Lipoplex-mediated gene delivery to the lung occurs within 60 minutes of intravenous administration

Ionisation and swelling behaviour of weak polyampholyte core-shell networks - a Monte Carlo study

The network charge of polyampholyte microgels can be tuned by varying the pH of the surrounding solution, and a charge reversal from a positively charged microgel at low pH to a negatively charged microgel at high pH can be achieved. In a titration experiment, it is difficult to tell apart the ionisation of the acidic and basic monomers in the network and to determine the distribution of charges in the network, whereas using Metropolis Monte Carlo simulations, both the degree of ionisation and the distribution of ionised monomers can be determined separately for both species. Building on our earlier work on alternating polyampholyte microgels, we now investigated the pH-dependent ionisation and the swelling behaviour of polyampholyte core-shell microgels under good solvent conditions. For this purpose, we performed Metropolis Monte Carlo simulations for a bead-spring model using the constant-pH method. As in our previous study on alternating microgels, the width of the U-shaped curve of the microgels volume as a function of pH depends on the relative dissociation constants of acid and base, and the microgel volume can be approximated by a linear function of the total network charge. Due to the spatial separation of acid and base in core-shell systems, the ionisation is less enhanced compared to a microgel with an alternating distribution of the two species. Nevertheless, we still see an influence of the presence of one species on the ionisation behaviour of the other species under good solvent conditions. Furthermore, the isoelectric point is shifted towards higher pH, which is caused by a higher charge density in the core compared to that in the shell. Added salt changes the Donnan equilibrium, which determines the counterion distribution within and outside of the microgel. At the same time, it contributes to the electrostatic screening of the network charges, leading to a narrowing of the U-shaped volume transition curve.

Transgene expression in mice of the Opa1 mitochondrial transmembrane protein through bicontinuous cubic lipoplexes containing gemini imidazolium surfactants

BACKGROUND

Lipoplexes are non-viral vectors based on cationic lipids used to deliver DNA into cells, also known as lipofection. The positively charge of the hydrophilic head-group provides the cationic lipids the ability to condensate the negatively charged DNA into structured complexes. The polar head can carry a large variety of chemical groups including amines as well as guanidino or imidazole groups. In particular, gemini cationic lipids consist of two positive polar heads linked by a spacer with different length. As for the hydrophobic aliphatic chains, they can be unsaturated or saturated and are connected to the polar head-groups. Many other chemical components can be included in the formulation of lipoplexes to improve their transfection efficiency, which often relies on their structural features. Varying these components can drastically change the arrangement of DNA molecules within the lamellar, hexagonal or cubic phases that are provided by the lipid matrix. Lipofection is widely used to deliver genetic material in cell culture experiments but the simpler formulations exhibit major drawbacks related to low transfection, low specificity, low circulation half-life and toxicity when scaled up to in vivo experiments.

RESULTS

So far, we have explored in cell cultures the transfection ability of lipoplexes based on gemini cationic lipids that consist of two C16 alkyl chains and two imidazolium polar head-groups linked with a polyoxyethylene spacer, (C16Im)2(C4O). Here, PEGylated lipids have been introduced to the lipoplex formulation and the transgene expression of the Opa1 mitochondrial transmembrane protein in mice was assessed. The addition of PEG on the surface of the lipid mixed resulted in the formation of Ia3d bicontinuous cubic phases as determined by small angle X-ray scattering. After a single intramuscular administration, the cubic lipoplexes were accumulated in tissues with tight endothelial barriers such as brain, heart, and lungs for at least 48 h. The transgene expression of Opa1 in those organs was identified by western blotting or RNA expression analysis through quantitative polymerase chain reaction.

CONCLUSIONS

The expression reported here is sufficient in magnitude, duration and toxicity to consolidate the bicontinuous cubic structures formed by (C16Im)2(C4O)-based lipoplexes as valuable therapeutic agents in the field of gene delivery.

The Effect of Repeat Administration of Lipoplexes on Gene Delivery, Biodistribution, and Cytokine Response in Immunocompetent Tumor-bearing Mice

It is becoming increasingly clear that the intravenous administration of nanoparticles elicits an immune response that compromises delivery efficiency and can be life threatening. This study investigated both the systemic and tissue-level cytokine response to repeat administration of lipoplexes coated with either lactose or PEG. We report that blood cytokine levels differ significantly from that observed in individual tissues. While we consistently observed a reduced cytokine response to lactosylated particles, this did not result in enhanced delivery or expression as compared to PEGylated formulations. We also document that repeat injection did not increase plasmid levels in the liver, lung, or spleen, but delivery to the tumor was enhanced under these conditions. In addition, we show that changes in neither blood nor tissue cytokines correlated strongly with reporter gene expression, and we observed relatively constant expression efficiencies (RLU/ng plasmid) across all tissues despite a considerably reduced cytokine response in the tumor. Together, these results indicate that both biodistribution and cytokine responses are dramatically altered by a repeat intravenous injection of lipoplexes, and that the mechanisms regulating reporter gene expression are not straightforward.

P-selectin targeted RAGE-shRNA lipoplexes alleviate atherosclerosis-associated inflammation

The receptor for advanced glycation end products (RAGE) plays a central role in the chronic inflammatory process associated with atherosclerosis development. We aimed to develop lipoplexes carrying RAGE-short hairpin (sh) RNA, targeted to the adhesion molecule P-selectin, selectively expressed on the surface of activated endothelium (Psel-lipo/shRAGE) to down-regulate RAGE expression as a therapeutic strategy for atherosclerosis. In vitro, Psel-lipo/shRAGE lipoplexes were efficiently taken up by activated endothelial cells (EC), decreased the expression of RAGE protein, and proved to be functional by reducing the monocyte adhesion to activated EC. In ApoE-deficient mice, the targeted lipoplexes accumulated specifically and efficiently transfected the aorta. The repeated administration of Psel-lipo/shRAGE lipoplexes, twice per week for one month: i) reduced the expression of RAGE protein in the aorta by decreasing the expression of NF-kB and TNF-α; ii) diminished the plasma levels of TNF-α, IL6, IL-1β, and MCP-1; iii) inhibited the atherosclerotic plaque development and iv) had no significant adverse effects. In conclusion, the newly developed Psel-lipo/shRAGE lipoplexes reduce the inflammatory processes associated with RAGE signaling and the progression of atherosclerosis in ApoE-deficient mice. Downregulation of RAGE employing these lipoplexes may represent a promising new targeted therapy to block atherosclerosis progression.

