Robust bulk micro-nano hierarchical copper structures possessing exceptional bactericidal efficacy

Conventional copper (Cu) metal surfaces are well recognized for their bactericidal properties. However, their slow bacteria-killing potency has historically excluded them as a rapid bactericidal material. We report the development of a robust bulk superhydrophilic micro-nano hierarchical Cu structure that possesses exceptional bactericidal efficacy. It resulted in a 4.41 log₁₀ reduction (>99.99%) of the deadly Staphylococcus aureus (S. aureus) bacteria within 2 min vs. a 1.49 log₁₀ reduction (96.75%) after 240 min on common Cu surfaces. The adhered cells exhibited extensive blebbing, loss of structural integrity and leakage of vital intracellular material, demonstrating the rapid efficacy of the micro-nano Cu structure in destructing bacteria membrane integrity. The mechanism was attributed to the synergistic degradation of the cell envelope through enhanced release and therefore uptake of the cytotoxic Cu ions and the adhesion-driven mechanical strain due to its rapid ultimate superhydrophilicity (contact angle drops to 0° in 0.18 s). The scalable fabrication of this micro-nano Cu structure was enabled by integrating bespoke precursor alloy design with microstructure preconditioning for dealloying and demonstrated on 2000 mm² Cu surfaces. This development paves the way to the practical exploitation of Cu as a low-cost antibiotic-free fast bactericidal material.

Bacterial Dye Release Measures in Response to Antimicrobial Peptides

Assessment of bacterial dye release following exposure to antimicrobial peptides (AMPs) provides a detailed understanding regarding their interaction with the inner and outer membrane of bacteria, and the leak of bacterial intracellular materials. This underpins the overall antimicrobial mechanism of these membrane-active peptides. DiSC3(5) is a membrane potential sensitive dye and can characterize the changes in bacterial membrane potential following exposure to AMPs (see Note 1). SYTOX Green is a nucleic acid stain that enters the cell upon loss of membrane integrity after exposure to AMPs and binds to DNA. SYTO9 is another nucleic acid stain, whereas propidium iodide (PI) is a fluorescent intercalating agent that can be used to stain cells and nucleic acids. Both of these stains are widely used to monitor the viability of bacteria following exposure to AMPs. This chapter describes the methods of using these as bacterial dye release experiments for assessment of the antimicrobial mechanism of AMPs.

Copper hydroxide nanosheets-assembled nanofibrous membranes for anti-biofouling water disinfection

Copper hydroxide (Cu(OH)₂) has been elected as a newly-emerging green disinfectant to deal with membrane biofouling in the treatment of bacteria-contaminated water; however, the decoration strategy of it with the granular form on membrane substrates limits the practical application. Here a novel surface-confined methodology was proposed for preparing freestanding Cu(OH)₂ nanosheet-assembled nanofibrous membranes (CNNMs) with the anti-biofouling property via the in-suit coprecipitation and heat-induced growth method. The vertically aligned Cu(OH)₂ nanosheets were in-suit rooted on the surface of the nanofiber scaffold with high binding fastness. The acquired CNNMs possess comprehensive performances of high porosity, prominent mechanical strength, fatigue resistance, and superior bactericidal efficiency of 99.999%, which endowed the CNNMs ultrahigh filtration fluxes (24000 L m^-2 h^-1) and durability to disinfect bacteria-containing water effectively. This facile strategy may throw light on manufacturing novel inorganic nanosheet-rooted nanofibrous membranes for water disinfection and public health.

Antibacterial effects of octadecyl trimethylammonium micelle-clay complex against bacterial eye pathogens: potential as a contact lens disinfectant

AIM

In this study, we utilized a micelle-clay complex composed of the surfactant octadecyltrimethylammonium bromide and montmorillonite clay and evaluated its antibacterial effects.

METHODS

Using Pseudomonas aeruginosa, Staphylococcus epidermidis, and Micrococcus luteus, bactericidal assays were performed to determine the effects of ODTMA-clay complex on the viability of bacterial pathogen at various doses and different intervals of time. Cytotoxicity assays were performed to investigate ODTMA-clay complex effects on human cells, as determined by release of intracellular lactate dehydrogenase.

