The bactericidal activity of glutaraldehyde-impregnated polyurethane

Changes in environmental and engineered conditions alter the plasma membrane lipidome of fractured shale bacteria

IMPORTANCE

Microorganisms inadvertently introduced into the shale reservoir during fracturing face multiple stressors including brine-level salinities and starvation. However, some anaerobic halotolerant bacteria adapt and persist for long periods of time. They produce hydrogen sulfide, which sours the reservoir and corrodes engineering infrastructure. In addition, they form biofilms on rock matrices, which decrease shale permeability and clog fracture networks. These reduce well productivity and increase extraction costs. Under stress, microbes remodel their plasma membrane to optimize its roles in protection and mediating cellular processes such as signaling, transport, and energy metabolism. Hence, by observing changes in the membrane lipidome of model shale bacteria, Halanaerobium congolense WG10, and mixed consortia enriched from produced fluids under varying subsurface conditions and growth modes, we provide insight that advances our knowledge of the fractured shale biosystem. We also offer data-driven recommendations for improving biocontrol efficacy and the efficiency of energy recovery from unconventional formations.

Delivery of a peptide/microRNA blend via electrospun antimicrobial nanofibres for wound repair

Downregulation of microRNA-31 (miR-31) and microRNA-132 (miR-132) has been associated with delayed wound healing. Therefore, it was hypothesised that intracellular delivery of miR-31 and miR-132, both as individual and blend formulations, could promote tissue repair. The use of a blend could minimise potential toxicity and achieve synergistic effects, thus maximising the therapeutic effect. miR-31 and miR-132 were condensed with a 30-mer positively charged amphipathic peptide, RALA, to form nanocomplexes with an average size <200 nm and zeta-potential ≥10 designed to facilitate cellular internalisation. This enabled a fold increase in miR-31 and miR-132 expression of ≥100,000 in a murine fibroblast cell line (NCTC-929) and a skin human keratinocyte cell line (HaCaT), with intracellular delivery >70% for individual and blend formulations. Moreover, incubation with the nanocomplexes increased the migration of HaCaT cells ≥25% at 4 and 8 h post-incubation, as well as downregulation of EMP-1 and RASA1 and HB-EGF and RASA1, target genes for miR-31 and miR-132, respectively. Electrospinning was then employed to produce an alginate/polyvinyl alcohol/ciprofloxacin nanofibrous wound patch to facilitate the controlled delivery of the nanocomplexes. Nanofibres were crosslinked with glutaraldehyde to improve stability in aqueous solvents, and they were proven to be biocompatible with antimicrobial activity without cellular attachment to avoid injury upon removal. RALA/miR nanoparticles were incorporated to the nanofibrous wound dressing and in vivo wound healing studies using C57BL/6J mice demonstrated a >60% acceleration in the wound closure rate at Day 7 post-wounding, a ≥1.5 increase in epidermal thickness, and a ≥2 increase in blood vessel count with respect to commercial and untreated controls. Taken together, this data proves that delivery of RALA/miR-31 and RALA/miR-132 from an alginate/polyvinyl alcohol/ciprofloxacin nanofibrous wound dressing constitutes an advanced therapy for wound healing, by accelerating wound closure and improving healed tissue quality. STATEMENT OF SIGNIFICANCE: In this study, we report for the first time the use of the RALA peptide to deliver two miRNA 31 & 132 simultaneously from an electrospun patch. Both miRs have been shown to be downregulated in wounds and this study endeavoured to deliver a blend of the miRs from a nanofibre patch. Electrospinning was used to produce an alginate/polyvinyl alcohol/ciprofloxacin wound patch to enable controlled delivery of the miRs without cellular attachment to the wound with the added benefit of anti-microbial activity. Application of the nanofibre patch loaded with the blended RALA/miR nanoparticles demonstrated a synergistic effect with acceleration of wound closure rate, a significant increase in epidermal thickness and blood vessel count with respect to commercial and untreated controls.