The impact of chemical engineering and technological advances on managing diabetes: present and future concepts

Monitoring blood glucose levels for diabetic patients is critical to achieve tight glycaemic control. As none of the current antidiabetic treatments restore lost functional β-cell mass in diabetic patients, insulin injections and the use of insulin pumps are most widely used in the management of glycaemia. The use of advanced and intelligent chemical engineering, together with the incorporation of micro- and nanotechnological-based processes have lately revolutionized diabetic management. The start of this concept goes back to 1974 with the description of an electrode that repeatedly measures the level of blood glucose and triggers insulin release from an infusion pump to enter the blood stream from a small reservoir upon need. Next to the insulin pumps, other drug delivery routes, including nasal, transdermal and buccal, are currently investigated. These processes necessitate competences from chemists, engineers-alike and innovative views of pharmacologists and diabetologists. Engineered micro and nanostructures hold a unique potential when it comes to drug delivery applications required for the treatment of diabetic patients. As the technical aspects of chemistry, biology and informatics on medicine are expanding fast, time has come to step back and to evaluate the impact of technology-driven chemistry on diabetics and how the bridges from research laboratories to market products are established. In this review, the large variety of therapeutic approaches proposed in the last five years for diabetic patients are discussed in an applied context. A survey of the state of the art of closed-loop insulin delivery strategies in response to blood glucose level fluctuation is provided together with insights into the emerging key technologies for diagnosis and drug development. Chemical engineering strategies centered on preserving and regenerating functional pancreatic β-cell mass are evoked in addition as they represent a permanent solution for diabetic patients.

Modeling the Kinetics of Lipid-Nanoparticle- Mediated Delivery of Multiple siRNAs to Evaluate the Effect on Competition for Ago2

Drug combinations can improve the control of diseases involving redundant and highly regulated pathways. Validating a multi-target therapy early in drug development remains difficult. Small interfering RNAs (siRNAs) are routinely used to selectively silence a target of interest. Owing to the ease of design and synthesis, siRNAs hold promise for combination therapies. Combining siRNAs against multiple targets remains an attractive approach to interrogating highly regulated pathways. Currently, questions remain regarding how broadly such an approach can be applied, since siRNAs have been shown to compete with one another for binding to Argonaute2 (Ago2), the protein responsible for initiating siRNA-mediated mRNA degradation. Mathematical modeling, coupled with in vitro and in vivo experiments, led us to conclude that endosomal escape kinetics had the highest impact on Ago2 depletion by competing lipid-nanoparticle (LNP)-formulated siRNAs. This, in turn, affected the level of competition observed between them. A future application of this model would be to optimize delivery of desired siRNA combinations in vitro to attenuate competition and maximize the combined therapeutic effect.

Nanoparticle uptake by circulating leukocytes: A major barrier to tumor delivery

Decades of research into improving drug delivery to tumors has documented uptake of particulate delivery systems by resident macrophages in the lung, liver, and spleen, and correlated short circulation times with reduced tumor accumulation. An implicit assumption in these studies is that nanoparticles present in the blood are available for distribution to the tumor. This study documents significant levels of lipoplex uptake by circulating leukocytes, and its effect on distribution to the tumor and other organs. In agreement with previous studies, PEGylation dramatically extends circulation times and enhances tumor delivery. However, our studies suggest that this relationship is not straightforward, and that particle sequestration by leukocytes can significantly alter biodistribution, especially with non-PEGylated nanoparticle formulations. We conclude that leukocyte uptake should be considered in biodistribution studies, and that delivery to these circulating cells may present opportunities for treating viral infections and leukemia.

Assessing the effect of a nude mouse model on nanoparticle-mediated gene delivery

The relevance of using nude mouse models for evaluating drug delivery to human tumors has recently been questioned by numerous researchers. While the immune response is known to play a critical role in cancer, this study assesses the effect of using immunocompromised "nude" mice on drug delivery. By inoculating both nude and immunocompetent mice with a mouse mammary carcinoma cell line (4T1), differences in the "first pass effect", distribution, and reporter gene expression due to the use of the nude mouse model could be elucidated. Our results indicate that initial tumor deposition (5 min) was slightly lower in nude mice but comparable after 24 h. In addition, some small differences in tissue deposition/accumulation and reporter gene expression were observed between the two mouse models. The results with this one tumor model suggest that delivery studies conducted in nude mice can provide comparable results to those in immunocompetent mouse models.

Minicircle: Next Generation DNA Vectors for Vaccination

The use of DNA vaccines requires pharmaceutical grade DNA that causes the immunization on the basis of a nucleic acid sequence that encodes the protein to be vaccinated against. This nucleic acid sequence can be a circular or linear plasmid, preferably a double stranded one and should not contain any other and especially not any "toxic" sequences. Sequences that are not desirable to be part of the DNA drug can be those deriving from the (typically) bacterial amplification system to produce the DNA vaccine. These could be those portions of a plasmid that are only used for controlling the bacterial replication of the plasmid or those used to select for the plasmid during cloning or even worse during production. After initial approaches to avoid the presence of these sequences in DNA vaccine plasmids with "mini-plasmids," a significant improvement in product safety was obtained by use of minicircles-circular and ccc-supercoiled expression cassettes of the DNA vaccine. Initial results proofed their extremely high expression level and recent comparison of DNA vaccines based on either plasmid or minicircle DNA show successful vaccination against HBV in mice, as shown in this overview chapter.

Cytofectin amine head group modification and degree of liposome pegylation: factors influencing gene transfer

The effectiveness of liposome-mediated gene transfer methods hinges, in part, on the nature of the interaction between the DNA cargo and the liposomes. Here we have examined the effect of quaternization of the cytofectin cationic head group on this interaction and the effect of concentration of the biocompatible, protective polymer polyethylene glycol₂₀₀₀ (PEG₂₀₀₀) on transfection activity. Thus 3β[N-(N’,N’-dimethylaminopropane)-carbamoyl] cholesterol (Chol-T) and 3β[N-(N’,N’,N’-trimethylammonium propane)-carbamoyl] cholesterol iodide (Chol-Q), differing only in the degree of head group methylation, have been formulated into liposomes with polyethylene glycol₂₀₀₀-distearoylphosphatidyl ethanolamine (DSPE PEG₂₀₀₀) and the neutral co-lipid dioleoylphosphatidylethanolamine (DOPE). Their DNA-binding characteristics have been determined and the gene transfer capabilities of resulting lipoplexes have been examined in HEK 293 human embryonic kidney cells. Quaternary ammonium Chol-Q liposomes were found to bind DNA more avidly than their tertiary amine Chol-T counterparts. The inclusion of PEG₂₀₀₀ in liposome formulations resulted in an increase in the optimal liposome-DNA binding ratio. Chol-T liposomes promoted transgene activity levels 5 times greater than those obtained with Chol-Q lipoplexes. Furthermore, a drop in transfection activity of only 17% was noted on increase of liposome pegylation from 2 to 5 mole percent. The study's findings suggest that strong association between cationic liposomes and DNA may lead to reduced levels of transfection activity as a result of poor release of nucleic acid after cellular uptake.

