Controlled drug release from contact lenses prepared by usi̇ng the layer-by-layer method

In this study it is aimed to use the drug loaded p-HEMA contact lenses for the treatment of the conjunctivitis and glaucoma at the same time, which are the most important eye diseases. A synthetic polymer p-HEMA is used frequently for controlled release applications as well as being used as a soft material. Dexametasone and Timolol were used as model drugs. The surfaces of hydrogels were modified via ''Layer by Layer'' (LbL) technique. This method is based on the electrostatic interaction between complementary functional groups. By using LBL method, we modified the surface of hydrogels with chitosan and hyaluronic acid. Furthermore it is important that the studied material must be biodegradable and biocompatible for using the biomedical applications. Hydrogels were characterized by using FT-IR (Fourier Transform Infrared Spectroscopy), DSC (Differential Scanning Calorimetry) and SEM (Scanning Electron Microscope). The formation of each layer was monitored by measuring the absorbance of methylene blue, light transmittance and water contact angle of the lenses. Drug release concentration was measured by using UV-vis spectroscopy. Hydrogels prepared by LbL methods (2 double layer) have sustained drug release in which only 50 % of drug was released in 25 hours. It was demonstrated that the formed CH/HA layers act as a barrier for drug release. Furthermore, addition of the drug-free chitosan layers on top of this surface modified hydrogels (2 double layer) at different thickness gave rise to further reduction at the drug release. As a unique result, for the first time in literature, it is seen that addition of drug free chitosan layers on the top of the surface modified hydrogels had allowed us to observe a "delay time". The observed delay time varied with the changing thickness of the layer applied. Thickness of drug free chitosan layer is 1,85 μm. The delay time increased from 5 minutes to 25 minutes with increasing thickness. Thus, controlled drug release was accomplished. Moreover, addition of chitosan layer on top of the contact lenses allowed us to see a delay time before the release of drug as well as preventing the burst release. Also, side effects of the drug were eliminated, which was released at the beginning. The dose of drug, which each patient must receive according to his/her drug regimen, can be adjusted by varying the thickness or the changing the number of the layers applied without losing the other functions of contact lenses such as correcting the vision. A system treating multiple diseases at the same time has been provided. The material which was never used before was developed for transport of the ophthalmic drug release.