Tissue-compatible and adhesive polyion complex hydrogels composed of amphiphilic phospholipid polymers

To investigate the tissue adhesive function of a hydrogel composed of biocompatible amphiphilic polymers, polymers with various architectures were prepared from 2-methacryloyloxyethyl phosphorylcholine (MPC), electrolyte monomers and hydrophobic n-butyl methacrylate (BMA). A polyion complex (PIC) hydrogel was formed within a few minutes after aqueous solutions containing the cationic and anionic MPC polymers were mixed. Provided the electrical charge of the cationic and anionic MPC polymers was approximately balanced, the PIC hydrogel existed stably in a large amount of aqueous medium. The results of the fluorescence study of the MPC polymers suggested that dissociation was suppressed and that the electrostatic interaction was enhanced in the block and graft polymers compared to the random polymers. This is due to the strategically designed architectures and the hydrophobic BMA units. Based on the results of the cytotoxicity test, the cytotoxicity of the MPC polymers was lower than that of glutaraldehyde, a cross-linker contained in aldehyde-type tissue adhesives. The cationic MPC polymers demonstrated higher cytotoxicity compared to the anionic ones, which demonstrated no significant cytotoxicity at examined concentrations. The tissue adhesion of the PIC hydrogels was evaluated with a dura incision model. The results indicated that the tissue adhesion strength of the PIC hydrogel was lower than that of a commercially available fibrin glue. However, the tissue adhesion strength increased with an increase in the polymer concentration and could be controlled by the water content of the hydrogel. Although further investigation of the biocompatibility of the PIC hydrogels and control of the water content is crucial, it can be concluded that the PIC hydrogels formed by the amphiphilic MPC polymers can be promising tissue adhesives which demonstrate properties according to the architectures and chemical structures.