscale, researchers have unlocked new possibilities in various fields, including energy, healthcare, agriculture, construction, transportation, and environmental conservation. This paper explores the potential of nanotechnology and nanostructures in contributing to the achievement of the United Nations (UN) Sustainable Development Goals (SDGs) by improving energy efficiency and energy conversion, leading to a more sustainable and clean energy future, improving water purification processes, enabling access to clean drinking water for communities, enabling targeted drug delivery systems, early disease detection, and personalized medicine, thus revolutionizing healthcare, improving crop yields, efficient nutrient delivery systems, pest control mechanisms, and many other areas, therefore addressing food security issues. It also highlights the potential of nanomaterials in environmental remediation and pollution control. Therefore, by understanding and harnessing nanotechnology's potential, policymakers, researchers, and stakeholders can work together toward a more sustainable future by achieving the 17 UN SDGs.

Nanobiomaterials: exploring mechanistic roles in combating microbial infections and cancer

The initiation of the "nanotechnology era" within the past decade has been prominently marked by advancements in biomaterials. This intersection has opened up numerous possibilities for enhancing the detection, diagnosis, and treatment of various illnesses by leveraging the synergy between biomaterials and nanotechnology. The term "nano biomaterials" referring to biomaterials featuring constituent or surface feature sizes below 100 nm, presents a realm of extraordinary materials endowed with unique structures and properties. Beyond addressing common biomedical challenges, these nano biomaterials contribute unprecedented insights and principles that enrich our understanding of biology, medicine, and materials science. A critical evaluation of recent technological progress in employing biomaterials in medicine is essential, along with an exploration of potential future trends. Nanotechnology breakthroughs have yielded novel surfaces, materials, and configurations with notable applications in the biomedical domain. The integration of nanotechnology has already begun to enhance traditional biomedical practices across diverse fields such as tissue engineering, intelligent systems, the utilization of nanocomposites in implant design, controlled release systems, biosensors, and more. This mini review encapsulates insights into biomaterials, encompassing their types, synthesis methods, and the roles of organic and inorganic nanoparticles, elucidating their mechanisms of action. Furthermore, the focus is squarely placed on nano biomaterials and their versatile applications, with a particular emphasis on their roles in anticancer and antimicrobial interventions. This review underscores the dynamic landscape of nanotechnology, envisioning a future where nano biomaterials play a pivotal role in advancing medical applications, particularly in combating cancer and microbial infections.

Nanosurface Texturing for Enhancing the Antibacterial Effect of Biodegradable Metal Zinc: Surface Modifications

Zinc (Zn) as a biodegradable metal has attracted research interest for bone reconstruction, with the aim of eliminating the need for a second removal surgery and minimizing the implant-to-bone transfer of stress-shielding to maintain bone regeneration. In addition, Zn has been shown to have antibacterial properties, particularly against Gram-negative bacteria, and is often used as a surface coating to inhibit bacterial growth and biofilm formation. However, the antibacterial property of Zn is still suboptimal in part due to low Zn ion release during degradation that has to be further improved in order to meet clinical requirements. This work aims to perform an innovative one-step surface modification using a nitric acid treatment to accelerate Zn ion release by increasing surface roughness, thereby endowing an effective antimicrobial property and biofilm formation inhibition. The antibacterial performance against Staphylococci aureus was evaluated by assessing biofilm formation and adhesion using quantitative assays. The surface roughness of acid-treated Zn (Ra ~ 30 nm) was significantly higher than polished Zn (Ra ~ 3 nm) and corresponded with the marked inhibition of bacterial biofilm, and this is likely due to the increased surface contact area and Zn ion accumulation. Overall, surface modification due to nitric acid etching appears to be an effective technique that can produce unique morphological surface structures and enhance the antibacterial properties of biodegradable Zn-based materials, thus increasing the translation potential toward multiple biomedical applications.

