Cationic liposome-mediated intravenous gene delivery

A journey into siRNA therapeutics development: A focus on Pharmacokinetics and Pharmacodynamics

siRNA therapeutics are emerging novel modalities targeting highly specific mRNA via RNA interference mechanism. Its unique pharmacokinetics (PKs) and pharmacodynamics (PDs) are significant challenges for clinical use. Furthermore, naked siRNA is a highly soluble macromolecule with a negative charge, making plasma membrane penetration a significant hurdle. It is also vulnerable to nuclease degradation. Therefore, advanced formulation technologies, such as lipid nanoparticles and N-acetylgalactosamine conjugation, have been developed and are now used in clinical practice to enhance target organ delivery and stability. The innate complex biological mechanisms of siRNA, along with its formulation, are major determinants of the PK/PD characteristics of siRNA products. To systematically and quantitatively understand these characteristics, it is essential to develop and utilize quantitative PK/PD models for siRNA therapeutics. In this review, the effects of formulation on the PKs and PK/PD models of approved siRNA products were presented, highlighting the importance of selecting appropriate biomarkers and understanding formulation, PKs, and PDs for quantitative interpreting the relationship between plasma concentration, organ concentration, biomarkers, and efficacy.

Nucleic Acid Delivery to the Vascular Endothelium

This Review examines the state-of-the-art in the delivery of nucleic acid therapies that are directed to the vascular endothelium. First, we review the most important homeostatic functions and properties of the vascular endothelium and summarize the nucleic acid tools that are currently available for gene therapy and nucleic acid delivery. Second, we consider the opportunities available with the endothelium as a therapeutic target and the experimental models that exist to evaluate the potential of those opportunities. Finally, we review the progress to date from investigations that are directly targeting the vascular endothelium: for vascular disease, for peri-transplant therapy, for angiogenic therapies, for pulmonary endothelial disease, and for the blood-brain barrier, ending with a summary of the future outlook in this field.

Liposomes, new carriers for delivery of genes and anticancer drugs: a systematic review

Today, nanoscience has grown and developed in various fields of medicine and treatment, including cancer treatment. Currently, the existing treatments, including chemotherapy and radiotherapy, cause side effects that are unpleasant to the patient. Due to the fact that anticancer drugs cause severe and widespread side effects, liposomes are considered as new drug carriers to minimize the untimely destruction of the drug when it is delivered to the target tissue and to prevent the side effects of toxic drugs. This systematic review study examined the importance of using liposomes as new drug carriers for the delivery of genes and anticancer drugs. The articles published in English in the databases of Google scholar, WoS, PubMed, Embase, Scopus and science direct were reviewed. According to the results of this study, a new targeted nanosystem has been used for loading and delivering anticancer drugs, genes and controlled drug release which has a significant therapeutic effect compared to the same amount of free drug. In general, liposomal systems have been considered because of their capability in preserving the effect of the drug along with reducing the side effects and toxicity of the drug, especially in the case of anticancer drugs. Accumulation of the drug in a target tissue which results in a reduction of the drug entry into other tissues is the main reason for reducing the side effects of these drugs.

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.

From Nanoparticles to Cancer Nanomedicine: Old Problems with New Solutions

Anticancer nanomedicines have been studied over 30 years, but fewer than 10 formulations have been approved for clinical therapy today. Despite abundant options of anticancer drugs, it remains challenging to have agents specifically target cancer cells while reducing collateral toxicity to healthy tissue. Nanocompartments that can be selective toward points deeply within malignant tissues are a promising concept, but the heterogeneity of tumor tissue, inefficiency of cargo loading and releasing, and low uniformity of manufacture required from preclinical to commercialization are major obstacles. Technological advances have been made in this field, creating engineered nanomaterials with improved uniformity, flexibility of cargo loading, diversity of surface modification, and less inducible immune responses. This review highlights the developmental process of approved nanomedicines and the opportunities for novel materials that combine insights of tumors and nanotechnology to develop a more effective nanomedicine for cancer patients.

Liposomes: Advancements and innovation in the manufacturing process

Liposomes are well recognised as effective drug delivery systems, with a range of products approved, including follow on generic products. Current manufacturing processes used to produce liposomes are generally complex multi-batch processes. Furthermore, liposome preparation processes adopted in the laboratory setting do not offer easy translation to large scale production, which may delay the development and adoption of new liposomal systems. To promote advancement and innovation in liposome manufacturing processes, this review considers the range of manufacturing processes available for liposomes, from laboratory scale and scale up, through to large-scale manufacture and evaluates their advantages and limitations. The regulatory considerations associated with the manufacture of liposomes is also discussed. New innovations that support leaner scalable technologies for liposome fabrication are outlined including self-assembling liposome systems and microfluidic production. The critical process attributes that impact on the liposome product attributes are outlined to support potential wider adoption of these innovations.

