• Characterisation and in vitro antimicrobial activity of biosynthetic silver-loaded bacterial cellulose hydrogels.

      Gupta, Abhishek; Low, Wan Li; Britland, Stephen T; Mohd Amin, Mohd Cairul Iqbal; Martin, Claire; Radecka, Iza (Taylor & Francis Online, 2016-11-28)
      Wounds that remain in the inflammatory phase for a prolonged period of time are likely to be colonised and infected by a range of commensal and pathogenic microorganisms. Treatment associated with these types of wounds mainly focuses on controlling infection and providing an optimum environment capable of facilitating re-epithelialisation, thus promoting wound healing. Hydrogels have attracted vast interest as moist wound-responsive dressing materials. In the current study, biosynthetic bacterial cellulose hydrogels synthesised by Gluconacetobacter xylinus and subsequently loaded with silver were characterised and investigated for their antimicrobial activity against two representative wound infecting pathogens, namely S. aureus and P. aeruginosa. Silver nitrate and silver zeolite provided the source of silver and loading parameters were optimised based on experimental findings. The results indicate that both AgNO3 and AgZ loaded biosynthetic hydrogels possess antimicrobial activity (p < .05) against both S. aureus and P. aeruginosa and may therefore be suitable for wound management applications.
    • Development and characterisation of biosynthetic hydrogels for wound management applications

      Radecka, Iza; Gibson, Hazel; Kowalczuk, Marek; Gupta, Abhishek (University of Wolverhampton, 2020-04)
      Wounds that remain in the inflammatory phase for a prolonged period of time are likely to be colonised and infected by a range of commensal and pathogenic microorganisms. Treatment associated with these types of wounds mainly focuses on controlling infection and providing an optimum environment capable of facilitating re-epithelialisation, thus promoting wound healing. Hydrogels have attracted vast interest as moist wound-responsive dressing materials. Hydrogels facilitate wound healing due to unique properties and 3D network structures which allows encapsulation of healing agents. In the current study, biosynthetic bacterial cellulose hydrogels synthesised by Gluconacetobacter xylinus (ATCC 23770) and subsequently loaded with antimicrobial healing agents, were characterised for their wound healing properties. Loading parameters were optimised based on experimental findings. Natural bioactive materials with wound healing properties such as curcumin are attracting interest due to the emergence of resistant bacterial strains. The hydrophobicity of curcumin has been counteracted by using solubility enhancing cyclodextrins. In this study, water soluble curcumin:hydroxypropyl-β-cyclodextrin supramolecular inclusion complex was produced by a solvent evaporation method. The ratios of solvents to solubilise curcumin and hydroxypropyl-β-cyclodextrin were tested for the production of the inclusion complex with optimum encapsulation efficacy. The results confirmed that hydroxypropyl-β-cyclodextrin enhanced the aqueous solubility of curcumin and allowed loading into bacterial cellulose to produce antimicrobial hydrogels. Silver is a broad spectrum natural antimicrobial agent with wide applications extending to proprietary wound dressings. Based on the broad spectrum antimicrobial properties of silver, silver nitrate-loaded and silver zeolite-loaded bacterial cellulose hydrogels were produced. Recently silver nanoparticles have also attracted attention in wound management. A novel green synthesis of nanoparticles was accomplished in this study using a natural reducing agent, curcumin which is a natural polyphenolic compound, well known as a wound healing agent. In addition to physicochemical properties, these hydrogels were characterised (in vitro) for wound management applications. The results indicate that both silver nitrate and silver zeolite-loaded biosynthetic hydrogels possess antimicrobial activity against both Staphylococcus aureus and Pseudomonas aeruginosa. Furthermore, the curcumin:hydroxypropyl-β-cyclodextrin-loaded bacterial cellulose hydrogels possess unique properties including haemocompatability, cytocompatability, anti-staphylococcal and antioxidant abilities. In addition to high cytocompatibility, curcumin reduced silver nanoparticles-loaded bacterial cellulose hydrogels dressings exhibited antimicrobial activity against representative wound infecting pathogenic microbes Pseudomonas aeruginosa and Staphylococcus aureus. In conclusion, the results presented support the potential use of all the investigated bacterial cellulose hydrogels for wound management applications as dressings.
    • Lipsome encapsulated antimicrobial metal ions and essential oils