RESULTS

The results revealed that ODTMA-clay complex abolished bacterial viability at 100 μg/mL within 45 min against P. aeruginosa, S. epidermidis, and M. luteus. Cytotoxicity assays revealed that ODTMA-clay complex exhibited minimal toxicity of the human cells.

CONCLUSION

Rapid and potent antibacterial effects of ODTMA micelle-clay complex were observed in vitro; however, research is needed to determine precise formulation of contact lens disinfectants comprising ODTMA micelle-clay complex. Additionally, studies should be conducted using in vivo models of keratitis, progressing to pre-clinical and clinical trials. ODTMA micelle-clay complex is an ideal candidate to be incorporated in a novel contact lens disinfectant given the cost-effectiveness and ease of application and can be incorporated as an effective preventative strategy.

Hepato and nephroprotective activity of methanol extract of Hygrophila spinosa and its antibacterial potential against multidrug resistant Pandoraea sputorum

This research was aimed to evaluate the phytochemical profile, bactericidal activity of Hygrophila spinosa against multidrug resistant Pandoraea sputorum and assess their antioxidant competence against various radicals and studied their hepatoprotective and nephroprotective activity on HepG2 and HEK 293 cell line. The results showed that the methanol extract has various phytochemical components with reasonable quantity. Fortunately, the multidrug-resistant P. sputorum was sensitive (22.8 ± 0.2 mm of the zone of inhibition) at 15 mg mL^-1 concentration of methanol extract. The higher concentration of phenolic and other phytochemical components, showed significant antioxidant activity against ferric, DPPH, hydroxyl, and ABTS radicals, with IC₅₀ values of 71.09, 64.333, 91.157, and 104.931 g mL^-1, respectively. Surprisingly, the methanol extract possesses hepato and nephroprotective activity against CCl₄ and cisplatin-induced cytotoxicity on HepG2 and HEK 293 cell lines, respectively. It maintains the cell viability as up to 90.48% and 90.35% of HepG2 and EK 293 cell line at the concentration of 20 μg mL^-1. The FTIR analysis states that the methanol extract possesses a significant functional group responsible for these multi-potential activities. These results suggest that, the methanol extract of H. spinosa might contain the most significant bioactive components with outstanding medicinal properties.

Biogenic Synthesis, Characterization and Antibacterial Potential Evaluation of Copper Oxide Nanoparticles Against Escherichia coli

The development of resistance against antibiotics used to treat bacterial infections along with the prevalence of medication residues presents significant public health problems globally. Antibiotic-resistant germs result in infections that are difficult or impossible to treat. Decreasing antibiotic effectiveness calls for rapid development of alternative antimicrobials. In this respect, nanoparticles (NPs) of copper oxide (CuO) manifest a latent and flexible inorganic nanostructure with noteworthy antimicrobial impact. Green synthesis of CuO NPs was performed in the current study, which was then doped with varying amounts of ginger (Zingiber officinale, ZO) and garlic (Allium sativum, AS) extracts. In low and high doses, the synthesized compound was used to measure the antimicrobial effectiveness against pathogenic Escherichia coli. The present research successfully demonstrated a renewable, eco-friendly synthesis technique with natural materials that is equally applicable to other green metal oxide NPs.

Facile synthesis of ZnO nanoparticles by Actinidia deliciosa fruit peel extract: Bactericidal, anticancer and detoxification properties

Synthesis of nanoparticles by eco-friendly method pulled an extensive concern worldwide due its biocompatibility and wide range of applications as catalysts, microbicidal agents, cancer treatment, sensors etc. Though different chemical methods available for preparation of ZnO nanoparticles, synthesis by utilizing plant material is an excellent substitute and green method as well. The present study describes preparation of ZnO nanoparticles by low-cost green synthetic way using Actinidia deliciosa (kiwi) fruit peel extract and its excellent biological and catalytic properties. The synthesized nanoparticles were well characterized by UV visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDAX). The bactericidal activity of the ZnO nanoparticles was determined by using Staphylococcus aureus (S. aureus), while mechanism of cell death was studied by SEM images. Superior anticancer activity was also observed in inhibiting the colon cancer cells (HCT116) by the ZnO nanoparticles. In addition, ZnO nanoparticles showed efficient photocatalytic activity towards degradation of p-bromophenol, about 96.3% within 120 min. Furthermore, phytotoxicity of the intermediate products was analyzed using Vigna radiata (V. radiata) as a model plant. About 8.0% of germination index (GI) was observed in pure p-BP while it increased to 82.3%, and exhibited that the detoxification of p-BP was attained after 120 min of degradation. Thus, the present study demonstrates ZnO nanoparticles prepared from simple, rapid, inexpensive, eco-friendly and efficient green method gives alternative root for biomedicine and wastewater treatment technologies.