Durable multitransgene expression in vivo using systemic, nonviral DNA delivery

Recombinant adeno-associated virus (AAV) vectors are transforming therapies for rare human monogenic deficiency diseases. However, adaptive immune responses to AAV and its limited DNA insert capacity, restrict their therapeutic potential. HEDGES (high-level extended duration gene expression system), a nonviral DNA- and liposome-based gene delivery platform, overcomes these limitations in immunocompetent mice. Specifically, one systemic HEDGES injection durably produces therapeutic levels of transgene-encoded human proteins, including FDA-approved cytokines and monoclonal antibodies, without detectable integration into genomic DNA. HEDGES also controls protein production duration from <3 weeks to >1.5 years, does not induce anti-vector immune responses, is reexpressed for prolonged periods following reinjection, and produces only transient minimal toxicity. HEDGES can produce extended therapeutic levels of multiple transgene-encoded therapeutic human proteins from DNA inserts >1.5-fold larger than AAV-based therapeutics, thus creating combinatorial interventions to effectively treat common polygenic diseases driven by multigenic abnormalities.

Development of Targeted siRNA Nanocomplexes to Prevent Fibrosis in Experimental Glaucoma Filtration Surgery

RNAi induced by double-stranded small interfering RNA (siRNA) molecules has attracted great attention as a naturally occurring approach to silence gene expression with high specificity. The myocardin-related transcription factor/serum response factor (MRTF/SRF) pathway is a master regulator of cytoskeletal gene expression and, thus, represents a promising target to prevent fibrosis. A major hurdle to implementing siRNA therapies is the method of delivery, and we have, thus, optimized lipid-peptide-siRNA (LPR) nanoparticles containing MRTF-B siRNAs as a targeted approach to prevent conjunctival fibrosis. We tested 15 LPR nanoparticle formulations with different lipid compositions, surface charges, and targeting or non-targeting peptides in human conjunctival fibroblasts. In vitro, the LPR formulation of the DOTMA/DOPE lipid with the targeting peptide Y (LYR) was the most efficient in MRTF-B gene silencing and non-cytotoxic compared to the non-targeting formulation. In vivo, subconjunctival administration of LYR nanoparticles containing MRTF-B siRNAs doubled bleb survival in a pre-clinical rabbit model of glaucoma filtration surgery. Furthermore, MRTF-B LYR nanoparticles reduced the MRTF-B mRNA by 29.6% in rabbit conjunctival tissues, which led to significantly decreased conjunctival scarring with no adverse side effects. LYR-mediated delivery of siRNA shows promising results to increase bleb survival and to prevent conjunctival fibrosis after glaucoma filtration surgery.

Lipoplex-Mediated Deintercalation of Doxorubicin from Calf Thymus DNA-Doxorubicin Complex

In this paper, we report the lipoplex-mediated deintercalation of anticancer drug doxorubicin (DOX) from the DOX-DNA complex under controlled experimental conditions. We used three zwitterionic liposomes, namely, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC), which are widely different in their phase transition temperatures to form a lipoplex with calf thymus DNA in the presence of Ca(2+) ions. The study revealed that DPPC being in sol-gel phase was more effective in releasing the drug from the DOX-DNA complex compared with liposomes that remain in liquid crystalline phase (DMPC and POPC). The higher extent of drug release in the case of DPPC liposomes was attributed to the stronger lipoplex formation with DNA as compared with that of other liposomes. Owing to the relatively smaller head group area, the DPPC liposomes in their sol-gel phase can absorb a larger number of Ca(2+) ions and hence offer a strong electrostatic interaction with DNA. This interaction was confirmed by time-resolved anisotropy and circular dichroism spectroscopy. Apart from the electrostatic interaction, the possible hydrophobic interaction between the liposomes and DNA was also taken into account for the observed deintercalation. The successful uptake of drug molecules by liposomes from the drug-DNA complex in the post-release period was also confirmed using confocal laser scanning microscopy (CLSM).

Evaluation of New Fluorescent Lipophosphoramidates for Gene Transfer and Biodistribution Studies after Systemic Administration

The objective of lung gene therapy is to reach the respiratory epithelial cells in order to deliver a functional nucleic acid sequence. To improve the synthetic carrier's efficacy, knowledge of their biodistribution and elimination pathways, as well as cellular barriers faced, depending on the administration route, is necessary. Indeed, the in vivo fate guides the adaptation of their chemical structure and formulation to increase their transfection capacity while maintaining their tolerance. With this goal, lipidic fluorescent probes were synthesized and formulated with cationic lipophosphoramidate KLN47 (KLN: Karine Le Ny). We found that such formulations present constant compaction properties and similar transfection results without inducing additional cytotoxicity. Next, biodistribution profiles of pegylated and unpegylated lipoplexes were compared after systemic injection in mice. Pegylation of complexes led to a prolonged circulation in the bloodstream, whereas their in vivo bioluminescent expression profiles were similar. Moreover, systemic administration of pegylated lipoplexes resulted in a transient liver toxicity. These results indicate that these new fluorescent compounds could be added into lipoplexes in small amounts without perturbing the transfection capacities of the formulations. Such additional properties allow exploration of the in vivo biodistribution profiles of synthetic carriers as well as the expression intensity of the reporter gene.

