Gene delivery by lipoplexes and polyplexes

Biomaterial Scaffolds for Controlled, Localized Gene Delivery of Regenerative Factors

SIGNIFICANCE

Biomaterials play central roles in tissue regeneration by maintaining a space for tissue growth and facilitating its integration with the host. The regenerative capacity of materials can be enhanced through delivery of factors that promote tissue formation. Gene delivery is a versatile strategy to obtain sustained production of tissue inductive factors. Biomaterial scaffolds capable of gene delivery have been shown to induce transgene expression and tissue growth.

CRITICAL ISSUES

The widespread application of biomaterial scaffold systems requires identifying the design principles for the material and vectors that modulate transgene expression temporally and spatially. These technologies and others will ultimately enable spatial and temporal control over expression to recreate the cellular organization and gene expression required for formation of complex tissues.

RECENT ADVANCES

The design parameters for the biomaterials and vectors that modulate the extent and duration of transgene expression and the distribution of transgene-expressing cells within and around the injury are emerging. The cellular interactions with the biomaterial, such as adhesion or migration rate, can influence expression. Furthermore, modulating the interaction between the vector and biomaterial can control vector release while minimizing the exposure to harsh processing conditions.

FUTURE DIRECTIONS

Biomaterial scaffolds that deliver genes encoding for regenerative factors may provide a platform for regenerating complex tissues such as skin, blood vessels, and nerves. Biomaterials capable of localized gene delivery can synergistically target multiple cell processes and will have application to the regeneration of many tissues, with great promise for clinical therapies.

Dendrimers for siRNA Delivery

Since the discovery of the “starburst polymer”, later renamed as dendrimer, this class of polymers has gained considerable attention for numerous biomedical applications, due mainly to the unique characteristics of this macromolecule, including its monodispersity, uniformity, and the presence of numerous functionalizable terminal groups. In recent years, dendrimers have been studied extensively for their potential application as carriers for nucleic acid therapeutics, which utilize the cationic charge of the dendrimers for effective dendrimer-nucleic acid condensation. siRNA is considered a promising, versatile tool among various RNAi-based therapeutics, which can effectively regulate gene expression if delivered successfully inside the cells. This review reports on the advancements in the development of dendrimers as siRNA carriers.

Oligonucleotides and polynucleotides condensation onto liposome surface: effects of the base and of the nucleotide length

The association behavior of different nucleic acids with cationic liposomes has been monitored, in order to find out how the polymer length, the type of base and the charge density affect the lipoplex formation. In particular the associative features displayed by the homopolymer 20-mer of adenine, Oligo (dA), of timine, Oligo (dT), and of guanine, Oligo (dG), were compared to understand the role of the base. The effects of the nucleic acid length and of the charge density were evaluated taking account of the association of the polyadenylic acid and of the DNA onto the liposomes. The results show that the homopolymer Oligo (dG) is able to interact with the cationic liposomes to the same extent as DNA, in spite of the fact that Oligo (dG) is a short polymer made of 20 residues and DNA is a longer and dual strand polymer having a higher charge density.

In vitro transfection mediated by dendrigraft poly(L-lysines): the effect of structure and molecule size

Dendritic poly(L-lysines) (DGL) constitute promising nanomaterials applicable as a nonviral gene-delivery vector. In this study, we evaluate the transfection abilities of four DGL generations with special emphasis on the systematic description of the relationship of how generation (i.e., molecule size) affects the transfection efficacy. Using Hep2 cells, we demonstrated that the capability of unmodified DGL to deliver plasmid is of a magnitude lower than that of jetPEI. On the other hand, employing the Hep2 cell line stably transduced with eGFP, we observed that DGL G5 delivers the siRNA oligonucleotide with the same efficiency as Lipofectamine 2000. In further experiments, it was shown that DGL affords excellent ability to bind DNA, protect it against DNase I attack, and internalize it into cells.

Structure relationship of cationic lipids on gene transfection mediated by cationic liposomes

The aim of this study was to investigate the transfection efficiency of cationic liposomes formulated with phosphatidylcholine (PC) and novel synthesized diethanolamine-based cationic lipids at a molar ratio of 5:1 in comparison with Lipofectamine™ 2000. Factors affecting transfection efficiency and cell viability, including the chemical structure of the cationic lipids, such as different amine head group (diamine and polyamine; and non-spermine and spermine) and acyl chain lengths (C14, C16, and C18) and the weight ratio of liposomes to DNA were evaluated on a human cervical carcinoma cell line (HeLa cells) using the pDNA encoding green fluorescent protein (pEGFP-C2). Characterizations of these lipoplexes in terms of size and charge measurement and agarose gel electrophoresis were performed. The results from this study revealed that almost no transfection was observed in the liposome formulations composed of cationic lipids with a non-spermine head group. In addition, the transfection efficiency of these cationic liposomes was in the following order: spermine-C14 > spermine-C16 > spermine-C18. The highest transfection efficiency was observed in the formulation of spermine-C14 liposomes at a weight ratio of 25; furthermore, this formulation was safe for use in vitro. In conclusion, cationic liposomes containing spermine head groups demonstrated promising potential as gene carriers.

