Gene delivery by lipoplexes and polyplexes

Cationic nanomicelles for delivery of plasmids encoding interleukin-4 and interleukin-10 for prevention of autoimmune diabetes in mice

PURPOSE

To evaluate the in vivo transfection efficiency of N-acyl derivatives of low-molecular weight chitosan (LMWC) to deliver pVIVO2-mIL4-mIL10 plasmid encoding interleukin-4 (IL-4) and interleukin-10 (IL-10) in multiple, low-dose streptozotocin induced diabetic mouse model.

METHODS

N-acyl LMWC nanomicelles were characterized for size and charge. The pVIVO2-mIL4-mIL10/N-acyl LMWC polyplexes were injected intramuscularly in mice and compared for transfection efficiency with naked DNA and FuGENE® HD. Bicistronic pVIVO2-mIL4-mIL10 plasmid was compared with individual plasmids encoding IL-4 and IL-10 for efficacy. The levels of blood glucose and serum IL-4, IL-10, TNF-α and IFN-γ were monitored. The ability of plasmid administration to protect from insulitis and biocompatibility of N-acyl LMWC were studied.

RESULTS

The N-acyl LMWC led to significantly higher (p < 0.05) expression of IL-4 and IL-10 and reduced the levels of blood glucose, TNF-α and IFN-γ, especially in animals treated with pVIVO2-mIL4-mIL10 plasmid. The pancreas of pDNA/N-acyl LMWC polyplex treated animals exhibited protection from insulitis and the delivery systems were found to be biocompatible.

CONCLUSIONS

N-acyl derivatives of LMWC are efficient and biocompatible gene delivery vectors, and the administration of bicistronic pVIVO2-mIL4-mIL10 plasmid polyplexes can protect the pancreatic islets from insulitis, possibly due to the synergistic effect of IL-4 and IL-10 encoding plasmids.

Hepatitis B virus envelope L protein-derived bio-nanocapsules: mechanisms of cellular attachment and entry into human hepatic cells

A bio-nanocapsule (BNC) is a hollow nanoparticle consisting of an approximately 100-nm-diameter liposome with about 110 molecules of hepatitis B virus (HBV) surface antigen L protein embedded as a transmembrane protein. BNC can encapsulate various drugs and genes and deliver them specifically to human hepatic cells based on the ability of HBV to recognize human hepatocyte, which is integrated in the N-terminal region of L protein. However, it is elusive whether the cellular attachment and entry into hepatic cells of BNC utilize the early infection mechanism of HBV. In this study, we have found that while all human hepatic cells show distinct affinities for BNC compared to non-hepatic cells, primary hepatocytes shows the highest efficiency for cellular binding and incorporation of BNC. Amounts of BNCs bound weakly and strongly to cell membranes and those entered into the cells varied significantly depending on the types of human hepatic cells. The weak and strong binding modes of BNC are likely mediated through binding to two distinct HBV receptors (heparin-mediated low-affinity and unidentified high-affinity receptors), which play major roles in the early infection mechanism of HBV. The rates of cellular uptake of BNC are similar to those reported for HBV. The BNCs incorporated into the cells are swiftly sorted to either early endosomes or macropinosomes and then to late endosomes and/or lysosomes. These findings strongly suggest that BNC is bound to and incorporated into human hepatic cells according to the early infection mechanism of HBV.

A new liposome-based gene delivery system targeting lung epithelial cells using endothelin antagonist

We formulated a new gene delivery system based on targeted liposomes. The efficacy of the delivery system was demonstrated in in vitro and in vivo models. The targeting moiety consists of a high-affinity 7-amino-acid peptide, covalently and evenly conjugated to the liposome surface. The targeting peptide acts as an endothelin antagonist, and accelerates liposome binding and internalization. It is devoid of other biological activity. Liposomes with high phosphatidyl serine (PS) were specially formulated to help their fusion with the endosomal membrane at low pH and enable release of the liposome payload into the cytoplasm. A DNA payload, pre-compressed by protamine, was encapsulated into the liposomes, which directed the plasmid into the cell's nucleus. Upon exposure to epithelial cells, binding of the liposomes occurred within 5-10 min, followed by facilitated internalization of the complex. Endosomal escape was complete within 30 min, followed by DNA accumulation in the nucleus 2h post-transfection. A549 lung epithelial cells transfected with plasmid encoding for GFP encapsulated in targeted liposomes expressed significantly more protein than those transfected with plasmid complexed with Lipofectamine. The intra-tracheal instillation of plasmid encoding for GFP encapsulated in targeted liposomes into rat lungs resulted in the expression of GFP in bronchioles and alveoli within 5 days. These results suggest that this delivery system has great potential in targeting genes to lungs.

