A.A. Patil

Hydrogels are three-dimensional, hydrophilic & polymeric networks capable of absorbing large amounts of water or biological fluids. Due to their high water content, porosity & soft consistency, they closely simulate natural living tissues, more so than any other class of synthetic biomaterials. Hydrogels can be formulated in a variety of physical forms, including slabs, micro-particles, Nano-particles, coatings and films. As a result, hydrogels are commonly used in clinical practice & medicine for a wide range of applications, including Tissue engineering & Regenerative medicine, Diagnostics, Cellular immobilization, separation of biomolecules or cells, & barrier materials to regulate biological adhesions. Hydrogels are also relatively deformable & can conform to the shape of the surface to which they are applied. In the latter context, the bioadhesive properties of some hydrogels can be advantageous in immobilizing them at the site of application or in applying them on surfaces that aren’t horizontal. They have started to create a niche in several fields of medicine like in specific site drug delivery, tissue reconstruction & tissue engineering and even as biosensors. In this review article an attempt has been made to explain the properties of hydrogels, their methods of preparation & its applications.

Free Radicals are molecules with an unpaired electron. They are generated in our body by various endogenous systems, exposure to different physicochemical conditions or pathophysiological states. At low levels, free radicals exert beneficial effects while at high concentrations, they generate oxidative stress and damage all cell structures. This review deals with the sources of the free radicals, their beneficial and deleterious effects on cellular activities; it highlights the role of free radicals and oxidative stress in various physiological states like cancer, cardiovascular diseases, Alzheimer’s disease, kidney disease, etc. The harmful effect of free radicals is neutralized by antioxidants, which prevents oxidative damage by reacting with free radicals. Therefore, the best remedy is to increase the intake of natural antioxidant.

The ocular drug delivery is one of the most challenging & interesting endeavors facingthe pharmaceutical companies in the market.  To circumvent the protective barriers of the eye without causing permanent tissue damage is the challenge to the formulator. Hence to improve the bioavailability of ocular drug considerable amount of research has been focused in developing the controlled drug delivery systems. The main aim of preparing the ocular insert is to increase the bioavailability of ocular drug. The Ocular inserts maintain the concentration of drug within the desired range. The Ideal ophthalmic drug delivery must be able to sustain the release of drug & to remain in the vicinity of front of the eye for the prolong period of time. In this review, we have focused on the Barriers for Ocular drug delivery system, mechanism of action, classification of ocular insert.