Stimuli-responsive nanocarriers for bacterial biofilm treatment

ABSTRACT

Bacterial biofilm infections have been threatening the human's life and health globally for a long time because they typically cause chronic and persistent infections. Traditional antibiotic therapies can hardly eradicate biofilms in many cases, as biofilms always form a robust fortress for pathogens inside, inhibiting the penetration of drugs. To address the issues, many novel drug carriers emerged as promising strategies for biofilm treatment. Among them, stimuli-responsive nanocarriers have attracted much attentions for their intriguing physicochemical properties, such as tunable size, shape and surface chemistry, especially smart drug release characteristic. Based on the microenvironmental difference between biofilm infection sites and normal tissue, many stimuli, such as bacterial products accumulating in biofilms (enzymes, glutathione, etc.), lower pH and higher H₂O₂ levels, have been employed and proved in favor of "on-demand" drug release for biofilm elimination. Additionally, external stimuli including light, heat, microwave and magnetic fields are also able to control the drug releasing behavior artificially. In this review, we summarized recent advances in stimuli-responsive nanocarriers for combating biofilm infections, and mainly, focusing on the different stimuli that trigger the drug release.

摘要

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Bactericidal effect of ultraviolet C light-emitting diodes: Optimization of efficacy toward foodborne pathogens in water

The elimination of bacterial pathogens from water using ultraviolet C light-emitting diodes (UVC-LEDs) is a critical technology in terms of hygiene and sanitation. This technology has several advantages, such as low energy consumption, no heating requirements, and high effectiveness. Although several studies have reported the bactericidal effect of UVC-LEDs, little information is available on their bactericidal effect on water reservoirs contaminated with microorganisms. Therefore, the aim of this study was to optimize the bactericidal effects of UVC-LED irradiation, particularly at a wavelength of 278 nm, against major foodborne gram-positive and gram-negative pathogenic bacteria, such as Escherichia coli, Staphylococcus aureus, Bacillus cereus, Salmonella Typhimurium, and Listeria monocytogenes. The efficiency of the bactericidal effect of UVC-LED irradiation was determined based on three variables: exposure time (A, 0-60 min), stirring speed (B, 0-100 rpm), and volume of water (C, 400-1200 mL). To optimize the conditions, the operation of the designed model and results analysis were carried out using Box-Behnken design (BBD) and response surface method (RSM). The final conditions optimized for an effective bactericidal activity included a 60 min exposure time, a 100 rpm stirring speed, and 400 mL of liquid volume. Furthermore, the validation of the optimized model using the predicted values was calculated by the program, which was conducted by matching the actual values within standard deviations. The present study revealed that the optimization of a UVC-LED irradiation model is a promising approach for effectively controlling the contamination of water reservoirs by bacterial pathogens.

Pharmacological importance of TG12 from tachykinin and its toxicological behavior against multidrug-resistant bacteria Klebsiella pneumonia

Development of antimicrobial drugs against multidrug-resistant (MDR) bacteria is a great focus in recent years. TG12, a short peptide molecule used in this study was screened from tachykinin (Tac) protein of an established teleost Channa striatus (Cs) transcriptome. Tachykinin cDNA has 345 coding sequence, that denotes a protein contained 115 amino acids; in which a short peptide (TG12) was identified at 83-94. Tachykinin mRNA upregulated in C. striatus treated with Aeromonas hydrophila and Escherichia coli lipopolysaccharide (LPS). The mRNA up-regulation was studied using real-time PCR. The up-regulation tachykinin mRNA pattern confirmed the immune involvement of tachykinin in C. striatus during infection. Further, the identified peptide, TG12 was synthesized and its toxicity was demonstrated in hemolytic and cytotoxic assays using human erythrocytes and human dermal fibroblast cells, respectively. The toxicity study exhibited that the toxicity of TG12 was similar to negative control, phosphate buffer saline (PBS). Moreover, the antibiogram of TG12 was active against Klebsiella pneumonia ATCC 27736, a major MDR bacterial pathogen. Further, the antimicrobial activity of TG12 against pathogenic bacteria was screened using minimum inhibitory concentration (MIC) and anti-biofilm assays, altogether TG12 showed potential activity against K. pneumonia. Fluorescence assisted cell sorter flow cytometer analysis (FACS) and field emission scanning electron microscopy (FESEM) was carried on TG12 with K. pneumonia; the results showed that TG12 significantly reduced K. pneumonia viability as well as TG12 disrupt its membrane. In conclusion, TG12 of CsTac is potentially involved in the antibacterial immune mechanisms, which has a prospectus efficiency in pharma industry against MDR strains, especially K. pneumonia.

