The Application Of Electrospinning Biodegrable Polymer Ultrafine Fiber In Tissue Engineering And Drug Delievery

Human health has always been threatened by disease, cancer, accident, trauma, surgical injury and so on, hence, effective therapies are a pressing need. In recent years, tissue engineering and controlled drug release system have drawn more and more attention, because using tissue engineering technology, combining biology, medicine, materials science and engineering together, allows us to effectively design tissue engineering graft for repairing or replacing the damaged tissues, while using controlled drug delivery system, drug or bioactive factors can be delivered on demand of physiological and pharmaceutical need and clinical recipes at predetermined rate and predefined period of time. So these two technologies, can complement and promote each other at the same time. Electrospinning is currently one of the most commonly used method for preparing tissue engineering scaffolds, meanwhile electrospun fibers is a widely investivaged controlled release drug carrier. Thus, the advantages of these two technologies can be integrated by electrospinning, which will have huge potentials in clinical research and application.This dissertation aims to study the integration and application of tissue engineering and controlled drug release system by electrospinning technology. In this dissertation, biocompatible and biodegradable polylactic acid (PLA), poly (s-caprolactone) (PCL), poly(caprolactone-polyethylene glycol) block copolymer (PCL-b-PEG, PCE) were served as the polymeric matrix, electrospinning fiber scaffolds composited with magnetic nanoparticles, the controlled delivery and dual-drug loaded tissue engineering scaffolds and thermally switched nanogels-in-fiber device were prepared. The morphology of nanoparticles, the structure of electrospinning fibers, the mechanical properties, degradation performance and the controlled drug delivery properties were investigated. At the same time, the evaluation of cellular behavior on these these electrospinning fiber scaffolds in vitro and the zoological experiment were also carried out.Firstly, in chapter 2, oleic acid modified superparamagnetic ferroferric oxide nanoparticles (SPIONs) were prepared by chemical coprecipitation, the diameter and morphology of SPIONs was measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and the superparamagnetism was verified by vibrating sample magnetometer (VSM). After that, ethanol slurry (solid content were tested) was dispersed in the PLA’s DCM/DMF solution, then random oriented and aligned electrospinning nanofibers containing 0% to 8% (w/w)of SPIONs were prepared by these solution. The morphology of the magnetic nanofiber was further observed by scanning electron microscopy (SEM), the fiber orientations were characterized through the fast fourier transform (FFT) and the mechanical properties were tested by universal mechanical testing machine. The influence of magnetic nanofiber and the magnetic field which parallel or perpendicular to the cells spread out plant on osteoblasts individually or jointly was also examined.In chapter 3, BSA nanoparticles (NPs) and BMP-2 loaded bovine serum albumin (BSA) nanoparticles (BNPs) were prepared by desolvation and then chitosan shell was assembled on nanoparticles through electrostatic self-assembly to stabilize the prepared nanoparticles. The diameters and morphologies of nanoparticles were measured by DLS and TEM. Then BNPs togather with dexamethasone were encapsulated in PCE fiber by electrospinning and formed controlled delivery dual drug loaded tissue engineering scaffolds, independent DEX-loaded, BNPs-loaded and NPs-loaded scaffolds served as control groups, and morphology and structure of the electrospun fibers characterized by SEM and TEM. Drug-loading efficiency and in vitro drug release of fiber were measured ultraviolet-visible spectrophotometer (UV-Vis) and human BMP-2 elisa kit. MSCs were seeded on drug-loaded PCE fiber scaffolds in vitro, alamarBlue and living/dead cells assay were used to investigated the cytotoxicity of scaffold and the spreading and migration ability of MSCs on scaffolds, alkaline phosphatase (ALP) activity through 21 days and and alizarin red staining of 21st day were measured to determine osteogenesis ability of scaffolds in vitro.In chapter 4, the repair ability of the as-prepared dual drug loaded PCE fiber scaffolds on rats skull 8 mm diameter of critical size defect in vivo was examined. After MSCs were seeded on our scaffolds for one day in vitro, scaffolds were implanted into rats skull critical size defect. Then rat’s full skulls were haversted at 4,8 and 12 weeks, and observed by the X-ray apparatus to study the skull repair level. The remaining materials in rat’s skull critical size defect area were collected and observed by SEM to check their morphologies, and validated by energy dispersive X-ray detector (EDX) to confirm Ca, P deposition.Tetrahydrofuran (THF) was used to extract the polymer composition to measure degradation. After sectioning, histochemical and immunohistochemical staining were carried out and microscope were used to observe the therapeutic effects and evaluate bone repair level, finally we illustrated the repair defect mechanism of these scaffolds according to the literature and our results.In addition, in the last chapter, we investigated the effect of AAc concentration on lower critical solution temperature (LCST) and sensitivity of thermal responsive poly(IPAAm-co-AAc) microgel, and the LCST was successfully adjusted to human body temperature (-37 ℃). LCST was measured by UV-Vis, and the diameter of the thermal responsive microgel variating with temperature was measured by DLS. Then, poly(IPAAm-co-AAc) microgels were incorporated into the PCL shell of the core-shell PCL/PEO fibers as thermal responsive on-off switches, and methyl orange,chosen as the drug template and color indicator was electrospun in the PEO core, thus the thermally switched nanogel-in-microfiber device was fabrecated, the fiber morphology was observed by SEM, and the nanogels-incorporated fiber structure was verified by TEM. Then the drug release properties of thermal responsive core-shell fibers was investigated. Moreover, doxorubicin hydrochloride (DOX) loaded stimuli-responsive core-shell fiber mat was also prepared, and then inhibition of this DOX loaded stimuli-responsive core-shell fiber mat on the mice breast cancer 4T1 cells were investigated, which demonstrated the potential application of stimuli-responsive core-shell fibers mat.