Glutathione Immobilized Polycaprolactone Nanofiber Mesh as a Dermal Drug Delivery Mechanism for Wound Healing in a Diabetic Patient

Glutathione (GSH) is an anti-inflammatory and antioxidant biomolecule. Polycaprolactone (PCL) nanofiber mesh (NFM) is capable of the attachment and release of biomolecules for prolonged periods and has the potential as a transdermal drug delivery system during wound healing for a diabetic patient. Our earlier study found that high levels of sugar in diabetic male mice were significantly decreased by daily doses of glutathione administered on the mice. Furthermore, oxidative stress found in diabetic male mice led to the total depletion of glutathione levels in the body’s organs (pancreas, spleen, epididymis, and testis). The objective of this study was to attach GSH with PCL NFM for the controlled release of GSH biomolecules for long periods of time from the fiber mesh into a diabetic body. This study produced PCL NFM using an electrospun technique and tested it on mice to evaluate its efficiency as a dermal drug delivery mechanism. This study dissolved GSH (2.5 mg/mL) with phosphate-buffered saline (PBS) and glutaraldehyde (GLU) solution to create GSH-PBS and GSH-GLU complexes. Each complex was used to soak PCL NFM for 24 h and dried to create PCL-GSH-PBS and PCL-GSH-GLU meshes. Fiber morphology, degradation, fibroblast cell proliferation, cytotoxicity, and GSH release activities from each mesh were compared. Fibroblast cell adhesion and cytotoxicity tests found excellent biocompatibility of both GSH-immobilized PCL meshes and no degradation until 20 days of the study period. The disk diffusion method was conducted to test the antibacterial properties of the sample groups. Release tests confirmed that the attachment of GSH with PCL by GSH-GLU complex resulted in a steady release of GSH compared to the fast release of GSH from PCL-GSH-PBS mesh. The disk diffusion test confirmed that PCL-GSH-GLU has antibacterial properties. The above results conclude that GSH-GLU immobilized PCL NFM can be a suitable candidate for a transdermal anti-oxidative and anti-bacterial drug delivery system such as bandage, skin graft for wound healing application in a diabetic patient.

Degradation of Decabromodiphenyl Ether in an Aerobic Clay Slurry Microcosm Using a Novel Immobilization Technique

A novel chitosan immobilization technique that entraps photocatalyst and microbes was developed and applied to decompose decabromodiphenyl ether (BDE-209) in a clay slurry microcosm. The optimized conditions for immobilization were obtained by mixing 1.2% (w/v) chitosan dissolved in 1% (v/v) acetic acid with nano-TiO2 particles and the BDE-209-degrading bacterial mixed culture. This aqueous mixture was injected into 1% (w/v) water solution containing sodium tripolyphosphate to form spherical immobilized beads. The surface of the immobilized beads was reinforced by 0.25% (v/v) glutaraldehyde cross-linking. These beads had enough mechanical strength during BDE-209 degradation to maintain their shape in the system at a stirring rate of 200-rpm, while undergoing continuous 365 nm UVA irradiation. This novel TiO2-Yi-Li immobilized chitosan beads system allowed a successful simultaneous integration of photolysis, photocatalysis and biodegradation to remove BDE-209. The remaining percentage of BDE-209 was 41% after 70 days of degradation using this system. The dominant bacteria in the BDE-209-degrading bacterial mixed culture during remediation were Chitinophaga spp., Methyloversatilis spp., Terrimonas spp. and Pseudomonas spp. These bacteria tolerated the long-term UVA irradiation and high-level free radicals present, while utilizing BDE-209 as their primary carbon resource. This new method has great potential for the treatment of a range of pollutants.

Zinc Oxide and Copper Chitosan Composite Films with Antimicrobial Activity

The role of the oral microbiome and its effect on dental diseases is gaining interest. Therefore, it has been sought to decrease the bacterial load to fight oral cavity diseases. In this study, composite materials based on chitosan, chitosan crosslinked with glutaraldehyde, chitosan with zinc oxide particles, and chitosan with copper nanoparticles were prepared in the form of thin films, to evaluate a new alternative with a more significant impact on the oral cavity bacteria. The chemical structures and physical properties of the films were characterized using by Fourier transform infrared spectroscopy (FTIR,) Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle measurements. Subsequently, the antimicrobial activity of each material was evaluated by agar diffusion tests. No differences were found in the hydrophilicity of the films with the incorporation of ZnO or copper particles. Antimicrobial activity was found against S. aureus in the chitosan film crosslinked with glutaraldehyde, but not in the other compositions. In contrast antimicrobial activity against S. typhimurium was found in all films. Based on the data of present investigation, chitosan composite films could be an option for the control of microorganisms with potential applications in various fields, such as medical and food industry.

