Hydrogels

As an emerging drug carrier, hydrogels have been widely used for tumour drug delivery. A hydrogel drug carrier can cause less severe side effects than systemic chemotherapy and can achieve sustained delivery of a drug at tumour sites. In addition, hydrogels have excellent biocompatibility and biodegradability and lower toxicity than nanoparticle carriers. Smart hydrogels can respond to stimuli in the environment (e.g., heat, pH, light, and ultrasound), enabling in situ gelation and controlled drug release, which greatly enhance the convenience and efficiency of drug delivery. Here, we summarize the different sizes of hydrogels used for cancer treatment and their related delivery routes, discuss the design strategies for stimuli-responsive hydrogels, and review the research concerning smart hydrogels reported in the past few years

The field of ocular drug delivery is one of the most challenging and interesting field for pharmaceutical scientist. In ophthalmic in situ gels various polymers are used. Generally hydrogels are used. These polymers will increase solution viscosity the field of ocular drug delivery is one of the most challenging and interesting field for pharmaceutical scientist. From last 10 to 20 years the field has been significantly improved1. Due the site of delicacy and the many restrains of the site of application caution has to be taken during formulation of new product2. According to physiology of eye this organ is impermeable to foreign substances. It is difficult to formulation to cross the protective barriers of eye so that drug reaches to site of action in sufficient concentration.1 Novel drug delivery systems aimed to overcome the biological barrier which can obstruct efficient ocular drug delivery.3 Crossing protective barrier without damaging the permanent tissue is major challenge to formulator during formulation. Some common diseases which are cured by topical drug delivery are blepharitis, conjunctivitis, keratitis, trachoma, glaucoma etc4. The major disadvantages of conventional formulation such as solutions, suspensions, emulsions, ointments etc. are poor bioavailability, increased precorneal elimination, high variability in efficacy respectively.5 Because of convenience and safety for ophthalmic chemotherapy optical application of drug is most preferred formulation.

Hydrogels are cross-linked polymers with the capacity to swell in a fluid medium. Crosslinking in hydrogels happens by synthetic or physical means relying upon the polymer properties and exploratory conditions. Attributable to a vast assortment in concoction structure and crosslinking strategies, different hydrogels have been set up for different applications in pharmaceutical and biomedical fields. This part starts with brief presentation, preferences, detriments, order, sorts of hydrogel are talked about likewise. They are insoluble because of the nearness of compound (tie-focuses, intersections) and/or physical crosslinks, for example, ensnarement’s and crystallites. These materials can be blended to react to various physiological boosts present in the body, for example, pH, ionic quality and temperature. At last, the part finishes up with known hydrogel applications in the pharmaceutical area.1