| Chitosan(CS), as a natural cation polysaccharide generated from the N-deacetylated chitin, has good biocompatibility, antimicrobial and antioxidative property. The drug delivery systems based on chitosan not only improve the stability, and prolong the release time of drug but also have a promising future in the field of modern agriculture and biomedical owing to its good biodegradability and low toxicity for human and environment. Here three drug delivery systems with CS and its derivatives were discussed, the results are as follows:In the first section, two types of modified CS microcapsules(MCs) with the unchanged CS-MCs as a control were perpared by emulsion cross-linking method, where N-(2-hydroxy)propyl-3-trimethyl ammonium chitosan chloride(HTCC) and biguanidinochitosan(BGCS) served as the shell materials, and the auxins indoleacetic acid(IAA) served as a model drug. Meanwhile the mechanism of sustained drug release was studied. Firstly, chemical modified was carried on CS to get two CS derivatives with different degree of substitution(DS), and the lower DS was selected. Next, the optimum preparation conditions of the BGCS-MCs, HTCC-MCs and CS-MCs were depended on a univariate analysis, including the amount of the cross-linker GA, cross-linking time, the concentration of shell walls, and the oil/water(O/W) ratio. In addition, the structural information, thermostability and morphology of the MCs with IAA were investigated by infrared spectroscopy(IR), Ultraviolet-visible spectrometer(UV-vis), thermogratimetry(TG/DTG) and scanning electron microscopy(SEM). The results indicated that the MCs prepared by modified CS superiored to the CS in the thermal stability and encapsulation efficiency(EE), and BGCS-MCs has more smoother and compacter surface as well as the smallest particle size(6.69 ?m) than HTCC-MCs. Drug-release behavior in vitro revealed three types of MCs all had better cumulative release in PBS buffer than in methol. HTCC-MCs better improved the deficiency of sudden release at the first stage of delivery than the two other MCs. Based on the results of drug release kinetics model fit, the drug release the MCs all fit to Korsmeyer-Peppas model. Drug-release process in PBS buffer or in methol all followed by Fickian diffusion.In the second section, anionic polymers sodium ligninsulfonate(SL) was added into shell walls constructed by CS derivatives, and three types of microcapsules(MCs), BGCS/SL-MCs, HTCC/SL-MCs and CS/SL-MCs, were prepared by complex coacervation method,with the plant growth regulator methyl naphthyl-1-acetate(MNAA) as Oily drug model. The optimum conditions for preparation of the three MCs were depended on a univariate analysis, including the concentration of CS and SL, p H values, and the core-shell ratio. Besides, the performance and surface morphology of three MCs was characterized by IR, UV-vis, TGA and SEM. The results exhibited that MCs prepared by BGCS/SL and HTCC/SL had more stable construction, higher EE and better thermal stability than CS/SL due to electrostatic interaction between positive group in CS derivatives and sulfo group in SL. Drug-release behavior in vitro showed that sustained release effect of BGCS/SL-MCs was the best, and the release level of the three MCs increased with the increase of ambient temperature, moreover, they followed Korsmeyer-Peppas model.In the last section, modified CS was introduced into the drug dilivery system of sodium alginate hydrogel beads(SA-HGBs) to improve the drug encapsulation efficiency and release controllability. Herein, CS/SA-HGBs?BGCS/SA-HGBs and HTCC/SA-HGBs, with fluorouracile(5-FU) as a model drug, and Ca Cl2 as cross-linking agent, were prepared by the extrusion-exogenous gelation method with CS as control. The physicochemical performance was investigated by IR, UV-vis and TGA. Beside, swelling property and sustained drug release behavior of HGBs was determined. By single variable test, the optimum concentration of SA and modified CS and Ca2+ was as follows: the concentration of SA and modified CS and Ca2+ was 3%, 0.5%, and 2%, respectively. Compared with the control, EE of BGCS/SA-HGBs and HTCC/SA-HGBs were improved to 7.58% and 10.96%, respectively, due to strongly H-bond interaction between quaternary ammonium group or biguanide group in CS derivatives and carboxyl in SA., Which resulted in the superior EE, mechanical properties and swelling capacity of BGCS/SA-HGBs and HTCC/SA-HGBs. The results of swelling and drug release experiment showed that the three control release matrix of HGBs were found to have a p H-dependent behavior. On the other hand, the sustained releasing properties were decreased in this order: HTCC/SA-HGBs, BGCS/SA-HGBs and CS/SA-HGBs. |
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