In Vitro Study Of Degradable Materials For Colon-targeted Drug Delivery System

Degradable materials are widely used in the colon-targeted drug delivery system. In this research, two degradable materials were selected for our experiments. Sulfasalazine was used as model drugs, and two different structure drug carriers were designed in this paper, pectin-chitosan mono-layer pellet and multi-layer pellet. The aim of this paper was to improve the rate of cumulative release for model drug in the colon and study the behavior of their swelling and degradation.The main results of this research are as follows:(1) The mean diameter of the mono-layer pellets was 3±0.5 mm, drug content was 0.16±0.01 mg/g. The swelling ratio and the degrading ratio decreased as the concentrations of CaCl₂ and chitosan increased. In pH 6.8 buffer solution, the swelling ratio was much higher than that in pH 2.2 buffer solution. In drug release experiments, the concentrations of CaCl₂ and chitosan solution greatly influenced on the drug release behavior. The increased concentration of CaCl₂ and chitosan led to the lower amount of release drug.(2) The mean diameter of the multi-layer pellets was 4.5±0.5 mm, drug content was 0.60±0.1 mg/g. The swelling ratios of mutilayer pellets were different in pH 2.2 and pH 6.8 buffer solution. In drug release experiments, the 1st group (4% pectin + chitosan) and the second group (4% pectin + chitosan) released more slowly than that in other groups. At 6h, the releasing rates of the five group (1-5) were 3.21%, 1.78%, 5.29%, 6.61%, 5.84% respectively, and at 13h, the releasing rate were 8.70%, 9.07%, 6.90%, 7.00%, 6.72% respectively. The decreased release was attributed to the thickness of outer layer. The release with enzymatical degradation was 10% higher than that without enzymes.(3) In the research of hydrogel experiments, the swelling ratio was obviously influenced by the structure of hydrogel, and it was limited by the cross-linking degree. Phase transition was also greatly influenced by the hydrophobic effect of the gel. The azogel(a, b, c) which didn't contain hydrophobic group started to swelling in the pH 3, but azogel-d containing hydrophobic group had no swelling behavior in the pH 3. As the increase of the cross-linking degree and hydrophobic group, the enzymitically degrading rate and ratio decreased significantly.The results indicated that the pectin-chitosan complex pellet and azo-hydrogel could be used as the materials with good ability of colon-specific drug delivery. It might be devepoped to a novel oral colon-specific drug delivery system for peptides.