Every year, about 550,000 patients receive medical attention for minor and major burns in the United States.1 In 2020, it was estimated that 11 million people worldwide suffered from burn injuries, with 150,000 of those burns being fatal.2 Burns are among the most painful and debilitating recalcitrant wounds that can often turn terminal when infection occurs. The different grades for burns that we aim to treat are first, second, and third degrees.2 Each burn type is susceptible to secondary infection that can be life threatening, and as a result, are extensively treated with antimicrobial agents.2 At present, only a handful of FDA-approved products are available in the market that can successfully treat second and third degree burn wounds and scars.3 Topical agents such as sodium hypochlorite, iodine, H2O2, silver etc. are used to combat burn wound infections.3 However, the relentless emergence of antibiotic resistant strains of pathogens, often with multiple antibiotic resistances together with the discovery of novel antibiotics, has necessitated investigating and developing better alternative treatments.
In this effort, a cost-effective approach to engineer a microbe-resistant bandage system utilizing clay was undertaken as the research project. This unique microbe-resistant material has been developed using organo-modification and metal-ion exchanged clay scaffolds, and has been fully characterized using analytical techniques such as powder XRD, ATR-FTIR, XPS, ICP-OES etc. The hybrid clay samples have also been tested for their antimicrobial efficacy against Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) bacteria in promoting the process of wound healing to serve as a representative of the ESKAPE group of bacteria, which includes Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species. By leveraging the excellent hydrophilic and moisture retention properties of clay, we can postulate achieving optimal moisture transport from the dressing through the wound area to accelerate the healing cascade by hassle-free self-application at the point of injury.4
The proposed research deals with the antimicrobial effects associated with metal cations within a clay matrix that can be used for the treatment of burn injuries and scars. Currently, most burn treatments involve high doses of silver-based products that make them costly.3 Moreover, most of these treatments are ointment-based, which exposes the wounds to cross-contamination when in contact with dust, debris, moisture, water, liquids, particulates etc. The goal is to develop a free-standing film composed of controlled amounts of silver ions tethered to the clay scaffolds that can be used to treat severe burns and scars. Performing animal studies using in vivo models for first or second degree burn injuries and scars exceeded the budget for this project, hence, antimicrobial efficacy against ESKAPE pathogens, viz. gram-negative and gram-positive bacteria using the engineered hybrid films was the focal point for this project. This unique and cost-effective system is much cheaper compared to ointments and other bandage systems. Moreover, the meso- and micro-porosities present within the clay can be easily leveraged for easy moisture and oxygen transport from bandage to skin, which is essential for natural healing of the wounds and burn injuries.4 Additionally, the antimicrobial/antibacterial efficacy of this unique bandage system can be suitable for prolonged use, thereby minimizing the inconveniences of frequent changing and reapplication. This helps to reduce the risk of infection and contamination, drastically.
Clay has the well-known property of retaining moisture and has been used as a promoter for hemostasis, thereby, helping the composite films to serve multiple purposes in the burn and scar healing process.8 The hydroxyl groups in the clay used will be functionalized with trimethyl glycine (Betaine), expanding the clay galleries through intercalation, while Group II metal ions and silver ions can be easily exchanged with the sodium cations present in clay within the interstitial space. The metal ions (Ag+) exchanged organo-clay gallery is the main driving force for eliminating the microbes or bacteria. Thus, one of the prime goals for this effort is to develop an organo-modified Betaine-composite film that can be conformable to various shapes and sizes and will garner anti-microbial/ bacterial/ fungal properties. Other future goals include developing films with optimal metal ion concentrations in the clay scaffolds to reduce the cost (by replacing Ag+ ions with group II metal ions in the silicate scaffolds) without compromising the efficacy of the product.
This research exhibits a novel, cost-effective solution to engineer microbe-resistant “hybrid” clay membranes by chemical modification, metal incorporation, intercalation, and exfoliation of clay-silicate galleries to prevent infections from ESKAPE pathogens. Results from the physico-chemical analyses have shown mechanical durability of the films. Antimicrobial efficacy tests using Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) showed a significant reduction in bacterial growth, which indicates the antimicrobial efficacy of the clay films. In typical bacterial kill study experiments, the zone of inhibition was at or above 1 cm for both the gram-positive and gram-negative bacteria, with four samples tested with three 0.6 cm diameter discs against a clay control. Evidently, these matrices are effective at preventing the growth of bacteria that can prove to be infectious. This unique “hybrid” bandage system promotes: (a) prevention and control of both gram-negative and gram-positive bacteria, (b) nontoxic and biodegradable features, (and c) easy application on wounds. Beyond the antimicrobial efficacy, physical tests have been used to analyze the resulting clay films. X-Ray photoelectron spectroscopy is used to determine the quantitative elemental analysis, and binding energies and oxidation states of the elements. Powder X-Ray diffraction, ATR-FTIR, X-Ray fluorescence spectroscopy and viscosity have been used to determine physical properties, structures, and mechanical durability of the films.
Bachelor of Science (B.S.)
College of Medicine
Burnett School of Biomedical Sciences
Rigby, Kasey L., "Novel Microbe-Resistant Clay Dressing for Healing Burn Wounds" (2022). Honors Undergraduate Theses. 1193.