Synthesis Of Gold Graphitic Nanocapsules Doped Hydrogel For Efficient Photothermal Antibacterial Applications

Conventional antibiotic-based therapy through interfering with the normal metabolic process of pathogenic bacteria to cure disease could suffer from some intrinsic limitations including high systemic cytotoxicity,poor solubility and dose dependence.It is urgent to fabricate versatile antibacterial materials to efficiently inhibit bacteria and reduce the risk of bacterial drug-resistance.In the past few decades,near-infrared(NIR)laser-induced photothermal therapy as a powerful tool has been extensively applied to combat cancer and bacterial infection due to the noninvasive manipulation,good controllability and high tissue penetration.It is critical to select an appropriate photothermal reagent that can absorb NIR light and generate photothermal heat for effective therapy or antibacterial applications.Among different photothermal reagents,gold nanorods(AuNRs)have aroused widespread attention due to the tunable surface plasmon and photothermal effects in the NIR region.However,it is hard to keep efficient and stable heat generation with the alteration of morphology under a long-time laser exposure.Our previous work reported that AuNR-encapsulated graphitic nanocapsules(AuNR@G)with good thermostability and biocompatibility could act as an effective and NIR-induced photothermal reagent for antitumor therapy.Hence,AuNR@G could also be a desirable candidate for highly stable and NIR laser-induced antibacterial applications.A hydrogel is a soft material with vastly hydrophilic macromolecular three-dimensional networks,which is prepared by chemical or physical crosslinking of diverse hydrophilic polymers.It possesses great potential in biomedical applications including biosensing,cell culturing,wound healing and tissue engineering,which is attributed to their low toxicity,excellent flexibility,hydrophilicity and sensitive environmental stimuli-responsive nature.Great interests have been devoted to the development of smart NIR laser induced hydrogel systems for photothermal therapy and bacterial inactivation.However,the released photothermal reagents could enter cells by endocytosis and even participate in blood circulation when they were applied in the actual traumatic area,which could result in chronic toxicity.Meanwhile,the application of antibiotics might lead to a much higher risk of developing resistant bacteria.Based on that,we expected to design an antibiotic-free and highly stable hydrogel without the release of photothermal reagents for effective antibacterial applications.In view of the above problems,we designed and synthesized a highly stable AuNR@G-doped poly(vinyl alcohol)(PVA)/chitosan(CS)(AG-PC)hydrogel and achieved effective antibacterial performance under the irradiation of NIR laser.The details are as follows:(1)In Chapter 2,the preparation and characterization of AuNR@G were studied.A confinement chemical vapor deposition(CVD)method was used to fabricate AuNR@G.To improve its solubility for further hydrogel fabrication,hydrophilic PVA molecules were modified onto the AuNR@G surface through the hydrophobic interaction.At the same time,the stability and the photothermal sterilization effect of AuNR@G were investigated.(2)In Chapter 3,we fabricated a AuNR@G-doped poly(vinyl alcohol)(PVA)/chitosan(CS)hydrogel(AG-PC hydrogel)by mixing the PVA modified AuNR@G with PVA and CS.We observed its mechanical property,stability and swelling properties.(3)In Chapter 4,we further explored the in vivo photothermal sterilization effects of AG-PC hydrogel.the resultant AG-PC hydrogel exhibited high efficiency for the sterilization of both gram-negative Escherichia coli(E.coli)and gram-positive Staphylococcus aureus(S.aureus)under the irradiation of 808 nm laser due to the superior photothermal conversion efficiency and stability of AuNR@G.Moreover,the swelling performance of the stable AG-PC hydrogel could effectively absorb the bacterial solution and enhance the antibacterial performance.