The Healing Mechanism Of Sol-gel Bioactive Glass On Diabetic Cutaneous Wounds

The development of new types of skin soft tissue wound repair materials to help repair thedefect or refractory patients with skin wound tissue and better recovery of human skin softtissue function has been an important issue for the medical and biomedical materialscommunities for many years. The traditional bioactive glass is the melt-derived45S bioactiveglass (BG) with the mass composition of45%SiO2,4.5%Na2O,24.5%CaO and6%P2O5,which was developed by Professor Hench in the early1970s. The bioactivity and osteogenicability of45S5BG have made it widely known for the repair and regeneration of hard tissuesuch as bone and teeth defect. Meanwhile, studies have shown that the45S5can accelerate thewound healing of skin soft tissue, however, very little research about the sol-gel bioactive glass(SGBG) and nanoscale bioactive glass (NBG) for the application of soft tissue repair has beenreported. In fact, these new types of bioactive glass has better properties in chemicalhomogeneity, nano or mesoporous structure, specific surface area and absorb ability. They mayhave better healing effect than the traditional45S5BG.In this thesis, the use of sol-gel BG on the diabetic wound repair evaluation system hasbeen developed and its potential healing mechanism has been studied. The streptozotocin (STZ)induced diabetic SD rats was used to mimic the healing process of diabetic impaired wounds.Through the data of wound healing rates, the analysis of H&E staining, immunochemicalstaining and TEM results, the skin wound healing related cells such as the fibroblasts, epithelialcells and endothelial cells and the growth factors such as the vascular endothelial growth factor(VEGF) and basic fibroblasts growth factor (FGF-2) as well as their potential function wereinvestigated. Meanwhile, the cellular responses of fibroblasts on the sol-gel BG were alsostudied. The detailed work is summarized as follows:Firstly, Nanoscale bioactive glass (NBG) powders were prepared using the sol-gel co-precipitation and freeze-drying methods in this study, also effects of polyethylene glycol(PEG-10000) as a dispersing agent on their nanoscale morphology and bioactivity wasinvestigated. The results showed that NBG particles prepared without without adding PEG werefound with an irregular particle morphology and the particle size was less than50nm.Withaddition of PEG, the spherical bioactive glass particles formed and the particle size ranged inapproximately40～100nm. The higher PEG concentration was, the particle size decreased.Thein vitro bioactivity test in a simulated body fluid (SBF) demonstrated that NBG possessed ahigher bioactivity than the sol-gel derived bioactive glass(SGBG).Secondly, through the in vitro cell culture of fibroblasts with BGs (45S5, SGBG and NBG),the effect of different concentrations of the extracts of BGs and the culture time on theproliferation of fibroblasts was investigated. The original fibroblasts were obtained from thepatients’foreskin byenzymolysis approach, and immunostaining results showed the obtainedcells were skin fibroblasts with the positive staining of HMB45and vimentin, negative stainingof keratin and S100. MTT assay results showed that the extracts of the three kinds of bioactiveglass had no obvious cytotoxicity and they can stimulate the proliferation the fibroblasts inappropriate concentration. However, the functions of the three BGs were different;45S5hadbetter stimulating effect at the early culture time, while the NBG had more obvious effect at thelate stage of the culture time.Thirdly, For the development of diabetic wound animal model, This study aimed toinvestigate the effect of bioactive glasses on cutaneous wound healing in both normal rats andstreptozotocin-induced diabetic rats. Bioactive glass ointments, prepared by mixing the sol–gelbioactive glass58S (SGBG-58S), nanobioactive glass (NBG-58S) and the melt-derived45S5bioactive glass (45S5) powder with Vaseline (V) at18%weight percentage, were used to healfull thickness excision wounds. Pure V was used as control in this study. Compared toSGBG-58S, NBG-58S consists of relatively dispersible nanoparticles with smaller size. The analysis of wound healing rate and wound healing time showed that bioactive glasses promotedwound healing. The ointments containing SGBG-58S and NBG-58S healed the wounds morequickly and efficiently than the ointment containing45S5.Histological examination indicatedthat bioactive glasses promoted the proliferation of fibroblasts and growth of granulation tissue.Immunohistochemical staining showed that the production of two growth actors, VEGF andFGF2, which are beneficial to wound healing,was also stimulate during the healing process.Transmission electron microscope observations showed that fibroblasts in wounds treated withbioactive glasses contained more rough endoplasmic reticula and had formed new capillarymicrovessels by the seventh day.The effects of SGBG-58S and NBG-58S were better than thoseof45S5. All results suggest that bioactive glasses, especially SGBG-58S and NBG-58S, canaccelerate the recovery of skin wounds in both normal and diabetes-impaired healing modelsand have a great potential for use in wound repair in the future.Furthermore, the healing effect of45S5BG combine Yunnan baiyao ointment on thediabetic wounds were firstly investigated and evaluated here, which provided a new thought andapproach for the development of drugs for the diabetic wounds.