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As a natural product, chitosan has the inherent properties of being biodegradable, biocompatible and nontoxic. These properties render it an ideal matrix in enzyme immobilization for clinical analysis. In this work, the feasibility of electrochemical biosensor fabrication using chitosan has been demonstrated. As a test case, the enzyme, sulfite oxidase (SOD), was covalently immobilized onto the matrix of chitosan-poly(hydroxyethyl methacrylate) (chitosan-HEMA), a natural/synthetic polymer hybrid material obtainable via a UV curing process. An electron transfer mediator, pbenzoquinone was coupled onto the polymer network for the activation of chitosan-HEMA copolymer after the photo-induced polymerization reaction. The biological activity of the immobilized SOD and the electroactivity of the coupled p-benzoquinone were examined.

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. © 2002 Society of Chemical Industry

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