Enhancing microparticle internalization by nonphagocytic cells through the use of noncovalently conjugated polyethyleneimine

Development of micro- and nanotechnology for the study of living cells, especially in the field of drug delivery, has gained interest in recent years. Although several studies have reported successful results in the internalization of micro- and nanoparticles in phagocytic cells, when nonphagocytic cells are used, the low internalization efficiency represents a limitation that needs to be overcome. It has been reported that covalent surface modification of micro- and nanoparticles increases their internalization rate. However, this surface modification represents an obstacle for their use as drug-delivery carriers. For this reason, the aim of the present study was to increase the capability for microparticle internalization of HeLa cells through the use of noncovalently bound transfection reagents: polyethyleneimine (PEI) Lipofectamine™ 2000 and FuGENE 6^®. Both confocal microscopy and flow cytometry techniques allowed us to precisely quantify the efficiency of microparticle internalization by HeLa cells, yielding similar results. In addition, intracellular location of microparticles was analyzed through transmission electron microscopy and confocal microscopy procedures. Our results showed that free PEI at a concentration of 0.05 mM significantly increased microparticle uptake by cells, with a low cytotoxic effect. As determined by transmission electron and confocal microscopy analyses, microparticles were engulfed by plasma-membrane projections during internalization, and 24 hours later they were trapped in a lysosomal compartment. These results show the potential use of noncovalently conjugated PEI in microparticle internalization assays.

We still have a long way to go to effectively deliver genes!

Gene therapy is emerging as a revolutionary alternative to conventional therapeutic approaches. However, its clinical application is still hampered by the lack of safe and effective gene delivery techniques. Among the plethora of diverse approaches used to ferry nucleic acids into target cells, non-viral vectors represent promising and safer alternatives to viruses and physical techniques. Both cationic lipids and polymers spontaneously wrap and shrink the genetic material in complexes named lipoplexes and polyplexes, respectively, thereby protecting it and shielding its negative charges. The development of non-viral vectors commenced more than two decades ago. Since then, some major classes of interesting molecules have been identified and modified to optimize their properties. However, the way towards the final goal of gene delivery, i.e. protein expression or gene silencing, is filled with obstacles and current non-viral carriers still have concerns about their overall efficiency. We strongly believe that the future of non-viral gene delivery relies on the development of multifunctional vectors specifically tailored with diverse functionalities that act more like viruses. Although these vectors are still a long way from clinical practice they are the ideal platform to effectively shuttle the genetic material to target cells in a safe and controlled way. In this review, after briefly introducing the basis of gene delivery and therapeutic applications we discuss the main polymeric and lipidic vectors utilized for gene delivery, focusing on the strategies adopted to overcome the major weaknesses inherent to their still limited activity, on the way towards ideal multifunctional vectors.

Nanoparticle-based delivery for the treatment of inner ear disorders

PURPOSE OF REVIEW

The delivery of targetable synthetic vectors that can carry a variety of drugs, proteins, and nucleic acids, such as DNA and small interfering RNA (siRNA), to mammalian cells is important as a potential therapeutic system that avoids the problems that are associated with viruses.

RECENT FINDINGS

The so-called multifunctional nanocarriers that are equipped with several functions, such as targetability, shelter from the immune system, and opsonization, and are capable of delivering payload across the nuclear envelope, have been synthesized. To improve transfection efficiency, a group of novel peptides have been attached to the surface of the carrier that will enhance endosomal escape and promote nuclear entry. The targeting of tropomyocin receptor kinase B (TrkB) with ligands enhances uptake in spiral ganglion cell culture. Treatment cargos have included growth factors such as the Math-1 gene, short hairpin RNA, and steroids. The problems with current synthetic nanocarriers are poorer selectivity, internalization, and transfection rate compared with viral vectors.

SUMMARY

Within a few years, when the synthetic vectors have been optimized, the first human drugs/proteins/gene product-based therapies will become available in a phase I study.