Multiple components in serum contribute to hepatic transgene expression by lipoplex in mice

BACKGROUND

Interaction of cationic liposome/plasmid DNA complex (lipoplex) with serum was not a limiting factor for in vivo transfection. After intraportal injection of lipoplex, hepatic transgene expression was enhanced by interaction with serum in mice. In the present study, we analyzed the mechanism of enhanced hepatic transgene expression of lipoplex by interaction with serum components.

METHODS

Lipoplexes were incubated with several serum components for 5  min at 37  ° C before administration. Transfection efficiency of lipoplexes was measured 6  h after intraportal injection of lipoplex in mice.

RESULTS

Depletion of divalent cation from serum decreased hepatic transgene expression. The addition of calcium ion to divalent cation-depleted serum restored transgene expression. Heat-inactivated serum and bovine serum albumin diminished the enhancing effect of serum on hepatic transgene expression. On the other hand, removal of anionic proteins from serum using an anion-exchanging column was critical for the enhancing effect of serum on transgene expression. Among the serum components tested, fibronectin and complement component C3 enhanced hepatic transgene expression.

CONCLUSIONS

Hepatic transgene expression by lipoplex was enhanced by interaction with multiple components in serum. Interaction of lipoplex with serum could be an important factor for successful in vivo gene transfer. Hence, the information obtained in the present study is valuable for the future development of effective gene carriers.

Ligands located within a cholesterol domain enhance gene delivery to the target tissue

Targeted gene delivery provides enormous potential for clinical treatment of many incurable diseases. Liposomes formulated with targeting ligands have been tested extensively both in vitro and in vivo, and many studies have strived to identify more efficacious ligands. However, the environment of the ligand within the delivery vehicle is generally not considered, and this study assesses the effect of ligand microenvironment by utilizing a lipoplex possessing a cholesterol domain. Our recent work has shown that the presence of the targeting ligand within the cholesterol domain promotes more productive transfection in cultured cells. In the present study, lipoplexes having the identical lipid composition were formulated with different conjugates of the folate ligand such that the ligand was included in, or excluded from, the cholesterol domain. The effect of locating the ligand within the cholesterol domain was then tested in a xenograft tumor model in mice. Lipoplexes that included the ligand within the cholesterol domain showed significantly higher luciferase expression and plasmid accumulation in tumors as compared to lipoplexes in which the ligand was excluded from the domain. These results demonstrate that the microenvironment of the ligand can affect gene delivery to tumors, and show that ligand-mediated delivery can be enhanced by locating targeting ligands within a cholesterol domain.

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.

In vivo gene delivery by cationic tetraamino fullerene

Application of nanotechnology to medical biology has brought remarkable success. Water-soluble fullerenes are molecules with great potential for biological use because they can endow unique characteristics of amphipathic property and form a self-assembled structure by chemical modification. Effective gene delivery in vitro with tetra(piperazino)fullerene epoxide (TPFE) and its superiority to Lipofectin have been described in a previous report. For this study, we evaluated the efficacy of in vivo gene delivery by TPFE. Delivery of enhanced green fluorescent protein gene (EGFP) by TPFE on pregnant female ICR mice showed distinct organ selectivity compared with Lipofectin; moreover, higher gene expression by TPFE was found in liver and spleen, but not in the lung. No acute toxicity of TPFE was found for the liver and kidney, although Lipofectin significantly increased liver enzymes and blood urea nitrogen. In fetal tissues, neither TPFE nor Lipofectin induced EGFP gene expression. Delivery of insulin 2 gene to female C57/BL6 mice increased plasma insulin levels and reduced blood glucose concentrations, indicating the potential of TPFE-based gene delivery for clinical application. In conclusion, this study demonstrated effective gene delivery in vivo for the first time using a water-soluble fullerene.

Nonviral gene delivery: principle, limitations, and recent progress

Gene therapy is becoming a promising therapeutic modality for the treatment of genetic and acquired disorders. Nonviral approaches as alternative gene transfer vehicles to the popular viral vectors have received significant attention because of their favorable properties, including lack of immunogenicity, low toxicity, and potential for tissue specificity. Such approaches have been tested in preclinical studies and human clinical trials over the last decade. Although therapeutic benefit has been demonstrated in animal models, gene delivery efficiency of the nonviral approaches remains to be a key obstacle for clinical applications. This review focuses on existing and emerging concepts of chemical and physical methods for delivery of therapeutic nucleic acid molecules in vivo. The emphasis is placed on discussion about problems associated with current nonviral methods and recent efforts toward refinement of nonviral approaches.

Vectors for pulmonary gene therapy

The success of gene transfer in preclinical animal models and proof of principle clinical studies has made gene therapy an attractive concept for disease treatment. A variety of diseases affecting the lung are candidates for gene therapy. Delivery of genes to the lungs seems to be straightforward, because of the easy accessibility of epithelial cells via the airways. However, efficient delivery and expression of the therapeutic transgene at levels sufficient to result in phenotypic correction of the diseased state have proven elusive. This review presents a brief summary about current status and future prospects in the development of viral and non-viral strategies for pulmonary gene therapy.

Synthetic vs. natural/biodegradable polymers for delivery of shRNA-based cancer therapies

DNA vector-based short hairpin RNA (shRNA) as a means of effecting RNA interference (RNAi) is a promising mechanism for the precise disruption of gene expression to achieve a therapeutic effect. The clinical usage of shRNA therapeutics in cancer is limited by obstacles related to effective delivery into the nuclei of target cancer cells. Significant pre-clinical data have been amassed about biodegradable and non-biodegradable polymeric delivery vehicles that are relevant for shRNA delivery into humans. Here, we will review some leading candidates for clinical usage with a focus on studies relating to their potential for usage in cancer shRNA therapeutics and discuss some of the advantages and disadvantages of using biodegradable and non-biodegradable delivery vehicles.

