In-vivo evaluation of tissue scaffolds containing simvastatin loaded nanostructured lipid carriers and mesenchymal stem cells in diabetic wound healing

Efficacy of simvastatin on wound healing and stem cell treatment, in addition to the cholesterol lowering mechanism, has been investigated in recent studies. In this study we have focused on formulation of tissue scaffolds comprised of mesenchymal stem cells and simvastatin loaded nanostructured lipid carriers (NLCs) dispersed in a polymeric matrix. These three dimensional and biodegradable systems were designed to bring a new perspective in treatment of diabetic wound. Therefore, NLC formulations containing simvastatin at the concentrations of 10% or 20% of lipid phase were prepared by high pressure homogenization technique. Simvastatin loaded NLC formulations were characterized with mean particle size of 158.15 +/- 1.229 nm, PDI values lower than 0.17 and encapsulation efficiency above 99%. In-vitro release studies of simvastatin loaded NLC formulations were characterized by a high burst-release followed by sustained up to 12-24 h. Tissue scaffold formulations containing simvastatin loaded NLCs were prepared by freeze drying method. Cross-linked tissue scaffold formulations were prepared with 2:1 chitosan:collagen polymer ratio and 2-fold concentrated NLC formulation, having a three-dimensional structure with porosity value of 74.38%, pore size distribution within 20-200 mu m, 710.88% high water absorption capacity, 57.7% weight loss and suitable mechanical strength for in-vivo studies. Incorporation of NLCs into tissue scaffolds decreased the initial simvastatin burst release ratio and provided controlled release profile. Tissue scaffolds containing simvastatin lipid nanoparticles increased wound closure rate, promoted vascularization of injured tissue and enhanced viability and proliferation of stem cells. Thereupon, tissue scaffold formulation containing simvastatin lipid nanoparticles and stem cells together provided effective wound healing with increased epithelialization, proliferation and vascularization.