Natural dye from Caesalpinia sappan L. heartwood for eco-friendly coloring of recycled paper based packing material and its in silico toxicity analysis

The uses of natural dyes are getting popularized due to the increased awareness regarding the toxicity of many chemical colorants. The chemical colorants are being replaced by the natural colorants for the various industrial applications. The plant-based natural colorants are considered eco-friendly and toxic free. In the present study, we report a natural dye from the heartwood of Caesalpinia sappan suitable for paper based packing materials. This forms the first report on the study of natural dye obtained from the heartwood of C. sappan on paper material. The extracted dye had a good photostability and able to make imprints on recycled paper bags. Moreover, a significant inhibition of bacterial growth was observed at a higher dye concentration of 100 μg mL^-1 against P. aeruginosa which was higher than the standard antibiotics. Growth inhibition was also observed in case of B. subtilis (22 ± 0.17 mm) and K. pneumonia (21 ± 0.53 mm) at 100 μg mL^-1. The dye could be used in making medicated packing materials and have many other bio-potential which was validated through in silico toxicity analysis. The application of such natural dyes in paper material value addition will help in a cleaner and sustainable process during paper recycling.

Effect of photodynamic treatments on quality and antioxidant properties of fresh-cut potatoes

This study evaluated the feasibility of curcumin based photodynamic sterilization technology (PDT) applied to fresh-cut potato slices. Potato samples with 30 μmol L^-1 curcumin solution were exposed to 420 nm light emitting diodes (LED) at a total dose of 0.7 kJ cm^-2. Results showed that PDT inactivated 2.43 log CFU mL^-1 of Escherichia coli (BL 21) and 3.18 log CFU mL^-1 of Staphylococcus aureus and maintained the color, texture, weight as well as total solid content of treated potatoes. Additionally, loss of phenols and flavonoids was significantly prevented, increasing the total antioxidant capacity. This was attributed to changes in enzyme activity that PDT decreased the activity of polyphenol oxidase (PPO) and peroxidase (POD) by 59.7% and 47.8% and increased the activity of phenylalanine ammonia-lyase (PAL). Therefore, curcumin-based PDT has the potential to maintain the commercial quality of producing and achieving microbiological safety.

Structural elucidation upon binding of antimicrobial peptides into binary mixed lipid monolayers mimicking bacterial membranes

HYPOTHESIS

Antimicrobial peptides (AMPs) kill microorganisms by causing structural damage to bacterial membranes. Different microorganisms often require a different type and concentration of an AMP to achieve full microbial killing. We hypothesise that the difference is caused by different membrane structure and composition.

EXPERIMENTS

Given the complexities of bacterial membranes, we have used monolayers of the binary DPPG/TMCL mixture to mimic the cytoplasmic membrane of Gram-positive bacteria and the binary DPPG/DPPE mixture to mimic the cytoplasmic membrane of Gram-negative bacteria, where DPPG, TMCL and DPPE stand for 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol), 1',3'-bis[1,2-dimyristoyl-sn-glycero-3-phospho]-sn-glycerol, and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, respectively. A Langmuir trough was specially designed to control the spread lipid monolayers and facilitate neutron reflectivity measurements.

