Upendra Patel

Aerogel is world’s lightest material and drug delivery system. Aerogel having more than 15 entries in Guinness Book of the world’s record is very low density solid state gel which is derived by replacing the dispersion phase of gel with gas. Aerogels are prepared by sol-gel process to extract liquid component of gel through super-critical drying. This allows the liquid removed without causing the solid matrix in gel to collapse due to capillary action. Aerogel possesses some properties like lowest density, lowest optical index of reflection, lowest electric constant and highest specific surface area. Materials used for preparation of aerogel include silica, metal oxides, organic and biological polymers, carbon nanotubes etc. Both hydrophilic and hydrophobic gels can be prepared. Solvents used for preparation of gel are explosive so, they are replaced by non inflammable liquid carbon dioxide. Applications of aerogel are very wide. Aerogels are used as a composite, as an absorbent, as a sensor, as a catalyst, as a thermal insulator, for improving dissolution properties of some drugs etc.

  Self Micro-emulsifying drug delivery systems (SMEDDS) are usually used to improve the bioavailability of hydrophobic drugs. Approximately 60-70% of new chemical entities exhibit poor aqueous solubility and present a major challenge to modern drug delivery system, because of their low bioavailability. SMEDDS is isotropic (one phase system) mixture of oil or modified oils, surfactants and co-surfactants, which form the fine oil-in-water microemulsion when introduced into aqueous phase under condition of gentle agitation. The digestive motility of the stomach and intestine provide the agitation necessary for self-microemulsion in-vivo. Triglyceride is the one of the component of SMEDDS, which helps in the absorption of drugs from the GI tract. SMEDDS enhance the bioavailability enabling reduction in dose of the drug. SMEDDS is evaluated by various methods like visual assessment, droplet polarity and droplet size, size of emulsion droplet, dissolution test, charge of oil droplets, viscosity determination, in-vitro diffusion study. This article gives an overview of improvement in the rate and extent of oral absorption of drugs by SMEDDS approach. The characterization of SMEDDS and application of SMEDDS is also introduced, with particular emphasis being placed on the developments of Solid self micro-emulsifying delivery system and dosage form of SMEDDS.

  Now a days as very few drugs are coming out of research and development and already existing drugs are suffering the problem of resistance due to their irrational use specifically in case of drugs like antibiotics. Hence, change in the operation is a suitable and optimized way to make the some drug more effective by slight alteration in the drug delivery. An appropriately designed controlled release drug delivery system can be a major advance towards solving problems concerning the targeting of a drug to a specific organ or tissue and controlling the rate of drug delivery to the target sites. The development of oral controlled release systems has been a challenge to formulation scientists due to their inability to restrain and localize the system at targeted areas of the gastrointestinal tract. Matrix type drug delivery systems are an interesting and promising option when developing an oral controlled release system. This review focuses on the progress made in the design of controlled release dosage forms employing various types of matrices as carriers for the active ingredients.   Key Words: Controlled drug delivery, Matrices, Oral controlled release system, Matrix tablets.