| Bletilla striata(Thunb.)Reichb.f.,also known as BaiJi,belongs to the family of Orchidaceae.For thousands of years,the pseudobulb of BaiJi was used for treating hematemesis and promoting wound healing in traditional Chinese medicine(TCM).Nowadays,researchers widely recognized that polysaccharides(BSP)are an essential component responsible for the exhibition of bioactivity of B.striata.An increasing number of reports suggested that BSP showed excellent biocompatibility and bioactivities,including anti-oxidant,anti-tumor,anti-aging,immune-regulation and promoting wound healing.Additionally,BSP,relatively simple monosaccharide composition and abundant hydroxyl group for modification,have become a hot spot research topic in food,medicine and cosmetics field.In daily life,trauma is the most common type of skin injury,which not only affect the appearance of the individual,but also threaten the life of the patient.It was reported that about 100 million patients need wound treatment in China every year,and the medical costs paid will exceed 60 billion CHY.Moreover,in American,this expenditure is as high as 25 billion USD.Therefore,in the world,it was become one of the urgent public health problems for accelerating wound healing and shortening the healing times.In conclusion,this study extracted and purified the BSP from B.striata.The primary chemical structure of BSP was characterized and obtained.The BSP hydrogel was prepared by oxidized BSP(OBSP)and chitosan(CS)trough Schiff based reaction.Moreover,the effect of BSP hydrogel on the polarization of macrophages was explored by RAW264.7 and peritoneal macrophage models in vitro.Additionally,the promoting wound healing activity in vivo of BSP hydrogel were evaluated using a full-thickness excision model.The main results are as follows:(1)The crude polysaccharide of B.striata was extracted by water extract-alcohol precipitation method,and its yield was 26.31%.The crude polysaccharide was further purified by DEAE-52 and Sephadex G-100 column chromatography.The structural characterization of BSP was identified by FT-IR,IC,HPGPC,methylation,GC-MS and NMR analysis.Results showed that BSP was a catenulate glucomannan with MW 58461 Da,which probably structure was?4)-?-D-Glcp-(1?[4)-?-D-Manp-(1]2?4)-?-D-2ace-Manp-(1?.(2)The OBSP was prepared by periodic acid oxidation method,and the aldehyde group in OBSP was determined using FT-IR and 1H NMR.The BSP hydrogel was designed through Schiff base reaction that based on amino and aldehyde in OBSP and CS,respectively.Results showed that BSP hydrogel exhibited outstanding rheology,swelling,self-healing properties,low degradation rate,suitable water vapor transmission rate and antibacterial activity in vitro.Besides,BSP hydrogel presented negative charge and no hemolysis and cytotoxicity,exhibiting excellent biological safety.(3)The influence of BSP hydrogel on the polarization of macrophages was obtained by RAW264.7 and peritoneal macrophages models in vitro.Results indicated that BSP hydrogel promoted M2 type macrophages polarization,decreasing the level of inflammatory cytokine(TNF-? and IL-6),increasing the secretion of anti-inflammatory cytokine(IL-10 and TGF-?1),which then accelerated the proliferation of L929.(4)The promoting wound healing activity of BSP hydrogel were determined using a full-thickness excision model in vivo.Results suggested that BSP hydrogel effective defensed bacterial infection in wound surface,which significantly shortened the wound healing time and exhibited outstanding promoting wound healing activity. |
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