黏均分子质量对O-羧甲基壳聚糖/海藻酸钠微球溶胀性能、稳定性及微观结构的影响

Effect of Viscosity-Average Molecular Weight on the Swelling Behavior, Stability and Microstructure of O-Carboxymethyl Chitosan/Sodium Alginate Hydrogel Beads

O-羧甲基壳聚糖(OCC)与海藻酸钠(SAL)形成的水凝胶微球,在肠道靶向传输过程中具有很大的应用潜力。将不同的OCC与SAL混合后滴入Ca Cl2溶液中制备微球,研究OCC黏均分子质量对OCC/SAL微球在p H 1.2,p H 6.8和p H 7.4溶液中溶胀性的影响。采用扫描电子显微镜分析微球的微观结构。结果表明:OCC黏均分子质量对OCC/SAL微球在p H 1.2溶液中的溶胀性和稳定性无显著影响,而对其在p H 6.8和p H 7.4溶液中的溶胀差异、稳定性和微观结构有重要影响,并且该影响与OCC的取代度有密切关系。当OCC取代度为0.9时,OCC的黏均分子质量对OCC/SAL水凝胶微球在不同p H条件下的溶胀性能均无显著影响,而显著影响水凝胶的稳定性。OCC的黏均分子质量越小,水凝胶在中性及弱碱性条件下的稳定性越差。当OCC取代度为0.83时微球的稳定性也有相似的变化规律,而对其在p H 6.8和p H 7.4溶液中的溶胀性有显著影响,即溶胀率随着黏均分子质量的增加而降低。当取代度为0.53时,OCC/SAL微球在p H 6.8和p H 7.4溶液中的溶胀率随着OCC黏均分子质量的增加而增加,且高黏均分子质量OCC/SAL水凝胶微球在p H 6.8和p H 7.4溶液中均未被观察到裂解,而低分子质量OCC与SAL形成的微球在p H 6.8和p H 7.4溶液中均发生了裂解。扫描电子显微镜分析表明,OCC的黏均分子质量越大,微球表面的凸起越明显,而且聚集很多纳米级的小微球。

The hydrogel beads formed between O-carboxymethyl chitosan （OCC） and sodium alginate （SAL） have great potential applications in the intestine-targeted delivery of drugs and sensitive compounds. In this research, OCCs with different viscosity-average molecular weight （My） were mixed with SAL and then CaC12 was added to form hydrogel beads. The influences of the Mv of OCC on the swelling properties and stability of the hydrogel beads in solutions of pH 1.2, 6.8 and 7.4 as well as their microstructures were investigated. The results indicated that the My of OCC did not significantly influence the swelling behavior or stability of the beads in the pH 1.2 solution, but markedly affected the swelling behavior and stability in pH 6.8 and pHT.4 solutions as well as the microstructure and the effects greatly depen- dent on the degree of substitution （DS） of OCC. In DS 0.9, the Mv of OCC displayed no impact on the swelling behav- ior of the hydrogel beads in the three solutions, but markedly affected the stability of the beads. That is the stability in pH 6.8 and pH 7.4 solutions reduced along with the decrease of OCC My. In DS0.83, the OCC/SAL beads displayed similar stability variation pattern as that in DS0.9, but the swelling ratio decreased as the Mv elevated. In DS0.53, the swelling ratios of the beads in pH 6.8 and pH 7.4 solutions increased along with the Mv increase and the beads formed by low-My OCC integrated readily in pH 6.8 and pH 7.4 solutions in contrast to that formed by high-Mv OCC. SEM ob- servation revealed that the smoothness of OCC/SAL hydrogel bead surface decreased along with the increase of OCC Mvs and many nanometer-scale particles were attached to the surface.