Efficient in vivo transfection and safety profile of a CpG-free and codon optimized luciferase plasmid using a cationic lipophosphoramidate in a multiple intravenous administration procedure

As any drug, the success of gene therapy is largely dependent on the vehicle that has to selectively and efficiently deliver therapeutic nucleic acids into targeted cells with minimal side-effects. In the case of chronic diseases that require a life-long treatment, non-viral gene delivery vehicles are less likely to induce an immune response, thereby allowing for repeated administration. Beyond the gene delivery efficiency of a given vector, the nature of nucleic acid constructs also has a central importance in gene therapy protocols. Herein, we investigated the impact of two firefly luciferase encoding plasmids on the transgene expression profile following systemic delivery of lipoplexes in mice, as well as their potential to be safely and efficiently readministered. Whereas pTG11033 plasmid is driven by a strong ubiquitous cytomegalovirus promoter, pGM144 plasmid, which has been designed to avoid inflammation and provide sustained transgene expression in lungs, is CpG-free and is under control of the human elongation factor-1 alpha promoter. Combined to the efficient cationic lipophosphoramidate BSV4, bioluminescence data showed that both plasmids were mostly expressed in the lungs of mice following a primary injection of lipoplexes. However, mice transfected with pGM144 exhibited a higher and more sustained transgene expression than those treated with pTG11033. Repeated administration studies revealed that several injections of lipoplexes could lead to similar transgene expression profiles if an interval of several weeks between subsequent injections was respected. A transient hepatotoxicity and a partial inflammatory response were caused by lipoplex injection, irrespective of the plasmid used. Altogether, these results indicate that repeated systemic administration of lipophosphoramidate-based lipoplexes in mice conducts to an effective lung transfection without serious side effects, and highlight the need to use long-lasting expressing and well tolerated plasmids in order to efficiently renew transgene expression by the successive doses.

Optimizing cationic and neutral lipids for efficient gene delivery at high serum content

BACKGROUND

Cationic liposome (CL)-DNA complexes are promising gene delivery vectors with potential application in gene therapy. A key challenge in creating CL-DNA complexes for application is that their transfection efficiency (TE) is adversely affected by serum. In particular, little is known about the effects of a high serum content on TE, even though this may provide design guidelines for application in vivo.

METHODS

We prepared CL-DNA complexes in which we varied the neutral lipid [1,2-dioleoyl-sn-glycerophosphatidylcholine, glycerol-monooleate (GMO), cholesterol], the headgroup charge and chemical structure of the cationic lipid, and the ratio of neutral to cationic lipid; we then measured the TE of these complexes as a function of serum content and assessed their cytotoxicity. We tested selected formulations in two human cancer cell lines (M21/melanoma and PC-3/prostate cancer).

RESULTS

In the absence of serum, all CL-DNA complexes of custom-synthesized multivalent lipids show high TE. Certain combinations of multivalent lipids and neutral lipids, such as MVL5(5+)/GMO-DNA complexes or complexes based on the dendritic-headgroup lipid TMVLG3(8+) exhibited high TE both in the absence and presence of serum. Although their TE still dropped to a small extent in the presence of serum, it reached or surpassed that of benchmark commercial transfection reagents, particularly at a high serum content.

CONCLUSIONS

Two-component vectors (one multivalent cationic lipid and one neutral lipid) can rival or surpass benchmark reagents at low and high serum contents (up to 50%, v/v). We propose guidelines for optimizing the serum resistance of CL-DNA complexes based on a given cationic lipid.

Current progress in gene delivery technology based on chemical methods and nano-carriers

Gene transfer methods are promising in the field of gene therapy. Current methods for gene transfer include three major groups: viral, physical and chemical methods. This review mainly summarizes development of several types of chemical methods for gene transfer in vitro and in vivo by means of nano-carriers like; calcium phosphates, lipids, and cationic polymers including chitosan, polyethylenimine, polyamidoamine dendrimers, and poly(lactide-co-glycolide). This review also briefly introduces applications of these chemical methods for gene delivery.