Zein nanospheres assisting inorganic and organic drug combination to overcome stent implantation-induced thrombosis and infection

The complication of stent implantation is the biggest obstacle to the success of its clinical application. In this study, we developed a combination way of 3D printing and the coating technique for preparation of functional polyurethane stents against stent implantation-induced thrombosis and postoperative infection. SEM, XPS, static water contact angle, and XRD demonstrated that the functional polyurethane stent had a 37 μm-thickness membrane composed of zein nanospheres (250-350 nm). Meanwhile, ZnO nanoparticles were encapsulated in zein nanospheres while heparin was adsorbed on the surface, causing 97.1 ± 6.4 % release of heparin in 120 min (first-order kinetic model) and 62.7 ± 5.6 % release of Zn²⁺ in 9 days (Korsmeyer-Peppas model). The mechanical analysis revealed that the functional polyurethane stents had about 8.61 MPa and 2.5 MPa tensile strength and bending strength, respectively. The in vitro biological analysis showed that the functional polyurethane stents had good EA.hy926 cells compatibility (97.9 ± 3.8 %), anti-coagulation response (comparable plasma protein, platelet adhesion and suppressed clotting) and sustained antibacterial activities by comparison with the bare polyurethane stent. The preliminary evaluation by rabbit ex vivo carotid artery intervention experiment demonstrated that the functional polyurethane stents could maintain blood circulation under the continuous stresses of blood flow. Meanwhile, the detailed data from the simulated implant infection experiment in vivo showed the functional polyurethane stents could effectively reduce microbial infection by 3-6 times lower and improve fibrosis and macrophage infiltration.

Recent Advances and Mechanistic Insights into Antibacterial Activity, Antibiofilm Activity, and Cytotoxicity of Silver Nanoparticles

The substantial increase in multidrug-resistant (MDR) pathogenic bacteria is a major threat to global health. Recently, the Centers for Disease Control and Prevention reported possibilities of greater deaths due to bacterial infections than cancer. Nanomaterials, especially small-sized (size ≤10 nm) silver nanoparticles (AgNPs), can be employed to combat these deadly bacterial diseases. However, high reactivity, instability, susceptibility to fast oxidation, and cytotoxicity remain crucial shortcomings for their uptake and clinical application. In this review, we discuss various AgNPs-based approaches to eradicate bacterial infections and provide comprehensive mechanistic insights and recent advances in antibacterial activity, antibiofilm activity, and cytotoxicity (both in vitro and in vivo) of AgNPs. The mechanistic of antimicrobial activity involves four steps: (i) adhesion of AgNPs to cell wall/membrane and its disruption; (ii) intracellular penetration and damage; (iii) oxidative stress; and (iv) modulation of signal transduction pathways. Numerous factors affecting the bactericidal activity of AgNPs such as shape, size, crystallinity, pH, and surface coating/charge have also been described in detail. The review also sheds light on antimicrobial photodynamic therapy and the role of AgNPs versus Ag⁺ ions release in bactericidal activities. In addition, different methods of synthesis of AgNPs have been discussed in brief.

Variation in the Performance of MWCNT/ZnO Hybrid Material with pH for Efficient Antibacterial Agent

In the present work, multiwalled carbon nanotube (MWCNT)/zinc oxide (ZnO) nanoparticles at pH 6.0, 7.0, 8.0, and 10.0 were prepared through the coprecipitation method to improve the antibacterial activity. Morphological, structural, and optical analysis, such as Fourier transform infrared spectroscopy, X-ray diffraction, and field emission scanning electron microscopy, was used to investigate the formation of composites. Analysis revealed that there were variations in morphology from agglomerated structures to rod-like then flower-like structures as pH varied from 6.0 to 10.0. The MWCNT/ZnO composite enhanced the antibacterial activity especially for Staphylococcus aureus as a maximum 20 mm zone of inhibition was observed. The data presented in the present study proves that such composites are an efficient antibacterial agent and suitable for therapy for severe infections.

