Preparation And Properties Of Poly (?-caprolactone)-Chitosan-based Organic/Inorganic Composite Materials

The drug-loaded micro/nano composite fibers prepared by the electrospinning technique can effectively delay or control the release rate of the drug,which will not only maintain the effective drug concentration,reduce the number of times and pains of the patient's administration,but also improve the therapeutic effect.Polycaprolactone(PCL)and chitosan(CS)are two commonly used polymer materials in the field of biomedicine,and it is expected to obtain a composite material with excellent comprehensive performance by combining bioactive silicon dioxide(Si O₂),hydroxyapatite(HA)or other inorganic materials.In this thesis,drug-loaded PCL-CS-Si O₂ composite fibers with continuous morphology and uniform particle size were fabricated via the electrospinning technique by using 90%acetic acid as the green solvent and tetracycline hydrochloride(TCH)as the target drug.The composition,surface morphology,diameter distribution and wettability of the composite fibers were characterized by FT-IR,TG-DSC,SEM,and contact angle tester.Moreover,the feasibility of the PCL-CS-Si O₂ composite fibers as a new type of drug carrier material in the field of bone tissue repair was evaluated through biological activity test,antibacterial experiment and in vitro drug release study.In addition,by using 90%acetic acid as the suitable solvent,the PCL-CS-HA composite coatings were spin-coated on the surface of the medical titanium sheets by adding dry powder or wet precipitation of HA to the PCL-CS system.Then,the influence of experimental parameters on the composition,structure and performance of the composite coatings was discussed.The main research results obtained in this paper are listed as follows:1.The drug-loaded PCL-CS-Si O₂ composite fibers with a continuous,uniform and defect-free morphology were prepared by using 90%acetic acid as the green solvent.The optimal preparation parameters were listed as:the concentration of PCL was 20%(w/v);the concentration of chitosan was 1.5%(w/v);the Si O₂content was20 wt%;the concentration of TCH was 4%(w/v).The average diameter of the as-prepared fibers was about 430 nm,and the fibers was found to be super-hydrophilic(?_water?0).The TG/DSC results showed that the actual content of Si O₂ in the composite fibers was about 15.8 wt%,which was slightly lower than the theoretical value(20 wt%).Moreover,the addition of Si O₂ improved the thermal stability of the PCL-CS fibers.2.Compared with the drug-loaded PCL-CS fiber,the drug-loaded PCL-CS-Si O₂composite fibers had better antibacterial properties and ability to form bone-like apatite in vitro.Moreover,the in vitro drug release studies showed that adding a certain amount of Si O₂ can effectively improve the sustained release behavior of the fibers,and the cumulative release rate of TCH in the composite fiber increased with the increase of the Si O₂ contents.Therefore,the PCL-CS-Si O₂ composite fibers is expected to be used as a new type of drug carrier in the field of bone defect repair.3.By using 90%acetic acid as the solvent,porous PCL-CS coatings were prepared on the titanium substrates by the spin-coating technology under the PCL concentration of 10%(w/v)and the CS concentration of 1%(w/v).The bonding strength between the obtained PCL-CS-HA composite coatings and the Ti substrate reached 22 MPa after adding the freeze-dried HA powders,which was 120%higher than the PCL-CS coatings.Moreover,the composite coating exhibited excellent in vitro biological activity.4.Under the PCL concentration of 5%(w/v)and the CS concentration of 2%(w/v),the PCL-CS-HA composite coating was prepared on the titanium substrates by adding HA wet precipitation into the PCL-CS solution,with 90%acetic acid as the solvent.However,the results indicated that the HA phase in the coatings was transformed into rod-shaped or bow-shaped calcium pyrophosphate.Compared with the PCL-CS-HA(dry powder)coatings,the composite coatings prepared by the wet precipitation of HA had a denser and more uniform surface structure,a higher hydrophilicity,but a decreased bonding strength.Moreover,those coatings did not show obvious in vitro biological activity.The paper has 53 picture,6 table,and 113 reference.