Enhanced siRNA delivery and silencing gold-chitosan nanosystem with surface charge-reversal polymer assembly and good biocompatibility

A simple nanocarrier coated with chitosan and the pH-responsive charge-reversible polymer, PAH-Cit, was constructed using layer-by-layer assembly to deliver siRNA. Gold nanoparticles (AuNPs) were di-rectly reduced and stabilized by chitosan (CS), forming a positively charged AuNP-CS core. Charge-reversible PAH-Cit and polyethylenimine (PEI) were sequentially deposited onto the surface of AuNP-CS through electrostatic interaction, forming a PEI/PAH-Cit/AuNP-CS shell/core structure. After loading siRNA, the cytotoxicity of siRNA/PEI/PAH-Cit/AuNP-CS against HeLa and MCF-7R cells was negligible. This vehicle completely protected siRNA against enzymatic degradation at vector/RNA mass ratios of 2.5:1 and above. An in vitro release profile demonstrated an efficient siRNA release (79%) from siRNA/PEI/PAH-Cit/AuNP-CS at pH 5.5, suggesting a pH-induced charge-reversing action of PAH-Cit. This mechanism also worked in vivo and facilitated the escape of siRNA from endosomes. Using this carrier, the uptake of cy5-siRNA by HeLa cells was significantly increased compared to PEI, an efficient polycationic transfection reagent. In drug-resistant MCF-7 cells, specific gene silencing effectively reduced expression of MDR1, the gene encoding the drug exporter P-gp, and consequently promoted the uptake of doxorubicin. This simple charge-reversal polymer assembly nanosystem has three essential benefits (protection, efficient uptake, and facilitated escape) and provides a safe strategy with good biocompatibility for enhanced siRNA delivery and silencing.

Genetic nanomedicine: gene delivery by targeted lipoplexes

Cationic liposome-DNA complexes (lipoplexes) are used for the delivery of plasmid DNA to cultured cells and various tissues in vivo. In this chapter, we describe the preparation and evaluation of plain and targeted lipoplexes, using targeting ligands, including epidermal growth factor and transferrin. Ligand-associated lipoplexes may be used to target DNA or other nucleic acid drugs to specific cells, particularly cancer cells that overexpress the receptors for the ligands. We provide examples of the enhancement of gene expression mediated by epidermal growth factor in murine and human oral squamous cell carcinoma cells, and human hepatoblastoma and rat colon adenocarcinoma cells. We also summarize the studies on the use of transferrin-lipoplexes for enhancing gene delivery to cervical carcinoma, murine colon carcinoma, and African green monkey kidney cells. We outline two animal models in which transferrin-lipoplexes have been used for antitumor therapy by delivering either the gene encoding interleukin-12 or a suicide gene: a CT26 murine colon carcinoma, and a syngeneic, orthotopic murine oral squamous cell carcinoma.

Therapeutic delivery opportunities, obstacles and applications for cell-penetrating peptides

Advancements in the development of large bioactive molecules as therapeutic agents have made drug delivery an active and important field of research. Cell-penetrating peptides (CPPs) have the ability to deliver an array of molecules and even nano-size particles into cells in an efficient and non-toxic manner, both in vitro and in vivo. This review aims to give a perspective on the obstacles that CPP-mediated drug delivery is currently facing as well as the great opportunities for improvements that lie ahead. Strategies for delivery of novel gene-modulating agents and enhancing efficacy of classical drugs will be discussed, as well as methods for increasing bioavailability and tissue specificity of CPPs. The usefulness and potential of CPPs as therapeutic drug-delivery vectors will be exemplified by their use in the treatment of cancer, viral infection and muscular dystrophy.

Advances in polymeric and inorganic vectors for nonviral nucleic acid delivery

Nonviral systems for nucleic acid delivery offer a host of potential advantages compared with viruses, including reduced toxicity and immunogenicity, increased ease of production and less stringent vector size limitations, but remain far less efficient than their viral counterparts. In this article we review recent advances in the delivery of nucleic acids using polymeric and inorganic vectors. We discuss the wide range of materials being designed and evaluated for these purposes while considering the physical requirements and barriers to entry that these agents face and reviewing recent novel approaches towards improving delivery with respect to each of these barriers. Furthermore, we provide a brief overview of past and ongoing nonviral gene therapy clinical trials. We conclude with a discussion of multifunctional nucleic acid carriers and future directions.

Polymeric vectors for ocular gene delivery

Gene therapy holds promise for the treatment of many inherited and acquired diseases of the eye. Successful ocular gene therapy interventions depend on efficient gene transfer to targeted cells with minimal toxicity. A major challenge is to overcome both intracellular and extracellular barriers associated with ocular gene delivery. Numerous viral and nonviral vectors were explored to improve transfection efficiency. Among nonviral delivery systems, polymeric vectors have gained significant attention in recent years owing to their nontoxic and non-immunogenic nature. Polyplexes or nanoparticles can be prepared by interaction of cationic polymers with DNA, which facilitate cellular uptake, endolysosomal escape and nuclear entry through active mechanisms. Chemical modification of these polymers allows for the generation of flexible delivery vectors with desirable properties. In this article several synthetic and natural polymeric systems utilized for ocular gene delivery are discussed.

