Development of a Transparent Peptide Functionalized Bacterial Derived Cellulose Wound Dressing

van Zyl, Elizabeth

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Development of a Transparent Peptide Functionalized Bacterial Derived Cellulose Wound Dressing

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By 2030, one in six people worldwide will be over the age of 60. With this aging population and the increased prevalence of antibiotic-resistant bacteria, the prevalence of chronic wounds is of great concern. Chronic wounds, or those that fail to complete the normal wound healing process within three months, affect 2.4 to 4.5 million people annually in the United States alone. Chronic wounds house senescent cell populations with impaired proliferative and secretory capacities, making them unresponsive to conventional wound healing signals. In at least 90% of chronic wounds, this lack of wound healing activity allows invading pathogens to access the wound site and flourish in the moist, nutrient-rich wound bed. Bacterial cellulose (BC), synthesized by Acetobacter species, is a pure biopolymer with a nanofibrous network architecture comparable to human extracellular matrix. BC has been proposed as a wound dressing due to its biocompatibility, ability to provide a moist environment, high liquid absorption capabilities, and oxygen diffusion properties. Additionally, BC’s native fibrillar structure and extensive hydrogen bonding is believed to effectively scavenge reactive oxygen species from the wound bed, resulting in increased wound healing and reepithelization. However, its lack of wound visualization capabilities and antibacterial surface functionality limits its clinical effectivity. In this thesis, we aimed to address these identified limitations. To address the lack of material transparency, we developed a novel method for producing BC by investigating alternative culture supplements. Increasing ratios of D-arabitol/D-glucose in culture showed increased material transparency, irrespective of cellulose yield and thickness. Increased optical transparency values of the synthesized BC were observed compared to commercially available transparent hydrogel wound dressings. The fibrillar and overarching hierarchical BC structures were investigated to elucidate the mechanism behind this induced transparency. We identified no differences in crystallinity between BC samples but did observe decreased microfiber width. Liquid absorption capabilities were assessed to determine the effects of increased transparency and altered microstructure on the material functionality. Though decreased liquid absorption capabilities of BC with higher transparency were observed, all BC samples had higher absorption values than commercially available foam-based and hydrogel-based dressings. Overall, the increased transparency increases BC's potential use application without compromising the effectiveness of BC's inherent wound healing capabilities. To address BC's lack of antibacterial surface functionality, we designed bifunctional chimeric peptides to functionalize the BC surface by combining cellulose binding peptides (CBPs) with antimicrobial peptides (AMPs), specifically KR-12. By linking the two functional peptides, the peptide solutions exhibited decreased antibacterial activity but increased cellulose binding capabilities compared to the individual unlinked AMP and CBP peptides. The functionalized BC material exhibited active surface antibacterial activity while maintaining biocompatibility in vitro. In summary, we developed a method for producing bacterial derived cellulose materials with tunable transparency while maintaining the inherent wound healing capabilities associated with native BC. Further, we designed and evaluated chimeric peptide sequences for retained surface antibacterial activity once tethered to the BC surface. The primary scientific contribution of this work is the development of transparent native BC materials for use in a broader range of applications that are not limited to chronic wound care. Additionally, the investigation of novel chimeric peptide design provides insights into more advanced means of antibacterial treatment without the use of antibiotic agents.

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