Zahra Emami Meybodi - Novel Drug Delivery Systems Dept., Iran Polymer and Petrochemical Institute, P.O.Box: ۱۴۹۶۵/۱۱۵, Tehran, Iran.
Mohammad Imani
Mohammad Atai

Polysaccharide-based hydrogels have attracted much attention during the recent years due to their green characteristics e.g., developing dextran-based hydrogels as hemostatic agents by the same authors. The exact pot time of dextran crosslinking has been the question of this research hence, curing behavior and gel properties of epichlorohydrin-crosslinked systems were investigated by means of rheometric and swelling studies. Epichlorohydrin (2-8 %v/v) was added to 2 mL of dextran solution (25 wt%), in aqueous NaOH solution (1.2-2.4 M), and transferred into a cone-and-plate rheometer. Crossover of storage and loss modulus with time was considered as the gel point as a function of NaOH and ECH concentrations. The same formulations were prepared as cylindrical specimens and their swelling behavior was studied gravimetrically. According to the results, both parameters increase the crosslinking reaction rate significantly leading to shorter gel points. This can be attributed to more ionization of hydroxyl groups by increasing in NaOH concentration. The findings were supported by equilibrium swelling studies (ESR) showing a sharp decrement in ESR of the samples upon more progress of the reaction by increasing NaOH and ECH concentrations. In contrast, higher NaOH concentrations increases the swelling ratio due to alkali degradation of dextran chains.

Dextran, Crosslinking, Kinetics, Rheometry, Equilibrium swelling study