Microbicidal Effect Research Articles

An Investigation on Synthesis of Silver Nanoparticles

Introduction: Nano science and nano biotechnology provided enormous opportunities for exploring the bactericidal and fungicidal activities. Since ancient times, silver was known for its anti-bacterial effects and for centuries it has been used for prevention and control of disparate infections. On the effective use silver nanomaterials synthesized and characterized play a vital role of the modern science.
 Aims: Our goal is to prepare silver nanomaterials since studies have shown that silver nanoparticles have efficient activity against bacterial biofilms.
 Methodology: The silver nanoparticles were generally synthesized by non-aqueous sol-gel technique in the presence of different precursor by chelating agent.
 Results: Here found a cubic unit cell with miller indices (111) (200) (220) (311) (222) and crystallite size around 50.00nm by XRD. The morphology of the prepared nano particles has been revealed by SEM below 10.00 nm and TEM is below 5.00nm in size of graphical presentation such as size, shape, surface etc. of the nanoparticles. DLS is a unique technique to discern particle size around 65.00nm and size distributions in aqueous or physiological solutions of the nanoparticles.
 Conclusion: The studies on the combined synthesized and use of AgNPs with other antimicrobial agents generally help reduce the problem of toxicity and to avoid the potential for development of resistance and strongly enhance the microbicidal effect. This paper describes a short and very precise description about the chemical synthesis process of silver nanoparticles like no aqueous SGM. Also, this paper contains a brief description about different characterization technique of nanoparticles like X-ray Diffraction review the shape of crystal a cubic unit cell with miller indices (111) (200) (220) (311) (222) where crystallite size around 50.00nm, the morphology of the prepared nanoparticles has been revealed with size 10.00nm by SEM, Dynamic Light Scattering discern particle size around 65.00nm and Transmission Electron Microscope review the spherical shape of the nanomaterials. Further investigation will be continuing the antimicrobial activity test of AgNPs with ceramic coating.

Characterization and Molecular Modelling of Non-Antibiotic Nanohybrids for Wound Healing Purposes.

The healing process of chronic wounds continues to be a current clinical challenge, worsened by the risk of microbial infections and bacterial resistance to the most frequent antibiotics. In this work, non-antibiotic nanohybrids based on chlorhexidine dihydrochloride and clay minerals have been developed in order to design advanced therapeutic systems aimed to enhance wound healing in chronic lesions. To prepare the nanohybrids, two methodologies have been compared: the intercalation solution procedure and the spray-drying technique, the latter as a one-step process able to reduce preparation times. Nanohybrids were then fully studied by solid state characterization techniques. Computational calculations were also performed to assess the interactions between the drug and the clays at the molecular level. In vitro human fibroblast biocompatibility and antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa were assessed to check biocompatibility and potential microbicidal effects of the obtained nanomaterials. The results demonstrated the effective organic/inorganic character of the nanohybrids with homogeneous drug distribution into the clayey structures, which had been confirmed by classical mechanics calculations. Good biocompatibility and microbicidal effects were also observed, especially for the spray-dried nanohybrids. It was suggested that it could be due to a greater contact area with target cells and bacterial suspensions.

Antimicrobial Nano-Zinc Oxide Biocomposites for Wound Healing Applications: A Review

Chronic wounds are a major concern for global health, affecting millions of individuals worldwide. As their occurrence is correlated with age and age-related comorbidities, their incidence in the population is set to increase in the forthcoming years. This burden is further worsened by the rise of antimicrobial resistance (AMR), which causes wound infections that are increasingly hard to treat with current antibiotics. Antimicrobial bionanocomposites are an emerging class of materials that combine the biocompatibility and tissue-mimicking properties of biomacromolecules with the antimicrobial activity of metal or metal oxide nanoparticles. Among these nanostructured agents, zinc oxide (ZnO) is one of the most promising for its microbicidal effects and its anti-inflammatory properties, and as a source of essential zinc ions. This review analyses the most recent developments in the field of nano-ZnO-bionanocomposite (nZnO-BNC) materials-mainly in the form of films, but also hydrogel or electrospun bandages-from the different preparation techniques to their properties and antibacterial and wound-healing performances. The effect of nanostructured ZnO on the mechanical, water and gas barrier, swelling, optical, thermal, water affinity, and drug-release properties are examined and linked to the preparation methods. Antimicrobial assays over a wide range of bacterial strains are extensively surveyed, and wound-healing studies are finally considered to provide a comprehensive assessment framework. While early results are promising, a systematic and standardised testing procedure for the comparison of antibacterial properties is still lacking, partly because of a not-yet fully understood antimicrobial mechanism. This work, therefore, allowed, on one hand, the determination of the best strategies for the design, engineering, and application of n-ZnO-BNC, and, on the other hand, the identification of the current challenges and opportunities for future research.

