PEGylation improves nanoparticle formation and transfection efficiency of messenger RNA.

PURPOSE: Cationic polymers have been intensively investigated for plasmid-DNA (pDNA), but few studies addressed their use for messenger-RNA (mRNA) delivery. We analyzed two types of polymers, linear polyethylenimine (l-PEI) and poly-N,N-dimethylaminoethylmethacrylate P(DMAEMA), to highlight specific requirements for the design of mRNA delivery reagents. The effect of PEGylation was investigated using P(DMAEMA-co-OEGMA) copolymer. METHODS: The influence of polymer structure on mRNA binding and particle formation was assessed in a side-by-side comparison with pDNA by methods such as agarose-retardation assay and scanning probe microscopy. Transfection studies were performed on bronchial epithelial cells. RESULTS: Binding of cationic polymers inversely correlated with type of nucleic acid. Whereas P(DMAEMA) bound strongly to pDNA, only weak mRNA binding was observed, which was vice versa for l-PEI. Both polymers resulted in self-assembled nanoparticles forming pDNA complexes of irregular round shape; mRNA particles were significantly smaller and more distinct. Surprisingly, PEGylation improved mRNA binding and transfection efficiency contrary to observations made with pDNA. Co-transfections with free polymer improved mRNA transfection. CONCLUSIONS: Gene delivery requires tailor-made design for each type of nucleic acid. PEGylation influenced mRNA-polymer binding efficiency and transfection and may provide a method of further improving mRNA delivery.

Self-assembly of ternary insulin-polyethylenimine (PEI)-DNA nanoparticles for enhanced gene delivery and expression in alveolar epithelial cells.

Enhancing gene delivery and expression in alveolar epithelial cells could offer the opportunity for the treatment of acquired and inherited lung diseases. Here, we show that particle adsorption of human insulin (INS) is capable of increasing plasmid DNA (pDNA) delivery from polyethylenimine (PEI) nanoparticles specifically in alveolar epithelial cells. INS receptors were predominantly detected on alveolar but not on bronchial epithelial cells. INS was adsorbed on the surface of PEI gene vectors by spontaneous self-assembly resulting in ternary PEI-pDNA-INS nanoparticles. Surface adsorption was confirmed by particle size, surface charge, and fluorescence resonance energy transfer (FRET) measurements. INS adsorption significantly increased gene expression of PEI-pDNA nanoparticles up to 16-fold on alveolar epithelial cells but not on bronchial epithelial cells. This increased gene expression was INS receptor specific. Our results demonstrate that targeting INS receptor for gene delivery in alveolar epithelial cells represents a promising approach for enhanced gene delivery and expression.

Aerosolized BC-819 inhibits primary but not secondary lung cancer growth.

Despite numerous efforts, drug based treatments for patients suffering from lung cancer remains poor. As a promising alternative, we investigated the therapeutic potential of BC-819 for the treatment of lung cancer in mouse tumor models. BC-819 is a novel plasmid DNA which encodes for the A-fragment of Diphtheria toxin and has previously been shown to successfully inhibit tumor growth in human clinical study of bladder carcinoma. In a first set of experiments, we examined in vitro efficacy of BC-819 in human lung cancer cell-lines NCI-H460, NCI-H358 and A549, which revealed >90% reduction of cell growth. In vivo efficacy was examined in an orthotopic mouse xenograft lung cancer model and in a lung metastasis model using luminescent A549-C8-luc adenocarcinoma cells. These cells resulted in peri- and intra-bronchiolar tumors upon intrabronchial application and parenchymal tumors upon intravenous injection, respectively. Mice suffering from these lung tumors were treated with BC-819, complexed to branched polyethylenimine (PEI) and aerosolized to the mice once per week for a period of 10 weeks. Using this regimen, growth of intrabronchially induced lung tumors was significantly inhibited (p = 0.01), whereas no effect could be observed in mice suffering from lung metastasis. In summary, we suggest that aerosolized PEI/BC-819 is capable of reducing growth only in tumors arising from the luminal part of the airways and are therefore directly accessible for inhaled BC-819.

Dry powder aerosols of polyethylenimine (PEI)-based gene vectors mediate efficient gene delivery to the lung.

Aerosol gene delivery holds great therapeutical potential for many inherited and acquired pulmonary diseases. The physical instability of aqueous suspensions of non-viral vector complexes is a major limitation for their successful application. In this study, we investigated dry powder aerosols as novel gene vector formulations for gene transfer in vitro and murine lungs in vivo. Lyophilization was used to produce dry powder cakes followed by powderization to produce dry powder aerosols. Different sugars, namely lactose, sucrose and trehalose, were tested as lyoprotectants for gene delivery complexes consisting of branched polyethylenimine 25 kDa and plasmid DNA. Biophysical particle characterization demonstrated that lyophilization and powderization in the presence of lyoprotectants were well tolerated. In vitro transfection efficiency remained unaffected by the choice of lyoprotectant and subsequent lyophilization and/or powderization. In vivo screening of powderized samples, by applying the powder with an insufflator, resulted in highest gene expression with lactose as lyoprotectant. Delivering a plasmid coding for murine erythropoietin together with lactose as lyoprotectant resulted in increased blood hematocrit values post application thereby demonstrating the potential of dry powder aerosol as a promising method for pulmonary gene delivery.

Efficient, specific and targeted delivery of genes to the lung.

Many inherited and acquired pulmonary disorders without satisfactory therapies may be amenable to gene therapy. Despite numerous advances, efficient delivery and expression of the therapeutic transgene at physiological levels for phenotypic correction of disease has proved elusive. This article focuses on various strategies aimed at achieving targeted delivery to the lungs. Both physical methods and biological targeting have been successfully applied in various gene delivery systems. Targeting of different cell types has been achieved by pseudotyping of viral vectors with capsids from different serotypes and modification of nonviral vectors with targeting ligands. Both classes of vectors are discussed with respect to their gene delivery and expression efficiencies, longevity of expression and immunogenicity. Moreover, gene therapy clinical trials for different lung diseases are discussed.