In vivo comparative study of lipid/DNA complexes with different in vitro serum stability: effects on biodistribution and tumor accumulation

To evaluate the in vivo biodistribution and expression of DOTAP-Chol/DNA complexes (lipoplexes) with different in vitro serum stability, quantitative real-time PCR, in vitro luciferase expression and whole body luminescence imaging were used. In general, less tissue biodistribution, lower luciferase expression and whole body luminescence were observed for DOTAP:Chol (mol/mol 1:4)/DNA lipoplexes which had higher in vitro serum stability as compared to DOTAP:Chol (mol/mol 1:1)/DNA lipoplexes. Plasmid DNA biodistribution and expression were mainly confined to the lungs, and the results suggest that in vitro serum stability may serve as a predictor of transfection in the lung. No correlation between plasmid DNA tissue biodistribution and gene expression was observed by simultaneous determination of the level of plasmid DNA tissue biodistribution and gene expression. While high doses of the formulation possessing increased in vitro serum stability did exhibit reduced entrapment in the lung, no corresponding increase in the plasmid levels of other tissues was observed. However, this formulation did show increased accumulation in tumors that was not further enhanced by PEGylation.

Lipid-based nanoparticles for nucleic acid delivery

Lipid-based colloidal particles have been extensively studied as systemic gene delivery carriers. The topic that we would like to emphasize is the formulation/assembly of lipid-based nanoparticles (NP) with diameter under 100 nm for delivering nucleic acid in vivo. NP are different from cationic lipid-nucleic acid complexes (lipoplexes) and are vesicles composed of lipids and encapsulated nucleic acids with a diameter less than 100 nm. The diameter of the NP is an important attribute to enable NP to overcome the various in vivo barriers for systemic gene delivery such as: the blood components, reticuloendothelial system (RES) uptake, tumor access, extracellular matrix components, and intracellular barriers. The major formulation factors that impact the diameter and encapsulation efficiency of DNA-containing NP include the lipid composition, nucleic acid to lipid ratio and formulation method. The particle assembly step is a critical one to make NP suitable for in vivo gene delivery. NP are often prepared using a dialysis method either from an aqueous-detergent or aqueous-organic solvent mixture. The resulting particles have diameters about 100 nm and nucleic acid encapsulation ratios are >80%. Additional components can then be added to the particle after it is formed. This ordered assembly strategy enables one to optimize the particle physico-chemical attributes to devise a biocompatible particle with increased gene transfer efficacy in vivo. The components included in the sequentially assembled NP include: poly(ethylene glycol) (PEG)-shielding to improve the particle pharmacokinetic behavior, a targeting ligand to facilitate the particle-cell recognition and in some case a bioresponsive lipid or pH-triggered polymer to enhance nucleic acid release and intracellular trafficking. A number of groups have observed that a PEG-shielded NP is a robust and modestly effective system for systemic gene or small interfering RNA (siRNA) delivery.

Emerging Applications of Polymersomes in Delivery: from Molecular Dynamics to Shrinkage of Tumors

Polymersomes are self-assembled shells of amphiphilic block copolymers that are currently being developed by many groups for fundamental insights into the nature of self-assembled states as well as for a variety of potential applications. While recent reviews have highlighted distinctive properties - particularly stability - that are strongly influenced by both copolymer type and polymer molecular weight, here we first review some of the more recent developments in computational molecular dynamics (MD) schemes that lend insight into assembly. We then review polymersome loading, in vivo stealthiness, degradation-based disassembly for controlled release, and even tumor-shrinkage in vivo. Comparisons of polymersomes with viral capsids are shown to encompass and inspire many aspects of current designs.

Nonviral delivery vehicles for use in short hairpin RNA-based cancer therapies

The use of DNA vector-based short hairpin (sh)RNA for RNA interference shows promise as a precise means for the disruption of gene expression to achieve a therapeutic effect. The in vivo usage of shRNA therapeutics in cancer is limited by obstacles related to effective delivery into the nuclei of target cancer cells. Nonviral delivery vehicles that are relevant for shRNA delivery into humans belong to a group of substances about which significant preclinical data has been amassed to show an acceptable safety profile, resistance to immune defenses and good transfection efficiency. Here, we review the most promising current nonviral gene delivery vehicles with a focus on their potential use in cancer shRNA therapeutics.

Increased target specificity of anti-HER2 genospheres by modification of surface charge and degree of PEGylation

Genospheres are cationic lipid-nucleic acid nanoparticles prepared by the assembly of the lipids and nucleic acids from an aqueous/organic liquid monophase that independently dissolves the components, where the resultant particles are homogeneously sized (70-110 nm), with efficiently incorporated and protected DNA. In the present study, we demonstrate pH-dependent modulation of the Genosphere surface charge using pH-titratable lipids. By incorporation of the lipids with titratable anionic or imidazole headgroups, Genospheres with neutral or anionic surface charge at neutral pH were produced and compared for cellular uptake and transfection of a reporter gene (luciferase) in culture of breast cancer cells. The extent of particle-cell association was also studied by fluorescent microscopy and quantified by cytofluorometery. The effects of Genosphere surface modification with poly(ethylene glycol) (molecular weight 2000) at low (0.5 mol %) and high (5 mol %) grafting densities, as well as the effects of HER2-receptor-directed targeting by an internalizable anti-HER2 scFv F5, linked via PEG spacer, were also studied. Inclusion in the Genosphere formulation of pH-titratable lipids CHEMS (cholesteryl hemisuccinate), CHIM (1-(3-(cholesteryloxycarbonylamino)propyl)imidazole), or DSGG (1,2-distearoyl-sn-glycero-3-hemiglutarate) rendered the particles surface-charge neutral or slightly anionic at neutral pH, and cationic at mildly acidic pH, as shown by zeta-potential measurements. In HER2-targeted systems, transfection activity and target specificity with HER2-overexpressing SKBR-3 breast cancer cells were dependent on Genosphere surface charge and PEGylation. The highest target specificity correlated with low cationic charge at neutral pH, while incorporation of 5 mol % PEG-lipid had only minor effects on Genosphere-cell association, internalization, and transfection activity. The implications of this work for potential in vivo applications are discussed.