Chemical oxidation of a redox-active, ferrocene-containing cationic lipid: influence on interactions with DNA and characterization in the context of cell transfection

We report an approach to the chemical oxidation of a ferrocene-containing cationic lipid [bis(11-ferrocenylundecyl)dimethylammonium bromide, BFDMA] that provides redox-based control over the delivery of DNA to cells. We demonstrate that BFDMA can be oxidized rapidly and quantitatively by treatment with Fe(III)sulfate. This chemical approach, while offering practical advantages compared to electrochemical methods used in past studies, was found to yield BFDMA/DNA lipoplexes that behave differently in the context of cell transfection from lipoplexes formed using electrochemically oxidized BFDMA. Specifically, while lipoplexes of the latter do not transfect cells efficiently, lipoplexes of chemically oxidized BFDMA promoted high levels of transgene expression (similar to levels promoted by reduced BFDMA). Characterization by SANS and cryo-TEM revealed lipoplexes of chemically and electrochemically oxidized BFDMA to both have amorphous nanostructures, but these lipoplexes differed significantly in size and zeta potential. Our results suggest that differences in zeta potential arise from the presence of residual Fe(2+) and Fe(3+) ions in samples of chemically oxidized BFDMA. Addition of the iron chelating agent EDTA to solutions of chemically oxidized BFDMA produced samples functionally similar to electrochemically oxidized BFDMA. These EDTA-treated samples could also be chemically reduced by treatment with ascorbic acid to produce samples of reduced BFDMA that do promote transfection. Our results demonstrate that entirely chemical approaches to oxidation and reduction can be used to achieve redox-based 'on/off' control of cell transfection similar to that achieved using electrochemical methods.

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.

Gene therapy approaches for lysosomal storage disorders, a good model for the treatment of mendelian diseases

This review describes the different gene therapy technologies applied to approach lysosomal storage disorders, monogenic conditions, with known genetic and biochemical defects, for many of which animal models are available. Both viral and nonviral procedures are described, underlying the specific needs that the treatment of genetic disorders requires.

CONCLUSIONS

Lysosomal storage disorders represent a good model of study of gene therapeutic procedures that are, or could be, relevant to the treatment of several other mendelian diseases.

Physical factors affecting plasmid DNA compaction in stearylamine-containing nanoemulsions intended for gene delivery

Cationic lipids have been used in the development of non-viral gene delivery systems as lipoplexes. Stearylamine, a cationic lipid that presents a primary amine group when in solution, is able to compact genetic material by electrostatic interactions. In dispersed systems such as nanoemulsions this lipid anchors on the oil/water interface confering a positive charge to them. The aim of this work was to evaluate factors that influence DNA compaction in cationic nanoemulsions containing stearylamine. The influence of the stearylamine incorporation phase (water or oil), time of complexation, and different incubation temperatures were studied. The complexation rate was assessed by electrophoresis migration on agarose gel 0.7%, and nanoemulsion and lipoplex characterization was done by Dynamic Light Scattering (DLS). The results demonstrate that the best DNA compaction process occurs after 120 min of complexation, at low temperature (4 ± 1 °C), and after incorporation of the cationic lipid into the aqueous phase. Although the zeta potential of lipoplexes was lower than the results found for basic nanoemulsions, the granulometry did not change. Moreover, it was demonstrated that lipoplexes are suitable vehicles for gene delivery.

Novel delivery strategies for glioblastoma

Brain tumors--particularly glioblastoma multiforme--pose an important public health problem in the United States. Despite surgical and medical advances, the prognosis for patients with malignant gliomas remains grim: current therapy is insufficient with nearly universal recurrence. A major reason for this failure is the difficulty of delivering therapeutic agents to the brain: better delivery approaches are needed to improve treatment. In this article, we summarize recent progress in drug delivery to the brain, with an emphasis on convection-enhanced delivery of nanocarriers. We examine the potential of new delivery methods to permit novel drug- and gene-based therapies that target brain cancer stem cells and discuss the use of nanomaterials for imaging of tumors and drug delivery.

Effect of unsaturated alkyl chains on transfection activity of poly(amidoamine) dendron-bearing lipids

In an earlier study, we developed a new type of gene vector using poly(amidoamine) (PAMAM) dendron-bearing lipids and reported that their transfection activity was affected by their structures, such as dendron generation and alkyl chain length. In this study, for improvement of their performance as gene vectors, we examined the effect of unsaturated chains of the dendron-bearing lipids using DL-G1-2C(18), which consists of PAMAM G1 dendron moiety and two octadecyl chains, and achieved the most efficient transfection activity among the dendron-bearing lipids having saturated alkyl chains, and DL-G1-2C(18)-U2, which consists of the same dendron-moiety and two octadecenyl chains. DL-G1-2C(18)-U2 showed a higher ability to form lipoplexes with plasmid DNA than DL-G1-2C(18). The DL-G1-2C(18)-U2 lipoplexes exhibited much smaller particle sizes than the DL-G1-2C(18). In addition, the DL-G1-2C(18)-U2 lipoplexes exhibited more efficient transfection of HeLa cells than DL-G1-2C(18) did. Results demonstrate the importance of unsaturated chains for the production of the dendron-bearing lipids having excellent gene transfection performance. Without the help of additional fusogenic lipids such as dioleoylphosphatidylethanolamine, DL-G1-2C(18)-U2 lipoplexes achieved the highly efficient transfection of the cells without marked cellular toxicity, in the presence of serum. Therefore, DL-G1-2C(18)-U2 might be promising as a potent gene vector.

