Microspheres are free flowing powder that consist of proteins or synthetic polymers that are biodegradable in nature ranging between 1-1000nmin size. A well designed controlled drug delivery system can overcome some of the problems of conventional therapy and enhance the therapeutic efficacy of a given drug. There are various approaches in delivering a therapeutic substance to the target site in a sustained controlled release fashion. Among them microspheric drug delivery system has gained enormous attention due to its wide range of application as it covers targeting the drug to particular site to imaging and helping the diagnostic features. Microspheres received much attention not only for prolonged release, but also for targeting of anticancer drugs to the tumour. Microsphere are spherical micro particles, and are used where consistent and predictable particle surface area is important. A microspheres has a drug located centrally within the particle, where it is encased within a unique polymeric membrane. The purpose of the review is to compile various types of microspheres, different methods to preparation, its applications and also various parameters to evaluate their efficiency.