A review of recent and emerging antimicrobial nanomaterials in wastewater treatment applications

In this paper, we present a critical review on antimicrobial nanomaterials with demonstrated potential for application as a disinfection technology in wastewater treatment. Studies involving fabrication and testing of antimicrobial nanomaterials for wastewater treatment were gathered, critically reviewed, and analyzed. Our review shows that there are only a few eligible candidate nanoparticles (NPs) (metal and metal oxide) that can adequately serve as an antimicrobial agent. Nanosilver (nAg) was the most studied and moderately understood metal NPs with proven antimicrobial activity followed by ZnO (among antimicrobial metal oxide NPs) which outperformed titania (in the absence of light) in efficacy due to its better solubility in aqueous condition. The direction of future work was found to be in the development of antimicrobial nanocomposites, since they provide more stability for antimicrobial metal and metal oxides NPs in water, thereby increasing their activity. This review will serve as an updated survey, yet touching also the fundamentals of the antimicrobial activity, with vital information for researchers planning to embark on the development of superior antimicrobial nanomaterials for wastewater treatment applications.

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.

Hybrid Materials Based on Multi-Walled Carbon Nanotubes and Nanoparticles with Antimicrobial Properties

In this study, multi-walled carbon nanotubes (MWCNTs) were decorated with different types of nanoparticles (NPs) in order to obtain hybrid materials with improved antimicrobial activity. Structural and morphological analysis, such as Fourier transformed infrared spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, environmental scanning electron microscopy/energy-dispersive X-ray spectroscopy and the Brunauer-Emmett-Teller technique were used in order to investigate the decoration of the nanotubes with NPs. Analysis of the decorated nanotubes showed a narrow size distribution of NPs, 7-13 nm for the nanotubes decorated with zinc oxide (ZnO) NPs, 15-33 nm for the nanotubes decorated with silver (Ag) NPs and 20-35 nm for the nanotubes decorated with hydroxyapatite (HAp) NPs, respectively. The dispersion in water of the obtained nanomaterials was improved for all the decorated MWCNTs, as revealed by the relative absorbance variation in time of the water-dispersed nanomaterials. The obtained nanomaterials showed a good antimicrobial activity; however, the presence of the NPs on the surface of MWCNTs improved the nanocomposites' activity. The presence of ZnO and Ag nanoparticles enhanced the antimicrobial properties of the material, in clinically relevant microbial strains. Our data proves that such composite nanomaterials are efficient antimicrobial agents, suitable for the therapy of severe infection and biofilms.

Understanding the first half-ALD cycle of the ZnO growth on hydroxyl functionalized carbon nanotubes

We report the adsorption of diethylzinc on hydroxyl functionalized carbon nanotubes. This study intends to understand, at the atomic level, the initial stages of ZnO formation by atomic layer deposition. Our study begins with the molecule physisorbed on the nanotube (initial state of the reaction). The final state of this reaction is when the H atom of the hydroxyl group is abstracted and migrates to one ethyl group of diethylzinc. The oxygen atom relaxes towards the nanotube and forms a strong bond with a carbon atom, while the remaining part of the molecule forms a bond with the H atom and physisorbs on top of the ZnO unit. The probability for this process to happen is very high since the energy to desorb the diethylzinc molecule is higher than the energy needed to break down the O-H bond. Non-covalent interactions and charge density distributions are plotted to confirm the break-down, formation of bonds, and repulsion during the reaction pathway.