Polymersomes

Polymersomes are self-assembled polymer shells composed of block copolymer amphiphiles. These synthetic amphiphiles have amphiphilicity similar to lipids, but they have much larger molecular weights, so for this reason--along with others reviewed here--comparisons of polymersomes with viral capsids composed of large polypeptide chains are highly appropriate. We summarize the wide range of polymers used to make polymersomes along with descriptions of physical properties such as stability and permeability. We also elaborate on emerging studies of in vivo stealthiness, programmed disassembly for controlled release, targeting in vitro, and tumor-shrinkage in vivo. Comparisons of polymersomes with viral capsids are shown to encompass and inspire many aspects of current designs.

In vitro and in vivo gene-transferring characteristics of novel cationic lipids, DMKD (O,O'-dimyristyl-N-lysyl aspartate) and DMKE (O,O'-dimyristyl-N-lysyl glutamate)

We chemically synthesized two different cationic lipids consisting of a core of lysine, two C-14 hydrocarbon chains, and either aspartatic acid or glutamic acid. The lipids were assigned the acronyms, DMKD and DMKE. Cationic liposomes prepared with the two different lipids were tested for their gene-transferring capabilities in various cell lines compared with that of control DOTAP liposomes. Under the same experimental conditions, the order of in vitro gene transfection efficiency was DMKE>or=DMKD>DOTAP. To identify the parameters influencing transfection efficiency, the DNA-binding affinities of the liposomes were compared and changes in particle size and surface charge were examined after complex formation. Both the DNA-binding affinity of the liposomes and the cell surface-binding affinity of the liposome-pDNA complexes were crucial for gene transfection. In addition, intravenously administered DMKE and DMKD liposomes exhibited different biodistribution characteristics and intensity of in vivo organ transfection from the DOTAP liposomes. Compared to the DOTAP liposomes, they were more readily transferred to the liver. Interestingly, when they were directly injected into tumor tissues, the DMKE lipoplexes were able to induce more efficient transgene expression in these tissues than the DOTAP and DMKD lipoplexes. This study suggests that a small difference in the cationic lipid backbone structure significantly affects gene-transferring capabilities. DMKE and DMKD liposomes can be utilized as efficient gene-transferring vehicles for hepatic or intra-tumoral gene transfection.

In vivo electroporation and ubiquitin promoter--a protocol for sustained gene expression in the lung

BACKGROUND

Gene therapy applications require safe and efficient methods for gene transfer. Present methods are restricted by low efficiency and short duration of transgene expression. In vivo electroporation, a physical method of gene transfer, has evolved as an efficient method in recent years. We present a protocol involving electroporation combined with a long-acting promoter system for gene transfer to the lung.

METHODS

The study was designed to evaluate electroporation-mediated gene transfer to the lung and to analyze a promoter system that allows prolonged transgene expression. A volume of 250 microl of purified plasmid DNA suspended in water was instilled into the left lung of anesthetized rats, followed by left thoracotomy and electroporation of the exposed left lung. Plasmids pCiKlux and pUblux expressing luciferase under the control of the cytomegalovirus immediate-early promoter/enhancer (CMV-IEPE) or human polyubiquitin c (Ubc) promoter were used. Electroporation conditions were optimized with four pulses (200 V/cm, 20 ms at 1 Hz) using flat plate electrodes. The animals were sacrificed at different time points up to day 40, after gene transfer. Gene expression was detected and quantified by bioluminescent reporter imaging (BLI) and relative light units per milligram of protein (RLU/mg) was measured by luminometer for p.Pyralis luciferase and immunohistochemistry, using an anti-luciferase antibody.

RESULTS

Gene expression with the CMV-IEPE promoter was highest 24 h after gene transfer (2932+/-249.4 relative light units (RLU)/mg of total lung protein) and returned to baseline by day 3 (382+/-318 RLU/mg of total lung protein); at day 5 no expression was detected, whereas gene expression under the Ubc promoter was detected up to day 40 (1989+/-710 RLU/mg of total lung protein) with a peak at day 20 (2821+/-2092 RLU/mg of total lung protein). Arterial blood gas (PaO2), histological assessment and cytokine measurements showed no significant toxicity neither at day 1 nor at day 40.

CONCLUSIONS

These results provide evidence that in vivo electroporation is a safe and effective tool for non-viral gene delivery to the lungs. If this method is used in combination with a long-acting promoter system, sustained transgene expression can be achieved.

Genospheres: self-assembling nucleic acid-lipid nanoparticles suitable for targeted gene delivery

We describe the assembly of a cationic lipid-nucleic acid nanoparticle from a liquid monophase containing water and a water miscible organic solvent where both lipid and DNA components are separately soluble prior to their combination. Upon removal of the organic solvent, stable and homogenously sized (70-100 nm) lipid-nucleic acid nanoparticles (Genospheres) were formed. The low accessibility (<15%) of the nanoparticle-encapsulated DNA to a DNA intercalating dye indicated well-protected nucleic acids and high DNA incorporation efficiencies. It was demonstrated that Genospheres could be stably stored under a variety of conditions including a lyophilized state where no appreciable increase in particle size or DNA accessibility was observed following reconstitution. Finally, Genospheres were made target-specific by insertion of an antibody-lipopolymer (anti-HER2 scFv (F5)-PEG-DSPE) conjugate into the particle. The target specificity (>100-fold) in HER2 overexpressing SK-BR-3 breast cancer cells was dependent on the degree of PEGylation, where the incorporation of high amounts of PEG-lipid on the particle surface (up to 5 mol%) had only a minor effect on the transfection activity of the targeted Genospheres. In summary, this work describes a novel, readily scalable method for preparing highly stable immunotargeted nucleic acid delivery vehicles capable of achieving a high degree of specific transfection activity.