      Kenward, M.A. Dr, Martin Claire Dr, Hill D. J. Dr; Low, Wan Li (University of Wolverhampton, 2012-01)
      Abstract This study investigates the feasibility of using TTO and Ag+ alone and in combination either as free or liposome encapsulated agents. Based on the minimum lethal concentration (MLC), the fractional lethal concentration index (FLCI) showed that treatment with unencapsulated combinations of TTO and Ag+ exerted a synergistic effect against P. aeruginosa (FLCI = 0.263) and indifferent effects against S. aureus and C. albicans (0.663 and 0.880, respectively). Using polyvinyl alcohol (PVA) emulsified agents in combination, showed synergistic effects against P. aeruginosa and S. aureus (FLCI = 0.325 and 0.375, respectively), but C. albicans remained indifferent (FLCI = 0.733). Time kill experiments revealed that the combined agent concentrations and elimination time (to the lowest limit of detection, LOD) are as follows: C. albicans: 0.12%v/vTTO:2.5x10-4Ag+:1.5hrs, P. aeruginosa: 1%v/vTTO:3.2x10-4Ag+:15mins and S. aureus: 1.2%v/vTTO:3.2x10-4Ag+:30mins. Repeating these experiments with emulsified TTO encapsulated in liposomes (lipo-TTO:PVA30-70kDa) against P. aeruginosa and S. aureus reduced the effective amount of TTO required (compared to free TTO). However, this was not observed in C. albicans. The required effective concentration of Ag+ from liposome encapsulated Ag+ (lipo-Ag+) was shown to remain the same as free Ag+. The effective concentration and elimination time of liposomal agents in combination are as follows: C. albicans: 0.05%v/vTTO:PVA:8.9x10-5Ag:PVA:2.0hrs, P. aeruginosa: 0.25%v/vTTO:PVA:3.2x10-4Ag:PVA:30mins and S. aureus: 0.05%v/vTTO:PVA:6.0x10-4Ag:PVA:1.5hrs. These results showed the potential of using TTO and Ag+ in combination, along with liposome delivery systems to effectively lower the MLC. Scanning electron micrographs of microorganisms exposed to Ag+ showed a reduction in cell size when compared to untreated cells. Transmission electron micrograph of C. albicans showed the cell surface damaging potential of Ag+. Furthermore, this investigation also demonstrated the feasibility of using chitosan hydrogels as an alternative delivery system for TTO and/or Ag+. The development of these controlled release systems to deliver alternative antimicrobial agents may allow sustained targeted delivery at microbiocidal concentrations.
    • Recent advances and applications of bacterial cellulose in biomedicine

      Swingler, Sam; Gupta, Abhishek; Gibson, Hazel; Kowalczuk, Marek; Heaselgrave, Wayne; Radecka, Iza (MDPI AG, 2021-01-28)
      Bacterial cellulose (BC) is an extracellular polymer produced by Komagateibacter xylinus, which has been shown to possess a multitude of properties, which makes it innately useful as a next-generation biopolymer. The structure of BC is comprised of glucose monomer units polymerised by cellulose synthase in β-1-4 glucan chains which form uniaxially orientated BC fibril bundles which measure 3–8 nm in diameter. BC is chemically identical to vegetal cellulose. However, when BC is compared with other natural or synthetic analogues, it shows a much higher performance in biomedical applications, potable treatment, nano-filters and functional applications. The main reason for this superiority is due to the high level of chemical purity, nano-fibrillar matrix and crystallinity. Upon using BC as a carrier or scaffold with other materials, unique and novel characteristics can be observed, which are all relatable to the features of BC. These properties, which include high tensile strength, high water holding capabilities and microfibrillar matrices, coupled with the overall physicochemical assets of bacterial cellulose makes it an ideal candidate for further scientific research into biopolymer development. This review thoroughly explores several areas in which BC is being investigated, ranging from biomedical applications to electronic applications, with a focus on the use as a next-generation wound dressing. The purpose of this review is to consolidate and discuss the most recent advancements in the applications of bacterial cellulose, primarily in biomedicine, but also in biotechnology.