ABSTRACTNon-healing wounds are a serious complication in diabetic patients. One of the detrimental factors contributing to limited wound healing is the accumulation of metalloproteinase-9 (MMP-9) in the wound. Selective inhibition of MMP-9 is one of the established therapeutic targets for diabetic wound healing and is therefore of great interest. Here we focused on development of gene silencing system for localized delivery of antisense siRNA against MMP-9 into the wound. We have developed a functional and biocompatible wound dressing allowing controlled release of a traceable vector loaded with the target siRNA. Specifically, the dressing consists of a degradable scaffold of polymer nanofibers embedded with the vector nanosystem, polymer-coated fluorescent nanodiamonds (FNDs). The biocompatible cationic polymer shell on FNDs was designed and optimized for binding of siRNA and formation of colloidally stable FND-siRNA complexes in physiological environment. A hybrid nanofiber scaffold consisting of poly(vinyl alcohol) and poly(caprolactone) ensured continuous release of FND-siRNA complexes from the dressing. The photostable luminescence of FNDs allowed us to monitor the vector system in the wound. Our dressing was tested on murine fibroblasts and also applied to wounds in a diabetic murine model to evaluate its suitability in terms ofin vivotoxicity, biological efficacy and manipulation. The treatment resulted in significant local inhibition of MMP-9 and reduction of the wound healing time. The scar formation for treated diabetic-like animals became comparable with non-treated diabetes-free mice. Our results suggest that the application of our biocompatible dressing loaded with a non-toxic vector nanosystem is an effective and promising approach in gene therapy of non-healing wounds.