Study Of Bioactive Glasses-Introduced Nanofibrous Membranes With Multifunctions Potentially For Wound Dressing

In the process of wound healing, the main role of conventional dressings is to provide the best environment for wound healing, including relieving pain, preventing twice injury and infection. By improving patients’ nutritional status and providing appropriate wound care, such treatment can ensure most wounds healing. However, the chronic, nonhealing wounds are involved progressively tissue loss and bacterial colonization, particularly in venous stasis, diabetic ulcer, and bed sores, and thus give rise to big challenge to wound-care product researchers.This paper will focus on the distinctive features of biological glass in the wound healing, especially on chronic wounds such as diabetic foot wound nursing, and developing new multifunctional biological dressing research. First of all, this thesis explores the feasibility of electro spinning of the chitosan and gelatin composites (C/G), so as to build bionic dressings with an extracellular matrix nanofibrous network structure; Secondly, by added bioglass nanoparticles (BG) which has excellent antibacterial activity, vascularization, wound healing and many other functions, the G/C-nBG composite nanofibers film dressings were prepared; In addition, by establishing the skin deep 2 degrees of scald rats model, the effect of biological glass in promoting wound healing was analyzed. The study details and results are as follows:1. The study of the feasibility of electro spinning of chitosan and gelatin composites.Gelatin was dissolved in deionized water and chitosan was dissolved in acetic acid solution (70 wt%). Then, the gelatin solution and chitosan solution were mixed with different ratios under magnetic stirring to form hybrid solution which was then electrospun. The experimental results show that when the chitosan/gelatin (C/G) ratio is 1:19,3:17 and 5:15, the uniform and smooth nanofibers were prepared. When C/G ratio is more than 5:15, the feasibility of electrospinning was not so good. The more the chitosan is, the worse the feasibility of electrospinning is and the thinner the diameter of the fibers is. In order to make the best use of CS component which has hemostatic, anti-infectious activity, and preventing adhesion characteristics, further research in this paper work will keep C/G ratio to be 3:17. The parameters in the electrospinning process, such as electric field and spinning distance, were studied on electrospinnability and morphology. It was found out that the best voltage and spinning distance were 15 kV and 15 cm.2. The preparation and study of G/C-nBG composite nanofibrous membrane.Firstly, the BG based on 45S5, composed of 36.4 SiO2,22.5 CaO,14.5 B2O3,9.2 P2O5,0.4 CuO,0.4 ZnO,13.9 K2O,3.7 Na2O (wt%), was prepared through sol-gel method. After ball-milling treatment, the diametes of the BG powders were about 840-1660 nm.Under the electrospinning conditions decided in the second chapter, nanofibrous membranes with nBG doped were prepared and analyzed. The results showed, the BG powders were successfully anchored into the fibrous network, and the mats still grew some continuous fibrous network with the BG/(G+C) increasing up to 15%. The BG-introduced mats exhibited considerable tensile strength, meanwhile the increase of BG content produced a further increase in mechanical strength, indicating that the inorganic-organic interaction between G/C and BG could reinforce the mechanical stability of the mats. The tensile strength, young’s modulus and elongation at break of G/C-15BG mats was improved 286%,100%and 150%, respectively, compared with G/C-0BG mats. The hydrophilicity of the electrospun mats can be adjusted by changing the amount of BGs. With increasing BG content, the hydrophilicity would decline, which was bounded to help heal the wound. The G/C-BG mats were well tolerated by the surrounding host tissue without causing any inflammation, and were fully degraded in subcutaneous tissue in rats after 4 weeks postoperatively, indicating the the G/C-BG mats were biocompatible and biodegradable. In addition, the spinnability of the G/C nanofibrous membranes with silica microspheres instead of nBG were prepared and studied preliminarily. The results show that the G/C mats could still be got with silica microspheres whose diameter was about 300 nm. And organic-inorganic compound nanofibrous membranes with pearl necklace structure were prepared. The finding is bound to make breakthrough in the development of chronic wound dressing with drug-loading and slow-release functions.3. Study of vitro and vivo effect of bioactive glass.In order to further prove that the BG in the research of this thesis has a variety of effects on wound healing, bacteriostasis experiments in vitro and the rat skin deep 2 degrees of scald test was conducted. BG was proved to have better bactericidal properties than commercial 45S5 Bioglass in vitro antibacterial evaluation firstly. And rats model results show that the new synthetic BG has more significant effect on promote wound healing than physiological saline and chitosan, and also show a unique biological effect on anti-infection and scabby efficiency. It was deduced that G/C-nBG composite nanofibrous membranes show great potential applications in the dealing with chronic wound.In summary, this thesis preliminarily developed a kind of G/C-nBG composite nanofibrous membranes which has bionic micro-nano structures and the ability to significantly promote the process of wound healing, and this research is expected to show great value in solving clinical nonhealing chronic wounds.