Synthesis of hydrogel for drug delivery studies utilizing photoinitiator-free photopolymerization based on the donor/acceptor pair, N-vinylpyrrolidinone and hydroxypentyl maleimide

Photo-differential scanning calorimetry (photo-DSC) was used to study the rate of photoinitiator-free copolymerization of a donor/acceptor pair involving N-vinylpyrrolidinone (NVP), and a water-soluble N-substituted maleimide, hydroxypentyl maleimide (HPMI). Glucose, 1,1-diethoxy ethane (DEE) and isopropyl alcohol (IPA) were included for the evaluation of their efficiencies as hydrogen donors, and glucose was shown to be the most efficient in enhancing the rate of polymerization. This photoinitiator (PI)-free system was extended to hydrogel preparation using the radiation method with UV as the radiation source based on the same donor/acceptor pair, ie NVP/HPMI, in the presence of glucose as the hydrogen donor. Swelling and drug release tests showed that this hydrogel exhibited high swelling ability and a rather fast drug release rate when using theophylline as the model drug. These tests also revealed that the drug release kinetics and the water diffusion into this hydrogel did not adhere to the Fickian model. Cytotoxicity testing showed no evidence of this hydrogel being cytotoxic.