Development of biomaterials for gene therapy

RNAi for treating hepatitis B viral infection

Chronic hepatitis B virus (HBV) infection is one of the leading causes of liver cirrhosis and hepatocellular carcinoma (HCC). Current treatment strategies of HBV infection including the use of interferon (IFN)-α and nucleotide analogues such as lamivudine and adefovir have met with only partial success. Therefore, it is necessary to develop more effective antiviral therapies that can clear HBV infection with fewer side effects. RNA interference (RNAi), by which a small interfering RNA (siRNA) induces the gene silence at a post-transcriptional level, has the potential of treating HBV infection. The successful use of chemically synthesized siRNA, endogenous expression of small hairpin RNA (shRNA) or microRNA (miRNA) to silence the target gene make this technology towards a potentially rational therapeutics for HBV infection. However, several challenges including poor siRNA stability, inefficient cellular uptake, widespread biodistribution and non-specific effects need to be overcome. In this review, we discuss several strategies for improving the anti-HBV therapeutic efficacy of siRNAs, while avoiding their off-target effects and immunostimulation. There is an in-depth discussion on the (1) mechanisms of RNAi, (2) methods for siRNA/shRNA production, (3) barriers to RNAi-based therapies, and (4) delivery strategies of siRNA for treating HBV infection.

Bioreducible poly(amido amine)s with oligoamine side chains: synthesis, characterization, and structural effects on gene delivery

A group of bioreducible poly(amido amine)s containing multiple disulfide linkages in main chain and oligoamines in side chain (SS-PAOAs) were prepared by Michael-type polyaddition of N-tert-butyloxycarbonyl (N-Boc) protected oligoamine to the disulfide-containing cystaminebisacrylamide, followed by deprotection of the Boc-protective groups. These linear polymers show strong DNA condensation capability at low N/P ratios. The chemical structure of oligoamine side chains (i.e. amine type and amino spacer length) in the SS-PAOAs has a distinct effect on their buffer capacity, transfection efficiency and toxicity profile. The SS-PAOAs containing secondary amino functions in the side chain show high buffer capacities and are able to transfect COS-7 cells in vitro at low N/P ratios, with transfection efficiencies similar or even higher than those of 25 kDa branched pEI, along with very low cytotoxicity as determined by XTT assay. Increase of the alkyl spacer from ethylene to propylene between the amino units in side chains results in significant lower transfection and increased toxicity. This study presents detailed factors influencing the relationship between structure and gene delivery properties and may provide helpful insights for the further development of safe and efficient non-viral vectors.

RNA interference and antiviral therapy

RNA interference (RNAi) is an evolutionally conserved gene silencing mechanism present in a variety of eukaryotic species. RNAi uses short double-stranded RNA (dsRNA) to trigger degradation or translation repression of homologous RNA targets in a sequence-specific manner. This system can be induced effectively in vitro and in vivo by direct application of small interfering RNAs (siRNAs), or by expression of short hairpin RNA (shRNA) with non-viral and viral vectors. To date, RNAi has been extensively used as a novel and effective tool for functional genomic studies, and has displayed great potential in treating human diseases, including human genetic and acquired disorders such as cancer and viral infections. In the present review, we focus on the recent development in the use of RNAi in the prevention and treatment of viral infections. The mechanisms, strategies, hurdles and prospects of employing RNAi in the pharmaceutical industry are also discussed.

Biomaterial-mediated retroviral gene transfer using self-assembled monolayers

Biomaterial-mediated gene delivery has recently emerged as a promising alternative to conventional gene transfer technologies that focus on direct delivery of viral vectors or DNA-polymer/matrix complexes. However, biomaterial-based strategies have primarily targeted transient gene expression vehicles, including plasmid DNA and adenovirus particles. This study expands on this work by characterizing biomaterial properties conducive to the surface immobilization of retroviral particles and subsequent transduction of mammalian cells at the cell-material interface. Self-assembled monolayers (SAMs) of functionally-terminated alkanethiols on gold were used to establish biomaterial surfaces of defined chemical composition. Gene transfer was observed to be greater than 90% on NH(2)-terminated surfaces, approximately 50% on COOH-functionalized surfaces, and undetectable on CH(3)-terminated SAMs, similar to controls of tissue culture-treated polystyrene. Gene delivery via the NH(2)-SAM was further characterized as a function of retrovirus coating time, virus concentration, and cell seeding density. Finally, SAM-mediated gene delivery was comparable to fibronectin- and poly-l-lysine-based methods for gene transfer. This work is significant to establishing safe and effective gene therapy strategies, developing efficient methods for gene delivery, and supporting recent progress in the field of biomaterial-mediated gene transfer.