Acanthamoeba castellanii Genotype T4: Inhibition of Proteases Activity and Cytopathic Effect by Bovine Apo-Lactoferrin.

Acanthamoeba castellanii genotype T4 is a clinically significant free-living amoeba that causes granulomatous amoebic encephalitis and amoebic keratitis in human beings. During the initial stages of infection, trophozoites interact with various host immune responses, such as lactoferrin (Lf), in the corneal epithelium, nasal mucosa, and blood. Lf plays an important role in the elimination of pathogenic microorganisms, and evasion of the innate immune response is crucial in the colonization process. In this study, we describe the resistance of A. castellanii to the microbicidal effect of bovine apo-lactoferrin (apo-bLf) at different concentrations (25, 50, 100, and 500 µM). Acanthamoeba castellanii trophozoites incubated with apo-bLf at 500 µM for 12 h maintained 98% viability. Interestingly, despite this lack of effect on viability, our results showed that the apo-bLf inhibited the cytopathic effect of A. castellanii in MDCK cells culture, and analysis of amoebic proteases by zymography showed significant inhibition of cysteine and serine proteases by interaction with the apo-bLf. From these results, we conclude that bovine apo-Lf influences the activity of A. castellanii secretion proteases, which in turn decreases amoebic cytopathic activity.

A Review on Nano Ti-Based Oxides for Dark and Photocatalysis: From Photoinduced Processes to Bioimplant Applications.

Catalysis on TiO2 nanomaterials in the presence of H2O and oxygen plays a crucial role in the advancement of many different fields, such as clean energy technologies, catalysis, disinfection, and bioimplants. Photocatalysis on TiO2 nanomaterials is well-established and has advanced in the last decades in terms of the understanding of its underlying principles and improvement of its efficiency. Meanwhile, the increasing complexity of modern scientific challenges in disinfection and bioimplants requires a profound mechanistic understanding of both residual and dark catalysis. Here, an overview of the progress made in TiO2 catalysis is given both in the presence and absence of light. It begins with the mechanisms involving reactive oxygen species (ROS) in TiO2 photocatalysis. This is followed by improvements in their photocatalytic efficiency due to their nanomorphology and states by enhancing charge separation and increasing light harvesting. A subsection on black TiO2 nanomaterials and their interesting properties and physics is also included. Progress in residual catalysis and dark catalysis on TiO2 are then presented. Safety, microbicidal effect, and studies on Ti-oxides for bioimplants are also presented. Finally, conclusions and future perspectives in light of disinfection and bioimplant application are given.

Inactivation of Bacillus cereus endospores on black pepper by pulsed superheated steam system

In this study, a superheated steam (SHS) system was constructed to inactivate Bacillus cereus endospores on the surface of black pepper, and continuous and pulsed treatment was applied to compare sporicidal effects. Additionally, inactivation mechanisms were analyzed to investigate the differences between pulsed and continuous SHS treatments. SHS at 250 °C and 300 °C for 1 min achieved more than a 3 log reduction, whereas SHS at 200 °C for 1 min achieved less than 2 log reduction in the number of endospores. In addition, higher microbicidal effects were confirmed with pulsed SHS treatment with a shorter duty ratio. To elucidate the inactivation mechanisms, inner membrane damage (dipicolinic acid release), intracellular enzyme activities, and DNA integrity were measured after 300 °C SHS pulsed or continuous treatments. After pulsed SHS treatment for up to 20 s, intracellular enzymes were inactivated more rapidly than after continuous treatment, and more DPA was released after 40 s of treatment, indicating that enzyme inactivation occurred prior to inner membrane damage, and pulsed treatment accelerated this mode of action. DNA integrity was significantly lower after 60 s of pulsed or continuous treatment; however, there was no difference in between pulsed and continuous treatments. Our results provide fundamental insights for the sterilization of black pepper by SHS treatment in food industries.

