Approaches to Modulate the Chronic Wound Environment Using Localized Nucleic Acid Delivery.

Significance: Nonhealing wounds have been the subject of decades of basic and clinical research. Despite new knowledge about the biology of impaired wound healing, little progress has been made in treating chronic wounds, leaving patients with few therapeutic options. Diabetic ulcers are a particularly common form of nonhealing wound. Recent Advances: Recently, investigation of therapeutic nucleic acids (TNAs), including plasmid DNA, small interfering RNA, microRNA mimics, anti-microRNA oligonucleotides, messenger RNA, and antisense oligonucleotides, has created a new treatment strategy for chronic wounds. TNAs can modulate the wound toward a prohealing environment by targeting gene pathways associated with inflammation, proteases, cell motility, angiogenesis, epithelialization, and oxidative stress. A variety of delivery systems have been investigated for TNAs, including dendrimers, lipid nanoparticles (NPs), polymeric micelles, polyplexes, metal NPs, and hydrogels. This review summarizes recent developments in TNA delivery for therapeutic targets associated with chronic wounds, with an emphasis on diabetic ulcers. Critical Issues: Translational potential of TNAs remains a key challenge; we highlight some drug delivery approaches for TNAs that may hold promise. We also describe current commercial efforts to locally deliver nucleic acids to modulate the wound environment. Future Directions: Localized nucleic acid delivery holds promise for the treatment of nonhealing chronic wounds. Future efforts to improve targeting of these nucleic acid therapies in the wound with both spatial and temporal control through drug delivery systems will be crucial to successful clinical translation.

A design approach for layer-by-layer surface-mediated siRNA delivery.

The ability to coat scaffolds and wound dressings with therapeutic short interfering RNA (siRNA) holds much potential for applications in wound healing, cancer treatment, and regenerative medicine. Layer-by-layer (LbL) technology is an effective method to formulate polyelectrolyte thin films for local delivery of siRNA; however, the formation and efficacy of LbL coatings as drug delivery systems are highly contingent on the assembly conditions. Here, we investigate the effects of LbL assembly parameters on film composition and consequent siRNA-mediated gene knockdown efficiency in vitro. Films comprising poly(ß-amino ester) (PBAE) and siRNA were built on polyglactin 910 (Vicryl) sutures consisting of poly(10% L-lactide, 90% glycolide). A fractional factorial design was employed, varying the following LbL assembly conditions: pH, ionic strength, PBAE concentration, and siRNA concentration. Effects of these parameters on PBAE loading, siRNA loading, their respective weight ratios, and in vitro siRNA-mediated knockdown were elucidated. The parameter effects were leveraged to create a rationally designed set of solution conditions that was predicted to give effective siRNA-mediated knockdown, but not included in any of the original experimental conditions. This level of knockdown with our rationally designed loading conditions (47%) is comparable to previous formulations from our lab while being simpler in construction and requiring fewer film layers, which could save time and cost in manufacturing. This study highlights the importance of LbL solution conditions in the preparation of surface-mediated siRNA delivery systems and presents an adaptable methodology for extending these electrostatically-assembled coatings to the delivery of other therapeutic nucleic acids. STATEMENT OF SIGNIFICANCE: Short interfering RNA (siRNA) therapeutics are powerful tools to silence aberrant gene expression in the diseased state; however, the clinical utility of these therapies relies on effective controlled delivery approaches. Electrostatic self-assembly through the layer-by-layer (LbL) process enables direct siRNA release from surfaces, but this method is highly dependent upon the specific solution conditions used. Here, we use a fractional factorial design to illustrate how these assembly conditions impact composition of siRNA-eluting LbL thin films. We then elucidate how these properties mediate in vitro transfection efficacy. Ultimately, this work presents a significant step towards understanding how optimization of assembly conditions for surface-mediated LbL delivery can promote transfection efficacy while reducing the processing and material required.