Targeted gene delivery to hepatocytes with galactosylated amphiphilic cyclodextrins

Objectives

Achieving targeted delivery of gene medicines is desirable to maximise activity. Here, galactosylated amphiphilic cyclodextrins (CDs) are examined in terms of their ability to transfect asialoglycoprotein receptor-bearing HepG2 cells.

Methods

Cationic amphiphilic CDs were synthesised as well as amphiphilic CDs bearing galactose-targeting ligands with different linker lengths. Binding of galactosylated CDs to a galactose-specific lectin was examined by surface plasmon resonance. CDs were formulated with and without the helper lipid DOPE and complexed with plasmid DNA. Transfection was evaluated by luciferase assay. Intracellular trafficking was assessed by confocal microscopy.

Key findings

Binding of targeted CDs to a galactose-specific lectin was achieved. Binding decreased with linker length between the galactosyl group and the CD core. Contrary to the lectin binding results, transfection levels increased with an increase in linker length from 7 atoms to 15. Compared to non-targeted formulations, a significant increase in transfection was observed only in the presence of the helper lipid DOPE. Confocal microscopy revealed that DOPE caused a pronounced effect on cellular distribution.

Conclusions

The galactose-targeting ligand induced substantial increases in transfection over non-targeted formulations when DOPE was included, indicating the potential for targeted gene delivery using CD-based delivery systems.

Tumor vasculature targeting following co-delivery of heparin-taurocholate conjugate and suberoylanilide hydroxamic acid using cationic nanolipoplex

The chemical conjugate of low molecular weight heparin with taurocholate (LHT7) was previously designed to offer anticancer activity while minimizing the anticoagulant activity. In the present study, we found that the systemic administration of LHT7 in nanolipoplex could substantially enhance tumor vasculature targeting and anticancer effects. Moreover, we found that co-delivery of LHT7 with suberoylanilide hydroxamic acid (SAHA), a histone deacetylase inhibitor, in nanolipoplex could provide synergistic antitumor effect. LHT7/SAHA nanolipoplex was formulated by encapsulating SAHA inside cationic liposomes, followed by complexation of negatively charged LHT7 onto the cationic surfaces of SAHA-loaded liposomes (SAHA-L). LHT7/SAHA nanolipoplex was positively charged with a mean diameter of 117.6 nm, and stable in serum. The nanolipoplex form of LHT7 could alter its pharmacokinetics and biodistribution. Compared to the free form of LHT7, LHT7 in the nanolipoplex showed 1.9-fold higher mean residence time, and higher tumor vasculature accumulation after its intravenous administration. LHT7/SAHA nanolipoplex showed highest antitumor efficacy in SCC-bearing mice, compared to LHT7, SAHA-L and sequential co-administration of LHT7 and SAHA-L. Consistent with the enhanced antitumor effect, the reduction of abnormal vessels in the tumor site was also the highest in the LHT7/SAHA nanolipoplex-treated group. These results suggested the potential of LHT7/SAHA nanolipoplex for enhanced tumor vasculature targeting, and the importance of nanolipoplex-mediated co-delivery with a histone deacetylase inhibitor for maximal anticancer effect.

Synthesis and preliminary investigations of the siRNA delivery potential of novel, single-chain rigid cationic carotenoid lipids

The success of nucleic acid delivery requires the development of safe and efficient delivery vectors that overcome cellular barriers for effective transport. Herein we describe the synthesis of a series of novel, single-chain rigid cationic carotenoid lipids and a study of their preliminary in vitro siRNA delivery effectiveness and cellular toxicity. The efficiency of siRNA delivery by the single-chain lipid series was compared with that of known cationic lipid vectors, 3β-[N-(N',N'-dimethylaminoethane)carbamoyl]-cholesterol (DC-Chol) and 1,2-dimyristoyl-sn-glyceryl-3-phosphoethanolamine (EPC) as positive controls. All cationic lipids (controls and single-chain lipids) were co-formulated into liposomes with the neutral co-lipid, 1,2-dioleolyl-sn-glycerol-3-phosphoethanolamine (DOPE). Cationic lipid-siRNA complexes of varying (+/−) molar charge ratios were formulated for delivery into HR5-CL11 cells. Of the five single-chain carotenoid lipids investigated, lipids 1, 2, 3 and 5 displayed significant knockdown efficiency with HR5-CL11 cells. In addition, lipid 1 exhibited the lowest levels of cytotoxicity with cell viability greater than 80% at all (+/−) molar charge ratios studied. This novel, single-chain rigid carotenoid-based cationic lipid represents a new class of transfection vector with excellent cell tolerance, accompanied with encouraging siRNA delivery efficiency.

