Study On The Skin Wound Healing Mechanism Of Novel Bioactive Glass Microspheres And Their Composites

Once the skin tissue is seriously damaged,it will have a great impact on the life and health of the patients.Therefore,the development of novel biomedical materials with good bio-responsiveness,so as to achieve rapid repair of wounds,especially chronic wounds,is not only a major challenge in the biomaterials field,but also has great clinical significance and market value.Bioactive glass(BG)has great potential in the field of skin repair due to its high bioactivity.Therefore,bioactive glass microspheres with regular morphology were fabricated by combination of sol-gel method and template method in this study and exposed to various cells related to skin repair such as fibroblasts and macrophages to investigate the effects of BG microspheres on cell behaviors.Besides,a novel bioactive glass/Vaseline composite ointment was prepared and the effects of this ointment on wound healing was investigated by in vivo experiments.On this basis,bioactive glass microspheres and biomedical polymer were combined together to prepare novel electrospun fibrous membrane.The effects of the electrospun fibrous membrane on cell behaviors and wound healing were also investigated.The main research contents and conclusions of this study are as follows:(1)By combining sol-gel method and template method,the novel bioactive glass microspheres with uniform particle size as well as good dispersibility were prepared,and their surface morphology and particle size distribution were also characterized.On this basis,a novel bioactive glass/Vaseline composite ointment containing accurate concentration of well-dispersed bioactive glass microspheres was prepared;(2)The novel bioactive glass microspheres were directly exposed to fibroblasts to explore their effects and regulatory mechanism on cell behaviors of fibroblasts such as proliferation,migration,extracellular matrix secretion and differentiation.The results showed that bioactive glass can not only promote the migration of fibroblasts,but also inhibit the differentiation of fibroblast into myofibroblasts and restrict the excessive secretion of type I collagen and type III collagen by fibroblast.The inhibition effect may be achieved by blocking the expression of TGF-? receptor I in the TGF-?1-Smad2 signaling pathway;(3)The well-dispersed bioactive glass microspheres were fabricated in this study.And these microspheres were directly exposed to macrophases to explore the effects and the regulatory mechanism of different concentrations of BG on macrophage proliferation,directional migration,phagocytosis and phenotypic polarization.The results showed that the regulation of bioactive glass on macrophage behaviors was concentration-dependent.At low concentration(20?g/mL),the bioactive glass ingested by macrophages can be degraded faster than the high concentration group and promoted the proliferation of macrophages and accelerated the polarization of M1 phenotype to M2 phenotype via the NF-?B signaling pathway.On the contrary,at high concentrations(100 ?g/mL),owing to the lower degradation rate,the bioactive glass may destroy the integrity of the organelle structure,resulting in severe cytotoxicity and prolonging the inflammatory response.In addition,bioactive glass was also able to induce macrophage migration,but it was not relevant with the concentration of bioactive glass;(4)By applying bioactive glass microspheres/Vaseline composite ointment on the treatment of diabetic wound,the effects and regulatory mechanism of bioactive glass concentration on wound healing were explored by examining the healing rate of wounds,the composition and structure of wounded tissue,phenotypic polarization of macrophage at the wound site and the secretion of the related growth factors.The results showed that although the treatment of bioactive glass on the diabetic wound would cause inflammatory responses at first,low concentration of bioactive glass can accelerate the polarization of macrophages from M1 to M2 in diabetic wounds and thus promote the wound healing,while high concentration of bioactive glass would lead to long-term inflammatory phase at the wound site,which would significantly delay the wound repair process;(5)By adjusting the content of polycaprolactone,pore-forming agent and bioactive glass in the electrospinning solution,a novel bioactive glass/polycaprolactone electrospun fibrous membrane was successfully prepared by combining electrospinning technology and phase separation.The novel electrospun fibrous membrane was characterized by its surface morphology,hydrophobicity and ion release properties.The results showed that the beads in the fiber could be removed by increasing the concentration of PCL in the solution,and the porous structure on the surface of the fiber could be prepared by using suitable concentration of pore-forming agent.The excessive addition of bioactive glass leaded to the deformation of fiber morphology and the disappearance of surface pore structure.The prepared wound dressing has uniform fiber size and good distribution of bioactive glass.The porous structure on the surface of fibers can adsorb more proteins and promote the release of ionic products from bioactive glass;(6)The effects of bioactive glass/polycaprolactone electrospun fibrous membrane on the behaviors of macrophages and endothelial cells were investigated in vitro and its effects on diabetic wounds healing were explored by in vivo study.The results showed that the bioactive glass/polycaprolactone electrospun fibrous membrane promoted macrophage to polarize into M2 phenotype and enhanced the proliferation and angiogenic properties of HUVECs.Besides,the bioactive glass/polycaprolactone electrospun fibrous membrane also provided structural support for cell migration and adhesion in the early stage of wound healing and thus promoted the re-epithelialization process at the wound site.Moreover,it can also shorten the inflammatory stage of wounds and stimulate the secretion of restorative growth factors as well as accelerating the formation of blood vessels in the diabetic wounds,thereby promoting the healing of diabetic wounds.In summary,bioactive glass could inhibit the differentiation of fibroblasts into myofibroblasts and regulate the polarization process of macrophages,respectively.Besides,suitable amount of bioactive glass microspheres could promote the diabetic wound healing process by resolution of the inflammatory responses.On this basis,a novel electrospun fibrous membrane with bio-responsiveness was prepared by combination of bioactive glass and polycaprolactone.And this electrospun fibrous membrane was proved to promote the resolution of inflammatory responses and accelerate the formation of blood vessels in diabetic wounds.This paper not only clarifies the regulation of bioactive glass on wound repair,but also provides new ideas and theoretical basis for the design of biomaterials for skin tissue repair and regeneration.