FINDINGS

Surface pressure-area isotherm analysis revealed that all binary lipid systems mix non-ideally, but mixing is thermodynamically favoured. An increase in the surface pressure encourages demixing, resulting in phase separation and formation of clusters. Neutron reflectivity measurements were undertaken to study the binding of an antimicrobial peptide G(IIKK)₄-I-NH₂ (G₄) to the binary DPPG/TMCL and DPPG/DPPE monolayer mixtures at the molar ratios of 6/4 and 3/7, respectively. The results revealed stronger binding and penetration of G₄ to the DPPG/TMCL monolayer, indicating greater affinity of the antimicrobial peptide due to the electrostatic interaction and more extensive penetration into the more loosely packed lipid film. This work helps explain how AMPs attack different bacterial membranes, and the results are discussed in the context of other lipid models and antibacterial studies.

Nanostructures derived from expired drugs and their applications toward sensing, security ink, and bactericidal material

In this research, a facile and economical route is introduced for the transformation of pharmaceutical waste (i.e., expired medicines) into value-added fluorescent carbon quantum dots (pharmaceutically derived CQDs abbreviated as 'P-CQDs'). The synthesized P-CQDs were identified to have surface functionalities of -OH, C=O, and C=C with an average size of ~2-3 nm and a high quantum yield of 35.3%. The photoluminescence of P-CQDs recorded a maximum optical emission intensity at 2.8 eV (425 nm). The binding of Cu (II) ions by -COOH functionalities on the surface of P-CQDs led to its fluorescence quenching (turn-off) over a wide Cu (II) concentration range of 0.25-50 ppm. The P-CQDs exhibited the detection limit of 0.66 ppm (well below the WHO permissible limit of 2 ppm). The fluorescence intensity of the P-CQDs-Cu (II) complex was recovered from NaHCO_3.Hence, their "off-on" behavior was also explored for security ink applications for information encryption and decryption. Moreover, the rich oxygenated groups on the surface of the P-CQDs were utilized for green synthesis of plasmonic Ag@P-CQDs nanostructures, which were also demonstrated to have enhanced potential as bactericidal materials (e.g., against both E. coli and S. aureus). The overall results of this study are demonstrated to help create new and diverse routes for converting expired drugs into value-added nanostructures.

Single nozzle electrospinning promoted hierarchical shell wall structured zinc oxide hollow tubes for water remediation

HYPOTHESIS

Electrospun metal oxide hollow tubes are of great interest owing to their unique structural advantages compared to solid nanofibers. Although intensive research on preparation of hollow tubes have been devoted, formation of hierarchical shells remains a significant challenge.

EXPERIMENTS

Herein, we demonstrate the fabrication of highly uniform, reproducible and industrially feasible ZnO hollow tubes (ZHT) with two-level hierarchical shells via a simple and versatile single-nozzle electrospinning strategy coupled with subsequent controlled thermal treatment.

FINDINGS

The morphological investigation reveals that the hollow tubes built from nanostructures which has unique surface structure on their wall. The mechanism by which the composite fibers transferred to hollow tubes is primarily based on the evaporation rate of the polymeric template. Notably, tuning the heating rate from 5 °C to 50 °C/min possess adverse effect on formation of hollow tubes, thus subsequently produced ZnO nanoplates (ZNP). The comparative photocatalytic analysis emphasized that ZHT shows higher photocatalytic activity than ZNP. This finding has made an evident that the inherent abundant defects in the electrospun derived nanostructures are not only sufficient for improving the photocatalytic activity. Studies on bacterial growth inhibition showcased a superior bactericidal effect against Staphylococcus aureus and Escherichia coli implying its potentiality for disinfecting the bacteria from water.

Facile synthesis of gold-silver/copper sulfide nanoparticles for the selective/sensitive detection of chromium, photochemical and bactericidal application

In this project, bimetallic Au-Agnanoparticles/CuS nanoparticles were prepared via simple hydrothermal methods, which were used as highly efficient material for Cr (III) detection, photocatalytic, and biological process. The Au-Ag/CuS nanoparticles was studied via UV-visible spectroscopy, field-emission scanning electron microscopy, Dynamic light scattering, and X-ray diffraction. The zeta potential and effective size of Au-Ag/CuS nanoparticles was -32.1 mV and 25 nm respectively. The response time of Cr (III) ions interaction was 2 min. The lowest detection of Cr (III) by Au-Ag/CuS nanoparticles was 0.5 nM. The Au-Ag/CuS nano catalyst was applied to decomposition of drug under visible lamp irradiation. The photo degradation response of drug was 100.0% in 30 min irradiation. The particles exhibited excellent antibacterial activities.