Hyaluronic acid-bearing lipoplexes: physico-chemical characterization and in vitro targeting of the CD44 receptor

The mechanism by which hyaluronic acid (HA)-bearing lipoplexes target the A549 lung cancer cell line was evaluated. For this purpose, cationic liposomes targeting the CD44 receptor were designed thanks to the incorporation in their composition of a conjugate between high molecular weight HA and the lipid DOPE (HA-DOPE). Liposomes containing HA-DOPE were complexed at different lipids:DNA ratios with a reporter plasmid encoding the green fluorescent protein (GFP). Diameter, zeta potential, lipoplex stability and DNA protection from nucleases have been determined. Lipids:DNA ratios of 2, 4 and 6 provided a diameter around 250 nm with a zeta potential of -30 mV. The strength of lipids:DNA interaction and the fraction of DNA protected from enzymatic degradation increased with the lipids:DNA ratio. 2D-immunoelectrophoresis demonstrated the low capacity to activate the C3 fraction of the complement system of any of these three ratios, with and without HA-DOPE. Transfection efficiency in the presence of 0, 10 and 15% of HA-DOPE or unconjugated HA, was determined on the CD44-expressing A549 cells by flow cytometry. Lipoplexes at a lipids:DNA ratio of 2 containing 10% (w/w) of HA-DOPE were the most efficient for transfection. The maximal level of GFP expression was obtained after 6h of incubation demonstrating a slow transfection kinetics of lipoplexes. Finally, lipoplex cellular uptake, measured indirectly by the level of transfection using flow cytometry and validated by fluorescence microscopy, was shown to be mediated by the CD44 receptor and caveolae. These results demonstrate the strong specificity of DNA targeting through the CD44 receptor using HA of high molecular weight as a ligand.

Combined lentiviral and RNAi technologies for the delivery and permanent silencing of the hsp25 gene

Elevated heat shock protein 27 (Hsp27) expression has been found in a number of tumors, including breast, prostate, gastric, uterine, ovarian, head and neck, and tumor arising from the nervous system and urinary system, and determined to be a predictor of poor clinical outcome. Although the mechanism of action of Hsp27 has been well documented, there are currently no available inhibitors of Hsp27 in clinical trials. RNA interference (RNAi) has the potential to offer more specificity and flexibility than traditional drugs to silence gene expression. Not surprisingly, RNAi has become a major focus for biotechnology and pharmaceutical companies, which are now in the early stages of developing RNAi therapeutics, mostly based on short interfering RNA (siRNAs), to target viral infection, cancer, hypercholesterolemia, cardiovascular disease, macular degeneration, and neurodegenerative diseases. However, the critical issues associated with RNAi as a therapeutic are delivery, specificity, and stability of the RNAi reagents. To date, the delivery is currently considered the biggest hurdle, as the introduction of siRNAs systemically into body fluids can result in their degradation, off-target effects, and immune detection. In this chapter, we discuss a method of combined lentiviral and RNAi-based technology for the delivery and permanent silencing of the hsp25 gene.

Gene therapy for ALI/ARDS

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by acute respiratory failure and are associated with diverse disorders. Gene therapy is a potentially powerful approach to treat diseases related to ALI/ARDS, and numerous viral and nonviral methods for gene delivery to the lung have been developed. Discussed are recent advances in the development of more efficient viral and nonviral gene transfer systems, and the current status of gene therapy applied to ALI/ARDS-associated pulmonary diseases is reviewed. With the development of more efficient gene therapy vectors, gene therapy is a promising strategy for clinical application.

Influence of cationic lipid composition on gene silencing properties of lipid nanoparticle formulations of siRNA in antigen-presenting cells

Lipid nanoparticles (LNPs) are currently the most effective in vivo delivery systems for silencing target genes in hepatocytes employing small interfering RNA. Antigen-presenting cells (APCs) are also potential targets for LNP siRNA. We examined the uptake, intracellular trafficking, and gene silencing potency in primary bone marrow macrophages (bmMΦ) and dendritic cells of siRNA formulated in LNPs containing four different ionizable cationic lipids namely DLinDAP, DLinDMA, DLinK-DMA, and DLinKC2-DMA. LNPs containing DLinKC2-DMA were the most potent formulations as determined by their ability to inhibit the production of GAPDH target protein. Also, LNPs containing DLinKC2-DMA were the most potent intracellular delivery agents as indicated by confocal studies of endosomal versus cytoplamic siRNA location using fluorescently labeled siRNA. DLinK-DMA and DLinKC2-DMA formulations exhibited improved gene silencing potencies relative to DLinDMA but were less toxic. In vivo results showed that LNP siRNA systems containing DLinKC2-DMA are effective agents for silencing GAPDH in APCs in the spleen and peritoneal cavity following systemic administration. Gene silencing in APCs was RNAi mediated and the use of larger LNPs resulted in substantially reduced hepatocyte silencing, while similar efficacy was maintained in APCs. These results are discussed with regard to the potential of LNP siRNA formulations to treat immunologically mediated diseases.