Addition of ascorbic acid to the extracellular environment activates lipoplexes of a ferrocenyl lipid and promotes cell transfection

The level of cell transfection mediated by lipoplexes formed using the ferrocenyl lipid bis(11-ferrocenylundecyl)dimethylammonium bromide (BFDMA) depends strongly on the oxidation state of the two ferrocenyl groups of the lipid (reduced BFDMA generally mediates high levels of transfection, but oxidized BFDMA mediates very low levels of transfection). Here, we report that it is possible to chemically transform inactive lipoplexes (formed using oxidized BFMDA) to "active" lipoplexes that mediate high levels of transfection by treatment with the small-molecule reducing agent ascorbic acid (vitamin C). Our results demonstrate that this transformation can be conducted in cell culture media and in the presence of cells by addition of ascorbic acid to lipoplex-containing media in which cells are growing. Treatment of lipoplexes of oxidized BFDMA with ascorbic acid resulted in lipoplexes composed of reduced BFDMA, as characterized by UV/vis spectrophotometry, and lead to activated lipoplexes that mediated high levels of transgene expression in the COS-7, HEK 293T/17, HeLa, and NIH 3T3 cell lines. Characterization of internalization of DNA by confocal microscopy and measurements of the zeta potentials of lipoplexes suggested that these large differences in cell transfection result from (i) differences in the extents to which these lipoplexes are internalized by cells and (ii) changes in the oxidation state of BFDMA that occur in the extracellular environment (i.e., prior to internalization of lipoplexes by cells). Characterization of lipoplexes by small-angle neutron scattering (SANS) and by cryogenic transmission electron microscopy (cryo-TEM) revealed changes in the nanostructures of lipoplexes upon the addition of ascorbic acid, from aggregates that were generally amorphous, to aggregates with a more extensive multilamellar nanostructure. The results of this study provide guidance for the design of redox-active lipids that could lead to methods that enable spatial and/or temporal control of cell transfection.

Nanoparticle-mediated gene transfer specific to retinal pigment epithelial cells

Previously, we demonstrated that CK30PEG10k-compacted DNA nanoparticles (NPs) efficiently target photoreceptor cells and improve visual function in a retinitis pigmentosa model. Here, we test the ability of these NPs in driving transgene expression in the retinal pigment epithelium (RPE), using an RPE-specific reporter vector (VMD2-eGFP). NPs, uncompacted plasmid, or saline were subretinally delivered to adult BALB/c mice. NP-based expression was specific to RPE cells and caused no deleterious effects on retinal structure and function. eGFP expression levels in NP-injected eyes peaked at post-injection day 2 (PI-2), stabilized at levels ~3-fold higher than in naked DNA-injected eyes, and remained elevated at the latest time-point examined (PI-30). Unlike naked DNA, which only transfected cells at the site of injection, NPs were able to transfect cells throughout the RPE. Subretinal injections of rhodamine labeled NPs and naked DNA showed comparable initial uptake into RPE cells. However, at PI-7 and -30 days significantly more fluorescence was detected inside the RPE of NP-injected eyes compared to naked DNA, suggesting NPs are stable inside the cell which could possibly lead to higher and sustained expression. Overall, our results demonstrate that NPs can efficiently deliver genes to the RPE and hold great potential for the treatment of RPE-associated diseases.

Hydrophobic oxime ethers: a versatile class of pDNA and siRNA transfection lipids

The manipulation of the cationic lipid structures to increase polynucleotide binding and delivery properties, while also minimizing associated cytotoxicity, has been a principal strategy for developing next-generation transfection agents. The polar (DNA binding) and hydrophobic domains of transfection lipids have been extensively studied; however, the linking domain comprising the substructure used to tether the polar and hydrophobic domains has attracted considerably less attention as an optimization variable. Here, we examine the use of an oxime ether as the linking domain. Hydrophobic oxime ethers were readily assembled via click chemistry by oximation of hydrophobic aldehydes using an aminooxy salt. A facile ligation reaction delivered the desired compounds with hydrophobic domain asymmetry. Using the MCF-7 breast cancer, H1792 lung cancer and PAR C10 salivary epithelial cell lines, our findings show that lipoplexes derived from oxime ether lipids transfect in the presence of serum at higher levels than commonly used liposome formulations, based on both luciferase and green fluorescent protein (GFP) assays. Given the biological compatibility of oxime ethers and their ease of formation, this functional group should find significant application as a linking domain in future designs of transfection vectors.

