Astragaloside Ⅳ-loaded Solid Lipid Nanoparticles-enriched Hydrogel Induces Wound Healing And Anti-scar Activity

Aim:This study aims to investigate the novel preparation of solid lipid nanoparticle-enriched hydrogel (SLN-gel) for the topical delivery of astragaloside IV, which was selected by some preliminary experiments and to determine the effects and relevant mechanisms of astragaloside IV-based SLN-gel on wound healing and anti-scar formation.Methods:1. Select proper drug agents and determine astragaloside IV as the targeted drug. The regulation of astragaloside IV in the wound stages of re-epithelization, angiogenesis and extracellular matrix remodeling were demonstrated in vitro and in vivo.2. Solid lipid nanoparticles (SLNs) were prepared through the solvent evaporation method. The particle size, polydispersity index (PDI), zeta potential (ZP), encapsulation efficiency (EE), drug release, and morphological properties of the SLNs were characterized. The optimized SLNs were incorporated in carbomer hydrogel to form an SLN-enriched gel (SLN-gel) carrier.3. The effects of astragaloside IV-enriched SLNs on wound healing were detemined using the wound scratch test, and drug uptake by skin cells was tested in vitro. With the rat full-skin excision model, the in vivo regulation of astragaloside IV-based SLN-gel in the wound stages of re-epithelization, angiogenesis, and extracellular matrix remodeling was investigated. Results:1. Astragaloside Ⅳ could improve the strength of the repaired skin and promoted the angiogenesis and collagen synthesis. Meanwhile, the picrosirius-sirus red stain and Elisa test definitely showed the anti-scar effects of astragaloside Ⅳ by decreasing the levels of collagen Ⅰ/Ⅲ and TGF-β1secretion by fibroblasts.2. The best formulation of astragaloside IV-based SLNs had high EE (93%±5%) and ZP (23.6mV±1.5mV), with a PDI of0.18±0.03and a drug loading percentage of9%. The incorporation of SLNs in SLN-gel didn’t change the morphology and structure of nanoparticles. Astragaloside Ⅳ-based SLN and SLN-gel could release drug sustainably. Thixotropy was observed in astragaloside Ⅳ-based SLN-gel, which is a desirable feature of semi-solid drug carriers for topical application.3. Astragaloside Ⅳ-based SLN enhanced the migration and proliferation of keratinocytes and increased drug uptake on fibroblasts in vitro (P<0.01) through the caveolae endocytosis pathway, which was inhibited by methyl-β-cyclodextrin. Astragaloside Ⅳ-based SLN-gel strengthened wound healing and inhibited scar formation in vivo by increasing wound closure rate (P<0.05) and by contributing to angiogenesis and collagen regular organization.Conclusion:SLN-enriched gel is a promising topical drug delivery system. Astragaloside Ⅳ-loaded SLN-enriched gel was proven as an excellent topical preparation with wound healing and anti-scar effects.