Review: approaches to develop PLGA based in situ gelling system with low initial burst.

In situ gelling systems have gained much interest owing to their successful application in the preparation of controlled drug delivery and tissue engineering. The commonly used polymer for these systems is the biocompatible and biodegradable polymer of Poly (lactic-co-glycolic acid) (PLGA) that is available in the market as implants, microparticles and in situ implant. A polymeric solution is prepared by mixing the polymer with a biocompatible solvent which may be water miscible such as N-methyl pyrrolidone (NMP), 2-pyrrolidone and Dimethyl sulfoxide (DMSO) or partially water miscible solvents such as triacetin, benzyl benzoate, ethyl acetate, triethyl citrate and benzyl alcohol. Upon injection of this polymeric solution into buffer or physiological fluid, the system solidifies and the administered drug releases in a controlled manner. The major drawback of these systems is their high initial burst that characterized by release of a noticeable amount of the administered drug during the first release stage that usually results in drug toxicity and tissue irritation. This review focuses on presenting the different strategies utilized to decrease the initial burst from PLGA in situ gelling system.