Overexpression of GRF Encapsulated in PLGA Microspheres in Animal Skeletal Muscle Induces Body Weight Gain

Biodegradable nanospheres or microspheres have been widely used as a sustained release system for the delivery of bioagents. In the present study, injectable sustained-release growth hormone-releasing factor (GRF) (1-32) microspheres were prepared by a double emulsion-in liquid evaporation process using biodegradable polylactic-co-glycolic acid (PLGA) as the carrier. The entrapment efficiency was 89.79% and the mean particle size was 4.41 mum. The microspheres were injected into mouse tibialis muscle. After 30 days, mice injected with GRF (1-32) microspheres (group I) gained significantly more weight than any other treatment group, including mice injected with the naked plasmid (group II) (10.26 +/- 0.13 vs. 9.09 +/- 0.56; P < 0.05), a mixture of microspheres and plasmid (group III) (10.26 +/- 0.13 vs. 8.57 +/- 0.02; P < 0.05), or saline (IV) (10.26 +/- 0.13 vs. 6.47 +/- 0.26; P < 0.05). In addition, mice treated with the GRF (1-32) microspheres exhibited the highest expression levels of GRF as detected by PCR, RT-PCR, and ELISA (mean 2.56 +/- 0.40, P < 0.05, overall comparison of treatment with groups II, III, and IV). Additionally, rabbits were injected in the tibialis muscle with the same treatments described above. After 30 days, the group treated with GRF (1-32) microspheres gained the most weight. At day 30 postinjection, weight gain in group I was 63.93% higher than group II (plasmid) (877.10 +/- 24.42 vs. 535.05 +/- 26.38; P < 0.05), 108.59% higher than group III (blank MS) (877.10 +/- 24.42 vs. 420.50 +/- 19.39; P < 0.05), and 93.94% higher than group IV (saline) (877.10 +/- 24.42 vs. 452.25 +/- 27.38; P < 0.05). Furthermore, IGF-1 levels in the serum from GRF microsphere-treated group were elevated relative to all other groups. The present results suggest that encapsulation of GRF with PLGA increases GRF gene expression in muscle after local plasmid delivery, and stimulates significantly more weight gain than delivery of the naked plasmid alone.

Solid lipid nanoparticles: Formulation factors affecting cell transfection capacity

Since solid lipid nanoparticles (SLNs) were introduced as non-viral transfection systems, very few reports of their use for gene delivery have been published. In this work different formulations based on SLN-DNA complexes were formulated in order to evaluate the influence of the formulation components on the "in vitro" transfection capacity. SLNs composed by the solid lipid Precirol ATO 5, the cationic lipid DOTAP and the surfactant Tween 80, and SLN-DNA complexes prepared at different DOTAP/DNA ratios were characterized by studying their size, surface charge, DNA protection capacity, transfection and cell viability in HEK293 cultured cells. The incorporation of Tween 80 allowed for the reduction of the cationic lipid concentration. The formulations prepared at DOTAP/DNA ratios 7/1, 5/1 and 4/1 provided almost the same transfection levels (around 15% transfected cells), without significant differences between them (p>0.05). Other assayed formulations presented lower transfection. Transfection activity was dependent on the DOTAP/DNA ratio since it influences the DNA condensation into the SLNs. DNA condensation is a crucial factor which conditions the transfection capacity of SLNs, because it influences DNA delivery from nanoparticles, gene protection from external agents and DNA topology.

An efficient vector for gene delivery: α,β-poly (3-dimethylaminopropyl-d,l-aspartamide)

PSI, as the potential peptide-like intermediate, is subject to simple chemical modification in order to obtain good non-viral carriers for gene delivery. This paper describes the facile synthesis and preliminary evaluation of alpha,beta-poly (3-dimethylaminopropyl-D,L-aspartamide) (PDAI) as a vector. Reaction of PSI with 3-dimethylamino-1-propylamine afforded PDAI in N,N-dimethylformamide (DMF) solution. Such biophysical properties of PDAI/DNA complexes as the particle size and the zeta potential were determined by dynamic light scattering assay. The complexes prepared at weight ratios ranging from 2 to 3 have an average size of around 200 nm and a zeta potential of around 10.0 mV. Gel electrophoresis assays confirmed that PDAI could compact DNA to form the complexes and protect DNA from enzymatic degradation by DNase I at the weight ratio above 2.0. Furthermore, PDAI was found to transfect HepG2 cells at a much higher efficiency than commercially available polyethylenimine (PEI) (W(w)=75,000 Da). MTT cytotoxicity assay demonstrated that PDAI also showed much less toxicity than did PEI, suggesting that PDAI is a new class of transfection reagent to be used as a safe vector.

