壳聚糖纳米粒表面游离氨基与纳米粒特性研究

为研究对三聚磷酸钠(TPP)交联的壳聚糖纳米粒的表面游离氨基与纳米粒的性质之间的关联性,采用胶体滴定法测定壳聚糖纳米粒表面氨基游离率，考察表面游离氨基的数量及离解程度对纳米粒粒径、电位、形态及对药物包封率和体外释药特性的影响，并阐述这种变化机制。结果表明，随TPP浓度增加，表面游离氨基逐步减少，在一定TPP浓度范围内，纳米粒粒径减小，表面zeta电位降低，稳定性也随之下降，粒子易聚集，释药速度和程度也随之降低，但药物包封率未受到影响；随着pH升高，表面游离氨基离解程度降低，纳米粒粒径亦随之减小，表面zeta电位降低。酸性介质提高纳米粒的释药速度和程度，在中性和碱性介质中纳米粒的释药速度和程度明显降低。交联程度和pH影响表面游离氨基的数量或离解程度，进而影响纳米粒的体积相转变(溶胀/收缩过程)等重要性质。表面游离氨基与纳米粒性质间有密切的联系。

Free amino groups on the surface of chitosan nanoparticles and its characteristics

The relationship of free amino groups on the surface and the characteristics of chitosan nanoparticles(CS-NPs) prepared by ionic gelation method was investigated.Free amino groups on the surface of CS-NPs were determined by colloidal titration,and the effects of the amount of free amino groups and its ionizable level on the particle size,zeta potential,appearance,drug entrapment efficiency and drug release profile in vitro of CS-NPs were investigated.The result showed that the surface free amino groups reduced,the average size,zeta potential,stability of nanoparticles,and the drug release rate and degree all decreased while the drug entrapment efficiency was not affected with the increase of tripolyphosphate(TPP) concentration.With the increase of pH,the free amino groups could be deprotonated and the ionizable level was stepped down,correspondingly the particle size and zeta potential of CS-NPs decreased.Additionally,the drug release rate and degree were elevated in acid medium while descended in neutral or base medium.The amount and ionizable level of free amino groups on the surface are affected by the gelation degree and pH,which further affected the volume phase transitions(swelling / shrinking processes) of CS-NPs.The properties of CS-NPs have correlation with the surface free amino groups.