Synthesis and surface modification of chitosan containing hydrogel for ophthalmic drug delivery

Hydrogel contact lenses are ideal drug carriers for ophthalmic drug delivery. However, conventional hydroxyethyl methacrylate-N-vinyl pyrrolidone (HEMA-NVP) copolymer hydrogel has restricted applications in drug delivery due to low oxygen transmissibility, protein deposition, low ability of controlling drug loading, releasing, etc. In order to improve properties of hydrogel, cross-linkable chitosan (CH) was synthesised and polymerised with HEMA-NVP monomer. With the introduction of CH, gelation time shortened and oxygen transmissibility increased. Chitosan containing hydrogel could be loaded more norfloxacin than HEMA-NVP copolymer hydrogel, but it was loaded nearly same timolol as HEMA-NVP copolymer hydrogel. The sustained norfloxacin release in 2 h and the sustained timolol release in 1 h could be realised. Surface of chitosan (CS) containing hydrogel was modified by layer by layer self-assemble CS/hyaluronic acid (HA) multilayer. Surface modification improved hydrophilicity, reduced protein adsorption and enhanced water retention of CS containing hydrogel. The drug of norfloxacin or timolol was loaded into CS containing hydrogel during the layer by layer process. The CS containing hydrogel with CS/HA multifilms could control norfloxacin steadily release in 4 h, and timolol steadily release in the first hour.