Preparation, characterization, and sterilization of hydrogel sponges for iontophoretic drug-delivery use

Hydrogel sponges of hydroxyethyl methacrylate (HEMA) crosslinked with ethylene glycol dimethacrylate (EGDMA) were prepared and characterized for iontophoretic drug delivery. Various parameters were examined, including: morphological structure, thermal behavior, mechanical strength, absorption capacity, swelling profile, and hydrogel stability. Three sterilization methods, gamma irradiation, ethylene oxide, and autoclave sterilizations were assessed for revealing the optimal sterilization process avoiding alteration in hydrogel properties. Hydrogels prepared with 75% water and polymerized for 24 hr seem to preserve their physical properties, swelling capacity, and absorption kinetics at least over 5 years from preparation. Gamma irradiation was found to be the most suitable as sterilization method for the dried hydrogels causing minimal alteration of hydrogel properties. This work confirmed the feasibility of preparing stable hydrogel sponges of different shapes with desired mechanical strength and swelling capacities at a rapid rate profile suitable for iontophoretic application and drug delivery.