Preparation And Characterization Of Lecithin/Pectin Composite Microspheres As Colonic Delivery System

Lecithin/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 metal ions, and gel microspheres were produced.Swelling degree and the shape of the products were chosen to optimize the preparing conditions on concentration of pectin CaCl2, NaOH and lecithin. Then calcium lecithin/pectinate beads and zinc lecithin/pectinate beads were prepared.The calcium lecithin/pectinate beads were spherical with 1.23-1.41mm diameter, 1.30-2.49mg weight,22.52%-95.29%EE, and 2.25%-13.77%L. The zinc lecithin/pectinate beads were spherical with 1.10-1.63mm diameter,1.13-3.29mg weight,70.72%-101.72% EE, and 5.84-14.92% L.Effect of these parameters was investigated on size, weight, encapsulation efficiency (EE), drug loading (L), and drug release pattern of the microspheres. It indicates that the morphology of microspheres and their loading/releasing capacity are influenced by the lecithin concentration, the degree of saponification, and the ratio of indomethacin to pectin. The experiment result shows that the addition of lecithin has greatly improved the property of drug load and drug release of the gel microspheres in simulated intestinal fluid, for its two hydrophilic chains can reduce the Hydrophilic ability and swelling ability of microspheres. When calcium lecithin/pectinate beads prepared with the formulation of PC:pectin= 3:4 (mass ratio), concentration of NaOH 20g/L, concentration of CaCl240 g/L. IDM:pectin=3:8 (mass ratio), drug release in simulated intestines is only 2.26%.When zinc lecithin/pectinate beads prepared with the formulation of PC:pectin= 5:4 (mass ratio), concentration of NaOH 20g/L, concentration of ZnCl2 70g/L, IDM:pectin=1:4 (mass ratio), drug release in simulated intestines is only 8.93%. According to stability experiment, microspheres were more stable at 60℃ or exposing to sunlight than microspheres without adding lecithin. Observations from the present study revealed that optimized pectin-Zn-lecithin beads composited with lecithin can efficiently encapsulate indomethacin.