Exploratory investigation on the antibacterial effect of antimicrobial peptides of four mammalian plasmas

Antimicrobial peptides (AMPs) are presently being revisited as promising potential antimicrobial combat agents. Acquisition of resistance to AMPs is very rare compared to conventional antibiotics as they kill microbes by direct disruption of cellular components including the microbial membrane and DNA. In this study four sources of mammalian plasma (human, bovine, caprine and ovine) were explored for presence and effectiveness of antimicrobial peptides by the spot-on-lawn method, followed by the agar well diffusion assay to confirm their antibacterial activity. This was followed by determination of their minimum inhibitory concentrations (MIC) and minimum bactericidal concentration (MBC) by the broth macrodilusion method. The MICs were compared to those produced by the antibiotics Ampicillin, Amoxicillin, Doxycycline and Metronidazole. All four plasma types exhibited antibacterial activity in their native form (plasma^N) or in presence of added pepsin (plasma^p). The highest antibacterial activity was shown by ovine plasma^p against Klebsiella pneumoniae (MIC at dilution of 1:128), while least activity (MIC at dilution of 1:2) was shown by bovine plasma^p and ovine plasma^N against K. pneumoniae, ovine plasma^N against E. coli, and ovine plasma^p against Staph. aureus. All plasma sources achieved bactericidal effect. Activity of ovine plasma^N against K. pneumoniae was higher than that due to Ampilcillin, Amoxicillin, Doxycycline or Metronidazole. The least antibacterial activity was achieved by Ampicillin against K. pneumoniae, E. coli and Bacillus subtilis. Metronidazole had no effect on any of the four bacteria tested. These results indicate that AMPs hold great promise as a valuable renewed tool in the control of pathogenic microbes.

Antimicrobial effects of nitric oxide in murine models of Klebsiella pneumonia

RATIONALE

Inhalation of nitric oxide (NO) exerts selective pulmonary vasodilation. Nitric oxide also has an antimicrobial effect on a broad spectrum of pathogenic viruses, bacteria and fungi.

OBJECTIVES

The aim of this study was to investigate the effect of inhaled NO on bacterial burden and disease outcome in a murine model of Klebsiella pneumonia.

METHODS

Mice were infected with Klebsiella pneumoniae and inhaled either air alone, air mixed with constant levels of NO (at 80, 160, or 200 parts per million (ppm)) or air intermittently mixed with high dose NO (300 ppm). Forty-eight hours after airway inoculation, the number of viable bacteria in lung, spleen and blood was determined. The extent of infiltration of the lungs by inflammatory cells and the level of myeloperoxidase activity in the lungs were measured. Atomic force microscopy was used to investigate a possible mechanism by which nitric oxide exerts a bactericidal effect.

MEASUREMENTS AND MAIN RESULTS

Compared to control animals infected with K. pneumoniae and breathed air alone, intermittent breathing of NO (300 ppm) reduced viable bacterial counts in lung and spleen tissue. Inhaled NO reduced infection-induced lung inflammation and improved overall survival of mice. NO destroyed the cell wall of K. pneumoniae and killed multiple-drug resistant K. pneumoniae in-vitro.

CONCLUSIONS

Intermittent administration of high dose NO may be an effective approach to the treatment of pneumonia caused by K. pneumoniae.

C-2 derivatized 8-sulfonamidoquinolines as antibacterial compounds

A series of C-2 derivatized 8-sulfonamidoquinolines were evaluated for their antibacterial activity against the common mastitis causative pathogens Streptococcus uberis, Staphylococcus aureus and Escherichia coli, both in the presence and absence of supplementary zinc (50 µM ZnSO₄). The vast majority of compounds tested were demonstrated to be significantly more active against S. uberis when in the presence of supplementary zinc (MICs as low as 0.125 µg/mL were observed in the presence of 50 µM ZnSO₄). Compounds 5, 34-36, 39, 58, 79, 82, 94 and 95 were shown to display the greatest antibacterial activity against S. aureus (MIC ≤ 8 µg/mL; both in the presence and absence of supplementary zinc), while compounds 56, 58 and 66 were demonstrated to also exhibit activity against E. coli (MIC ≤ 16 µg/mL; under all conditions). Compounds 56, 58 and 66 were subsequently confirmed to be bactericidal against all three mastitis pathogens studied, with MBCs (≥3log₁₀ CFU/mL reduction) of ≤ 32 µg/mL (in both the presence and absence of 50 µM ZnSO₄). To validate the sanitizing activity of compounds 56, 58 and 66, a quantitative suspension disinfection (sanitizer) test was performed. Sanitizing activity (>5log₁₀ CFU/mL reduction in 5 min) was observed against both S. uberis and E. coli at compound concentrations as low as 1 mg/mL (compounds 56, 58 and 66), and against S. aureus at 1 mg/mL (compound 58); thereby validating the potential of compounds 56, 58 and 66 to function as topical sanitizers designed explicitly for use in non-human applications.