Zeolitic imidazolate framework-8 (ZIF-8) doped TiZSM-5 and Mesoporous carbon for antibacterial characterization

Drug resistant bacteria affects millions worldwide and remains a serious threat to health care system. The study reports the first application of hybrid nanocomposites based on zeolitic imidazolate framework-8 (ZIF-8) with MFI structured zeolite Ti-ZSM-5 (TiZ5) and mesoporous carbon (MC). The composite was designated as TiZ5/ZIF-8 and MC/ZIF-8 was studied for antibacterial activity. Bioactive components Zn2+ and 2-methyl imidazole present in ZIF-8 was found to exert significant antibacterial effect on Escherchia. coli and Staphyloccocus. No other antibiotic drugs are required. For comparative purpose, Fe-BTC MOF (BTC = 1,3,5-benzenetricarboxylate) was used as second set of nanoformulations (TiZ5/Fe-BTC and MC/Fe-BTC) but showed a lower antibacterial activity. The phase (X-ray diffraction), texture (BET surface area), coordination (DRS-UV-Vis), and morphology (TEM) was investigated. XRD showed the presence of nanosized ZIF-8 over TiZ5 and MC. Surface area calculation using N2 adsorption isotherm showed a reduction in the micropore surface area of ZIF-8 from 1148 m2/g to 224 m2/g (80%) and an increased meso surface area from 31 m2/g to 59 m2/g (90%). The mesopore pore volume increased significantly from 0.05 cm3/g to 0.12 m2/g. MC/ZIF-8 showed similar textural modifications. FT-IR spectra and DRS-UV-Vis spectra showed distinct composite formation with TiZ5, while a weak absorption of ZIF-8 observed over MC. TEM revealed the presence of nanocomposite MC/ZIF-8 and TiZ5/ZIF-8 distributed in nanosize ranging between 25 and 50 nm. TiZ5/ZIF-8 showed the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of 0.5 and 1 mg/ml, respectively against E. coli. The MIC and MBC of TiZ5/ZIF-8 against S. aureus were 1 and 2 mg/ml, respectively. MC/ZIF-8 composite had second best antibacterial activity. This study shows that ZIF-8 based composite holds a great potential against E. coli and S. aureus.

Pollution, Toxicity and Carcinogenicity of Organic Dyes and their Catalytic Bio-Remediation

Water pollution due to waste effluents of the textile industry is seriously causing various health problems in humans. Water pollution with pathogenic bacteria, especially Escherichia coli (E. coli) and other microbes is due to the mixing of fecal material with drinking water, industrial and domestic sewage, pasture and agricultural runoff. Among the chemical pollutants, organic dyes due to toxic nature, are one of the major contaminants of industrial wastewater. Adequate sanitation services and drinking quality water would eliminate 200 million cases of diarrhea, which results in 2.1 million less deaths caused by diarrheal disease due to E. coli each year. Nanotechnology is an excellent platform as compared to conventional treatment methods of water treatment and remediation from microorganisms and organic dyes. In the current study, toxicity and carcinogenicity of the organic dyes have been studied as well as the remediation/inactivation of dyes and microorganism has been discussed. Remediation by biological, physical and chemical methods has been reviewed critically. A physical process like adsorption is cost-effective, but can't degrade dyes. Biological methods were considered to be ecofriendly and cost-effective. Microbiological degradation of dyes is cost-effective, eco-friendly and alternative to the chemical reduction. Besides, certain enzymes especially horseradish peroxidase are used as versatile catalysts in a number of industrial processes. Moreover, this document has been prepared by gathering recent research works related to the dyes and microbial pollution elimination from water sources by using heterogeneous photocatalysts, metal nanoparticles catalysts, metal oxides and enzymes.

Novel synthesis of ZnO by Ice-cube method for photo-inactivation of E. coli

The ZnO particle with varieties of morphology was prepared from ice-cube of zinc ammonium complex at boiling water surface in 1 min induction of thermal shock. The zinc ammonium complex in ice cube was developed using zinc acetate and biologically activated ammonia in 1 hr and kept in the freezer. Temperature gradient behaviour of the water medium during thermal shock was captured by the thermal camera and thermometer. Morphology study revealed a variety of flower-like ZnO particles with variable size from 1.0 to 2.5 μm. Further, ZnO particle morphologies were tuned by adding trisodium citrate and hexamine to obtain uniform spherical (2–3 μm) and flower (3–4 μm) shapes, respectively. XRD patterns revealed that all ZnO samples are of a hexagonal structure. Photocatalytic inactivation of E. coli has been investigated using various particle morphologies of ZnO in an aqueous solution/overcoated glass slide under sunlight. The photo-inactivation of E. coli by ZnO particles in suspension condition was better when compared to a coated glass slide method. AFM study confirmed the destruction of bacterial cell wall membrane by the photocatalytic effect. The particles morphology of photocatalyst is well dependent on antibacterial activity under sunlight.

