Preparation, characterization, and in vitro evaluation of polymer-based wound dressings for the management of chronic wounds

Abstract

Microbial infections are responsible for the retarded recovery process of chronic wounds. Polymer-based scaffolds possess features suitable for the treatment of chronic injuries. However, these scaffolds are commonly encapsulated with therapeutic agents to enhance their biological activities, including antibacterial efficacy. In this research, two types of polymer-based scaffolds were formulated and evaluated as effective formulations for the treatment of chronic wounds: sponges and topical gels. Sponges were formulated from cross-linking of gelatin and PEG. Ag nanoparticles and metronidazole were incorporated into the sponges to improve their antibacterial activity. Topical gels were loaded with essential oils and Ag nanoparticles and prepared from CMC and poloxamer. The prepared sponges and topical gels were evaluated using various analysis and characterization techniques. SEM/EDX, FTIR, and TGA were employed to characterize gelatin/PEG hybrid sponges followed by porosity, in vitro biodegradability, cytotoxicity, and antibacterial studies. FTIR, SEM/EDX, and TGA confirmed their physicochemical properties and successful fabrication of sponges loaded with metronidazole and Ag nanoparticles. The sponges were biodegradable, indicating their capability to induce skin regeneration. The drug release studies showed a rapid release of metronidazole 28.32-71.97 percent from the sponges over the first hour, followed by a sustained drug release. The Ag nanoparticles were released in a sustained manner, suggesting that these sponges can rapidly destroy bacteria and inhibit persisting bacterial infections as well as protect the lesion bed from further bacteria infections. The in vitro antibacterial studies of sponges displayed superior antibacterial activity against most of the Gram-negative and Gram-positive bacteria strains commonly found in chronic wound infections with a MIC value of 15.625 μg/mL. In vitro cytotoxicity experiments revealed excellent biocompatibility with a percent cell viability of more than 70 percent. The in vitro wound scratch healing assay exhibited that the sponges encapsulated with only metronidazole promoted high cell migration than the dual drug-loaded sponges and untreated cells, suggesting its potential to quicken the wound healing process. CMC/Poloxamer topical gels were also characterized by FTIR, followed by pH, viscosity, spreadability, cytotoxicity, and antibacterial studies. FTIR showed successful preparation of CMC/Poloxamer topical gels loaded with essential oils and Ag nanoparticles. The topical gels exhibited pH in the range of 5.20-6.68, spreadability between 5.4 and 5.9 cm, and viscosity ranged from 216 to 1200 cP at 50 rpm and 210–858 cP at 100 rpm. The in vitro drug release studies demonstrated that Ag nanoparticles were released from the topical gels in a sustained manner. Most formulated topical gels demonstrated superior antimicrobial efficacy against Gram-positive and Gram-negative bacteria strains than the blank gel and controls. The cytotoxicity analysis displayed more than 90.83 percent cell viability for the topical gels, revealing excellent biocompatibility. The outcomes revealed that the topical gels enriched with essential oils lavender and tea tree and Ag nanoparticles and sponges incorporated with metronidazole and Ag nanoparticles are potential wound dressing scaffolds that can be employed for the treatment of chronic infected injuries. The in vitro wound healing experiments showed that the HaCaT cells cultured with gels co-enriched with lavender oil and Ag nanoparticles possessed a higher rate of closure in comparison to the untreated cells for 96 hours.Thesis (PhD) -- Faculty of Science and Agriculture, 202