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 °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 (λex: 390 nm, λem: 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.