DNA delivery to the mitochondria sites using mitochondrial leader peptide conjugated polyethylenimine

Some genetic diseases are associated with the defects of the mitochondrial genome. Direct DNA delivery to the mitochondrial matrix has been suggested as an approach for mitochondrial gene therapy for these diseases. We hypothesized that a mitochondrial leader peptide (LP) conjugated polyethylenimine (PEI) could deliver DNA to the mitochondrial sites. PEI-LP was synthesized by the conjugation of LP to PEI using disulfide bond. The complex formation of PEI-LP with DNA was confirmed by a gel retardation assay. In this study, DNA was completely retarded at a 0.4/1 PEI-LP/DNA weight ratio. In vitro delivery tests into isolated mitochondria or living cells were performed with rhodamin-labeled DNA and PEI-LP. In vitro cell-free delivery assay with isolated mitochondria showed that PEI-LP/DNA complexes were localized at mitochondria sites. Furthermore, the PEL-LP/DNA complexes were localized at the mitochondrial sites in living cells. However, a control carrier, PEI, did not show this effect. In addition, MTT assay showed that PEI-LP showed lower cytotoxicity than PEI. These results suggest that PEI-LP can deliver DNA to the mitochondrial sites and may be useful for the development of mitochondrial gene therapy.

Poly(ethylene glycol)-modified thiolated gelatin nanoparticles for glutathione-responsive intracellular DNA delivery

Poly(ethylene glycol) (PEG)-modified thiolated gelatin (PEG-SHGel) anoparticles were developed as a long-circulating passively targeted delivery system that responds to intracellular glutathione concentrations to enhance DNA delivery and transfection. Reporter plasmid expressing enhanced green fluorescent protein (EGFP-N1) was encapsulated in the nanoparticles. DNA-containing gelatin (Gel) and thiolated gelatin (SHGel) nanoparticles were found to have a size range of 220 to 250 nm, whereas surface modification with PEG resulted in particles with a slightly larger size range of 310 to 350 nm. PEG modification was confirmed by electron spectroscopy for chemical analysis (ESCA), where an increase in the ether peak intensities of the C1s spectra corresponds to the surface presence of ethylene oxide residues. In addition, the PEG-SHGel nanoparticles released encapsulate plasmid DNA in response to varying concentrations of glutathione (up to 5.0 mM GSH in phosphate-buffered saline, or PBS). The stability of the encapsulated DNA was confirmed by agarose gel electrophoresis. Finally, from the qualitative and quantitative results of in vitro transfection studies in murine fibroblast cells (NIH3T3), PEG-Gel and PEG-SHGel nanoparticles afforded the highest transfection efficiency of the reporter plasmid. The results of these studies show that PEG-modified thiolated gelatin nanoparticles could serve as a very efficient nanoparticulate vector for systemic DNA delivery to solid tumors where the cells are known to have significantly higher intracellular GSH concentrations.

Cationic star polymers consisting of alpha-cyclodextrin core and oligoethylenimine arms as nonviral gene delivery vectors

A series of novel cationic star polymers were synthesized by conjugating multiple oligoethylenimine (OEI) arms onto an alpha-cyclodextrin (alpha-CD) core as nonviral gene delivery vectors. The molecular structures of the alpha-CD-OEI star polymers, which contained linear or branched OEI arms with different chain lengths ranging from 1 to 14 ethylenimine units, were characterized by using size exclusion chromatography, 13C and 1H NMR, and elemental analysis. The alpha-CD-OEI star polymers were studied in terms of their DNA binding capability, formation of nanoparticles with plasmid DNA (pDNA), cytotoxicity, and gene transfection in cultured cells. All the alpha-CD-OEI star polymers could inhibit the migration of pDNA on agarose gel through formation of complexes with pDNA, and the complexes formed nanoparticles with sizes ranging from 100 to 200 nm at N/P ratios of 8 or higher. The star polymers displayed much lower in vitro cytotoxicity than that of branched polyethylenimine (PEI) of molecular weight 25K. The alpha-CD-OEI star polymers showed excellent gene transfection efficiency in HEK293 and Cos7 cells. Generally, the transfection efficiency increased with an increase in the OEI arm length. The star polymers with longer and branched OEI arms showed higher transfection efficiency. The best one of the star polymers for gene delivery showed excellent in vitro transfection efficiency that was comparable to or even higher than that of branched PEI (25K). The novel alpha-CD-OEI star polymers with OEI arms of different chain lengths and chain architectures can be promising new nonviral gene delivery vectors with low cytotoxicity and high gene transfection efficiency for future gene therapy applications.

