A Review on Smart Hydrogels: An Innovative Approach in New Drug Delivery Carriers

Abstract

In recent years, significant advancements in the field of advanced materials and hydrogel engineering have enabled the design and fabrication of smart hydrogels and nanogels that exhibit sensitivity to specific signals or pathological conditions, leading to a wide range of applications in drug delivery and disease treatment. Amongst the various novel routes of drug delivery, the field of ocular drug delivery is one of the most interesting and challenging .As an isolated and delicate organ, eye is very difficult to study from a drug delivery point of view. Despite this limitation, improvements have been made with the objective of maintaining the drug in the biophase for prolonged period of time. A major problem facing in ocular therapeutics is the attainment of an optimal drug concentration at the site of action. To achieve effective ophthalmic therapy, an adequate amount of active ingredient must be delivered and maintained within the eye. The most frequently used conventional dosage forms, i.e. eye solutions, ointments, gels, and suspensions are compromised in their effectiveness by several limitations leading to very poor ocular bioavailability and residing time. Ophthalmic use of viscosity-enhancing agents, penetration enhancers, cyclodextrins, prodrug approaches, and ocular inserts, and the ready existing drug carrier systems along with their application to ophthalmic drug delivery are common to improve ocular bioavailability. Amongst these stimuli sensitive hydro gels are important, which undergo reversible volume and/or sol-gel phase transitions in response to physiological (temperature, pH, ions, enzyme substrate) or other external (electric current, light) stimuli. They help to increase in precorneal residence time of drug to a sufficient extent that an ocularly delivered drug can exhibit its maximum biological action. The concept of this innovative ophthalmic delivery approach is to decrease the systemic side effects and to create a more pronounced effect with lower doses of the drug. The present article describes applications and results obtained by using stimuli sensitive hydrogel systems in ophthalmic drug delivery.