The antiseptic Miramistin: a review of its comparative in vitro and clinical activity

Miramistin is a topical antiseptic with broad antimicrobial action, including activity against biofilms and a clinical profile showing good tolerability. Miramistin was developed within a framework of the Soviet Union Cold War Space Program. It is available for clinical use in several prior Soviet bloc countries, but barely known outside of these countries and there is almost no mention of miramistin in the English literature. However, considering emerging antimicrobial resistance, the significant potential of miramistin justifies its re-evaluation for use in other geographical areas and conditions. The review consists of two parts: (i) a review of the existing literature on miramistin in English, Russian and Ukrainian languages; (ii) a summary of most commonly used antiseptics as comparators of miramistin. The oral LD50 was 1200 mg/kg, 1000 mg/kg and 100 g/L in rats, mice and fish, respectively. Based on the results of the review, we suggest possible applications of miramistin and potential benefits over currently used agents. Miramistin offers a novel, low toxicity antiseptic with many potential clinical uses that need better study which could address some of the negative impact of antimicrobial, antiseptic and disinfectant resistance.

Microbial influenced corrosion of processing industry by re-circulating waste water and its control measures - A review

In this review article, illustrating the impact and fundamental stuff of microbially influenced corrosion (MIC) along with mechanism, maintenance of materials, human life, wellbeing and inhibitors for cooling towers. Corrosion is a natural mechanism of oxidation and reduction of metal ions by chemical and electrochemical processes and microorganism accumulation. MIC occurs through the aggregation of microbes which can be secreting the extra polymeric substances (EPS) that oxidation of the metal surface. According to the reviews, in the cooling water system, the corrosion begins in the anode charge because its oxidation reaction quickly takes place on the metal surface than the cathode charge. Annihilate the corrosion process needs certain helper substances such as chemical or green compounds, called inhibitors. Corrosion inhibitors typically adopt the adsorption mechanism due to the presence of organic hetero atoms. Chemical and green inhibitors are used to prevent corrosion processes and since ancient times, vast quantities of chemical inhibitors have been used in industry due to their effectiveness and consistency. But still, the chemical inhibitors are more toxic to humans and the environment. Instead of chemical inhibitors, green inhibitors (natural products like plant leaves, flowers, stem, buds, roots and sea algae) are developed and used in industries. Generally, green inhibitors contain natural compounds, high inhibition efficiency, economic, eco- and human-friendly, and strong potential features against corrosion. Thus, a lot of research is ongoing to discover the green inhibitors in various parts of plants and seaweeds.

Anticipating Xenogenic Pollution at the Source: Impact of Sterilizations on DNA Release From Microbial Cultures

The dissemination of DNA and xenogenic elements across waterways is under scientific and public spotlight due to new gene-editing tools, such as do-it-yourself (DIY) CRISPR-Cas kits deployable at kitchen table. Over decades, prevention of spread of genetically modified organisms (GMOs), antimicrobial resistances (AMR), and pathogens from transgenic systems has focused on microbial inactivation. However, sterilization methods have not been assessed for DNA release and integrity. Here, we investigated the fate of intracellular DNA from cultures of model prokaryotic (Escherichia coli) and eukaryotic (Saccharomyces cerevisiae) cells that are traditionally used as microbial chassis for genetic modifications. DNA release was tracked during exposure of these cultures to conventional sterilization methods. Autoclaving, disinfection with glutaraldehyde, and microwaving are used to inactivate broths, healthcare equipment, and GMOs produced at kitchen table. DNA fragmentation and PCR-ability were measured on top of cell viability and morphology. Impact of these methods on DNA integrity was verified on a template of free λ DNA. Intense regular autoclaving (121°C, 20 min) resulted in the most severe DNA degradation and lowest household gene amplification capacity: 1.28 ± 0.11, 2.08 ± 0.03, and 4.96 ± 0.28 logs differences to the non-treated controls were measured from E. coli, S. cerevisiae, and λ DNA, respectively. Microwaving exerted strong DNA fragmentation after 100 s of exposure when free λ DNA was in solution (3.23 ± 0.06 logs difference) but a minor effect was observed when DNA was released from E. coli and S. cerevisiae (0.24 ± 0.14 and 1.32 ± 0.02 logs differences with the control, respectively). Glutaraldehyde prevented DNA leakage by preserving cell structures, while DNA integrity was not altered. The results show that current sterilization methods are effective on microorganism inactivation but do not safeguard an aqueous residue exempt of biologically reusable xenogenic material, being regular autoclaving the most severe DNA-affecting method. Reappraisal of sterilization methods is required along with risk assessment on the emission of DNA fragments in urban systems and nature.