Type and composition of surfactants mediating gene transfection of polyethylenimine-coated liposomes

Background:

The objective of this study was to compare the transfection efficiency of anionic liposomes coated with polyethylenimine (PEI) with that of PEI and Lipofectamine 2000^™ using the plasmid DNA encoding green fluorescent protein in a human hepatoma (Huh7) cell line.

Methods:

Factors affecting transfection efficiency, including type of surfactant, ratio of phosphatidylcholine (PC)/surfactant, carrier/DNA weight ratio, and the presence of serum have been investigated. Anionic liposomes, composed of PC and anionic surfactants, ie, sodium oleate (NaO), sodium taurocholate (NaT), or zwitterionic surfactant (3-[{3-cholamidopropyl}-dimethylammonio]-1-propanesulfonate, CHAPS) at molar ratios of 10:1, 10:1.5, and 10:2 were prepared by the sonication method. Subsequently, they were coated with PEI to produce polycationic liposomes (PCL).

Results:

PCL was able to condense with pDNA depending on the PCL/DNA weight ratio. PCL composed of PC:NaO (10:2) showed higher transfection efficiency than NaT and CHAPS at all weight ratios tested. Higher transfection efficiency and gene expression were observed when the carrier/DNA weight ratio increased. The highest transfection efficiency was found at a weight ratio of 0.5.

Conclusion:

This PCL showed remarkably high transfection efficiency with low cytotoxicity to Huh7 cells in vitro, in comparison with PEI and Lipofectamine 2000.

Gene delivery system based on highly specific recognition of surface-vimentin with N-acetylglucosamine immobilized polyethylenimine

Gene and drug-delivery systems that use immobilization of carbohydrates are useful for the specific targeting of lectin-expressing tissues. Here, we report that N-acetylglucosamine (GlcNAc) with polyethylenimine (GlcNAc-PEI) specifically interacted with vimentin-expressing cells such as 293FT and HeLa cells. Recently, the intermediate filaments vimentin and desmin have been reported to have GlcNAc-binding lectin-like properties on the cell surface. Therefore, GlcNAc-conjugated agents can be targeted to vimentin- and desmin-expressing cells and tissues. Vimentin-expressing 293FT and HeLa cells were efficiently transfected with green fluorescent protein and luciferase genes by using GlcNAc-PEI; the expression of these genes in vimentin-knockdown cells were low. Confocal microscopic analysis showed that GlcNAc-PEI complexes interacted with vimentin on the cell surface of HeLa cells. These results demonstrate that GlcNAc-PEI/DNA complexes were specifically taken up by 293FT and HeLa cells via vimentin. We suggest that this gene-delivery system could be used to target various vimentin-expressing cells such as fibroblasts and tumor cells.

Optimization of DNA delivery by three classes of hybrid nanoparticle/DNA complexes

Plasmid DNA encoding a luciferase reporter gene was complexed with each of six different hybrid nanoparticles (NPs) synthesized from mixtures of poly (D, L-lactide-co-glycolide acid) (PLGA 50:50) and the cationic lipids DOTAP (1, 2-Dioleoyl-3-Trimethyammonium-Propane) or DC-Chol {3β-[N-(N', N'-Dimethylaminoethane)-carbamyl] Cholesterol}. Particles were 100-400 nm in diameter and the resulting complexes had DNA adsorbed on the surface (out), encapsulated (in), or DNA adsorbed and encapsulated (both). A luciferase reporter assay was used to quantify DNA expression in 293 cells for the uptake of six different NP/DNA complexes. Optimal DNA delivery occurred for 10⁵ cells over a range of 500 ng - 10 μg of NPs containing 20-30 μg DNA per 1 mg of NPs. Uptake of DNA from NP/DNA complexes was found to be 500-600 times as efficient as unbound DNA. Regression analysis was performed and lines were drawn for DNA uptake over a four week interval. NP/DNA complexes with adsorbed NPs (out) showed a large initial uptake followed by a steep slope of DNA decline and large angle of declination; lines from uptake of adsorbed and encapsulated NPs (both) also exhibited a large initial uptake but was followed by a gradual slope of DNA decline and small angle of declination, indicating longer times of luciferase expression in 293 cells. NPs with encapsulated DNA only (in), gave an intermediate activity. The latter two effects were best seen with DOTAP-NPs while the former was best seen with DC-Chol-NPs. These results provide optimal conditions for using different hybrid NP/DNA complexes in vitro and in the future, will be tested in vivo.