Efficient siRNA delivery using water soluble lipopolymer for anti-angiogenic gene therapy

We examined the potential application of a non-viral gene carrier, water soluble lipopolymer (WSLP) for delivering siRNA targeting vascular endothelial growth factor (VEGF) in vitro and in vivo. WSLP was complexed with siRNA designed to inhibit human VEGF expression or scrambled siRNA as a control. WSLP readily formed nano-sized complexes ( approximately 100 nm) with siRNA and protected siRNAs from enzymatic degradation in serum conditioned media. WSLP/siRNA complexes were transfected in PC-3 cells derived from human prostate adenocarcinomas and, then the siRNA delivery efficiency of the complexes was evaluated by VEGF production inhibition assay. VEGF production was efficiently inhibited by the WSLP/siRNA complexes, while complexes of WSLP with scrambled siRNA did not show this inhibitory effect. WSLP/siRNA complexes reduced the VEGF production by 40% when compared to unmodified branched polyethylenimine (bPEI, MW=1800). Moreover, WSLP/siRNA complexes reduced tumor volume by 55% at 21 days, and by 65% at 28 days when compared to controls. These results indicate that WSLP has potential as a siRNA delivering agent and can be applied for anti-angiogenic tumor therapy.

Hydrophobization and bioconjugation for enhanced siRNA delivery and targeting

RNA interference (RNAi) is an evolutionarily conserved process by which double-stranded small interfering RNA (siRNA) induces sequence-specific, post-transcriptional gene silencing. Unlike other mRNA targeting strategies, RNAi takes advantage of the physiological gene silencing machinery. The potential use of siRNA as therapeutic agents has attracted great attention as a novel approach for treating severe and chronic diseases. RNAi can be achieved by either delivery of chemically synthesized siRNAs or endogenous expression of small hairpin RNA, siRNA, and microRNA (miRNA). However, the relatively high dose of siRNA required for gene silencing limits its therapeutic applications. This review discusses several strategies to improve therapeutic efficacy as well as to abrogate off-target effects and immunostimulation caused by siRNAs. There is an in-depth discussion on various issues related to the (1) mechanisms of RNAi, (2) methods of siRNA production, (3) barriers to RNAi-based therapies, (4) biodistribution, (5) design of siRNA molecules, (6) chemical modification and bioconjugation, (7) complex formation with lipids and polymers, (8) encapsulation into lipid particles, and (9) target specificity for enhanced therapeutic effectiveness.

Encapsulation of nucleic acids and opportunities for cancer treatment

The development of nucleic acid drugs for the treatment of various cancers has shown great promise in recent years. However, efficient delivery of these drugs to target cells remains a significant challenge towards the successful development of such therapies. This review provides a comprehensive overview of encapsulation technologies being developed for the delivery of nucleic acid-based anti-cancer agents. Both micro and nanoparticles systems are discussed along with their use in delivering plasmid DNA as well as oligonucleotides. The majority of the systems discussed have used DNA immunotherapy as the potential mode of anticancer therapy, which requires targeting to antigen presenting cells. Other applications, including those with oligonucleotides, focus on targeting tumor cells directly. The results obtained so far show the excellent promise of encapsulation as an efficient means of delivering therapeutic nucleic acids.