Shrinkage of a rapidly growing tumor by drug-loaded polymersomes: pH-triggered release through copolymer degradation

Carrier-mediated delivery of drugs into the cytosol is often limited by either release from the carrier or release from an internalizing endolysosome. Here, loading, delivery, and cytosolic uptake of drug mixtures from degradable polymersomes are shown to exploit both the thick membrane of these block copolymer vesicles and their aqueous lumen as well as pH-triggered release within endolysosomes. Our initial in vivo studies demonstrate growth arrest and shrinkage of rapidly growing tumors after a single intravenous injection of polymersomes composed of poly(ethylene glycol)-polyester. Vesicles are shown to break down into membrane-lytic micelles within hours at 37 degrees C and low pH, although storage at 4 degrees C allows retention of drug for over a month. It is then shown that cell entry of the polymersomes into endolysosomes is followed by copolymer-induced endolysosomal rupture with release of cytotoxic drugs. Above a critical poration concentration (CCPC) that is easily achieved within endolysosomes and that scales with copolymer proportions and molecular weight, the copolymer micelles are seen to disrupt lipid membranes and thereby enhance drug activity. Neutral polymersomes and related macrosurfactant assemblies can thus create novel pathways within cells for controlled release and delivery.

Assembly of nucleic acid-lipid nanoparticles from aqueous-organic monophases

Effective, reproducible, and scalable methods for DNA-lipid assembly are important for the success of non-viral vectors in in vivo gene therapy. We hypothesized DNA-lipid assembly would be optimal if started from a liquid monophase where both DNA and lipids separately form molecular or micellar solutions prior to mixing, without preexisting condensed lipid phases, thus allowing DNA-lipid assembly under conditions close to equilibrium. Previously, we found that mixing plasmid DNA, 1-palmitoyl-2-oleoyl-3-sn-phosphatidylcholine (POPC), cholesterol and a cationic lipid, 1, 2-dioleoyl-3-(trimethylammonio) propane (DOTAP) in 50% (v/v) aqueous ethanol spontaneously produced an optically transparent solution. Upon ethanol removal, DNA-lipid nanoparticles (Genospheres) were formed. For comparison with well-known technologies, different DNA-lipid particles were prepared by interaction of plasmid DNA and stable or ethanol-destabilized lipid vesicles by combining the components in water or 30% (v/v) aqueous ethanol, respectively. Among the three studied DNA-lipid assembly methods, only Genospheres combined the properties of small size (less than or around 100 nm), high incorporation of both lipid and DNA, high degree of DNA protection (dye accessibility 5-12%), a narrow distribution of particle density and when immuno-targeted, the highest transfection efficiency in HER2-overexpressing cells in vitro. We conclude that the Genosphere assembly methodology offers advantages for the development of effective, scalable and targetable non-viral gene delivery vectors.

Targeted gene delivery to cancer cells with nanometric DNA particles enveloped with folic acid using a polymerisable anchor

Progress in the design of gene delivery system is vital for cancer gene therapy since many physiological and intracellular barriers remain. We have developed a technology for condensing genes into nanometric delivery systems. In this paper, we present a novel strategy for decorating 30 nm DNA particles with folic acid for cancer cell recognition. Physicochemical and biological experiments show that these DNA complexes selectively bind to cells expressing the corresponding folic acid receptor.

Reversible mode of binding of serum proteins to DOTAP/cholesterol Lipoplexes: a possible explanation for intravenous lipofection efficiency

There are many indications that interaction of serum proteins with intravenously injected cationic lipoplexes disturbs lipofection in vitro and in vivo. However, transfection with certain lipid compositions such as N-[1- (2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTAP)/cholesterol appears to be more resistant to serum and more efficacious. We investigated the mechanism of interaction between fluorescently labeled lipoplexes of the above composition and fluorescently labeled serum proteins. Fluorescence resonance energy transfer measurements in vitro indicate that serum proteins interact instantly and closely with the DOTAP/cholesterol lipoplexes. In accord with this, preinjection of fluorescently labeled serum into mice before injection of lipoplexes showed an immediate association of proteins with lipoplexes. Serum proteins colocalized with the lipoplexes in the lung vasculature; however, they dissociated from the cationic lipid as soon as 1 hr postinjection, probably because of displacement of serum proteins from lipoplexes by extracellular proteoglycans. Indeed, this displacement was imitated by heparin, a typical glycosaminoglycan, and could be explained by the inability of weakly acidic serum proteins to neutralize the DOTAP/cholesterol electrical surface potential psi0. The stability of the cationic lipid psi0 in serum could be a key reason for the high lung association and transfection efficiency with this formulation.

Increased gene expression by cationic liposomes (TFL-3) in lung metastases following intravenous injection

We recently showed that size, not surface charge, is a major determinant of the in vitro lipofection efficiency of pDNA/TFL-3 complex (lipoplex), even in the presence of serum. In this study, the effect of lipoplex size as a result of interaction with serum proteins on in vitro lipofection and the relationship of this with in vivo lipofection was examined in a murine lung metastasis model. As previously described, the pDNA to lipid ratio (P/L ratio) affected both the size and zeta potential of the lipoplex. In vitro studies also indicated that transgene expression in B16BL6 cells was largely dependent on the size of the lipoplex, both in the absence or presence (50% (v/v)) of serum. An in vivo lipofection experiment showed that predominant gene expression in lungs occurred only in tumor-bearing mice, not in normal mice. Based on the in vitro study, this tumor-related gene expression was not related to lipoplex size in the presence of serum (50% (v/v)), suggesting that the size alteration, as the result of interactions with serum proteins in the blood stream may not play an important role in the case of systemic injections. In addition, the efficient gene expression in tumor-bearing lung was not related to the progression of lung metastases. The area-specific gene expression in tumor-bearing lungs, which was largely dependent on the P/L ratio of the lipoplexes, was observed by fluorescent microscopy. Although the underlying mechanism for the area-specific transgene expression is not clear, it may be related to the interaction of lipoplexes with tumor cells, vascular endothelial cells under angiogenesis and normal cells in the lungs. The possibility that TFL-3 is a useful utility to the targeted delivery of pDNA to lungs and tumor-related lipofection is demonstrated. This result suggests that area-specific gene expression in lung metastases may be achieved by controlling the physicochemical properties of the lipoplex, i.e. the P/L ratio.

Nanoparticle-mediated gene delivery: state of the art

With the development of genomic and proteomic technologies, the prospect for gene therapy has progressed rapidly. This has been partly possible due to the emergence of a diverse array of polymeric and non-polymeric nanoparticles that are being investigated for their ability to deliver genes and drugs. In this review, particles have been pragmatically divided as chitosan-related and chitosan-unrelated nanomaterials. The state of the art in terms of the development, characterisation and evaluation of their in vitro and/or in vivo potential is discussed for each of these various particles. Although substantial progress has been made, the potential of these particles in the clinical arena and human responses remain to be evaluated. It is hoped that this review will provide an impetus for further studies of these particles, with the ultimate intent that one or more of these diverse nanoparticle-based non-viral approaches for gene transfer will translate from 'bench to bedside' in the future.