α-Chymotrypsin Immobilized on a Low-Density Polyethylene Surface Successfully Weakens Escherichia coli Biofilm Formation

The protease α-chymotrypsin (α-CT) was covalently immobilized on a low-density polyethylene (LDPE) surface, providing a new non-leaching material (LDPE-α-CT) able to preserve surfaces from biofilm growth over a long working timescale. The immobilized enzyme showed a transesterification activity of 1.24 nmol/h, confirming that the immobilization protocol did not negatively affect α-CT activity. Plate count viability assays, as well as confocal laser scanner microscopy (CLSM) analysis, showed that LDPE-α-CT significantly impacts Escherichia coli biofilm formation by (i) reducing the number of adhered cells (-70.7 ± 5.0%); (ii) significantly affecting biofilm thickness (-81.8 ± 16.7%), roughness (-13.8 ± 2.8%), substratum coverage (-63.1 ± 1.8%), and surface to bio-volume ratio (+7.1 ± 0.2-fold); and (iii) decreasing the matrix polysaccharide bio-volume (80.2 ± 23.2%). Additionally, CLSM images showed a destabilized biofilm with many cells dispersing from it. Notably, biofilm stained for live and dead cells confirmed that the reduction in the biomass was achieved by a mechanism that did not affect bacterial viability, reducing the chances for the evolution of resistant strains.

Synergism between high hydrostatic pressure and glutaraldehyde for the inactivation of Staphylococcus aureus at moderate temperature

The sterilization of transplant and medical devices should be effective but not detrimental to the structural properties of the materials used. In this study, we examined the effectiveness of chemical and physical agents for inactivating Staphylococcus aureus, a gram-positive bacterium and important cause of infections and biofilm production. The treatment conditions in this work were chosen to facilitate their subsequent use with sensitive materials. The effects of temperature, high hydrostatic pressure, and glutaraldehyde disinfectant on the growth of two strains of S. aureus (ATCC 25923 and BEC 9393) were investigated individually and/or in combinations. A low concentration of glutaraldehyde (0.5 mM), high hydrostatic pressure (300 MPa for 10 min), and moderate temperature (50 °C), when used in combination, significantly potentiated the inactivation of both bacterial strains by > 8 orders of magnitude. Transmission electron microscopy revealed structural damage and changes in area that correlated with the use of pressure in the presence of glutaraldehyde at room temperature in both strains. Biofilm from strain ATCC 25923 was particularly susceptible to inactivation. The conditions used here provided effective sterilization that can be applied to sensitive surgical devices and biomaterials, with negligible damage. The use of this experimental approach to investigate other pathogens could lead to the adoption of this procedure for sterilizing sensitive materials.

The bactericidal activity of glutaraldehyde-impregnated polyurethane

Although glutaraldehyde is known to be bactericidal in solution, its potential use to create novel antibacterial polymers suitable for use in healthcare environments has not been evaluated. Here, novel materials were prepared in which glutaraldehyde was either incorporated into polyurethane using a simple "swell-encapsulation-shrink" method (hereafter referred to as "glutaraldehyde-impregnated polyurethane"), or simply applied to the polymer surface (hereafter referred to as "glutaraldehyde-coated polyurethane"). The antibacterial activity of glutaraldehyde-impregnated and glutaraldehyde-coated polyurethane samples was tested against Escherichia coli and Staphylococcus aureus. Glutaraldehyde-impregnated polyurethane resulted in a 99.9% reduction in the numbers of E. coli within 2 h and a similar reduction of S. aureus within 1 h, whereas only a minimal reduction in bacterial numbers was observed when the biocide was bound to the polymer surface. After 15 days, however, the bactericidal activity of the impregnated material was substantially reduced presumably due to polymerization of glutaraldehyde. Thus, although glutaraldehyde retains antibacterial activity when impregnated into polyurethane, activity is not maintained for extended periods of time. Future work should examine the potential of chemical modification of glutaraldehyde and/or polyurethane to improve the useful lifespan of this novel antibacterial polymer.