Interleukin-10 plasmid construction and delivery for the prevention of type 1 diabetes

Studies of animals with spontaneous autoimmune diabetes have revealed that autoreactive T cells that mediate islet beta cell destruction can be manipulated by the administration of Th(2) cytokines. In this article, the effect of interleukin-10 (IL-10) gene delivery was evaluated in vitro and in vivo with a novel IL-10 plasmid, pSI-IL-10-NFkappaB. In pSI-IL-10-NFkappaB, the expression of the IL-10 gene was driven by the SV40 promotor/enhancer. The nuclear factor kappaB (NFkappaB) binding sites were also introduced to facilitate nuclear transport of the plasmid in the cell. In vitro transfection assay with pSI-IL-10-NFkappaB showed a similar expression level of IL-10 to the plasmid without NFkappaB binding sites (pSI-IL-10). pSI-IL-10-NFkappaB and pSI-IL-10 were intravenously injected into 5-week-old nonobese diabetic (NOD) mice using polyethylenimine (PEI) as a gene carrier. Both groups had persistent gene expression, longer than 5 weeks, and secreted the similarly high IL-10 serum levels. Interestingly, the degree of insulitis in the pSI-IL-10-NFkappaB group was improved over the pSI-IL-10 group, PEI-only group, and noninjected controls. The serum glucose levels showed that single injection of pSI-IL-10-NFkappaB prevented the development of diabetes in 100% of the pSI-IL-10-NFkappaB-injected animals (5/5), while that of pSI-IL-10 prevented diabetes in 40% of the treated animals (2/5). These results suggest that pSI-IL-10-NFkappaB with PEI can effectively reduce the incidence of insulitis and type 1 diabetes in NOD mice.

A biodegradable poly(ester amine) based on polycaprolactone and polyethylenimine as a gene carrier

The aim of research was to develop and optimize delivery systems for plasmid DNA (pDNA) based on biodegradable polymers, in particular, poly(ester amine)s (PEAs), suitable for non-viral gene therapy. Poly(ester amine)s were successfully synthesized by Michael addition reaction between polycaprolactone (PCL) diacrylate and low molecular weight polyethylenimine (PEI). PEA/DNA complexes showed effective and stable DNA condensation with the particle sizes below 200nm, implicating its potential for intracellular delivery. PEAs showed controlled degradation and were essentially non-toxic in all three cells (293T: Human kidney carcinoma, HepG2: Human hepatoblastoma and HeLa: Human cervix epithelial carcinoma cell lines) at higher doses in contrast to PEI 25K. PEAs also revealed much higher transfection efficiencies in three cell lines as compared to PEI 25K. The highest reporter gene expression was observed for PCL/PEI-1.2 (MW 1200) complex having transfection efficiency 15-25 folds higher than PEI 25K in vitro. Also PEA/DNA complexes successfully transfected cells in vivo after aerosol administration than PEI 25K. These PEAs can be used as most efficient polymeric vectors which provide a versatile platform for further investigation of structure property relationship along with the controlled degradation, significant low cytotoxicity and high transfection efficiency.

Effects of alginate inclusion on the vector properties of chitosan-based nanoparticles

Chitosan nanoparticles have shown considerable promise as gene vectors but do not mediate transfection with satisfactory efficiency. To improve upon the transfection efficiency of chitosan, we approached the development of alginate-chitosan nanoparticles with the goals of maintaining low toxicity and biocompatibility. Through ionic gelation, particles were formed with a mean Z-average diameter of 157 nm and a zeta potential of +32 mV. Competition binding assays indicated that the presence of alginate reduces the strength of interaction between chitosan and DNA, contributing to improved transfection. Cell viability assays indicated that nanoparticles exhibit the same low toxicity as chitosan, and significantly reduced toxicity compared to a commercial liposome formulation. As well, complexation with nanoparticles maintained DNA integrity and protected it from nuclease degradation better than chitosan alone. Alginate-chitosan nanoparticles were able to mediate transfection of 293T cells four times that achieved by chitosan nanoparticles; at 48 h, the transfection efficiency was as high as with Lipofectamine, with significantly reduced cytotoxicity. Overall, alginate inclusion improved the vector properties of chitosan-based nanoparticles, demonstrating superior transfection ability while maintaining biocompatibility and low toxicity.

Toxicity of cationic lipids and cationic polymers in gene delivery

Gene therapy, as a promising therapeutics to treat genetic or acquired diseases, has achieved exciting development in the past two decades. Appropriate gene vectors can be crucial for gene transfer. Cationic lipids and polymers, the most important non-viral vectors, have many advantages over viral ones as non-immunogenic, easy to produce and not oncogenic. They hold the promise to replace viral vectors to be used in clinic. However, the toxicity is still an obstacle to the application of non-viral vectors to gene therapy. For overcoming the problem, many new cationic compounds have been developed. This article provides a review with respect to toxicity of cationic lipids and polymers in gene delivery. We evaluate the structural features of cationic compounds and summarize the relationship of toxicity and structure and hope to provide available suggestions on the development of these cationic compounds.