Novel cationic cardiolipin analogue-based liposome for efficient DNA and small interfering RNA delivery in vitro and in vivo

Cationic liposomes have been successfully used as an alternative approach to viral systems to deliver nucleic acids. However, high toxicity and inconsistent transfection efficiency have been associated with the currently available liposomes. Therefore, a novel cationic liposome was developed based on a synthetic cationic cardiolipin analogue (CCLA) to test the DNA transfection efficiency. This CCLA-based liposome was also used to determine the therapeutic efficacy of c-raf small interfering RNA (siRNA) in mice. In this report, we showed that the CCLA-based liposome was less toxic and effectively transfected reporter genes in vitro and in vivo. The transfection efficiency in mice was seven-fold higher than the commercially available DOTAP-based liposome. In addition, c-raf siRNA in the presence of CCLA-based liposome induced up to 62% of growth inhibition in cancer cells. Treatment of c-raf siRNA/CCLA complex in SCID mice bearing human breast xenograft tumors resulted in 73% of tumor growth suppression as compared to free c-raf siRNA group. In conclusion, a novel CCLA-based liposome showed less toxicity and broad usage both in vitro and in vivo with DNA and siRNA.

Preferential liver gene expression with polypropylenimine dendrimers

Previously, the lower generation (DAB 8-generation 2 and DAB 16-generation 3) polypropylenimine dendrimers have been shown to be effective gene delivery systems in vitro. In the current work, we sought to: (a) test the effect of the strength of the carrier, DNA electrostatic interaction on gene transfer and (b) to study the in vivo gene transfer activity of these low molecular weight (<1687 Da) non-amphiphilic plain and quaternary ammonium gene carriers. Towards this aim, methyl quaternary ammonium derivatives of DAB 4 (generation 1), DAB 8, DAB 16 and DAB 32 (generation 4) were synthesised to give Q4, Q8, Q16 and Q32, respectively. Quaternisation of DAB 8 proved to be critical in improving DNA binding, as evidenced by data from the ethidium bromide exclusion assay and dendrimer-DNA colloidal stability data. This improved colloidal stability had a major effect on vector tolerability, as Q8-DNA formulations were well tolerated on intravenous injection while a similar DAB 8-DNA dose was lethally toxic by the same route. Quaternisation also improved the in vitro cell biocompatibility of DAB 16-DNA and DAB 32-DNA dendrimer complexes by about 4-fold but not that of the lower generation DAB 4-DNA and DAB 8-DNA formulations. In contrast to previous reports with non-viral gene delivery systems, the intravenous administration of DAB 16-DNA and Q8-DNA formulations resulted in liver targeted gene expression as opposed to the lung targeted gene expression obtained with the control polymer-Exgen 500 [linear poly(ethylenimine)] and a lung avoidance hypothesis is postulated. We conclude that the polypropylenimine dendrimers are promising gene delivery systems which may be used to target the liver and avoid the lung and also that molecular modifications conferring colloidal stability on gene delivery formulations have a profound effect on their tolerability on intravenous administration.

Lipid Carrier Systems for Targeted Drug and Gene Delivery

For effective chemotherapy, it is necessary to deliver therapeutic agents selectively to their target sites, since most drugs are associated with both beneficial effects and side effects. The use of lipid dispersion carrier systems, such as lipid emulsions and liposomes, as carriers of lipophilic drugs has attracted particular interest. A drug delivery system can be defined as a methodology for manipulating drug distribution in the body. Since drug distribution depends on the carrier, administration route, particle size of the carrier, lipid composition of the carrier, electric charge of the carrier and ligand density of the targeting carrier, these factors must be optimized. Recently, the lipid carrier system has also been applied to gene delivery systems for gene therapy. However, in both drug and gene medicine cases, a lack of cell-selectivity limits the wide application of this kind of drug and/or gene therapy. Therefore, lipid carrier systems for targeted drug and gene delivery must be developed for the rational therapy. In this review, we shall focus on the progress of research into lipid carrier systems for drug and gene delivery following systemic or local injection.

Enhanced gene expression in lung by a stabilized lipoplex using sodium chloride for complex formation

BACKGROUND

In this study, we investigated the in vivo gene transfection efficacy of a 'surface charge regulated' (SCR) lipoplex, dispersed in the presence of an essential amount of NaCl during lipoplex formation.

METHODS

SCR lipoplexes were prepared and their physicochemical properties were analyzed. After intravenous (i.v.) administration, transfection efficacy, distribution characteristics, and liver toxicity were evaluated in mice.

RESULTS

At NaCl concentrations of 10 mM, the particle sizes of the SCR lipoplexes were about 120 nm and were compatible with a conventional lipoplex. However, fluorescent resonance energy transfer analysis revealed that cationic liposomes in the SCR lipoplexes increased fusion. After i.v. administration, the transfection activity in the lung of the SCR lipoplex (10 mM NaCl solution in the lipoplex) was approximately 10-fold higher than that of the conventional lipoplex. Pharmacokinetic studies demonstrated a higher distribution in lung by the SCR lipoplex. When the gene expression levels of the SCR lipoplex and conventional lipoplex were compared, the SCR lipoplex at a dose of 30 microg was compatible with that of the conventional lipoplex at a dose of 50 microg. A significantly higher serum alanine aminotransferase (ALT) activity and TNFalpha concentration was observed by the conventional lipoplex (pDNA dose; 50 microg), but this was not the case for the SCR lipoplex (pDNA dose; 30 microg).

CONCLUSIONS

We demonstrated that the SCR lipoplex could enhance the transfection efficacy in the lung without increasing the liver toxicity. Hence, the information will be valuable for the future use, design, and development of lipoplexes for in vivo applications.