Antibacterial effects of graphene- and carbon-nanotube-based nanohybrids on Escherichia coli: Implications for treating multidrug-resistant bacteria

Some nanomaterials including Fe⁰, Ag⁰, and ZnO are well known for their antibacterial effects. However, very few studies have examined antibacterial effects of nanohybrids. Given that metal oxides, mainly ZnO and TiO₂, are known to increase mobility, surface area, and photocatalysis when combined with carbon-based nanomaterials, ZnO- and TiO₂-conjugated carbon nanotube and graphene oxide nanohybrids were investigated for their antibacterial effects on Escherichia coli (DH5α, a multidrug-resistant coliform bacterium). Graphene-oxide (GO)-based nanohybrids (ZnO-GO and TiO₂-GO) induced increased dispersion compared to carbon-nanotube (CNT)-based nanohybrids (ZnO-CNT and TiO₂-CNT). Among the four types of nanohybrids, ZnO-conjugated nanohybrids exhibited a higher antibacterial property, resulting in the antibacterial effect (measured with growth inhibition of cells) in the order ZnO-GO > ZnO-CNT > TiO₂-GO > TiO₂-CNT. Among four possible antibacterial mechanisms (generation of reactive oxygen species (ROS), physicochemical characteristics, the steric effect, and release of metal ions), a primary mechanism-ROS generation-was identified; whereas, physicochemical characteristics and the steric effect were part of contributing mechanisms. The increasing dispersion of TiO₂/ZnO on GO may have contributed to the antibacterial effects due to increasing surface areas. Similarly, significant damages to E. coli cell membranes were found by the GO sheet with its sharp edges. Our results suggest that applying GO-based ZnO or TiO₂ could be an effective antibacterial method, especially for the treatment of multidrug-resistant bacteria in the water.

Environmentally benign fabrication of SnO2-CNT nanohybrids and their multifunctional efficiency as an adsorbent, catalyst and antimicrobial agent for water decontamination

Herein, we described a biogenic, additive fee, eco-friendly synthesized SnO₂-CNT nanohybrid as an efficient, re-collectable and reusable material for onsite water remediation. We demonstrated that the SnO₂-CNTs can provide a one stop solution for water remediation as it effectively accomplished the major treatment tasks like adsorption, catalytic transformation/degradation and disinfection. The structural, morphological, surface chemical compositions of the nanocomposite and the adsorption, catalytic and antimicrobial properties were investigated using common characterization and instrumental techniques. The results revealed the brilliant efficiency of SnO₂-CNT nanoadsorbent towards As (III) and a maximum Langmuir adsorption capacity of 106.95 mg/g was observed at high arsenite concentration (C₀ = 1 mg/L). The nanoadsorbent was also found to be equally efficient in low arsenite concentration ranges (C₀ = 100 μg/L) as it could bring down the arsenic concentration below maximum permissible limit. Moreover, using model pollutants like p-nitrophenol, Alizarin red S, Metronidazole, bacterial strains (Bacillus subtilis, Escherichia coli, Streptococcus pneumonia etc.), and fungal strains (Aspergillus niger and Candida albicans), the multifunctional capability of SnO₂-CNT towards water decontamination has been established. Our results suggested the promising potential of hierarchical nano-heterojunctions for engineering efficient water treatment processes.

