Lecithin/zinc-pectin composite microspheres were designed and developed as colon-specific carrier. The novel complex hydrogel microspheres were prepared from polymers: pectin, a carbohydrate from plants, and lecithin(PC), a phospholipid from soybean. Indomethacin (IDM) was chosen as model drug and sapond saponified high-methylated apple pectin as framework material. Intermolecular cross-links were formed between the negatively charged carboxyl groups and the positively charged zinc ions, and gel microspheres were produced. Effect of parameters on size, mass, encapsulation efficiency, drug loading, and drug release pattern of the microspheres were investigated. It is found that formulations were spherical with diameter of 1.13-1.42 mm, mass of 1.13-2.32 mg, encapsulation efficiency of 70.72%-94.76%, and drug loading of 5.84%-13.54%. It is also found that the morphology of microspheres and their loading/releasing capacity are significantly influenced by the lecithin concentration, the degree of saponification, and the mass ratio of indomethacin to pectin. The experiment results show that the lecithin has greatly improved the property of drug load and drug release of the gel microspheres in simulated intestinal fluid. With the mass ratio of PC to pectin 5:4, concentration of NaOH 30 g/L, mass ratio of IDM to pectin 1:4, drug release in simulated intestines is only 8.93% in 8 h. According to stability experiment, microspheres with lecithin were more stable at 60℃ or exposing to sunlight than that without lecithin. Observations from the present study reveals that optimized pectin-Zn-lecithin beads composited with lecithin can efficiently encapsulate indomethacin and have potential for colon-specific delivery to the lower gastrointestinal tract.
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