Polyamidoamine dendron-bearing lipids as a nonviral vector: influence of dendron generation

Recently, we demonstrated that octadecyl chains are important as alkyl chain moieties of polyamidoamine (PAMAM) dendron-bearing lipids for their serum-resistant transfection activity [Bioconjugate Chem.2007, 18, 1349-1354]. Toward production of highly potent vectors, we examined the influence of the generation of dendron moiety on transfection activity of PAMAM dendron-bearing lipids having two octadecyl chains. We synthesized dendron-bearing lipids with PAMAM G1, G2, and G3 dendrons, designated respectively as DL-G1-2C(18), DL-G2-2C(18), and DL-G3-2C(18). The DL-G2-2C(18) and DL-G3-2C(18) interacted with plasmid DNA effectively and formed stable lipoplexes with small sizes and spherical shape. However, DL-G1-2C(18) interacted with plasmid DNA less effectively and formed tubular-shaped lipoplexes with lower stability and larger size. Cells took up DL-G2-2C(18) and DL-G3-2C(18) lipoplexes efficiently, but cellular uptake of the DL-G1-2C(18) lipoplexes was less efficient. Nevertheless, DL-G1-2C(18) lipoplexes achieved 100-10 000 times higher levels of transgene expression, which was evaluated using luciferase gene as a reporter gene. Confocal scanning laser microscopic analysis of intracellular behaviors of the lipoplexes revealed that DL-G1-2C(18) lipoplexes generated free plasmid DNA molecules in the cytosol more effectively than other lipoplexes did. Moderate binding ability of DL-G1-2C(18) might be responsible for generation of lipoplexes which deliver plasmid DNA into cells, liberate it in the cytoplasm, and induce efficient transgene expression.

Roles of hydrophobicity and charge density on the dynamics of polyelectrolyte complex formation and stability under modeled physicochemical blood conditions

To improve the understanding of the physicochemical behavior of polyplexes (DNA-polycation complexes) and to avoid the complexity of blood, the formation and stability of polyelectrolyte complexes of degradable polycations and polyanions, we previously studied under pH, temperature, and ionic strength typical of human blood. In this study, the investigation is extended to polycationic macromolecules added into mixtures of polyanions selected to mimic polyanionic species present in blood. The poly(l-lysine) polycation was added to binary mixtures of degradable polyanions with different charge densities and hydrophobicity. The polyanions were poly(l-lysine citramide imide), poly(l-lysine citramide), and poly(l-lysine citramide) partially esterified with heptyl groups. We found selectivity and fractionation in the molar mass, which depended on the structural characteristics of the polyanions. The affinity of polycationic poly(l-lysine) macromolecules to polyanions increased in the following order: poly(l-lysine citramide imide) < poly(l-lysine citramide) < hydrophobized poly(l-lysine citramide). These data complements the previous information with respect to the possibility of polyplex destabilization and/or the interactions of polycationic macromolecules in excess with the polyanionic species present in blood, depending on the physicochemical characteristics of the polyplex, the excess polycation, and blood elements.

Detection of endogenous K-ras mRNA in living cells at a single base resolution by a PNA molecular beacon

Detection of mRNA alterations is a promising approach for identifying biomarkers as means of differentiating benign from malignant lesions. By choosing the KRAS oncogene as a target gene, two types of molecular beacons (MBs) based on either phosphothioated DNA (PS-DNA-MB) or peptide nucleic acid (TO-PNA-MB, where TO = thiazole orange) were synthesized and compared in vitro and in vivo. Their specificity was examined in wild-type KRAS (HT29) or codon 12 point mutation (Panc-1, SW480) cells. Incubation of both beacons with total RNA extracted from the Panc-1 cell line (fully complementary sequence) showed a fluorescent signal for both beacons. Major differences were observed, however, for single mismatch mRNA transcripts in cell lines HT29 and SW480. PS-DNA-MB weakly discriminated such single mismatches in comparison to TO-PNA-MB, which was profoundly more sensitive. Cell transfection of TO-PNA-MB with the aid of PEI resulted in fluorescence in cells expressing the fully complementary RNA transcript (Panc-1) but undetectable fluorescence in cells expressing the K-ras mRNA that has a single mismatch to the designed TO-PNA-MB (HT29). A weaker fluorescent signal was also detected in SW480 cells; however, these cells express approximately one-fifth of the target mRNA of the designed TO-PNA-MB. In contrast, PS-DNA-MB showed no fluorescence in all cell lines tested post PEI transfection. Based on the fast hybridization kinetics and on the single mismatch discrimination found for TO-PNA-MB we believe that such molecular beacons are promising for in vivo real-time imaging of endogenous mRNA with single nucleotide polymorphism (SNP) resolution.