Genetically manipulated adult stem cells for wound healing

New knowledge of the signal controls and activities of adult stem cells (ASCs) involved in wound repair have led to extensive investigation of the topical delivery of biomacromolecules and multipotent stem cells to injured tissues for scar-less regeneration. The transplantation of genetically recombinant stem cells, which have roles as both therapeutics and carriers for gene delivery to wound sites, represents an attractive strategy for wound treatment. Here, we compare viral and non-viral vectors and three-dimensional scaffold-based transfection strategies in terms of their biosafety, recombinant efficiency and influence on the differentiation of ASCs, to indicate the future direction of the application of recombinant ASCs in wound treatment.

Somatic genetics empowers the mouse for modeling and interrogating developmental and disease processes

With recent advances in genomic technologies, candidate human disease genes are being mapped at an accelerated pace. There is a clear need to move forward with genetic tools that can efficiently validate these mutations in vivo. Murine somatic mutagenesis is evolving to fulfill these needs with tools such as somatic transgenesis, humanized rodents, and forward genetics. By combining these resources one is not only able to model disease for in vivo verification, but also to screen for mutations and pathways integral to disease progression and therapeutic intervention. In this review, we briefly outline the current advances in somatic mutagenesis and discuss how these new tools, especially the piggyBac transposon system, can be applied to decipher human biology and disease.

HPMA-oligolysine copolymers for gene delivery: optimization of peptide length and polymer molecular weight

Polycations are one of the most frequently used classes of materials for non-viral gene transfer in vivo. Several studies have demonstrated a sensitive relationship between polymer structure and delivery activity. In this work, we used reverse addition-fragmentation chain transfer (RAFT) polymerization to build a panel of N-(2-hydroxypropyl)methacrylamide (HPMA)-oligolysine copolymers with varying peptide length and polymer molecular weight. The panel was screened for optimal DNA-binding, colloidal stability in salt, high transfection efficiency, and low cytotoxicity. Increasing polyplex stability in PBS correlated with increasing polymer molecular weight and decreasing peptide length. Copolymers containing K(5) and K(10) oligocations transfected cultured cells with significantly higher efficiencies than copolymers of K(15). Four HPMA-oligolysine copolymers were identified that met the desired criteria. Polyplexes formed with these copolymers demonstrated both salt stability and transfection efficiencies on-par with poly(ethylenimine) PEI in cultured cells.

Dynamics of polyelectrolyte complex formation and stability as a polyanion is progressively added to a polycation under modeled physicochemical blood conditions

To understand the fate of anionic macromolecular species when injected into blood, poly(acrylic acid) and poly(L-lysine citramide) polyanions, with better charge densities, and the poly(L-lysine) polycation were used as models of negatively charged polymer—drug conjugates and positively charged blood proteins, respectively. To mimic an intravenous injection, the polyanion was added to the poly(L-lysine) stepwise at room temperature. The polyelectrolyte complexes formed as precipitates and the molar mass fractionation was observed from one fraction to the other, especially in the case of largely polydispersed poly(L-lysine). The salt concentration necessary to return each fraction of complexed polyelectrolyte back to solution varied linearly with the logarithm of the molar mass of the polycation component. The physicochemical characteristics data of the polyelectrolytes and the media are compared to previously reported reverse mixing mode when the polycation is introduced into a solution of polyanions.

Nucleic acid delivery using magnetic nanoparticles: the Magnetofection™ technology

In recent years, gene therapy has received considerable interest as a potential method for the treatment of numerous inherited and acquired diseases. However, successes have so far been hampered by several limitations, including safety issues of viral-based nucleic acid vectors and poor in vivo efficiency of nonviral vectors. Magnetofection™ has been introduced as a novel and powerful tool to deliver genetic material into cells. This technology is defined as the delivery of nucleic acids, either ‘naked’ or packaged (as complexes with lipids or polymers, and viruses) using magnetic nanoparticles under the guidance of an external magnetic field. This article first discusses the principles of the Magnetofection technology and its benefits as compared with standard transfection methods. A number of relevant examples of its use, both in vitro and in vivo, will then be highlighted. Future trends in the development of new magnetic nanoparticle formulations will also be outlined.