Investigation of Some Biological Activities of Ajuga chamaepitys subsp. chia

Ajuga L., which is an Eastern Mediterranean element, is popularly known as ground pine, dwarf grass, ground cypress, bitter gourd, wormwood, yeast grass (mayasılotu in Turkish) (Zeybek and Zeybek, 1994). Ajuga chamaepitys L. Schreb species has been used since the Middle Ages as a diuretic, antidote for poisonous animal stings, and as an invigorating, wound-healing and diaphoretic plant. This study evaluated antibiofilm, time-kill potential and antioxidant activity of four extracts of A. chamaepitys subsp. chia (Schreb.) Arcang. Crystal violet binding assay were used to determinate antibiofilm activities of extracts against test microorganisms (4 Gram negative, 3 Gram positive and 1yeast). Antioxidant activity was evaluated by using 2,2-diphenyl1-picrylhydrazyl and reducing antioxidant capacity methods. The highest antibiofilm activity was obtained in acetone extract against P. aeruginosa ATCC 27853 and S. aureus ATCC 6538P bacteria. In the time-dependent killing test of plant extracts, microbicidal effect was obtained after 24 hours. The highest antioxidant activity was obtained from plants ethyl acetate extract.

Hypochlorous acid inactivates oral pathogens and a SARS-CoV-2-surrogate

BackgroundDroplets and aerosols produced during dental procedures are a risk factor for microbial and viral transmission. Unlike sodium hypochlorite, hypochlorous acid (HOCl) is nontoxic to tissues but still exhibits broad microbicidal effect. HOCl solution may be applicable as a supplement to water and/or mouthwash. This study aims to evaluate the effectiveness of HOCl solution on common human oral pathogens and a SARS-CoV-2 surrogate MHV A59 virus, considering the dental practice environment.MethodsHOCl was generated by electrolysis of 3% hydrochloric acid. The effect of HOCl on human oral pathogens, Fusobacterium nucleatum, Prevotella intermedia, Streptococcus intermedius, Parvimonas micra, and MHV A59 virus was studied from four perspectives: concentration; volume; presence of saliva; and storage. HOCl solution in different conditions was utilized in bactericidal and virucidal assays, and the minimum inhibitory volume ratio that is required to completely inhibit the pathogens was determined.ResultsIn the absence of saliva, the minimum inhibitory volume ratio of freshly prepared HOCl solution (45–60 ppm) was 4:1 for bacterial suspensions and 6:1 for viral suspensions. The presence of saliva increased the minimum inhibitory volume ratio to 8:1 and 7:1 for bacteria and viruses, respectively. Applying a higher concentration of HOCl solution (220 or 330 ppm) did not lead to a significant decrease in the minimum inhibitory volume ratio against S. intermedius and P. micra. The minimum inhibitory volume ratio increases in applications of HOCl solution via the dental unit water line. One week of storage of HOCl solution degraded HOCl and increased the minimum growth inhibition volume ratio.ConclusionsHOCl solution (45–60 ppm) is still effective against oral pathogens and SAR-CoV-2 surrogate viruses even in the presence of saliva and after passing through the dental unit water line. This study indicates that the HOCl solution can be used as therapeutic water or mouthwash and may ultimately reduce the risk of airborne infection in dental practice.

Sputtering of micro-carbon-silver film (μC-Ag) for endotracheal tubes to mitigate respiratory infections

Polyurethane (PU) substrates are biocompatible materials widely used to manufacture endotracheal tubes. However, in common with other biomedical materials, they are liable to the formation of microbial films. The occurrence of pneumonia in intubated patients treated at intensive care units often takes the form of ventilator-associated pneumonia (VAP). The issue relates to the translocation of pathogenic microorganisms that colonize the oropharyngeal mucosa, dental plaque, stomach, and sinuses. New protective materials can provide a more effective therapeutic approach to mitigating bacterial films. This work concerns microcrystalline carbon film containing dispersed silver nanoparticles (μC-Ag) deposited on PU substrates using a physical vapor deposition sputtering process. For the first time, carbon paper was used to produce a carbon target with holes exposing a silver disk positioned under the carbon paper, forming a single target for use in the sputtering system. The silver nanoparticles were well distributed in the carbon film. The adherence characteristics of the μC-Ag film were evaluated using a tape test technique, and electron dispersive x-ray mapping was performed to analyze the residual particles after the tape test. The microbicidal effect of the thin film was also investigated using species S. aureus, a pathogenic microorganism responsible for most infections of the lower respiratory tract involving VAP and ventilator-associated tracheobronchitis (VAT). The results demonstrated that μC-Ag films on PU substrates are promising materials for mitigating pathogenic microorganisms on endotracheal tubes.