Antibacterial activity of chitosan nano-composites and carbon nanotubes: A review

Bacteriological contamination of water sources is a major challenge that has a detrimental impact on both the environment and human health. This imposes the search for the most efficient disinfectant. Despite their antibacterial efficiency, traditional methods can often form disinfection byproducts through their reaction with organic and inorganic compounds. Substitutes for conventional bacterial inactivation methods should not produce harmful byproducts and must also be cost effective. Nanotechnology is an attractive option that is suited for surface reactions as nanostructures offer large surface to volume ratios. Technologies using chitosan-modified nanocomposites and carbon nanotubes have proven to offer promising alternatives for bacterial inactivation. To enhance their antibacterial efficiency, such technologies have been modified chemically and physically and have as well been associated with other treatment techniques. However, despite their high bacterial disinfection efficacy and lack of treatment byproducts, the vagueness in bacterial inactivation mechanisms and complexity in materials preparation have often obscured their wide scale application. The aim of this manuscript is to review the recent advances in bacterial disinfection using nanomaterials, in the form of chitosan and carbon nanotubes. The rapid rate of research and the notable progress in this area dictate the frequent compilation and dissemination of recent introductions to this field. Existing gaps in the literature are thus also highlighted and reported discrepancies are pinpointed so that roadmaps for future studies may be figured.

Shape-dependent antimicrobial activities of silver nanoparticles

Purpose: An important application of silver nanoparticles (Ag NPs) is their use as an antimicrobial and wound dressing material. The aim of this study is to investigate the morphological dependence on the antimicrobial activity and cellular response of Ag NPs. Materials and methods: Ag NPs of various shapes were synthesized in an aqueous solution using a simple method. The morphology of the synthesized Ag NPs was observed via TEM imaging. The antimicrobial activity of the Ag NPs with different morphologies was evaluated against various microorganisms (Escherichia coli [E. coli], Staphylococcus aureus [S. aureus], Pseudomonas aeruginosa [P. aeruginosa]). The antimicrobial activity of the Ag NPs was also examined according to the concentration in terms of the growth rate of E. coli. Results: The TEM images indicated that the Ag NPs with different morphologies (sphere, disk and triangular plate) had been successfully synthesized. The antimicrobial activity obtained from the inhibition zone was in the order of spherical Ag NPs > disk Ag NPs > triangular plate Ag NPs. In contrast, fibroblast cells grew well in all types of Ag NPs when the cell viability was evaluated via an MTT assay. An inductively coupled plasma mass assay showed that the difference in the antimicrobial activities of the Ag NPs was closely associated with the difference in the release rate of the Ag ions due to the difference in the surface area of the Ag NPs. Conclusion: The morphological dependence of the antimicrobial activity of the Ag NPs can be explained by the difference in the Ag ion release depending on the shape. Therefore, it will be possible to control the antimicrobial activity by controlling the shape and size of the Ag NPs.

Novel Antimicrobial Titanium Dioxide Nanotubes Obtained through a Combination of Atomic Layer Deposition and Electrospinning Technologies

The search for new antimicrobial substances has increased in recent years. Antimicrobial nanostructures are one of the most promising alternatives. In this work, titanium dioxide nanotubes were obtained by an atomic layer deposition (ALD) process over electrospun polyvinyl alcohol nanofibers (PVN) at different temperatures with the purpose of obtaining antimicrobial nanostructures with a high specific area. Electrospinning and ALD parameters were studied in order to obtain PVN with smallest diameter and highest deposition rate, respectively. Chamber temperature was a key factor during ALD process and an appropriate titanium dioxide deposition performance was achieved at 200 °C. Subsequently, thermal and morphological analysis by SEM and TEM microscopies revealed hollow nanotubes were obtained after calcination process at 600 °C. This temperature allowed complete polymer removal and influenced the resulting anatase crystallographic structure of titanium dioxide that positively affected their antimicrobial activities. X-ray analysis confirmed the change of titanium dioxide crystallographic structure from amorphous phase of deposited PVN to anatase crystalline structure of nanotubes. These new nanostructures with very large surface areas resulted in interesting antimicrobial properties against Gram-positive and Gram-negative bacteria. Titanium dioxide nanotubes presented the highest activity against Escherichia coli with 5 log cycles reduction at 200 μg/mL concentration.