Lipid-based nanotherapeutics for siRNA delivery

RNA interference (RNAi) is a specific gene-silencing mechanism triggered by small interfering RNA (siRNA). The application of RNAi in the clinic requires the development of safe and effective delivery systems. Inspired by progress with lipid-based systems in drug delivery, efforts have been dedicated to the development of liposomal siRNA delivery systems. Many of the lipid-based delivery vehicles self-assemble with siRNA through electrostatic interactions with charged amines, generating multi-lamellar lipoplexes with positively charged lipid bilayers separated from one another by sheets of negatively charged siRNA strands. Internalization of lipid-based siRNA delivery systems into cells typically occurs through endocytosis; accordingly, delivery requires materials that can facilitate endosomal escape. The size of the carrier is important as carriers <100 nm in diameter have been reported to have higher accumulation levels in tumours, hepatocytes and inflamed tissue, whereas larger particles tend to be taken up by Kupffer cells or other components of the reticuloendothelial system (RES). To reduce RES uptake and increase circulation time, carriers have been modified on the surface with hydrophilic materials, such as polyethyleneglycol. Herein, we review the molecular and structural parameters of lipid-based siRNA delivery systems.

Lipoplexes targeting the CD44 hyaluronic acid receptor for efficient transfection of breast cancer cells

Lipoplexes containing a hyaluronic acid-dioleoylphosphatidylethanolamine (HA-DOPE) conjugate were designed to target the CD44 receptor on breast cancer cells. Cationic liposomes composed of a mixture of [2-(2,3-didodecyloxypropyl)hydroxyethyl]ammonium bromide (DE) and dioleoylphosphatidylethanolamine (DOPE) with or without HA-DOPE were prepared, characterized, and used to form a complex with plasmid DNA pCMV-luc. Lipoplexes displayed a negative zeta potential and a mean diameter between 250-300 nm. Cytotoxicity and transfection efficiency of the lipoplexes were determined on the MDA-MB-231and MCF-7 breast cancer cell lines. Cytotoxicity was not modified by the presence of HA-DOPE. However HA-DOPE increased the level of transfection on CD44-expressing MDA-MB-231 cells compared to the MCF-7 line, which expresses very low levels of CD44. The transfection on the MDA-MB-231 cells was highly inhibited by anti-CD44 Hermes-1 antibody but not by the nonspecific anti-ErbB2 antibody. In conclusion, cationic liposomes containing the HA-DOPE conjugate mediated good transfection on CD44 expressing cell lines in culture.

Gene Transfer Mediated by Sphingosine/ Dioleoylphosphatidylethanolamine Liposomes in the Presence of Poloxamer 188

A cationic liposome system consisting of sphingosine (SP) and dioleoylphosphatidylethanolamine (DOPE) was developed for in vitro and in vivo gene transfer. A nonionic surface active agent of poloxamer 188 was incorporated in the formulations to stabilize the DNA/liposome complex. Comparison of the results obtained from systems with and without the effect of poloxamer 188 was made to investigate the efficiency of gene expression. In vitro transfection study of the DNA/liposome complex showed that with the effect of poloxamer 188, gene transfer into some cell lines was enhanced. In vivo systemic delivery of the DNA/liposome complex with poloxamer 188 demonstrated gene expression with improved luciferase activity in all major organs including lung, spleen, heart, liver, and kidney. High level transgene activity was found in lung and spleen with prolonged gene expression. This was attributed to poloxamer 188 that stabilized the liposome system and produced homogeneous DNA/liposome complex for enhancement of gene delivery.

Tumor targeting using liposomal antineoplastic drugs

During the last years, liposomes (microparticulate phospholipid vesicles) have been used with growing success as pharmaceutical carriers for antineoplastic drugs. Fields of application include lipid-based formulations to enhance the solubility of poorly soluble antitumor drugs, the use of pegylated liposomes for passive targeting of solid tumors as well as vector-conjugated liposomal carriers for active targeting of tumor tissue. Such formulation and drug targeting strategies enhance the effectiveness of anticancer chemotherapy and reduce at the same time the risk of toxic side-effects. The present article reviews the principles of different liposomal technologies and discusses current trends in this field of research.

Liposome-nucleic acid immunotherapeutics

Cationic liposome-nucleic acid complexes, which were originally developed for use as non-viral gene delivery vectors, may now have an equally important application as immunotherapeutic drugs. Recent studies have highlighted the ability of cationic liposomes to potently activate the innate immune system when used to deliver certain Toll-like receptor (TLR) agonists. The immune-enhancing properties of cationic liposomes have been most clearly demonstrated when combined with nucleic acid agonists for endosomally located TLRs, including TLR3, TLR7/8 and TLR9. Immune potentiation by cationic liposomes likely results from the combined effects of endosomal targeting, protection of nucleic acids from extracellular degradation, and from signaling via newly identified cytoplasmic receptors for nucleic acids. The potent innate immune stimulatory properties of liposome-nucleic acid complexes make them particularly attractive as non-specific immunotherapeutics and as vaccine adjuvants. Liposome-nucleic acid complexes have demonstrated impressive anticancer activity in a number of different animal tumor models. Moreover, liposome-nucleic acid complexes have also been shown to be effective for immunotherapy of acute viral and bacterial infections, as well as chronic fungal infections. When used as vaccine adjuvants, liposome-nucleic acid complexes target antigens for efficient uptake by dendritic cells and are particularly effective in eliciting CD8(+) T-cell responses to protein antigens. Thus, liposome-nucleic acid complexes form a potent and versatile immunotherapeutic platform.