Study on the effectiveness of the sanitization activity of a robot equipped with UV lamps

The increasing focus on the health of individuals has forced a strong acceleration on research and development of new technologies to abate the microbiological component. The pandemic generated by the spread of the SARS-CoV-2 virus has imparted an even greater impetus in this direction. In large and busy environments, it is essential to implement existing air purification and surface cleaning techniques, to reduce the concentrations of microorganisms present as much as possible: for the abatement of airborne bacterial loads, physical methods (e.g., HEPA filters) are used, while, for surfaces, chemicals of different compositions (detergents and bactericides) are often used. The use of ultraviolet radiation is proving to be a very viable alternative for this purpose. The use of UV lamps coupled with automated systems allow constant service to prevent the spread of microbiological populations. The study reported here aims to verify the features of the bactericidal action produced by the ARIS-K2 robot. This specific machine is equipped with 6 UV-C mercury lamps, which emit electromagnetic radiation at a wavelength value of 253.7 nm. Ultraviolet light is divided into three categories, depending on the wavelength: UV-A (315-400 nm), UV-B (280-315 nm) and UV-C (100-280 nm). UV-C radiation is demonstrated to have the greatest microbicidal effect. The conducted study analyzes the survival of bacterial populations distributed on surfaces at varying distances from the robot and in the presence of obstacles. The results were also analyzed considering the dose-exposure time relationship to which the colonies were subjected.

Monometallic complexes of novel dihydrazone‐oxime ligand: Synthesis, structure, spectral, DFT, and in vitro bioactivity investigation against fungal, bacterial, and tumor cells

In the current study, uni‐metallic Cu2+, Ni2+, Mn2+, Co2+, and Zn2+ complexes of ONN‐tridentate dihydrazone‐oxime incorporating indolin‐2‐one moiety (HL,1) were synthesized and structurally characterized employing elemental, spectral, thermo‐gravimetric, magnetic, and molar conductivity measurements, to investigate the structure and composition of these new uni‐metallic complexes. According to the results of several analyses, the dihydrazone‐oxime behaved as a mono‐negative or neutral tridentate ONN chelator bound the metal cations in molar ratio (1M:1L) through the isatinic carbonylic oxygen, azomethine nitrogen, and nitrogen atom of deprotonated/protonated oximatic moiety forming uni‐metallic complexes with formulae [M(L)XYZ(H2O)].nH2O (where M = Cu2+ (2–4), Ni2+, Mn2+, Co2+, or Zn2+, X = Cl, CH3COO, or NO3, Y = H2O or 0, Z = H2O or 0, n = 2, 0) and [Cu (HL)(SO4)(H2O)]. The Cu2+ complexes were found to have a tetragonally distorted octahedral or square pyramidal geometry, whereas those of Mn2+, and Ni2+, exhibited a tetrahedral geometry but Co2+ complex demonstrated a distorted octahedral geometry. Based on DFT‐B3LYP technique and 6‐311G++(d,p) basis set, The DFT data confirmed the structural investigation of dihydrazone‐oxime and its complexes, revealing that the complexes reactivity is more than un‐complexed dihydrazone‐oxime. Moreover, quantum chemical parameters of dihydrazone‐oxime and its uni‐metallic complexes like the energies of both lowest unoccupied molecular orbital (ELUMO) and highest occupied molecular orbital (EHOMO), separation energy (ΔE = ELUMO − EHOMO), chemical potential, absolute electronegativity, absolute hardness, and absolute softness were obtained. According to the thermogravimetric analysis, the complexes breakdown in two to four disintegrating phases in range of temperature 25°C to 575°C leaving the oxide of metal or metal oxide contaminated with carbon. In vitro microbicide effect of the un‐complexed dihydrazone‐oxime and its uni‐metallic complexes toward various bacterial and fungal strains was tested by agar‐well diffusion method. It is demonstrated that the complexes are more effective than free dihydrazone‐oxime. The antitumor activity has been also analyzed against three cell lines including prostate adenocarcinoma (PC‐3), ovarian adenocarcinoma (SKOV3), and cervical cancer (HeLa) cell lines. Studies showed that all complexes have greater inhibition activity against the above three cell lines than the free dihydrazone oxime and the most effective compound was the Zn2+ complex (9) with IC50, 27.42, 35.16, and 46.77 μg/ml, respectively.

