Preparation of shikonin liposome and evaluation of its in vitro antibacterial and in vivo infected wound healing activity

The emergence of antibiotic resistance over the past decade has made the treatment of Staphylococcus aureus infection difficult. Burn wounds infected with methicillin-resistant S. aureus (MRSA) can cause mortality in animals. Shikonin (SH) has been reported to possess antimicrobial and anti-inflammatory properties, and is also responsible for the process of wound healing. However, the pharmacological mechanism of its wound healing process remains poorly comprehended, hence the probable mechanism deserves further investigation. The current study was designed to develop a novel SH-liposome with improved anti-MRSA effect and to detect its beneficial wound healing effects. In vitro antibacterial tests and in vivo infected wound healing test were conducted. SH-liposome was produced by the film formation method, and the characteristics were measured using a laser particle size analyzer, transmission electron microscopy, and the dialysis method. Additionally, in vitro antibacterial tests were conducted to investigate the antibacterial effects and the relative mechanism of SH-liposome. Furthermore, the therapeutic effects and bioactivity of SH-liposome in MRSA infected burn wounds were investigated in rats. Sixty-four male Sprague Dawley rats (250 ± 10 g) were randomly divided into four groups, including Group I (control group); Group II (model group); Group III (SH-liposome group) and Group IV (Arnebia oil® group), and the drug treatments were applied topically twice daily for 21 days. Further, full thickness skin biopsies at different periods were collected aseptically to evaluate tissue cytokines, recognize flora, observe histopathological changes, and determine the mechanism underlying the wound healing effects of SH-liposome. The data were analyzed via one-way analysis of variance (ANOVA) and Duncan's multiple range test. The results showed that SH-liposome was successful with a drug load of 4.6 ± 0.17%. Moreover, SH-liposome showed a sustained-release behavior and improved antibacterial ability in a dose-dependent manner. For the possible antibacterial mechanism, we observed that SH-liposome achieved antibacterial activity by damaging the integrity of bacterial cell wall and membrane to further disturb the physiological activities of S. aureus. In addition, SH-liposome facilitated wound healing by inhibiting bacterial activities to control infection, regulating the I-κBα/NFκB-p65 pathway to alleviate inflammation, and directly promoting repair in burn wounds. In conclusion, SH-liposome showed an antibacterial effect against S. aureus, promoted effective healing of infected burn wounds; hence, it could be used as an alternative therapy for drug-resistant infections.