A new delivery system for antisense therapy: PLGA microspheres encapsulating oligonucleotide/polyethyleneimine solid complexes.

Microspheres for the controlled release of an antisense oligonucleotide against the Transforming growth factor beta(1) were designed. Free oligonucleotide or its solid complexes with polyethylenimine (PEI) at different nitrogen/phosphate (N/P) ratios, were encapsulated within poly(lactide-co-glycolide) (PLGA) microspheres prepared by the multiple emulsion-solvent evaporation technique. The encapsulation of the oligonucleotide in form of solid complexes, the N/P ratio, as well as the PLGA type affected microspheres characteristics in term of loading, morphology, oligonucleotide distribution inside matrix and in vitro release profile. The designed microspheres allow the encapsulation and slow release of oligonucleotide/PEI solid complexes that should be effectively internalized inside cells. Copyright 2002 Elsevier Science B.V.