Study On Preparation And Properties Of Chitosan Based Drug Carriers

Drug carriers have shown bright applications in recent years. Various studies have been carried out mostly based on synthetic polymers for their activity and functionality. However, safety still remains a challenge for clinical applications. To solve this problem, a series of chitosan based drug carriers were developed in this work, for example, microgels, micelles, lyophilized powder for injection and injectable hydrogels. These drug carriers were investigated and the main results were shown as follows:1. Water soluble chitosan crosslinked oxidized sodium alginate microgel (OSA/WSC) was prepared. Chemical structures of the polysaccharides and the electrostatic interactions of the microgel were investigated through fourier transform infrared (FTIR) spectroscopy. Zeta potential, morphology property, in vitro degradation and in vitro drug release properties of the microgel were also investigated. Cytotoxicity evaluation of the microgel was performed by3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. The results indicated that, OSAWSC microgel was successfully prepared and WSC was incorporated as the crosslinker. Schiff base bonds and electrostatic interactions were the main two interactions between OSA and WSC. OSA/WSC microgel had no obvious cytotoxicity and had great potential for applications in oral colon-specific drug delivery systems. In addition, this OSA/WSC microgel was degradable under physiological conditions.2. Based on our former work, OSA/CS core-shell microgel was synthesized to further decrease the drug release of5-ASA in the simulated gastric fluid. Chemical structures of the polysaccharides were investigated through FTIR spectroscopy. Particle size distributions, morphology properties, in vitro drug release properties of CS core and OSA/CS microgel were investigated. Similar methods were carried out to investigate the in vitro degradation properties of the microgel according to the above section. The results indicated that, bio-degradable OSA/CS microgel was successfully synthesized under the catalysis of EDC/NHS. OSA/CS core-shell microgel consisted of CS core and OSA shell, the OSA shell of the microgel prevented5-ASA from diffusing out in the simulated gastric fluid. OSA/CS microgel had great potential for applications in oral colon-specific drug delivery system and its colon targeting was better than OSA/WSC.3. Comb-shaped chitosan graft poly N-isopropylacrylamide (CS-g-PNIPAAm) was synthesized via atom transfer radical polymerization (ATRP) method. Chemical structure of CS-g-PNIPAAm was investigated through1H-nuclear magnetic resonance (1H NMR) spectroscopy and FTIR spectroscopy. LCSTs of CS-g-PNIPAAm were studied through UV-Vis. TEM and atomic force microscopy (AFM) were employed to study the self-assembly properties of CS-g-PNIPAAm. Particle size distributions and zeta potentials of the micelles were also investigated. The critical micelle concentration (CMC) was characterized chosen pyrene (Py) as the fluorescent probe. The results indicated that, LCSTs of CS-g-PNIPAAm in pH6.3and pH5.0solutions were calculated to be33℃and35℃, respectively. Micelles with chitosan shell and PNIPAAm core were formed at pH5.0/37℃, micelles with PNIPAAm shell and chitosan core were formed at pH6.3/25℃. CMC of CS-g-PNIPAAm micelle (formed at pH6.3/25℃) was calculated to be10-3mg/ml.4. CS-FA was obtained through the reaction between CS and FA, and its chemical structure was investigated through1H NMR, FTIR spectroscopy, UV-Vis and X-ray diffraction (XRD). NK/CS-FA was the compound of CS-FA and nattokinase (NK), in vitro and in vivo experiments were carried out to investigate the thrombolysis properties, enzymatic activities and stabilities of NK/CS-FA and NK. Cytotoxicity evaluation of NK, CS-FA and NK/CS-FA were performed by MTT assay. The results indicated that, NK/CS-FA compounds with the mass ratio of NK:CS-FA=100:1(NK/CS-FA (100:1)) behaved best in the thrombolysis experiments, enzymatic activities of NK/CS-FA (100:1) and NK were calculated to be672U/g and596U/g (37℃and pH=7.4), respectively. Enzymatic stability of NK/CS-FA (100:1) was better than NK (80℃or pH=2), MTT assays indicated that, NK/CS-FA (100:1) was less toxic than NK and had great potential for applications in lyophilized powder for injection.5. Oxidized pluronic F127(F127-CHO) was prepared under the oxidization of Dess-Martin reagent from pluronic F127. Chemical structure of F127-CHO was investigated through1H NMR spectroscopy. Micro-phase separated poloxamer/chitosan injectable hydrogels were prepared by the schiff base bonds formation between F127-CHO and chitosan. The micro-phase separated structures of the injectable hydrogels were proved by raman spectroscopy (Raman), differential scanning calorimetry (DSC), XRD and scanning electron microscope (SEM). Rheometer was employed to characterize the gelation times of the injectable hydrogels. Cytotoxicity evaluation, adhesion and in vivo drug release properties of the injectable hydrogels were also investigated. The results indicated that, gelation times of the injectable hydrogels were about1.32min and fitted for clinical applications. SEM images showed that, the hydrogels were interconnected and no visible phase separation could be observed. In vitro cytotoxicity tests indicated that, the injectable hydrogels had favorable adhesive properties and no obvious cytotoxicity. Bone repair experiments indicated that, after hydrogel injection, the bone repairation was accelerated and the inflammatory status of the cells was decreased.