| The skin serves as the body’s largest protective barrier.If the skin is not prop erly treated after the injury,it is likely to lead to inflammation,bacterial infection,secondary injury,and difficulty in healing.Polyvinyl alcohol(PVA)is a synthetic po lymer with good biocompatibility and physicochemical properties;Sodium alginate(S A)is a natural polymer compound with excellent moisturizing and water absorption properties.The composite hydrogel prepared by freeze-thawing polyvinyl alcohol an d sodium alginate can not only provide a moist environment and coverage protectio n for wounds,but also act as a drug carrier to achieve continuous slow release of drugs,which can solve the shortcomings of traditional dressings in wound treatment and accelerate wound healing.Natural plants contain a variety of functional active ingredients that play a positive role in improving the wound environment and prom oting healing.The Thesium chinense Turcz.is known as "plant antibiotic",contains flavonoids,organic acids,polysaccharides,alkaloids and other active ingredients with antibacterial,anti-inflammatory,analgesic,antioxidant,immunomodulatory and other biological activities,which have not been used in skin injury.Therefore,in this pap er,a composite hydrogels of PVA,SA,and Thesium chinense Turcz.extract were prepared,the properties of the hydrogel were characterized.and the repair ability of Thesium chinense Turcz.composite hydrogels on the whole-layer defective skin of rats was investigated.The extraction process of the active ingredients(flavonoid)of Thesium chinense Turcz.was optimized by single factor and response surface method through ethanol concentration,extraction time,temperature and material-to-liquid ratio.the antioxidant,cytotoxic,antibacterial and anti-inflammatory properties of Thesium chinense Turcz.extracts were also examined,to using it as a drug for dressing loading after meeting the criteria.PVA/SA hydrogels were prepared by physical freeze-thaw method using PVA and SA as hydrogel substrate materials.The physical properties of hydrogels such as moisture content,swelling rate,moisture retention rate,moisture giving rate and gel fraction were characterized,the ratio of substrate materials for PVA/SA hydrogels was optimized.The compound hydrogel of Thesium chinense Turcz.was prepared by freeze-thaw method after adding the Thesium chinense Turcz.extract,the morphology and structure of the hydrogels were characterized by SEM and FTIR.the mechanical properties,antioxidant properties,anti-inflammatory properties,cytotoxicity and blood compatibility of the composite Thesium chinense Turcz.hydrogel were evaluated.The drug release rate of the hydrogel for 24 h was examined in PBS buffer of different p H for continuous drug delivery of the dressing.the rat back total cortical excision model was constructed to observe the healing condition and histopathology of back skin tissues,evaluate the trauma repair ability of Thesium chinense Turcz.composite hydrogel.The experimental results showed that the extraction equivalent of active ingredients(in terms of flavonoid extraction equivalent weight)was 28.2 mg/g under the conditions of ultrasonication for 50 min,the ethanol concentration of 65 %,the material-to-liquid ratio of1:40 g/m L and the extraction temperature of 65 ℃.The extracts purified by extraction and chromatography showed 93.5±0.31 % and 98.96±0.33 % scavenging of DPPH and ABTS radicals at 400 μg/m L.The MIC of 10-12.5 mg/m L for E.coli and S.aureus.It was noncytotoxic in the concentration range of 1 mg/m L,had a pro-proliferative effect on macrophages,was able to inhibit LPS-induced NO secretion by RAW264.7,exhibited good anti-inflammatory activity.It indicates that the extract still has good biological activity in the concentration range of 1 mg/m L,which can provide a theoretical reference for the application of the active ingredients of Thesium chinense Turcz.The appropriate material ratio for the composite hydrogel prepared by the freeze-thaw method is the PVA content was5 wt%,the SA content was 0.6 wt%,and the final concentration of Thesium chinense Turcz.extract in the hydrogel was 2 mg/m L.The hydrogel’s molecules are connected by hydrogen bonds to form a 3D network,the addition of sodium alginate improved the physical properties of PVA hydrogel such as water retention,swelling,moisture giving rate,increased porosity,and improved tensile strength,the addition of Thesium chinense Turcz.extract did not change the internal morphology and structure of hydrogels.The drug release experiments revealed that the composite hydrogel could be released slowly in buffers of p H 6.0,7.4 and8.0,and the release rate was greater than 50 % for 24 h.the best release was achieved at p H7.4.The 24 h release rate at p H 7.4 was 56.82 ± 1.39 %.The results of the bioactivity assay of the Thesium chinense Turcz.composite hydrogel showed that the Thesium chinense Turcz.composite hydrogels were able to inhibit LPS-induced NO secretion by RAW264.7 and showed good anti-inflammatory activity.The scavenging rates of DPPH and ABTS were78.6±0.67 % and 90.61±0.11 %,respectively,with good antioxidant activity.It has ability to obstruct the penetration of Escherichia coli(E.Coli)and Staphylococcus aureus(S.Aureus),reducing the risk of bacterial infection;has good biocompatibility.The results of animal experiments showed that compared with the untreated blank group,Thesium chinense Turcz.composite hydrogel could reduce the inflammatory response by inhibiting the secretion of pro-inflammatory factors TNF-a,IL-6 and increasing the expression level of antiinflammatory factor IL-10.increase collagen production and deposition,the expression of VEGF and b FGF,promote angiogenesis,which rats treated with Thesium chinense Turcz.composite hydrogel basically healed by the day of 20,accelerating wound healing.In summary,Thesium chinense Turcz.extract has good biological activity,and Thesium chinense Turcz.composite hydrogel can cover the wound,provide coverage protection and moistening effect,has good biocompatibility,and the 3D network structure of the hydrogel can effectively release drug,taking advantage of the antioxidant,anti-inflammatory and antibacterial effects of Thesium chinense Turcz.extract to accelerate wound healing,which lays a theoretical foundation for the application of Thesium chinense Turcz.in wound repair. |
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