Delivery of Flightless I siRNA from Porous Silicon Nanoparticles Improves Wound Healing in Mice.

Flightless I (Flii), a cytoskeletal actin remodelling protein, is elevated in wounds and is a negative regulator of wound healing. Gene silencing using small interfering RNA (siRNA) is an attractive approach to antagonize Flii, and therefore holds significant promise as a therapeutic intervention. The development of siRNA therapeutics has been limited by an inability of the siRNA to cross the cell surface plasma membrane of target cells and also by their degradation due to endogenous nuclease action. To overcome these limitations, suitable delivery vehicles are required. Porous silicon (pSi) is a biodegradable and high surface area material commonly used for drug delivery applications. Here we investigated the use of pSi nanoparticles (pSiNPs) for the controlled release of Flii siRNA to wounds. Thermally hydrocarbonized pSiNPs (THCpSiNPs) were loaded with Flii siRNA and then coated with a biocompatible chitosan layer. Loading regimens in the order of 50 μg of Flii siRNA per mg of pSi were achieved. The release rate of Flii siRNA was sustained over 35 h. With addition to keratinocytes , reduced Flii gene expression in conjunction with lowered Flii protein was observed, in concert with increased cell migration and proliferation. A significant improvement in the healing of acute excisional wounds compared to controls was observed from day 5 onward when Flii siRNA-THCpSiNPs were intradermally injected. THCpSiNPs therefore are an effective vehicle for delivering siRNA, and nanoparticle-based siRNA delivery represents a promising therapeutic approach to improve wound healing.