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.

Innate immune response induced by gene delivery vectors

Gene therapy is a clinical strategy that has the potential to treat an array of genetic and nongenetic diseases. Vectors for gene transfer are the essential tools of gene therapy. For gene therapy to be successful, an appropriate amount of the therapeutic gene must be delivered into the target cells without substantial toxicity. A major limitation of the use of gene therapy vectors is the innate immune responses triggered by systemic administration of such vectors. It is essential to overcome vector-mediated innate immune responses, such as production of inflammatory cytokines, the maturation of antigen-presenting cells and tissue damage, because the induction of these responses not only shortens the period of gene expression but also leads to serious side effects. Viral vectors (for example, adenovirus (Ad) vectors) have been assumed to be more potent in inducing innate immune responses in spite of their high transduction efficiency since they contain pathogenic proteins. However, recent studies have demonstrated that not only viral vectors but also nonviral vectors, such as lipoplex (liposome/plasmid DNA complex), can induce innate immune responses. Indeed, nonviral vectors including lipoplex induce comparable or larger levels of innate immune response than viral vectors. In this review, we present an overview of the innate immune responses induced by Ad vector and lipoplex, which are used primarily for in vivo gene transfer.

Imaging the modulation of adenoviral kinetics and biodistribution for cancer gene therapy

To explore systemic utilization of Epstein-Barr virus (EBV)-specific transcriptionally targeted adenoviruses, three vectors were constructed to examine kinetics, specificity, and biodistribution: adv.oriP.luc, expressing luciferase under EBV-specific control; adv.SV40luc, expressing luciferase constitutively; and adv.oriP.E1A.oriP.luc, a conditionally replicating adenovirus, expressing both luciferase and E1A. Bioluminescence imaging (BLI) was conducted on tumor-bearing severe combined immunodeficient (SCID) mice (C666-1, EBV-positive human nasopharyngeal cancer) treated intravenously (i.v.) with 3 x 10(8) infectious units (ifu) of the adenoviral vectors. At 72 hours, adv.oriPluc demonstrated an 8.4-fold higher tumor signal than adv.SV40luc; adv.oriP.E1A.oriP.luc was 26.7-fold higher; however, a significant liver signal was also observed, necessitating further action to improve biodistribution. Several compounds were examined to this end, including norepinephrine, serotonin, clodronate liposomes, and STI571, to determine whether any of these measures could improve adenoviral biodistribution. Each of these interventions was assessed using BLI in mice i.v. injected with adv.oriP.luc. STI571 achieved the highest increase in tumor-to-liver ratio (TLR; 6.6-fold), which was associated with a 59% reduction in tumor interstitial fluid pressure (IFP) along with a decrease in platelet-derived growth factor-beta receptor (PDGF beta R) activation. This study reports the favorable modulation by STI571 of the biodistribution of adenoviral vectors, providing a potential approach to improving therapeutic outcome.

Comparison of gene expression efficiency and innate immune response induced by Ad vector and lipoplex

Vectors for gene expression are the essential tools for both gene therapy and basic research. There are two groups of gene therapy vectors, viral and non-viral vectors. At present, toxicity triggered by vectors is one of the major concerns for clinical trials. In general, non-viral vectors, such as plasmid DNA-cationic liposome complex (lipoplex), are thought to be safer than viral vectors, such as adenovirus (Ad) vector, although lipoplex is less efficient in term of gene expression than the Ad vector. However, there has been no study directly comparing the gene expression efficiency and safety of viral and non-viral vectors. Here, we present evidence that the Ad vector shows much more efficient gene expression and is safer than lipoplex, at least with respect to the innate immune response. After being systemically administered to mice, the Ad vector showed a transduction efficiency that was 2 to 5 log orders higher than that of lipoplex, depending on the organ. On the other hand, surprisingly, the administration of lipoplex produced a greater amount of inflammatory cytokines such as interleukin-6, interleukin-12, and tumor necrosis factor-alpha than did the administration of the Ad vector, whereas a comparable level of hepatotoxicity was induced by these vectors. The production of inflammatory cytokines induced by the injection of lipoplex was reduced when the CpG motifs were removed completely from plasmid DNA. Thus, care should be taken to ensure the innate immune response induced by gene therapy vectors, especially lipoplex.

