Reconstitutable charged polymeric (PLGA)2-b-PEI micelles for gene therapeutics delivery

This study investigated the potential of creating a charged polymeric micelle-based nucleic acid delivery system that could easily be reconstituted by the addition of water. (PLGA(36kDa))(2)-b-bPEI(25kDa) (PLGA MW 36 kDa, bPEI M-w 25 kDa, PLGA:bPEI block ratio = 2) was synthesized and used to prepare cationic micelles. The copolymer retained proton-buffering capability from the bPEI block within the endosomal pH range. Micelle/pDNA complexes retained their particle size (100-150 nm) and surface charge (30-40 mV) following reconstitution. It was found that adding a small amount of low molecular weight bPEI (1.8 kDa) completely shielded pDNA in the micelle/pDNA complexes and enhanced transfection efficiency 50-100 fold for both fresh and reconstituted complexes without affecting complex size. Transfection efficiency for reconstituted micelle/pDNA/bPEI(1.8kDa) (WR 1) complexes was 16-fold higher than its fresh counterpart. Although transfection levels achieved using reconstituted micelle/pDNA/bPEI1.8kDa complexes were 3.6-fold lower than control fresh bPEI(25kDa)/pDNA (N/P 5) complexes, transfection levels were 39-fold higher than reconstituted bPEI(25kDa)/pDNA (N/P 5) complexes. The micelle/pDNA/bPEI(1.8kDa) system showed very low cytotoxicity in MCF7 cells even with pDNA doses up to 20 mu g, and transfection levels increased linearly with increasing pDNA dose. These results indicate that this PLGA-b-bPEI polymeric micelle-based system is well suited as a reconstitutable gene delivery system, and has high potential for use as a delivery system for gene therapy applications. (C) 2011 Elsevier Ltd. All rights reserved.