Abstract: In this study, interpenetrating polymer network (IPN) hydrogels based on chitosan and gelatin using microbial transglutaminase (mTG) as the cross-linker were prepared and characterized. The formation of hydrogels was confirmed by intrinsic viscosity measurement. The structure and cross-linking mechanism of liposome immobilized IPN hydrogels (lips-in-gels) were examined. The results showed that lips-in-gels formulated from a mixture of gelatin and chitosan (4:1, m/m) and 10 mg/mL mTG had the best texture (18.68 g hardness). Moreover, swelling test, Fourier transform infrared spectroscopy, differential scanning calorimetry and cross-linking degree measurement suggested that the cross-linking of liposome immobilized hydrogels may be achieved through chemical linkages together with hydrogen bonding, and the liposome was located inside of the gel network. Hydrogels are attractive for a diverse range of applications in the protection, delivery and controlled release of liposomes; however, limited studies have been focused on the structure and cross-linking of lip-in-gels. It is expected that this liposome immobilized hydrogel will have potential as a new nutrient delivery system for application in biomedical and food industries.

Key words: liposome immobilized interpenetrating polymer network hydrogels, structure, cross-linking mechanism