Construction Of Bacterial Cellulose-based Multifunctional Nanocomposite Hydrogels And Their Applications In Wound Repair

Skin wounds that are delayed or difficult to heal seriously threaten the life and health of patients and become a major challenge for medical system.In order to solve the problems of skin wounds being easily infected and difficult to heal,two types of novel multifunctional nanocomposite hydrogel dressings based on bacterial cellulose（BC）including selenium nanoparticles decorated multifunctional hydrogel dressings,and MXene（Ti₃C₂T_x）incorporated electroactive hydrogel dressings,were developed.Meanwhile,a new strategy coupling electroactive hydrogels and electrical stimulation to synergistically treat wounds was also proposed.This thesis mainly focused on the construction of BC-based multifunctional nanocomposite hydrogels and their applications in wound treatments.The related studies were carried out as follows:（1）Preparation,characterization and in vitro biological evaluation of multifunctional selenium nanoparticles-decorated bacterial cellulose/gelatin hydrogels.In this study,a series of multifunctional selenium nanoparticles-decorated bacterial cellulose/gelatin（BC/Gel/Se NPs）nanocomposite hydrogels were prepared by physical infiltration and in situ synthesis.The results of the structure characterization showed that BC/Gel/Se NPs nanocomposite hydrogels with different Se NPs content all exhibited a connected three-dimensional network structure.The results of physical and chemical properties of the as-prepared hydrogels showed that the BC/Gel/Se NPs nanocomposite hydrogels presented good mechanical properties and flexibility,and favorable swelling performance,degradability,and antioxidant property,as well as slow,stable and sustainable release profiles of Se NPs.Among these nanocomposite hydrogels,the DPPH free radical scavenging efficiency of the BC/Gel/Se NPs-30 nanocomposite hydrogel could reach 70.30%in 24 h,and the release rate of Se NPs from the hydrogel after being immersed in PBS for72 h was only about 20.40%.The results of antibacterial tests indicated that the BC/Gel/Se NPs nanocomposite hydrogels had excellent antibacterial activities against both the common bacteria（E.coli and S.aureus）and their multidrug-resistant bacteria（MDR E.coli and MDR S.aureus）,in a Se NPs content-dependent manner,and that the antibacterial effects against the MDR bacteria were better than that against the common bacteria.Among them,the antibacterial rates of BC/Gel/Se NPs-30 nanocomposite hydrogel against the MDR E.coli and MDR S.aureus could reach 99.73%and 99.81%,respectively.The results of the hemolysis test and cell experiments indicated that these nanocomposite hydrogels all presented the favorable hemocompatibility,and that among these hydrogels,the BC/Gel/Se NPs-30 nanocomposite hydrogel exhibited the best biocompatibility.These results suggested that the BC/Gel/Se NPs-30 nanocomposite hydrogel is expected to be a novel wound dressing with outstanding antibacterial,antioxidant properties and bioactivity.（2）Multifunctional selenium-decorated bacterial cellulose/gelatin nanocomposite for wound repair evaluation.In order to evaluate the effectiveness and feasibility of the optimized BC/Gel/Se NPs-30 nanocomposite hydrogel as a potential wound dressing,a rat full-thickness defect model was created.The results of the in vivo tests showed that,compared to the gauze,pure BC hydrogel,and BC/Gel hydrogel,the BC/Gel/Se NPs hydrogel（BC/Gel/Se NPs-30）exhibited a remarkable anti-inflammatory capability,and wound healing performance in the rat full-thickness defect model,as evidenced by the significantly reduced inflammation and the wound areas,and the remarkably enhanced granulation tissue formation,collagen deposition,and angiogenesis,as well as fibroblast activation and differentiation to myofibroblast.Accordingly,the multifunctional bioactive BC/Gel/Se NPs nanocomposite hydrogel developed in this thesis,with excellent antibacterial,antioxidant,anti-inflammatory capabilities,could serve as a good alternative to current multifunctional wound dressings for preventing wound infection and accelerating skin wound healing and tissue regeneration in clinic.（3）Construction,characterization and biocompatibility evaluation of electroactive regenerated bacterial cellulose/MXene（Ti₂C₃T_x）nanocomposite hydrogels.A series of novel electroactive regenerated bacterial cellulose/MXene（r BC/MXene）nanocomposite hydrogels were constructed through chemical and physical double crosslinking.The structure of the as-prepared r BC/MXene nanocomposite hydrogels were characterized,and the results showed that all the nanocomposite hydrogels with different MXene content exhibited a double-layer structure,with relatively dense surface layer and interconnected three-dimensional porous layers.The results of the physical and chemical properties of the hydrogels showed that the incorporation of MXene enhanced the mechanical properties,thermal stability and electroactivity of the r BC/MXene nanocomposite hydrogels.Among all the hydrogels,the r BC/MXene nanocomposite hydrogel with 2 wt%of MXene exhibited the best thermal stability and electroactivity,and favorable flexibility and recoverability,as well as excellent hydrophilicity,swelling ability and degradability.The results of hemolysis and cell experiments showed that all the r BC/MXene nanocomposite hydrogels presented favorable hemocompatibility,and that the r BC/MXene hydrogels exhibited the better biocompatibility than the pure r BC hydrogel,with the r BC/MXene-2%hydrogel being confirmed as the best candidate to promote cell adhesion,proliferation and spreading among all these hydrogels.These results indicated that electroactive r BC/MXene hydrogel is expected to facilitate wound healing as a potential wound dressing.（4）Electroactive regenerated bacterial cellulose/MXene（Ti₂C₃T_x）nanocomposite hydrogels for wound repair study under electrical stimulation.The effects of the electroactive r BC/MXene-2%nanocomposite hydrogel and its coupling with electrical stimulation（ES）on wound healing were evaluated in an in vivo study using a rat full-thickness defect model.The results revealed that this r BC/MXene nanocomposite hydrogel exhibited a better therapeutic effect than the commercial Tegaderm^TM film.Furthermore,coupling with ES,the r BC/MXene hydrogel could significantly enhance the proliferation activity of NIH3T3 cells in vitro,and actively accelerate the in vivo wound healing process through upregulating vascular endothelial growth factor（VEGF）,transforming growth factor（TGF-β）and epidermal growth factor（EGF）,further promoting wound contraction,collagen synthesis,vascularization,and granulation tissue formation as well as re-epithelization,as compared to the non-ES r BC/MXene hydrogel-treated group.Therefore,this study suggested that electroactive r BC/MXene hydrogel is also an appealing candidate as a wound dressing for skin wound healing,while also providing an effective synergistic therapeutic strategy for accelerating active wound repair process through coupling ES with the electroactive hydrogel dressing.