Gene delivery using core-shell nanoparticles

Abstract

Recently, with the patented technology, we have developed a cationic amphiphilic core-shell nanoparticle composed of well defined poly(methyl methacrylate) hydrophobic cores and poly(ethyleneimine) hydrophilic shell. This particle has the combined properties of cationic polymers, nanoparticles and surface functional groups, making it excellent candidate as gene carrier in gene delivery systems. In our previous studies, we have demonstrated that this novel nanoparticle has comparative advantages over the PEI system for in vitro gene delivery. During the gene transfer process, there are a number of barriers that restrict the success of gene delivery. However, cytoplasmic microinjection studies have demonstrated that inefficient gene transfer from the cytosol to the nucleus is the major limiting step. In order to further enhance the transfection efficiency and to provide the nuclear targeting capability, we have tried the inclusion of a nuclear protein HMGBl in our system. It has been reported that the high mobility group protein HMGBl can enhance the transfection efficiency in both naked DNA and liposome-mediated transfections. When DNA is packed with the HMGBl protein, condensed molecules can form and the transfection efficiency is approximately similar to the calcium phosphate method. In the HVJ-liposome system, HMGB1 serves as a DNA binding protein. Within the nuclear envelop, it assists nuclear access and promotes gene stabilization. In our present study, HMGB1 protein was added together with DNA and the PMMA-PEI nanoparticles to form the gene delivery complexes. Formation of complexes was demonstrated using agarose gel retardation assay and the DNA with HMGB1 still bound can be released from the complexes with the use of poly(aspartic acids). Therefore, with the incorporation of HMGB1 in our existing PMMA-PEI core-shell nanoparticle system, the resultant HMGB1-DNA-nanoparticle complexes still maintain their DNA condensing capacity, DNA release ability and DNA protection ability. Furthermore, in in vitro transfection, complexes formed by first condensing the plasmid DNA with nanoparticles and then binding with the HMGB1 protein gave a transfection efficiency significantly higher than that of the PMMA-PEI nanoparticle system without the presence of HMGB1. We believe that this system with the inclusion of HMGB1 has the potential to be developed into a viable and efficient non-viral gene carrier for use in vivo.