Synergistic activity of tetrasodium EDTA, ethanol and chlorhexidine hydrochloride against planktonic and biofilm cells of clinically relevant pathogens

OBJECTIVES

Biofilms associated with implantable medical devices and wounds are clinically relevant, often requiring repeated use of antibiotics without success. A search for non-antibiotic antimicrobial and antibiofilm solutions is warranted, in line with antimicrobial stewardship. Our study aimed to evaluate the broad-spectrum antimicrobial efficacy of tetrasodium EDTA, ethanol and chlorhexidine hydrochloride (HCl) alone and in combination against clinically relevant planktonic and biofilm cells of bacterial and fungal pathogens.

METHODS

MICs and MBCs were determined for tetrasodium EDTA, ethanol and chlorhexidine HCl against planktonic cells of test pathogens. The MBEC Assay® biofilm inoculator device was used to evaluate the biofilm eradication ability of test antimicrobials alone and in combination against clinically relevant pathogens. The checkerboard microbroth dilution assay was performed to analyze the synergism between test antimicrobials.

RESULTS

Against planktonic cells, the combination of tetrasodium EDTA with ethanol or chlorhexidine HCl resulted in synergistic to indifferent activity, with no antagonism observed. Against mature biofilms, all combinations were synergistic. The MBEC of each test antimicrobial was decreased from 4- to -64-fold when used in combination as compared to when agents were used alone. We optimised the concentration of antimicrobials to achieve rapid eradication of pre-formed biofilms. A triple combination of 3% tetrasodium EDTA, 20% ethanol and 2.5 μg/mL chlorhexidine HCl completely eradicated 48-h-old biofilms of all test strains within 2 h.

CONCLUSION

All three antimicrobial agents can be used together for prevention and treatment of biofilms and biofilm-related infections. The observed in vitro efficacy should be tested further through in vivo and clinical studies.

In-silico driven design and development of spirobenzimidazo-quinazolines as potential DNA gyrase inhibitors

DNA gyrase and Topoisomerase IV are promising antibacterial drug targets as they regulate bacterial DNA replication and topology. In a quest for novel DNA topoisomerase inhibitors, a multidisciplinary approach was adopted that involves computational prediction of binding sites and molecular modelling followed by green synthesis and biological evaluation of antibacterial activity of spirobenzimidazo quinazolines derivatives. Using basic quantum chemistry principles, we evaluated spirobenzimidazo quinazolines derivatives with their pharmacokinetic profiles. Based on the results of the aforesaid in-silico studies, we synthesized a series of titled compounds using green synthetic methodology that were validated as potential antimicrobial agents. Quantum chemoinformatics based predicted activity for the synthesized compounds 9b, 9c, and 9j was concomitant with biological evaluation of broadspectrum antibacterial activity. Biological evaluation revealed that inhibition of biofilm formation was due to their potential antibacterial activity. We believe that the novel spirobenzimidazo quinazolines have the potential to be alternatives to aminocoumarins and classical quinazolines upon detailed target specific biological studies.

Antibacterial, proangiogenic, and osteopromotive nanoglass paste coordinates regenerative process following bacterial infection in hard tissue

