title: Controlled delivery of drugs from a novel injectable in situ formed biodegradable PLGA microsphere system.
abstract: A novel method for in situ preparation of injectable biodegradable microspheres from the copolymer, poly(lactide-co-glycolide) (PLGA), without incorporating unacceptable organic solvents is described. The delivery system is a dispersion of PLGA microglobules ('premicrospheres' or 'embryonic microspheres') in an acceptable vehicle mixture (continuous phase) and whose integrity is maintained by the use of appropriate stabilizers. A solution of PLGA, triacetin, a model protein (cytochrome c), PEG 400, and Tween 80 (oil phase 1) is added dropwise with continuous homogenization to Miglyol 812-Span 80 solution (oil phase 2), thereby inducing phase separation (coacervation) of PLGA and forming PLGA microglobules (containing cytochrome c) dispersed in the continuous phase. This novel drug delivery system (NDDS) is a dispersion and has a viscous consistency, but is sufficiently syringeable. When injected, it comes in contact with water from an aqueous buffer or physiological fluid and, as a result, the microglobules harden to form solid matrix type microparticles entrapping cytochrome c (in situ formed microspheres). Cytochrome c is then released from these microspheres in a controlled fashion. The composition, rationale, and optimization of the NDDS are described here. Various formulation variables such as the PLGA concentration and type and the substitution of the continuous phase by a fresh oil phase 2 influenced the characteristics of this system. A preliminary investigation of the reproducibility and stability of the NDDS, as well as the physical stability of the encapsulated cytochrome c, revealed that these characteristics were not adversely affected.
authors.affiliation: Department of Applied Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston 02881, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Jain
authors.forename: C T
authors.initials: CT
authors.lastname: Rhodes
authors.forename: A M
authors.initials: AM
authors.lastname: Railkar
authors.forename: A W
authors.initials: AW
authors.lastname: Malick
authors.forename: N H
authors.initials: NH
authors.lastname: Shah
mesh_terms: D000935:Antifungal Agents / Q000008:administration & dosage; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D003574:Cytochrome c Group / Q000008:administration & dosage / Q000737:chemistry; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D004339:Drug Compounding; D006863:Hydrogen-Ion Concentration; D007267:Injections; D019344:Lactic Acid; D008863:Microspheres; D009821:Oils; D010316:Particle Size; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D011136:Polysorbates; D014215:Triacetin / Q000008:administration & dosage
chemical_list: D000935:Antifungal Agents; D003574:Cytochrome c Group; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D009821:Oils; D011108:Polymers; D011136:Polysorbates; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D014215:Triacetin