Structural homology between 11 beta-hydroxysteroid dehydrogenase and Mycobacterium tuberculosis Inh-A enzyme: Dehydroepiandrosterone as a potential co-adjuvant treatment in diabetes-tuberculosis comorbidity.

Metabolic syndrome is considered the precursor of type 2 diabetes mellitus. Tuberculosis is a leading infection that constitutes a global threat remaining a major cause of morbi-mortality in developing countries. People with type 2 diabetes mellitus are more likely to suffer from infection with Mycobacterium tuberculosis. For both type 2 diabetes mellitus and tuberculosis, there is pulmonary production of anti-inflammatory glucocorticoids mediated by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). The adrenal hormone dehydroepiandrosterone (DHEA) counteracts the glucocorticoid effects of cytokine production due to the inhibition of 11β-HSD1. Late advanced tuberculosis has been associated with the suppression of the Th1 response, evidenced by a high ratio of cortisol/DHEA. In a murine model of metabolic syndrome, we determined whether DHEA treatment modifies the pro-inflammatory cytokines due to the inhibition of the 11β-HSD1 expression. Since macrophages express 11β-HSD1, our second goal was incubating them with DHEA and Mycobacterium tuberculosis to show that the microbicide effect was increased by DHEA. Enoyl-acyl carrier protein reductase (InhA) is an essential enzyme of Mycobacterium tuberculosis involved in the mycolic acid synthesis. Because 11β-HSD1 and InhA are members of a short-chain dehydrogenase/reductase family of enzymes, we hypothesize that DHEA could be an antagonist of InhA. Our results demonstrate that DHEA has a direct microbicide effect against Mycobacterium tuberculosis; this effect was supported by in silico docking analysis and the molecular dynamic simulation studies between DHEA and InhA. Thus, DHEA increases the production of pro-inflammatory cytokines in the lung, inactivates GC by 11β-HSD1, and inhibits mycobacterial InhA. The multiple functions of DHEA suggest that this hormone or its synthetic analogs could be an efficient co-adjuvant for tuberculosis treatment.

Cellular and humoral factors of innate antiviral immunity

The study presents new data on the biological effects of well-known cellular and humoral factors that ensure the functioning of innate immunity. Four mechanisms induced by viruses, which lead to the destruction of inhibitory proteins and trigger the transcription of interferon genes, are described. The paper also presented the order of synthesis of species of interferons and other pro-inflammatory cytokines in the development of an antiviral immune response. This is of great importance because viruses have significantly different resistance to the biological effects of interferons. Interferon lambda played a role in the development of innate immune reactions against many viruses, and the effectiveness of the functioning of the mechanisms of the innate and adaptive immunity in viral infections was evaluated, depending on the state of the stat l, 4, 6 genes and genes of interferon regulators. An interferon-independent variant of the innate immune response in viral infections that occurs a few hours after infection and is associated with chemokine CXCL10 has been described. Data on the most important role of the ubiquitin-proteasome cleavage pathway of proteins and the complement system in the implementation of antiviral effects of innate immunity are also presented. The uniqueness of the microbicidal effects of natural killers, which are realized only in cells that reduced the expression of major histocompatibility complex I molecules, has been established. In addition, natural killers can recognize and do not attack target cells carrying antigens of HLA-E, the sublocus of the major histocompatibility complex I molecules. The natural killers were found to acquire the properties of memory cells. This is facilitated by interleukins 12 and 18. The extracellular neutrophil traps of neutrophils showed microbicidal effects against many viruses. The congenital lymphoid cells have multifaceted effects on the development of an antiviral immune response.

Опыт использования гамма-облучения для стерилизации композиционного материала «Углекон-МЯ», применяемого в медицине

The carbon-composite material is actively used in medicine. In particular there is a successful practice of its use for replacing bone defects in orthopedics, traumatology and maxillofacial surgery. Meanwhile the cellular structure of the material and the presence of a large number of closed pores impose certain requirements on the process of its disinfection. The radiation method of sterilization of inorganic implants, as well as biotransplants, has recently become increasingly widespread in medicine. The purpose of this study was to evaluate the effectiveness of various doses of radiation for the sterilization of high-porous carbon material “Ugleсon-M”. Twelve samples of this material were infected with strains of various microorganisms and divided into 4 batches depending on the planned dose of radiation. Each batch was exposed to radiation doses 25, 50; 75 and 100 kGy respectively. The control sample was not irradiated. After the radiation exposure each sample, including the control one, was washed and inoculated on special liquid nutrient medium followed by seven-days incubation and daily inoculation on solid nutrient medium. All doses of ionizing radiation proposed in the study had a microbicidal effect, ensuring the sterility of the studied material. On the control sample the microorganisms remained viable. Experimental data on radiation sterilization of carbon material are presented for the first time. It has been established that all studied radiation doses, including the minimal one (25 kGy), cause the death of not only vegetative forms of microorganisms (bacteria, fungi), but also spores. A conclusion is made about the possibility of using radiation sterilization for highly porous carbon-composite material.

