Evaluation of wound healing effect of Solanum nigrum L. leaf extract-loaded sodium alginate nanoparticles embedded in chitosan hydrogel, In vivo study

Objective(s): Wound healing is one of the most fundamental issues in medical science. Solanum nigrum L. has been attracted great attention for its antioxidant, antimicrobial and anti-inflammatory activities. The aim of this study was to evaluate the effect of leaf extract of S. nigrum L-loaded sodium alginate nanoparticles (NPs) embedded in chitosan hydrogel on wound healing. Materials and Methods: Ethanolic extract of S. nigrum L. leaves (5% v/v) were loaded into sodium alginate NPs using the ionic gelation technique and characterized (Ext-AG NPs). Then, NPs were incorporated into chitosan hydrogel (Ext-AG-CS hydrogel) and the properties of this formulation such as viscosity and release profile were evaluated. The antimicrobial activity of the extract alone and loaded into the hydrogel (Ext-CS hydrogel) was measured on the Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilius by MIC assay. Finally, their wound healing effects were studied on full-thickness wound in rat animal model in 3, 7 and 14 days. Results: The particle size of Ext-AG NPs was obtained 437 +/- 15 nm. The encapsulation efficiency of extract was about 91.6%. The in vitro release profile from NPs showed that the maximum released extract was 30% during 6 days. However, by embedding of NPs into hydrogel, the release of extract was about 12% after 6 days. The results showed that the extract could be release from hydrogel about 30% in the first 4h followed by about 70% release on the fifth day. Therefore, this formulation was used in subsequent studies. Ext-CS hydrogel 5% exhibited lower MICs on all tested microorganisms in compared with aqueous extract alone. Finally, the results of in vivo wound healing analysis revealed that on day 3, the extract solution and Ext-CS hydrogel were more effective in reducing inflammation than chitosan gel and positive control. The process of epithelial tissue formation on day 14, in all treated groups, seemed to be better than negative control, which shows the positive effect of these compounds on faster epithelial tissue formation. Conclusion: In general, it seems that S. nigrum L. leaf extract 5% and Ext-CS hydrogel 5% were more effective in wound healing process than other treated groups. However, the chitosan hydrogel-extract formulation showed better antimicrobial activity.