Smart hydrogels are special type of hydrogels that undergo solution-gelation transition in response to alterations in the environment. Solution-gel transformation is brought about through either physical or chemical cross-linking that occur between the hydrogel chains. Various stimulating factors have been identified to be responsible for the change in the physical state of the intelligent hydrogel. The most important triggering factors are the temperature, pH, ions, electrical signalling, magnetic field, glucose, light and others. Each of these stimulating factors can trigger the swelling of the hydrogel through unique mechanism. Many of these triggering factors are characteristics of the biological systems which make the smart polymers quite beneficial for different biomedical applications. Numerous natural and synthetic polymers have been distinguished to act as smart materials. These polymers impressed the scientists to use them in many biomedical and industrial applications such as drug delivery systems, gene therapy applications, tissue engineering and many other applications.
Every year many drug molecules discovered to be effective in treatment of many diseases, however not all of these drugs succeed in reaching the market. One of the main reasons for such failure is the lipophilicity or low water solubility of these chemicals which results in poor bioavailability. Nanoemulsion has the ability to deliver these drugs in an efficient way. Nanoemulsion, which is usually o/w emulsion can incorporate this lipophilic drug into nanolipoidal droplets. However, the difficulty in applying liquid dosage form can be overcome by using nanoemulgel system. Nanoemulgel considered as a suitable way to deliver lipophilic drugs through topical route. This review tries to highlight the importance of nanoemulgel as a drug delivery system. The components of the systems have been explored and the methods of preparations including high energy methods and low energy methods have been discussed. Different methods were used in characterization of such delivery system; all of these methods and techniques were reviewed briefly. Finally, the recent researches about different applications of emulgel in local delivery or systemic delivery has been discussed. To conclude, the nanoemulgel applications in drug delivery is very promising and many products will find their way to the markets soon.
