γ-scintigraphic evaluation of enteric-coated capsules containing chitosan-brilliant blue gel beads as hydrophilic model for colon drug delivery

In the present study, a suitable enteric-coated capsule containing brilliant blue-chitosan beads was prepared and investigated by means of γ-scintigraphy for colon drug delivery. Chitosan brilliant blue gel beads were prepared by dropping drug-containing solution of chitosan into tripolyphosphate solution using ion complexation method. Moreover, effects of different variables were investigated using 23 factorial design experiments. It was shown that concentration of chitosan and tripolyphosphate, as well as, drug:polymer weight ratio had significant effects on drug entrapment and brilliant blue release from the beads. Moreover, decreasing drug solubility in the external phase has caused a significant increase in drug loading. Release data was studied kinetically and the drug release from chitosan beads was indicated to be a non-Fickian transport. It seemed that diffusion and/or relaxation of the polymer chains controlled the transport. γ-scintigraphy has shown that the gastric emptying of the enteric-coated capsule containing chitosan beads occurred at 37 ± 10 min under fasting condition. Small intestinal transit time in men was determined to be 228 ± 35 min; subsequently, the arrival time in the colon was 266 ± 41 min on average post-administration.