Study On Preparation And Properties Of Carbonized Polymer Dots And Its Composite Hydrogels

The treatment of chronic wounds remains a global challenge,bacterial infection and excess reactive oxygen species(ROS)are the most important factors contributing for the delayed healing of wounds.Therefore,designing wound dressing materials with outstanding biocompatibility,antibacterial and antioxidant property has great practical significance in skin wound healing.Benefit from their adequate flexibility,water absorption and moisturizing advantages,as well as the ability to load diverse agents,hydrogels are routinely described as an ideal wound dressing material.Carbonized polymer dots(CPDs),as a new type of carbon-based nanomaterial,possess a unique polymer/carbon hybrid structure,which retains abundant precursors during the carbonization process,and can be used to design multifunctional CPDs.In this paper,a kind of CPDs with photothermal effect,anti-oxidation and antibacterial properties were prepared from chitosan polymer modified by catechol,which was applied in hydrogels and two different types of gels were designed.The specific contents are summarized into the following three aspects:1.Chitosan and 3,4-dihydroxybenzaldehyde were used to synthesize modified chitosan polymer(DFC),and then the polymeric precursor is pyrolyzed into CPDs with abundant amino and catechol groups on the surface.The structure,morphology,photothermal conversion performance,antibacterial activity,anti-biofilm performance and antibacterial mechanism of CPDs were discussed.The CPDs can activate the photothermal effect under808 nm near-infrared(NIR)light irradiation.In terms of antibacterial,CPDs has inherent cationic antibacterial properties and show excellent antibacterial activity against Staphylococcus aureus.Combined with the assistance of NIR,the CPDs also exhibits the ability to effectively kill Escherichia coli.2.The nanocomposite hydrogel(PVA@CPDs)is constructed by direct mixing polyvinyl alcohol(PVA)with CPDs,utilizing the freeze-thaw cycle method to form gel.Improvements in the swelling behavior,mechanical properties and adhesive strength of hydrogel can be achieved with the suitable loading amount of CPDs.The in vitro experiments demonstrate that the PVA@CPDs hydrogel presents broad-spectrum and rapidly bactericidal activity,concurrently scavenges free radicals.In addition,no obvious cytotoxicity is observed for the multifunctional hydrogel after incubation with L02 cells.Furthermore,in vivo evaluation in infected skin wound model demonstrates the promoting wound closure of PVA@CPDs hydrogel without any toxicity to the main organs of mice.3.In order to better deal with irregular wounds and achieve fixed-point treatment,utilizing the amino and catechol structures on the surface of CPDs to form reversible Schiff base bonds and hydrogen bonds with oxidized dextran(ODA)and PVA,an injectable adhesive double network hydrogel(PCO)was prepared.This PCO hydrogel exhibited good injectability,self-healing and adhesion.The mechanical performance measurements indicated the content of CPDs substantially affected the compressive strength,deformability and viscoelasticity of hydrogel.The excellent antioxidant and antibacterial properties were acquired due to the incorporation of CPDs.