The Construction Of Hydrogel Systems With Photo-Inspired Functionalization On Titanium

As the largest organs in the body,bone plays a key role in the operating activities of human body.In recent years,there are more and more demands for bone implant biomaterials due to the increasing risk of bone related diseases,such as osteoporosis,bone tumors,traffic accidents caused by fracture,and so on.So it is necessary to build some coatings and scaffolds to promote bone formation.However,there are two major postsurgical complications of infection and insufficient bone tissue integration after orthopedic implantation which may lead to the failure of the implant.Therefore,there is an urgent need to develop advanced methods to quickly eliminate the serious infection and induce bone tissue regeneration.Titanium alloy has been widely used in the field of bone implant material due to its good biocompatibility and excellent mechanical properties.However,it is difficult for titanium alloy to stimulate biological signals to promote osteogenesis for its biological inert and poor bone integration ability.In addition,it is also difficult for titanium to proceed an interface chemical blend with the surrounding natural bone.At the same time,once the implant site infected,titanium alloy cannot effectively eliminate the infection.Based on the above problems,it is necessary to build some coatings which can not only possess good biological activity,but can rapidly and efficiently sterilize on titanium alloy.Hydrogel is a kind of environmental hydrophilic polymers which has a three-dimensional network structure with good biocompatibility,and it can be used as a carrier of antimicrobial agents and tissue regeneration material.Semiconductor materials,such as zinc oxide(ZnO),black phosphorus(BP),as well as the reduced graphene oxide(rGO),silver(Ag),silver chloride(AgCl)and so on,are widely used in solar energy conversion,antimicrobial,photocatalytic degradation of pollutants.Reactive oxygen species(ROS),including the singlet oxygen,hydroxyl free radical,superoxide free radicals,is closely related to semiconductor photocatalytic materials.At the same time,they also have excellent antimicrobial properties.Therefore,this thesis is focused on the preparation of coatings with hydrogel as the carrier to load BP,ZnO,Ag,AgCl and rGO,which can give the good biological activity and in-situ rapid effective sterilization to titanium.The basic contents of the thesis are as follows:1.Study of photodynamic antimicrobial properties and biocompatibility of hydrogel system embedded with Ag/Ag@AgCl/ZnO nanostructuresAg/Ag@AgCl/ZnO hybrid nanostructures are embedded in a hydrogel system by a simple two-step technique.The Ag/Ag@AgCl nanostructures are assembled in the hydrogel via ultraviolet light chemical reduction followed by incorporation of ZnO nanostructures by NaOH precipitation.The system exhibits high antibacterial efficiency against both Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)under light irradiation.The Ag/Ag@AgCl nanostructures enhance the photocatalytic and antibacterial activity of ZnO due to the enhancement of reactive oxygen species by visible light.This system kills 95.95%of E.coli and 98.49%of S.aureus within 20 min upon exposure to simulated visible light.In addition,this system provides controllable,sustained release of silver and zinc ions over a period of 21 days arising from the reversible swelling-shrinking transition of the hydrogel triggered by the changing pH value in the biological environment.About 90%Zn2+ release is observed in the acidic environment after 3 days,whereas only 10%Zn2+ release occurs in the neutral environment after 21 days.In vivo results show that release of Ag+ and Zn2+ stimulates the immune function to produce a large number of white blood cells and neutrophils(2 to 4 times more than the control),thereby producing the synergistic antibacterial effects.2.Study of photodynamic antimicrobial properties and biocompatibility of chitosan hydrogel system embedded with black phosphorusThis work fabricated a hybrid hydrogel system embedded with two-dimensional(2D)few-layer black phosphorus nanosheets(BP)via simple electrostatic interaction.Within 10 min,98.90%E.coli and 99.51%S.aureus can be killed rapidly by this hybrid,due to its powerful ability to produce singlet oxygen(1O2)under simulated visible light.In addition,this system also shows a high repeatability,i.e.,the antibacterial efficacy can still reach up to 95.6%and 94.58%against E.coli and S.aureus,respectively,even after challenging bacteria up to four times repeatedly.In vitro and in vivo results reveal that BP in this hybrid hydrogel can also trigger phosphoinositide 3-kinase(PI3K),phosphorylation of protein kinase B(Akt),and extracellular signal-regulated kinases(ERK1/2)signaling pathways for enhanced cellular proliferation and differentiation.Moreover,the system causes no appreciable abnormalities or damage to major organs(heart,liver,spleen,lung,and kidney)in rats during the wound healing process.Therefore,this BPs-based hydrogel system will have a great potential as a safe multimodal therapeutic system to regulate and control cell behavior and sterilize,3.Study of synergistic photodynamic and photothermal antimicrobial properties of hydrogel coating embedded with polydopamine and rGO modified Ag@AgCl nanostructuresIn this work,polyving akohol hydrogel coating embedded with polydopamine and rGO modified Ag@AgCl nanostructures was prepared on titanium alloy surface.Within 10 min,the coating can slowly heat up to 60.2 °C under light due to the excellent thermal ofpolydopamine.In addition,rGO enhance the photocatalytic and antibacterial activity of Ag@AgCl nanostructures due to the enhancement of reactive oxygen species,which lead to the quick and efficient sterilization under the dual function of photodynamic and photothermal.And over 99%E.coli and S.aureus can be killed rapidly by this hybrid in 10min.In addition,the coating has good biological activity.