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.

Public Health Relevance

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.

National Institute of Health (NIH)
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Exploratory/Developmental Grants (R21)
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Gene and Drug Delivery Systems Study Section (GDD)
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Tucker, Jessica
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Vanderbilt University Medical Center
Biomedical Engineering
Schools of Engineering
United States
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Martin, John R; Nelson, Christopher E; Gupta, Mukesh K et al. (2016) Local Delivery of PHD2 siRNA from ROS-Degradable Scaffolds to Promote Diabetic Wound Healing. Adv Healthc Mater 5:2751-2757
Werfel, Thomas A; Swain, Corban; Nelson, Christopher E et al. (2016) Hydrolytic charge-reversal of PEGylated polyplexes enhances intracellular un-packaging and activity of siRNA. J Biomed Mater Res A 104:917-27
Sarett, Samantha M; Werfel, Thomas A; Chandra, Irene et al. (2016) Hydrophobic interactions between polymeric carrier and palmitic acid-conjugated siRNA improve PEGylated polyplex stability and enhance in vivo pharmacokinetics and tumor gene silencing. Biomaterials 97:122-32
Beavers, Kelsey R; Nelson, Christopher E; Duvall, Craig L (2015) MiRNA inhibition in tissue engineering and regenerative medicine. Adv Drug Deliv Rev 88:123-37
Sarett, Samantha M; Nelson, Christopher E; Duvall, Craig L (2015) Technologies for controlled, local delivery of siRNA. J Control Release 218:94-113
Sarett, Samantha M; Kilchrist, Kameron V; Miteva, Martina et al. (2015) Conjugation of palmitic acid improves potency and longevity of siRNA delivered via endosomolytic polymer nanoparticles. J Biomed Mater Res A 103:3107-16
Nelson, Christopher E; Kim, Arnold J; Adolph, Elizabeth J et al. (2014) Tunable delivery of siRNA from a biodegradable scaffold to promote angiogenesis in vivo. Adv Mater 26:607-14, 506
Adolph, Elizabeth J; Nelson, Christopher E; Werfel, Thomas A et al. (2014) Enhanced Performance of Plasmid DNA Polyplexes Stabilized by a Combination of Core Hydrophobicity and Surface PEGylation. J Mater Chem B Mater Biol Med 2:8154-8164
Martin, John R; Gupta, Mukesh K; Page, Jonathan M et al. (2014) A porous tissue engineering scaffold selectively degraded by cell-generated reactive oxygen species. Biomaterials 35:3766-76
Yu, Shann S; Lau, Cheryl M; Barham, Whitney J et al. (2013) Macrophage-specific RNA interference targeting via ""click"", mannosylated polymeric micelles. Mol Pharm 10:975-87

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