Polyamidoamine dendron-bearing lipid assemblies: their morphologies and gene transfection ability

Assembly morphology made from lipids is controlled by the balance between the polar headgroup and the hydrophobic tails. In this study, we showed the various generations of polyamidoamine dendron-bearing lipids could form various assembly morphologies. Furthermore, the effect of the assembly morphologies made from dendron-bearing lipids for transfection abilities were examined. We synthesized three novel dendron-bearing lipids, DL-U2-G1 (G1), DL-U2-G2 (G2), and DL-U2-G3 (G3), which included first, second, and third generation polyamidoamine dendrons, respectively. Transmission electron microscopy showed that lipoplexes (complexes with cationic lipids and plasmid DNA) comprising G1 had multilamellar structures. G2 presented as aggregates of cubic particles and G3 exhibited clusters of spherical micelles. The ability to form complexes with plasmid DNA was in the decreasing order G3 > G2 > G1; calcein release from endosomes was in the order G3 > G2, G1; and transfection activity followed the order G1 > G2, G3. Interaction of the lipoplexes with heparin suggests that G3 had a lower level of plasmid DNA dissociation from lipoplexes than G1 in vitro. These results suggest that the size of the DL-U2 headgroup determines assembly morphology and that the structure markedly affects transfection activity.

Novel biomimetic vectors with endosomal-escape agent enhancing gene transfection efficiency

Low cytotoxicity and high transfection efficiency are critical issues in designing current non-viral gene delivery vectors. In the present study, a novel biomimetic lipid-polycation copolymer, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-graft-poly(l-lysine)-block-poly(ethylene glycol) (DOPE-g-PLL-b-PEG) was first synthesized and the potential of this novel hybrid lipid-polycation as efficient gene vector was further evaluated. DOPE-g-PLL-b-PEG and DNA could self-assemble into lipid modified polyion complex micelles (LPCM) through electrostatic interactions. Compared with PEG-b-PLL/DNA polyion complex micelles (PIC), LPCM could protect DNA from plasma, nuclease degradation in vitro and showed lower cytotoxicity to HepG2 and HeLa cells (P<0.05). The results of transfection study in vitro indicated that LPCM exhibited higher gene expression than PIC. Especially, the corresponding LPCM displayed the highest transfection efficiency in HeLa cells (P<0.05) when DOPE grafting ratio reached up to 30%. These results suggested that LPCM could facilitate gene transfer in cultured cells and might alleviate the drawbacks of the conventional cationic vector/DNA complexes. As a novel hybrid lipid-polycation, DOPE-g-PLL-b-PEG was valuable to be evaluated for its further application as gene carrier in vivo.

Nucleic acid therapy for lifespan prolongation: present and future

Lifespan prolongation is a common desire of the human race. With advances in biotechnology, the mechanism of aging has been gradually unraveled, laying the theoretical basis of nucleic acid therapy for lifespan prolongation. Regretfully, clinically applicable interventions do not exist without the efforts of converting theory into action, and it is the latter that has been far from adequately addressed at the moment. This was demonstrated by a database search on PubMed and Web of Science, from which only seven studies published between 2000 and 2010 were found to directly touch on the development of nucleic acid therapy for anti-aging and/or longevity enhancing purposes. In light of this, the objective of this article is to overview the current understanding of the intimate association between genes and longevity, and to bring the prospect of nucleic acid therapy for lifespan prolongation to light.

Lipopolyplexes as nanomedicines for therapeutic gene delivery

We describe an efficient, nonviral gene transfer system that employs polyethylenimine (PEI 800, 25, 22 kDa), and 1,2-dioleoyl-3-(trimethylammonium) propane (DOTAP) and cholesterol (Chol) as lipids (lipopolyplex), at three different lipid/DNA molar ratios (2/1, 5/1, and 17/1), employing five different formulation strategies. PEIs of 800, 25, and 22 kDa are highly effective in condensing plasmid DNA, leading to a complete condensation at N/P⁺/⁻ ratios above 4. Increasing the molar ratio lipid/DNA in the complex results in higher positive values of the zeta potential, while the particle size increases in some protocols, but not in others. PEI of molecular weight 800 kDa used in the formulation of lipopolyplexes results in bigger particles compared to that obtained with the smaller PEI species. Transfection activity is measured using pCMVLuc expressing luciferase is maximal by using strategies 3 and 4 and an N/P molar ratio of 17/1. These complexes have a high efficiency of gene delivery to liver cancer cells, even in the presence of a high serum concentration. Complexes formed with linear PEI are more effective than lipopolyplexes containing branched PEI. The ternary complexes are much more efficient than conventional lipoplexes (cationic lipid and DNA) and polyplexes (cationic polymer and DNA). The same behavior is observed for complexes prepared with the therapeutic gene pCMVIL-12 expressing interleukin-12.