Phytosynthesis of TiO2 Nanoparticles Using E. crassipes Leaf Extracts, Their Photocatalytic Evaluation and Microbicide Effect

In the present research work, the photocatalytic and microbicidal activities of titanium nanoparticles (TiO2 NPs) were evaluated. TiO2 NPs were obtained through the phytosynthesis process, using Eichhornia crassipes leaf extract. In order to determine whether particle size improves photocatalytic and microbicidal activities, the pH of the photosynthesized was modified to 12, 7, and 4. The TiO2 NPs modified were characterized by UV-Vis spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), and high-resolution transmission electron microscopy (HR-TEM) to reveal the crystalline and morphological nature of the phytosynthesized TiO2 NPs. UV-Vis analysis revealed that the wavelength for the TiO2 NPs was 327 nm, while FT-IR confirmed the presence of TiO2 NPs at peaks located between 536 and 532 cm-1. Finally, HR-TEM analysis showed that all nanoparticles had a TiO2 composition and a particle size ranging from 25 to 35 nm. For the photocatalytic and microbicidal tests, three concentrations of nanoparticles were used (100, 50, and 10 mg/L), and the results showed that TiO2 nanoparticles at a concentration of 10 mg·L-1 demonstrated excellent photocatalytic activity in photodegrading phenol [10 mg·L-1] up to 98.7%, while their microbicidal activity was more effective in contact with S. aureus than with E. coli, using a TiO2 NPs concentration of 100 mg·L-1.

Corneal cross-linking guards against infectious keratitis: an experimental model

BackgroundPACK-CXL (photo-activated chromophore for keratitis–corneal cross-linking) is an alternative option in treatment of corneal infections. It inhibits corneal melting by increasing the stromal resistance, besides the microbicidal effect of photo-activated riboflavin.MethodsCorneal infection with Pseudomonas aeruginosa and Staph aureus bacteria was induced in 20 eyes of 10 rabbits after 6 weeks of corneal cross-linking in half of the eyes, while the other acted as control group. Clinical and corneal histopathological examination was done to evaluate the extent of inflammation, ulceration, organism penetration, and depth of corneal stromal affection.ResultsThe control eyes developed severe inflammation compared to the cross-linked eyes. Corneal melting occurred in 6 eyes in the control versus none in cross-linked group. Histopathological examination showed that the inflammation was confined to the superficial part of the stroma with localization of the inflammation in the cross-linked eyes in contrast to the control eyes that showed deep infiltration.ConclusionPACK-CXL provides infection localization through increasing the corneal rigidity and resistance to enzymatic digestion, even in the absence of the riboflavin microbicidal role. So, early PACK-CXL is worth to be considered in the IK treatment algorithm.

A gas–liquid discharge reactor for water disinfection: Electrical properties and microbicidal effects on viruses and bacteria

As an eco-friendly oxidation technique, gas–liquid underwater discharge is considered a promising water disinfection method. In this study, we constructed a gas–liquid discharge reactor, in which the electrical properties, optimized discharging parameters, and microbicidal effects on coliphage virus and two bacteria (E. coli and S. aureus) were investigated. It is shown that, compared to direct underwater discharge without ventilation, gas–liquid discharges can release higher energy and generate more active species, thus resulting in better inactivation performance. A microbicidal reduction of over 99.9% can be achieved in 5 min of treatment for three types of microbes in 600 ml tap water (σ ∼ 590 μS/cm); specifically, 3.34, 3.95, and 3.65 log reductions were achieved for coliphages, E. coli, and S. aureus, respectively. The observations of microbial morphologies indicate that underwater discharges and their products can severely damage the external structures and internal substances of micro-organisms, which is responsible for the working mechanism of microbial inactivation. The reactor can decrease E. coli from 6.2 × 103–6.4 × 106 CFU/ml to ∼1000 CFU/ml in 5 min, suggesting that this gas–liquid discharge reactor has a low sensitivity to the initial density of suspension. In addition, the reactor can also achieve a satisfactory disinfection effect even in water with high conductivity, although the microbicidal performance of E. coli will be attenuated with an increase in solution conductivity (from 3.82 log reduction at 2 mS/cm to 2.22 log at 15 mS/cm). These advantages indicate the broad applicability of the reactor in water disinfection.