The role of organ vascularization and lipoplex-serum initial contact in intravenous murine lipofection

Following intravenous administration of cationic lipid-DNA complexes (lipoplexes) into mice, transfection (lipofection) occurs predominantly in the lungs. This was attributed to high entrapment of lipoplexes in the extended lung vascular tree. To determine whether lipofection in other organs could be enhanced by increasing the degree of vascularization, we used a transgenic mouse model with tissue-specific angiogenesis in liver. Tail vein injection of N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTAP)/cholesterol lipoplexes resulted in increased lipoplex entrapment in hypervascularized liver but did not boost luciferase expression, suggesting that lipoplex delivery is not a sufficient condition for efficient organ lipofection. Because the intravenously injected lipoplexes migrated within seconds to lungs, we checked whether the effects of immediate contact with serum correlate with lung lipofection efficiency of different DOTAP-based formulations. Under conditions mimicking the injection environment, the lipoplex-serum interaction was strongly dependent on helper lipid and ionic strength: lipoplexes prepared in 150 mM NaCl or lipoplexes with high (>33 mol%) cholesterol were found to aggregate immediately. This aggregation process was irreversible and was inversely correlated with the percentage of lung cells that took up lipoplexes and with the efficiency of lipofection. No other structural changes in serum were observed for cholesterol-based lipoplexes. Dioleoyl phosphatidylethanolamine-based lipoplexes were found to give low expression, apparently because of an immediate loss of integrity in serum, without lipid-DNA dissociation. Our study suggests that efficient in vivo lipofection is the result of cross-talk between lipoplex composition, interaction with serum, hemodynamics, and target tissue "susceptibility" to transfection.

Biodistribution study of phosphonolipids: a class of non-viral vectors efficient in mice lung-directed gene transfer

BACKGROUND

A multitude of cationic lipids have been synthesized since they were first proposed for use in gene therapy. Cationic lipids are able to efficiently transfect cells both in vitro and in vivo. Whereas most research groups have focused their investigations on the toxicity of these molecules, and on the location of expression of the DNA transferred by these vectors, little has been done to determine their biodistribution and elimination pathways. Our group has developed a family of cationic lipids termed phosphonolipids. Following a large in vitro screening experiment, we have selected several molecules for in vivo testing, with some of these phosphonolipids forming lipoplexes efficient in transfecting mouse lungs. It was thus of interest to study their fate after intravenous injection.

METHODS

The respective biodistributions of both the GLB43 phosphonolipid and plasmid DNA were investigated and compared with DNA expression sites. Using the optimal conditions determined for phosphonolipids, we followed the gene transfer agent and plasmid DNA distributions versus time by radiolabeling them with (14)C and (32)P, respectively. Otherwise, we performed imaging by radiolabeling plasmid DNA with (99m)Tc.

RESULTS

The lipoplexes appear to be directly located in the lung after administration. Secondly, the plasmid is released mainly into the lungs and the phosphonolipid vector is rapidly degraded. The hydrophilic moiety of the phosphonolipid is eliminated in the urine, as is the free plasmid.

CONCLUSIONS

This study reveals that there are slight differences in the observed results depending on the technique used to label the DNA; secondly, results show that the residence time of phosphonolipids in the mouse body is related to the DNA binding time.

Targeting of Synthetic Gene Delivery Systems

Safe, efficient, and specific delivery of therapeutic genes remains an important bottleneck for the development of gene therapy. Synthetic, nonviral systems have a unique pharmaceutical profile with potential advantages for certain applications. Targeting of the synthetic vector improves the specificity of gene medicines through a modulation of the carriers' biodistribution, thus creating a dose differential between healthy tissue and the target site. The biodistribution of current carrier systems is being influenced to a large extent by intrinsic physicochemical characteristics, such as charge and size. Consequently, such nonspecific interactions can interfere with specific targeting, for example, by ligands. Therefore, a carrier complex should ideally be inert, that is, free from intrinsic properties that would bias its distribution away from the target site. Strategies such as coating of DNA carrier complexes with hydrophilic polymers have been used to mask some of these intrinsic targeting effects and avoid nonspecific interactions. Preexisting endogenous ligand-receptor interactions have frequently been used for targeting to certain cell types or tumours. Recently exogenous ligands have been derived from microorganisms or, like antibodies or phage-derived peptides, developed de novo. In animal models, such synthetic vectors have targeted remote sites such as a tumour. Furthermore, the therapeutic proof of the concept has been demonstrated for fitting combinations of synthetic vectors and therapeutic gene.

Recharging cationic DNA complexes with highly charged polyanions for in vitro and in vivo gene delivery

The intravenous delivery of plasmid DNA complexed with either cationic lipids (CL) or polyethyleneimine (PEI) enables high levels of foreign gene expression in lung. However, these cationic DNA complexes cause substantial toxicity. The present study found that the inclusion of polyacrylic acid (pAA) with DNA/polycation and DNA/CL complexes prevented the serum inhibition of the transfection complexes in cultured cells. The mechanism mediating this increase seems to involve both particle size enlargement due to flocculation and electrostatic shielding from opsonizing serum proteins. The use of pAA also increased the levels of lung expression in mice in vivo substantially above the levels achieved with just binary complexes of DNA and linear PEI (lPEI) or CL and reduced their toxicity. Also, the use of a "chaser" injection of pAA 30 min after injection of the ternary DNA/lPEI/pAA complexes further aided this effort to reduce toxicity while not affecting foreign gene expression. By optimizing the amount of pAA, lPEI, and DNA within the ternary complexes and using the "chaser" injection, substantial levels of lung expression were obtained while avoiding adverse effects in lung or liver. These developments will aid the use of cationic DNA complexes in animals and for eventual human gene therapy.

Codelivery of NF-kappaB decoy-related oligodeoxynucleotide improves LPD-mediated systemic gene transfer

A systemic gene delivery vector for LPD (cationic liposome-polycation-DNA) has been reported previously to transfect the pulmonary endothelium and holds promise for treating pulmonary diseases. However, the uptake of LPD by immune cells triggers a strong inflammatory response that is toxic to animals and limits transgene expression. In this study, LPD was used to codeliver phosphorothioate oligodeoxynucleotides (ODNs) containing an NF-kappaB consensus binding sequence with plasmid DNA carrying a reporter gene. Codelivery of a single-stranded kappaB ODN inhibited TNF-alpha induction by LPD-plasmid delivery and increased transgene expression in the lung in a dose-dependent manner. A similar effect was observed with the double-stranded ODN of the same sequence at twice the dose, and the complementary ODN (antisense) had no effect. Sequence mutation study suggested that the effect was sequence specific and these ODNs may achieve their effect through interaction with NF-kappaB family proteins in a decoy manner. In addition to enhancing gene transfer, these single-stranded ODNs formulated in LPD may be explored as anti-inflammatory agents.