Intracellular trafficking is the important process that determines the optimal charge ratio on transfection by galactosylated lipoplex in HEPG2 cells

The purpose of the present study was to gain insight into the major factors affecting transfection efficiency with galactosylated lipoplex in HepG2 cells. In this study, lipoplex and galactosylated lipoplex were examined at different charge ratios (- : +): 1.0 : 1.2, 1.0 : 2.3, 1.0 : 3.1, 1.0 : 4.7, and 1.0 : 7.0. The particle size and zeta potential of the both lipoplexes was dependent on the charge ratio. Cellular uptake was evaluated by using [(32)P]-labeled pCMV-Luc and this showed that the cellular uptake of galactosylated lipoplex was significantly higher than that of lipoplex at a charge ratio ranging from 1.0 : 2.3 to 1.0 : 7.0. As the charge ratio increased in both lipoplexes, the apparent cellular uptake increased. Transfection activity by galactosylated lipoplex was significantly higher than that by lipoplex except at a charge ratio of 1.0 : 7.0. The optimal charge ratio for transfection efficacy was 1.0 : 2.3 and transfection was reduced at higher charge ratios. Both lipoplexes exhibited no significant cytotoxicity at any charge ratio. In conclusion, it is suggested that intracellular trafficking, rather than the degree of uptake and cytotoxicity, is the important process that determines the optimal charge ratio of galactosylated lipoplex in HepG2 cells.

Inhibition of pulmonary metastasis in mice by all-trans retinoic acid incorporated in cationic liposomes

The purpose of this study was to investigate whether all-trans retinoic acid (ATRA), an active metabolite of retinal, incorporated in cationic liposomes composed of 1,2 dioleoyl-3-trimethylammonium propane (DOTAP)/cholesterol could inhibit established metastatic lung tumors by delivery to the pulmonary tumor site after intravenous injection. After intravenous injection in mice, the highest lung accumulation of [(3)H]ATRA was observed by the DOTAP/cholesterol liposomes formulation, while other formulations including [(3)H]ATRA dissolved in serum or [(3)H]ATRA incorporated in distearoyl-l-phosphatidylcholine (DSPC)/cholesterol liposomes produced little accumulation in the lung. In mice used as a model of lung cancer metastasis, ATRA incorporated in DOTAP/cholesterol liposomes, injected intravenously, reduced the number of tumor nodules compared with free ATRA or ATRA incorporated in DSPC/cholesterol liposomes. These results suggest that ATRA incorporated in cationic liposomes would be an effective strategy for differentiation therapy of lung cancer metastasis.

Systemic co-administration of depsipeptide selectively targets transfection enhancement to specific tissues and cell types

Depsipeptide, a histone deacetylase (HDAC) inhibitor, kills tumor cells much more effectively than normal cells, and can produce significant antitumor activity in human cancer patients. Depsipeptide also increases the expression of lipoplex-delivered genes in cultured tumor cells, as well as following direct intra-tumoral injection. We now show that co-intravenous (i.v.) injection of depsipeptide with polyethylenimine (PEI):DNA complexes significantly increases the expression of PEI-delivered genes in normal, as well as in tumor-bearing mice. At the tissue level, depsipeptide-mediated enhancement of gene expression was selectively targeted to the lung, liver and spleen. At the cellular level, depsipeptide significantly increased the expression of the i.v., PEI co-delivered wild-type human p53 gene in metastatic breast cancer cells, but not in adjacent normal cells. Thus, the ability of depsipeptide to enhance the expression of systemically delivered genes is selectively targeted at both the tissue and cellular levels, without requiring the use of ligand- or promoter-based approaches. Analyzing HDAC-based targeting of gene expression may identify host genes that control the expression of systemically delivered genes.

Vaccination with liposome--DNA complexes elicits enhanced antitumor immunity

Cationic liposomes have been shown to potentiate markedly the ability of plasmid DNA to activate innate immune responses. We reasoned therefore that liposome-DNA complexes (LDC) could be used to produce more effective plasmid DNA vaccines for cancer. To test this hypothesis, tumor-bearing mice were vaccinated with conventional plasmid DNA vaccines or with LDC vaccines encoding model tumor antigens and CD8(+) T-cell responses and antitumor activity were assessed. We found that although plasmid DNA vaccines generated large increases in antigen-specific CD8(+) T cells, they failed to elicit significant antitumor immunity. In contrast, LDC vaccines elicited large numbers of antigen-specific CD8(+) T cells and also generated significant antitumor activity against established tumors. The antitumor activity elicited by immunization with LDC vaccines was mediated primarily by CD8(+) T cells. Studies of the interaction of LDC with antigen-presenting cells found that LDC triggered dendritic cell production of interleukin-12 and interferon (IFN)-gamma production by natural killer cells in vivo. Activation by LDC was also accompanied by upregulation of costimulatory molecule expression. These findings suggest that by concurrently activating strong systemic innate immune responses and generating cytotoxic T-lymphocyte responses, LDC may be used to increase the effectiveness of therapeutic plasmid DNA vaccination for cancer.