Influence of degree of substitution of HES–HEMA on the release of incorporated drug models from corresponding hydrogels

Comparison of in vitro and in vivo protein release from hydrogel systems

“…HES-P(EG) 6 MA and HES-MA microparticles were prepared according to the following general procedure by a water-in-water emulsion process [8,10]: aqueous solutions (PBS) of HES-P(EG) 6 MA or HES-MA (2 wt%, 9 g), the photoinitator Irgacure ® 2959 (0.1 wt%, 0.9 g) and FITC-IgG solution (65 µl containing 825.5 µg FITC-IgG) were filled in a 20 mL glass vial in the mentioned order. An aqueous solution (PBS) of PEG 12,000 (30 wt%, 6.0 g) was added.…”

“…Polymers were produced with various degree of substitution (DS) leading to variable network densities and consequently different release kinetics. In contrast to HES-based polymers derivatized with hydroxyethyl methacrylate (HES-HEMA) which show a limited water solubility [8], better properties were obtained for the new HES-based derivatives. Linkage of the methacrylate groups via polyethylene glycol spacers with 6 or 10 ethylenoxide units (HES-P(EG) 6 MA, HES-P(EG) 10 MA) increased the water solubility of the prepolymers.…”

“…Biodegradable natural substances like gelatin, pectin or dextran are often used as a polymeric backbone [1]. Recently, polymers based on modified hydroxyethyl starch (HES) have been used as matrix for drug delivery systems [7][8]. HES (MW 130,000) has been used as a plasma expander already since the 1970s and is considered as highly biocompatible material [9].…”

“…HES (MW 130,000) has been used as a plasma expander already since the 1970s and is considered as highly biocompatible material [9]. The synthesized polymers can be processed by UV-induced crosslinking into bulk hydrogels and hydrogel microparticles which were characterized in detail previously [7][8][10][11]. Polymers were produced with various degree of substitution (DS) leading to variable network densities and consequently different release kinetics.…”

Controlled Ondansetron Release Based on Hydroxyethyl Starch Hydroxyethyl Methacrylate

“…The presence of imidazole groups in route 2 comparative to unreacted hydroxylethyl (and hydroxyl) groups in route 1 may be the possible reason regarding the decreased solubility of resulting HESHEMA synthesized by route 2. Harling et al and Schwoerer et al 4,26 synthesized HESHEMA by route 1 and reactions were completed by stirring HEMACI and HES for 5 days at room temperature. Here in this study, after a series of optimization reactions of HEMACI and HES conducted at different temperature conditions, it was found that reactions executed at 80 ºC for 24 h (Scheme 1) gave almost same DS as reported by other researchers.…”