Bacterial infection raises serious concerns in tissue repair settings involved with implantable biomaterials, devastating the regenerative process and even life-threatening. When hard tissues are infected with bacteria (called 'osteomyelitis'), often the cases in open fracture or chronic inflammation, a complete restoration of regenerative capacity is significantly challenging even with highly-dosed antibiotics or surgical intervention. The implantable biomaterials are thus needed to be armored to fight bacteria then to relay regenerative events. To this end, here we propose a nanoglass paste made of ~200-nm-sized silicate-glass (with Ca, Cu) particles that are hardened in contact with aqueous medium and multiple-therapeutic, i.e., anti-bacterial, pro-angiogenic and osteopromotive. The nanoglass paste self-hardened via networks of precipitated nano-islands from leached ions to exhibit ultrahigh surface area (~300 m²/g), amenable to fill tunable defects with active biomolecular interactions. Also, the nanoglass paste could release multiple ions (silicate, calcium, and copper) at therapeutically relevant doses and sustainably (for days to weeks), implying possible roles in surrounding cells/tissues as a therapeutic-ions reservoir. The osteopromotive effects of nanoglass paste were evidenced by the stimulated osteogenic differentiation of MSCs. Also, the nanoglass paste promoted angiogenesis of endothelial cells in vitro and vasculature formation in vivo. Furthermore, the significant bactericidal effect of nanoglass paste, as assessed with E. coli and S. aureus, highlighted the role of copper played in elevating ROS level and destroying homeostasis, which salvaged tissue cells from co-cultivated bacteria contamination. When administered topically to rat tibia osteomyelitis defects, the nanoglass paste enhanced in vivo bone healing and fracture resistance. The developed nanoglass paste, given its self-setting property and the coordinated therapeutic actions, is considered to be a promising drug-free inorganic biomaterial platform for the regenerative therapy of bacteria-infected hard tissues.

Heterojunction formation between copper(II) oxide nanoparticles and single-walled carbon nanotubes to enhance antibacterial performance

We delineate the excellent bactericidal efficacy of stable heterojunction nanocomposites composed of single-walled carbon nanotubes (SWCNTs) and copper(II) oxide (CuO) synthesized via facile recrystallization and calcination. The bactericidal effectiveness of the fabricated nanocomposites was examined using the standard broth-dilution method and the growth-inhibition-zone analysis method, in which bacteria cultured in an incubator in tryptic soy broth medium were subjected to the prepared samples. The bactericidal activity of all of the as-synthesized samples is evident in both methods, displaying a substantial decrease in bacterial colonies and resulting in clear inhibition zones, respectively. Among the CuO-SWCNT nanocomposites, the sample subjected to calcination at 500 °C for 5 h was found to exhibit the best performance against Staphylococcus aureus and Escherichia coli, forming inhibition zones 182% and 162% larger than those formed by pure CuO, respectively.

Bacteriostatic and bactericidal clays: an overview

This article aims to draw an overview on the actual knowledge on bacteriostatic and bactericidal natural clays. Particular emphasis is given to the role of clay itself, the action of reduced metals located either in the structure of clay minerals or external to them as constituents of associate minerals, and the definition of the mechanisms of action based on the achievements found in all available studies being carried out so far. The term bactericidal is herein used when a clay or a clay mineral kill the bacteria, whereas the term bacteriostatic is used when those minerals stop bacteria growth and replication. The second part of this article deals with experimental studies on bactericidal natural clay, experience and perspective for the preparation of bactericidal natural clays, interesting on the authors perspective and experience for the preparation of pathogens safe both therapeutic and cosmetic natural mud/natural peloid, and better yet of both therapeutic 87oooand cosmetic peloid itself and designed and engineered peloid. The authors also show how to convert non-antimicrobial clay into antimicrobial one, opening the way in the field of pelotherapy to the preparation of sanitary safe peloids addressed, for instance, to the treatment of rheumatic disabilities, as well as to the preparation of antimicrobial peloids and, in particular, of dermatological ointments, all able to fight infectious skin disorders.

Functional-modified polyurethanes for rendering surfaces antimicrobial: An overview

Antimicrobial surfaces and coatings are rapidly emerging as primary components in functional modification of materials and play an important role in addressing the problems associated with biofouling and microbial infection. Polyurethane (PU) consisting of alternating soft and hard segments has been one of the most important coating materials that have been widely applied in many fields due to its versatile properties. This review attempts to provide insight into the recent advances in antimicrobial polyurethane coatings or surfaces. According to different classes of antimicrobial components along with their antimicrobial mechanism, the synthesis pathways are presented systematically herein to afford polyurethane with antimicrobial properties. Also, the challenges and opportunities of antimicrobial PU coatings and surfaces are also discussed. This review will be beneficial to the exploitation and the further studies of antimicrobial polyurethane materials for a variety of applications.