copper or zinc chloride) and acetate complexes integrated well into shellac/ethanol solutions. In the initial phase of development, we therefore assessed, visually, how well copper- and zinc-based materials mixed with shellac/ethanol solutions. Shellac is highly soluble in ethanol and its solutions readily yield solid adhesive layers upon evaporation: i.e. coli test’ would be a suitable triage system to answer the question of whether the material’s metal ions were available for bacterial contact killing or not. However, since copper ions and copper surfaces have broad spectrum antibacterial properties 19, 20 we considered that the ‘ E. coli, in contrast, is a standard laboratory model bacterium that is a facultative anaerobe. In digital dermatitis the causative organisms are typically anaerobes and very difficult to culture. To narrow down the various formulations for in vivo testing their in vitro efficacy was first determined against Escherichia coli. Continuous mechanical stress and exposure to bacterial-rich slurry make topical treatment of digital dermatitis extremely challenging 3. It impairs mobility, milk production and quality of life 17, 18. For proof-of-principle in vivo application and tolerability we considered a worst-case-scenario challenge, namely digital dermatitis, a chronic, contagious, polybacterial infection that afflicts the feet of dairy cows with painful lesions. In this work, we employed copper, zinc, and shellac-a natural, safe resin used in confectionary and cosmetics 16-to develop robust, rapid-setting, liquid bandages with inherent antibacterial repellent (contact killing) properties. In contrast, copper and zinc are physiologically essential trace-minerals and, if leached into the wound significantly, their antibacterial properties could be harnessed by the innate immune system as part of our natural repertoire for fighting infections 14, 15. Silver, if released into the wound, is also potentially problematic to eukaryotic cells 12, 13. In particular, silver has seen wide-spread topical usage 5, 7, 8, 9 and, although potent as a released ion, it is actually inferior to copper at contact killing 10, 11. Metal ions are attractive for this purpose, being antibiotic-sparing and having broad-spectrum activity 6. solid) bandages is to impart them with antimicrobial properties 2, 5 such that they remain sterile during use and are not harbingers for biofilm formation. One approach adopted by the more advanced conventional (i.e. Ideally, liquid bandage formulations should produce robust protective barriers, comprise safe, biodegradable components, and may even offer additional functionality to promote wound healing 4. Liquid bandage formulations are potentially well placed to redress these limitations, being facile to apply and intrinsically amenable to modification for added functionality or fine-tuning. The principal drawbacks of conventional bandages are (1) the inconvenient and/or labour-intensive application that is required (2) the requirement for regular changing, to avoid them becoming niduses for infection and (3) the requirement for antimicrobial under-dressings. This new class of bandage has promise for challenging topical situations in humans and other animals, especially away from controlled, sterile clinical settings where wounds urgently require protection from environmental and bacterial contamination.īandaging is an enduring approach to the medical and surgical management of wounds, with a myriad of benefits including, provision of structural support, prevention of ingress of dirt and infectious microbes from the environment, and the securing of dressings and topical therapeutics (e.g. Treatment was well-tolerated and clinical improvement was observed in animal mobility. The bandage self-degraded, appropriately, over 7 days despite extreme conditions (faecal slurry). When challenged in vivo with the polybacterial bovine wound infection ‘digital dermatitis’, Zn/Cu-shellac adhered rapidly and robustly over pre-applied antibiotic. The material demonstrated marked antibacterial contact properties and, in ex-vivo studies, effectively locked-in pre-applied therapeutics. We show here that antibacterial zinc (Zn) and copper (Cu) species greatly enhance the barrier properties of the natural, waterproof, bio-adhesive polymer, shellac. Rapid-set liquid bandages are efficient alternatives but lack durability or inherent infection control. Bandages must be changed and infection risk managed. Bandaging is a steadfast but time-consuming component of wound care with limited technical advancements to date.
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