A DNA microarray-based analysis of the host response to a nonviral gene carrier: a strategy for improving the immune response

The purpose of this study was to investigate the host response to systemically administered lipid nanoparticles (NPs) encapsulating plasmid DNA (pDNA) in the spleen using a DNA microarray. As a model for NPs, we used a multifunctional envelope-type nano device (MEND). Microarray analysis revealed that 1,581 of the differentially expressed genes could be identified by polyethylene glycol (PEG)-unmodified NP using a threefold change relative to the control. As the result of PEGylation, the NP treatment resulted in the reduction in the expression of most of the genes. However, the expression of type I interferon (IFN) was specifically increased by PEGylation. Based on the microarray and a pathway analysis, we hypothesize that PEGylation inhibited the endosomal escape of NP, and extended the interaction of toll-like receptor-9 (TLR9) with CpG-DNA accompanied by the production of type I IFN. This hypothesis was tested by introducing a pH-sensitive fusogenic peptide, GALA, which enhances the endosomal escape of PEGylated NP. As expected, type I IFN was reduced and interleukin-6 (IL-6) remained at the baseline. These findings indicate that a carrier design based on microarray analysis and the manipulation of intracellular trafficking constitutes a rational strategy for reducing the host immune response to NPs.

Liposomes for use in gene delivery

Liposomes have a wide array of uses that have been continuously expanded and improved upon since first being observed to self-assemble into vesicular structures. These arrangements can be found in many shapes and sizes depending on lipid composition. Liposomes are often used to deliver a molecular cargo such as DNA for therapeutic benefit. The lipids used to form such lipoplexes can be cationic, anionic, neutral, or a mixture thereof. Herein physical packing parameters and specific lipids used for gene delivery will be discussed, with lipids classified according to overall charge.

FUNCTIONAL NANOPARTICLES FOR MOLECULAR IMAGING GUIDED GENE DELIVERY

Gene therapy has great potential to bring tremendous changes in treatment of various diseases and disorders. However, one of the impediments to successful gene therapy is the inefficient delivery of genes to target tissues and the inability to monitor delivery of genes and therapeutic responses at the targeted site. The emergence of molecular imaging strategies has been pivotal in optimizing gene therapy; since it can allow us to evaluate the effectiveness of gene delivery noninvasively and spatiotemporally. Due to the unique physiochemical properties of nanomaterials, numerous functional nanoparticles show promise in accomplishing gene delivery with the necessary feature of visualizing the delivery. In this review, recent developments of nanoparticles for molecular imaging guided gene delivery are summarized.

Nuclear localization and antisense effect of PNA internalized by ASGP-R-mediated endocytosis with protein/DNA conjugates

In order for peptide nucleic acids (PNAs) to be effective as therapeutic agents, methods for cellular delivery must be developed. Here we demonstrate spontaneous nuclear localization and antisense effects of peptide nucleic acids (PNAs) delivered to hepatic cells through asialoglycoprotein receptor-mediated endocytosis. Asialofetuin conjugates with DNA oligonucleotides (AF/DNA) complementary to the PNA of interest were designed as cell-specific delivery vectors. PNAs hybridized to the asialofetuin-oligonucleotide conjugates were internalized into murine primary hepatocytes and human HepG2 hepatocarcinoma cells effectively through receptor-mediated endocytosis in vitro. After a 4-h incubation, PNAs were largely localized in the nuclei of the cells; the mechanisms involved are still unclear. More than 70% inhibition of telomerase activity was observed when PNAs complementary to the RNA template of human telomerase were delivered to HepG2 cells using AF/DNA. The PNAs were stably associated with the AF/DNA conjugates in 50% serum at 37°C for at least 3h. The PNAs were spontaneously released from the conjugate through a strand exchange mechanism when complementary nucleic acid was added. The complexation of PNAs with the AF/DNA conjugates resulted in delivery of PNAs to liver after intravenous injection into mice. The present study indicates that conjugation to a natural proteinous ligand can be used as a non-toxic vector for cellular delivery of oligonucleotide analogs.