Study On Preparation,characterization And Application Of PCL@CDs Composites

Polycaprolactone(PCL)is a kind of biomedical polymer material that is widely used in the medical field.Because of its unique physical and chemical properties,biodegradability and good biocompatibility,PCL has been widely used in biomedical fields,such as drug delivery systems,tissue engineering,and medical devices.In recent years,the ring-opening polymerization of PCL has been a research hotspot of researchers.Many methods of PCL synthesis have been reported,but the disadvantages of complex reaction conditions,high reaction energy consumption and non-environmental protection limit the application of PCL in biological aspects.Therefore,this thesis mainly starts from the perspective of bio-friendliness,using low-toxic phytic acid(PA)to catalyze the synthesis of biodegradable PCL for the first time and explore the influence of various factors on the polymerization system.The polymerization reaction conditions are mild and efficient,and provide a greener and more economical method for the preparation of PCL materials.In order to expand the application field of PCL,the copolymerization or doping of PCL have recently become an inevitable trend.Carbon dot(CDs)is a carbon nanomaterial with excellent optical properties.Due to its low toxicity,there have been many reports on its application in biomedical research.Considering that the introduction of CDs can bring PCL stable fluorescence performance,it can greatly expand the application of PCL in the field of biomedicine.Thus,caprolactone(?-CL)is used as the object of ring-opening research.PA and CDs are used to jointly catalyze the ?-CL ringopening polymerization to successfully prepare a chemically stable fluorescent PCL@CDs biomaterial and make application research on the biological material in drug delivery and antibacterial aspects.The main research contents are as follows:(1)First,PA was used as a catalyst to catalyze the ?-CL ring-opening polymerization,and the effects of different catalyst content and polymerization temperature on the polymerization reaction were studied.The research results show that the yield of PCL can reach 100% at 70°C.Excess PA can be completely removed by filtration through dissolving in ice water.The polymerization reaction is a highly efficient,non-toxic and environmentally friendly,and green PCL synthesis method.In addition,PCL was prepared with ?-CL as the reactive monomer and2-acrylamido-2-methylpropanesulfonic acid(AMPS)as the catalyst.Exploring the effect of different catalyst ratios and polymerization temperature on the reaction yield,the experiment shows that when 0.9 g ?-CL monomer is used for the reaction,0.0998 g AMPS can reach a monomer conversion rate of 96% at 80 ?.Finally,the structure of the reaction product was characterized by NMR and infrared to confirm the successful preparation of PCL(2)Using citric acid(CA)and ethylenediamine(EDA)as carbon and nitrogen sources,with a simple and efficient microwave method to synthesize CDs.PA is used as the main catalyst and CDs are used as co-catalysts to jointly catalyze the ?-CL ring-opening polymerization.The PCL@CDs binary composite material was successfully obtained,and the influence of the content of CDs on the yield and molecular weight of the reaction product was studied.The structure of binary materials was characterized by infrared and nuclear magnetic(NMR),which further confirmed the successful preparation of binary materials.The combination of the two materials can give PCL@CDs composites more advantages.The optical properties of PCL@CDs were studied using ultraviolet and fluorescence spectroscopy,and the results showed that the incorporation of CDs gave PCL excellent optical properties.The contact angle test results show that the introduction of CDs can greatly improve the hydrophilicity of PCL.RFT drugs are anti-tuberculosis drugs,which have strong antioxidant,anti-inflammatory and antibacterial activities and have been widely used in medical research.Finally,PCL@CDs microspheres(PCL@CDs@RFT)loaded with RFT were obtained by O/W emulsion solvent evaporation method.The drug release of PCL@CDs @RFT microspheres was studied in a simulated body fluid environment.The results showed that the maximum drug loading of RFT was 7.8% and the maximum encapsulation rate was 81%.In addition,there were two phases of drug release,the burst release phase was rapid release of the drug,and the sustained release phase could ensure sustained release,and the cumulative release rate of RFT drugs can reach64%.Therefore,the prepared PCL@CDs biomaterial has potential drug delivery and bioimaging application value.(3)Using PCL with a molecular weight of 8w as the matrix,and adding PCL@CDs to obtain spinning solutions of different mass ratios,fluorescent degradable multifunctional fibers(SFs)are obtained by electrospinning.The morphology and performance of multifunctional SFs were characterized,and the results showed that the incorporation of PCL@CDs could change the morphology of SFs and endow SFs with excellent optical properties and good hydrophilicity.Finally,silver nanoparticles with a size of 15 nm are prepared by the reduction method and immersed in SFs to obtain antibacterial fibers(Ag-SFs).The antibacterial test showed that Ag-SFs have good antibacterial properties against Escherichia coli and Staphylococcus aureus.