The antimicrobial peptides LL-37, KR-20, FK-13 and KR-12 inhibit the growth of a sensitive and a metronidazole-resistant strain of Trichomonas vaginalis.

The parasite Trichomonas vaginalis is the aetiologic agent of trichomoniasis, the most common non-viral sexually transmitted disease worldwide. This infection often remains asymptomatic and is related to several health complications. The traditional treatment for trichomoniasis uses drugs of the 5-nitroimidazole family, such as metronidazole; however, scientific reports indicate an increasing number of drug-resistant strains. Antimicrobial peptides could be an alternative or complementary treatment. In this sense, one attractive candidate is the human cathelicidin, being LL-37 its active form. LL-37 possesses microbicidal activity against many microorganisms such as bacteria, Candida albicans, and Entamoeba histolytica. Shorter sequences derived from this peptide, such as KR-20, FK-13 and KR-12, have been shown to possess a higher microbicidal effect than LL-37. In this study, we determined the activity of LL-37 and its derivatives against T. vaginalis, which was unknown. The results showed that the four peptides (LL-37, KR-20, FK-13-NH2 and KR-12) decreased the viability of T. vaginalis on a 5-nitroimidazole-sensitive and a 5-nitroimidazole-resistant strain; however, KR-20 was the most effective peptide, followed by FK-13-NH2. Low concentrations of all peptides showed a better effect when combined with metronidazole in the sensitive and resistant T. vaginalis strains. These results are promising for potential future therapeutic uses.

Study of the Antimicrobial Activity of Cuprite Synthesized by Chemical Route

With the rise of nanotechnology, inorganic nanomaterials have been developed which have a marked microbicide effect on a wide variety of microorganisms such as viruses, bacteria and fungi. In the present work, the synthesis, characterization and study of the antimicrobial activity of cuprite (copper (I) oxide, Cu2O), obtained by chemical route was carried out. To obtain cuprite, copper sulfate pentahydrate was used as a precursor and ascorbic acid and glucose as organic reductants. The synthesis using glucose as a reductant resulted in the obtaining of 100% cuprite with variable morphology, spheres, cubes and tetrahedra were observed, very dependent on the concentration of NaOH used in each synthesis, with particle sizes in the nanoscale and micrometer, that is, nanoparticles and Cu2O nanostructures were obtained. According to the results of the antimicrobial activity, it can be concluded that Cu2O copper oxide has an antimicrobial effect on Staphylococcus aureus bacteria, with the Minimum Inhibitory Concentration, MIC, 16 mg/mL.

Antimicrobial activity of mesoporous organic functionalized hexagon Fe3O4 nanosheets for wastewater treatment

Nano iron oxide has shown great potential to function as a universal and low-cost antimicrobial agent. In this work, we fabricated a new class of mesoporous hexagon magnetic iron oxide nanosheets (HMI-NS) modified by 3-aminopropyltriethoxysilane (APTES) through a simple synthesis route as a novel vehicle tracking building (VTB) antimicrobial agent. The VTB-MHI-NSs had a uniform platform-like structure with an average size of 45 nm and well-scattered active sites in the inner core and saline shell with microbicidal effect. Tests revealed that the modification of iron oxide nanosheets caused an improvement in antimicrobial activity against bacteria and fungi. The developed bioactive behavior of The VTB-MHI-NSs can be due to the system architectures, arrangement of crystal atomic-scale, and mesopore windows. This organically functionalized tailoring of The VTB-MHI-NSs can influence the particle size, shape, and surface properties, thereby creating significant extracellular interactions and exerting intracellular effects that cause antimicrobial activity. The appropriate functionalization of the hexagonal outer surface of the mesopore windows enabled the modulation of loading and microbial cell interaction and played a key role in offering sustained platform-like nanosheets that attached to the microbe, causing cell death. Therefore, the mesoporous organic functionalized hexagon iron oxide nanosheets can be considered in water future clean-up processes.