Diffusion-controlled hydrogel polymeric matrix devices have been among the most widely used drug delivery systems. How ever in homogeneous hydrogel the diffusional distance increase with time and hence, the release rate decreases. That results in high release of drug during first hours and days of implantation, which may is not necessary and sometimes it can cause side effects. To overcome this disadvantage of first-order diffusion behavior, various approaches have been developed to achieve constant release rates in polymeric matrix devices. As an alternative technique in this project we are interested to model the constant release profile by polymerizing some multi-laminated HEMA base hydrogels. HEMA hydrogel are widely used in biomedical applications and their diffusion properties and their porosity can be tuned by changing the water ratio during polymerization and also the amount of cross-linker. Having a multi-laminated hydrogel from different HEMA-crosslinker-water ratio can propose a solution for controlling the overall release profile and provide a constant release over time.
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