Inactivation of E. coli by nano-Cu/MWCNTs combined with hydrogen peroxide

This paper aims at the study on the antibacterial activity of nCu-MWCNTs combined with H₂O₂ against gram-negative bacteria Escherichia coli (E. coli). The antibacterial ability of nCu-MWCNTs/H₂O₂ was evaluated by traditional surface plating method, fluorescence and SEM imaging, and the effects of variables (contacting time, dose of nCu-MWCNTs and dose of H₂O₂) were investigated. By comparing with other five processes including H₂O₂, MWCNTs, nCu-MWCNTs, MWCNTs/H₂O₂ and nCu/H₂O₂, nCu-MWCNTs and H₂O₂ was proved to have superlative antimicrobial effectiveness against E. coli. The role of nano-Cu, MWCNTs and H₂O₂ in the antimicrobial activity of nCu-MWCNTs/H₂O₂ was clarified. The release of copper ions and formation of hydroxyl radicals (OH) both contributed the antibacterial ability of nCu-MWCNTs/H₂O₂ system. And MWCNTs as the support might be able to promote the electron transfer in nCu-MWCNTs for copper ion release.

Mechanism and In Vivo Evaluation: Photodynamic Antibacterial Chemotherapy of Lysine-Porphyrin Conjugate

Lysine-porphyrin conjugate 4i has potent photosensitive antibacterial effect on clinical isolated bacterial strains such as Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa. The mechanism of photodynamic antibacterial chemotherapy of 4i (4i-PACT) in vitro and the treatment effect in vivo was investigated in this paper. Atomic force microscopy (AFM) revealed that 4i-PACT can effectively destroy membrane and wall of bacteria, resulting in leakage of its content. This was confirmed by dual fluorescent staining with acridine orange/ethidium bromide and measuring materials absorption at 260 nm. Agarose gel electrophoresis measurement showed that 4i-PACT can damage genomic DNA. Healing of wound in rat infected by mixed bacteria showed that the efficiency of 4i-PACT is dependent on the dose of light. These results showed that 4i-PACT has promising bactericidal effect both in vitro and in vivo.

Shape effect on the antibacterial activity of silver nanoparticles synthesized via a microwave-assisted method

Silver nanoparticles (AgNPs) are used as sustained-release bactericidal agents for water treatment. Among the physicochemical characteristics of AgNPs, shape is an important parameter relevant to the antibacterial activity. Three typically shaped AgNPs, nanocubes, nanospheres, and nanowires, were prepared via a microwave-assisted method and characterized by TEM, UV-vis, and XRD. The antibacterial activity of AgNPs was determined by OD growth curves tests, MIC tests, and cell viability assay against Escherichia coli. The interaction between AgNPs and bacterial cells was observed by TEM. The results showed that the three differently shaped AgNPs were nanoscale, 55 ± 10 nm in edge length for nanocubes, 60 ± 15 nm in diameter for nanospheres, 60 ± 10 nm in diameter and 2-4 μm in length for nanowires. At the bacterial concentration of 10(4) CFU/mL, the MIC of nanocubes, nanospheres, and nanowires were 37.5, 75, and 100 μg/mL, respectively. Due to the worst contact with bacteria, silver nanowires exhibited the weakest antibacterial activity compared with silver nanocubes and silver nanospheres. Besides, silver nanocubes mainly covered by {100} facets showed stronger antibacterial activity than silver nanospheres covered by {111} facets. It suggests that the shape effect on the antibacterial activity of AgNPs is attributed to the specific surface areas and facets reactivity; AgNPs with larger effective contact areas and higher reactive facets exhibit stronger antibacterial activity.

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.