Design and development of polymeric nanoparticles for targeted delivery of nucleic acid-based therapeutics to tumor sites

Abstract

Nucleic acids are widely used as potent therapeutics in cancer research. They can either promote gene expression by bringing a gene either not expressed or under-expressed into tumor cells (cDNA), or alternatively silence expression of genes such as oncogenes (RNAi mediators). However, before they can be efficiently translated to the clinic, this technology requires some optimization: nucleic acids and their vehicles need for instance to be protected from rapid elimination from the bloodstream (opsonization, clearance, and nuclease-mediated degradation) and the specificity of tumor addressing has to be validated. Hence a polymeric nanoparticular carrier encapsulating nucleic acids, either plasmid DNA or siRNA, was developed. Nanoparticles are composed of (1) PLGA, a well tolerated and biodegradable polymer, (2) PEG groups to avoid opsonization, (3) PEI moieties to complex nucleic acids and to enhance cytosolic delivery and (4) RGD sequence for active tumor targeting. Nanoparticles were formulated by double emulsion or water-in-oil-in-water method. Physical properties of such nanoparticles were assessed by dynamic light scattering (size and polydispersity index) and laser doppler electrophoresis (zeta potential). The efficiency of nucleic acid encapsulation into the carrier was determined by the Picogreen assay. Cytotoxicity and transfection capacity were assessed in an in vitro model of B16F10 melanoma cells. To date, various designs of nanoparticles were successfully formulated with appropriate size, surface charge and encapsulation efficiency. The PLGA nanoparticles did not show cytotoxic effects on cells and, although less efficient than PEI alone, allowed DNA delivery into tumor cells.