Microfluidic approaches for gene delivery and gene therapy

Recent advances in microfluidics have created new and exciting prospects for gene delivery and therapy. The micro-scaled environment within microfluidic systems enables precise control and optimization of multiple processes and techniques used in gene transfection and the production of gene and drug transporters. Traditional non-viral gene transfection methods, such as electroporation, microinjection and optical gene transfection, are improved from the use of innovative microfluidic systems. Additionally, microfluidic systems have also made the production of many viral and non-viral vectors controlled, automated, and reproducible. In summary, the development and application of microfluidic systems are producing increased efficiency in gene delivery and promise improved gene therapy results.

Biodegradable poly(amine-co-ester) terpolymers for targeted gene delivery

Many synthetic polycationic vectors for non-viral gene delivery show high efficiency in vitro, but their usually excessive charge density makes them toxic for in vivo applications. Here we describe the synthesis of a series of high molecular weight terpolymers with low charge density, and show that they exhibit efficient gene delivery, some surpassing the efficiency of the commercial transfection reagents Polyethylenimine and Lipofectamine 2000. The terpolymers were synthesized via enzyme-catalyzed copolymerization of lactone with dialkyl diester and amino diol, and their hydrophobicity adjusted by varying the lactone content and by selecting a lactone comonomer of specific ring size. Targeted delivery of the pro-apoptotic TRAIL gene to tumour xenografts by one of the terpolymers results in significant inhibition of tumour growth, with minimal toxicity both in vitro and in vivo. Our findings suggest that the gene delivery ability of the terpolymers stems from their high molecular weight and increased hydrophobicity, which compensates for their low charge density.

Cationic glycopolymers for the delivery of pDNA to human dermal fibroblasts and rat mesenchymal stem cells

Progenitor and pluripotent cell types offer promise as regenerative therapies but transfecting these sensitive cells has proven difficult. Herein, a series of linear trehalose-oligoethyleneamine "click" copolymers were synthesized and examined for their ability to deliver plasmid DNA (pDNA) to two progenitor cell types, human dermal fibroblasts (HDFn) and rat mesenchymal stem cells (RMSC). Seven polymer vehicle analogs were synthesized in which three parameters were systematically varied: the number of secondary amines (4-6) within the polymer repeat unit (Tr4(33), Tr5(30), and Tr6(32)), the end group functionalities [PEG (Tr4(128)PEG-a, Tr4(118)PEG-b), triphenyl (Tr4(107)-c), or azido (Tr4(99)-d)], and the molecular weight (degree of polymerization of about 30 or about 100) and the biological efficacy of these vehicles was compared to three controls: Lipofectamine 2000, JetPEI, and Glycofect. The trehalose polymers were all able to bind and compact pDNA polyplexes, and promote pDNA uptake and gene expression [luciferase and enhanced green fluorescent protein (EGFP)] with these primary cell types and the results varied significantly depending on the polymer structure. Interestingly, in both cell types, Tr4(33) and Tr5(30) yielded the highest luciferase gene expression. However, when comparing the number of cells transfected with a reporter plasmid encoding enhanced green fluorescent protein, Tr4(33) and Tr4(107)-c yielded the highest number of HDFn cells positive for EGFP. Interestingly, with RMSCs, all of the higher molecular weight analogs (Tr4(128)PEG-a, Tr4(118)PEG-b, Tr4(107)-c, Tr4(99)-d) yielded high percentages of cells positive for EGFP (30-40%).

Polycationic amphiphilic cyclodextrin-based nanoparticles for therapeutic gene delivery

Aim: In this study, a set of polycationic amphiphilic cyclodextrins featuring self-assembling capabilities in the presence of nucleic acids have been evaluated as therapeutic gene vectors for in vivo purposes. Materials & Methods: A tetradecacationic structure incorporating 14 primary amino groups and 7 thioureido groups in the primary face of the cyclooligosaccharide core and 14 hexanoyl chains in the secondary face was judged to be optimal for therapeutic gene delivery. Results & Conclusion: This compound efficiently mediated serum-resistant transfection in HeLa and HepG2 cells, comparing favorably with branched poly(ethyleneimine), with a low associated toxicity. Further transfection experiments using an encoding therapeutic gene plasmid (pCMVIL-12) were effected to report expression levels of IL-12. Finally, in vivo gene delivery experiments by systemic injection in mice indicated relatively high transfection levels in the liver, overcoming trapping of the nanoparticles in lung cells, with low toxicity.