Release characteristics of salmon calcitonin from dextran hydrogels for colon-specific delivery

Biodegradable dextran hydrogels were synthesized by crosslinking dextran (T-70) with epichlorohydrin (ECH) for the in vitro colon-specific delivery of salmon calcitonin (sCT). Crosslinking reaction was performed in 2.8 M NaOH solution both in the presence and absence of ethanol at 10 and 23 degrees C. Biodegradation kinetics of dextran hydrogels were studied and, in the presence of 0.7 IU ml-1 dextranase, dextran discs lost 71.0% and 56.5% of their dry weight within 80 h at pH 5.5 and 7.0, respectively. sCT was derivatized with the fluorescamine (FSM) at borate buffer (pH 9.0) and the quantitative determinations were performed using spectrofluorimetric method (lambdaex: 390 nm, lambdaem: 475 nm). In vitro release studies for the hydrogels prepared in the presence of ethanol were carried out in simulated gastrointestinal fluids. Results indicated that 84.9% of the loaded-sCT was released for 17 h and dextran hydrogel prepared in the presence of ethanol may be a good delivery device for the colon-specific delivery of other peptide-type drugs as well as sCT.