Diabetic wound healing is a significant and growing problem in the United States and globally, but there are currently no effective treatments that consistently achieve closure of ulcerated wounds. We hypothesize that small interfering ribonucleic acid (siRNA)-based therapeutics provides a logical and potentially advantageous approach because diabetic wounds are characterized by aberrant overexpression of proinflammatory genes that hinder wound healing. Although siRNA provide a powerful tool for gene silencing, delivery is difficult because siRNA are large, polar molecules that are unable to diffuse through cell membranes to reach mRNA targets. To be internalized, siRNA must be endocytosed into membrane-bound endosomes, where they typically remain sequestered from the cytosol and are recycled out of the cell or trafficked for lysosomal degradation. In the current proposal, application of a novel, environmentally-responsive "smart" polymer nanoparticle (SPN) carrier for siRNA is proposed. This innovative polymer-based carrier responds to the acidic pH in endosomes to trigger disruption of these vesicles and enable siRNA cytosolic delivery. Initial applications of SPNs and other types of siRNA carriers have focused on systemic or local injection in saline to counteract aberrant gene expression, commonly for anticancer applications. However, siRNA activity is inherently transient, and development of scaffold-based controlled release systems for local delivery to pathological sites (i.e. wounds) has not been thoroughly explored. Here, a novel delivery system is proposed that consists of siRNA-carrying SPNs embedded into injectable polyurethane (PUR) scaffolds. We have previously shown that PUR scaffolds can be finely tuned to achieve burst or sustained release of growth factors. By formulation of SPNs into PUR scaffolds, we seek to achieve localized and sustained intracellular delivery of siRNA to skin wounds. We will first fabricate, validate, and optimize the PUR-SPN platform technology in vitro (Aim 1).
In Aim 2, we will employ a luciferase reporter mouse for in vivo validation of PUR-SPN gene silencing and will complete a therapeutic study on knockdown of tumor necrosis factor alpha in diabetic skin wounds.
These aims complement the stated mission of the NIBIB "to improve health by leading the development and accelerating the application of biomedical technologies". Our interdisciplinary team includes engineers, a pathologist, and a biologist, and the work encompasses elements of polymer science, chemistry, biology, medicine, and pharmaceutical sciences. The proposed project will focus on inflammatory gene silencing in nonhealing skin wounds, but we ultimately aspire to expand the pathological applications for this versatile platform technology.
Patients with diabetes are more prone to severe nonhealing skin wounds that, in the most dire cases, require limb amputation. The best biological drug currently available for diabetic wounds cannot stimulate wound healing in over 50% of patients, so there is a very important need for improved treatments. There is a promising new class of drugs called small interfering ribonucleic acids (siRNA) that have the potential to fill this clinical need, but difficult barriers exist for efficient delivery of siRNA to wounds. The goal of this proposal is to invent and validate a system that can efficiently deliver siRNA in order to develop better drugs to treat skin wounds.
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