The State of the Art of Nanobioscience in Japan

This paper reviews a part of the state of the art of nanobioscience in Japan. The importance of combination and integration of interdisciplinary principles is emphasized for the development of nanobioscience. Biomagnetics, biomechanics, nanomachining, self-replicating cell model, neuronal network, drug delivery system, and tissue engineering are discussed.

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

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

Antiviral applications of RNAi for coronavirus

Until the appearance of severe acute respiratory syndrome (SARS), caused by the SARS coronavirus (SARS-CoV) in early 2003, coronavirus infection was not considered to be serious enough to be controlled by either vaccination or specific antiviral therapy. It is now believed that the availability of antiviral drugs effective against SARS-CoV will be crucial for the control of future SARS outbreaks. Recently, RNA interference has been successfully used as a more specific and efficient method for gene silencing. RNA interference induced by small interfering RNA can inhibit the expression of viral antigens and so provides a new approach to the therapy of pathogenic viruses. This review provides an overview of current information on coronavirus and the application of small interfering RNA in viral therapeutics, with particular reference to SARS-CoV.

A versatile family of degradable non-viral gene carriers based on hyperbranched poly(ester amine)s

A variety of degradable hyperbranched poly(ester amine)s containing primary, secondary and tertiary amino groups, were synthesized and evaluated as non-viral gene carriers. The polymers were obtained in high yields through a Michael-type conjugate addition of diacrylate monomers with trifunctional amine monomers. Analysis of degradation products using liquid chromatography-mass spectroscopy (LC-MS) demonstrated that all poly(ester amine)s had a hyperbranched structure with a degree of branching of approximately 0.30. These poly(ester amine)s were readily water-soluble and degradable under physiological conditions (pH 7.4, 37 degrees C), in which more than 10% ester bonds were hydrolyzed within 4 h. Moreover, these hyperbranched poly(ester amine)s showed high buffering capacities between pH 5.1 and 7.4. Three out of nine synthesized polymers, i.e. p(HDDA-AEP), p(HDDA-AMP), and p(BDDA-AMP), were shown to effectively condense plasmid DNA into small-sized (approximately 94-135 nm) and positively charged complexes. Polymer/DNA complexes ('polyplexes') based on these three polymers, and larger complexes of p(BDDA-AEP) (approximately 497 nm) were able to transfect COS-7 cells in vitro. Importantly, the transfection activity of polyplexes was preserved in the presence of serum proteins. The highest transfection level was observed for p(HDDA-AEP) polyplex which had a transfection efficiency higher than or comparable to that polyplexes of polyethylenimine (PEI) and poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA). Furthermore, these poly(ester amine)s revealed no or low cytotoxicity. These results demonstrated that hyperbranched poly(ester amine)s can be applied as safe and efficient gene delivery polymers.

Galactosylated polyethylenimine-graft-poly(vinyl pyrrolidone) as a hepatocyte-targeting gene carrier

Polyethylenimine (PEI) has been used for the gene delivery system in vitro and in vivo since it has high transfection efficiency owing to proton buffer capacity. However, the use of PEI for gene delivery is limited due to cytotoxicity, non-specificity and unnecessary interaction with serum components. To overcome cytotoxicity and non-specificity, PEI was coupled with poly(vinyl pyrrolidone) (PVP) as the hydrophilic group to reduce cytotoxicity and lactose bearing galactose group for hepatocyte targeting. The galactosylated-PEI-graft-PVP (GPP) was complexed with DNA, and GPP/DNA complexes were characterized. GPP showed good DNA binding ability, high protection of DNA from nuclease attack. The sizes of DNA complexes show tendency to decrease with an increase of charge ratio and had a minimum value around 59 nm at the charge ratio of 40 for the GPP-1/DNA complex (PVP content: 4.1 mol%). The GPP showed low cytotoxicity. And GPP/DNA complexes were mediated by asialoglycoprotein receptors (ASGP-R)-mediated endocytosis. Also, the transfection efficiency of GPP-1/DNA complex at charge ratio of 40 in the HepG2 was higher than that of PEI/DNA one.

Cryoconserved shielded and EGF receptor targeted DNA polyplexes: cellular mechanisms

Recently, cryoconservable polyethylene glycol (PEG)-shielded and epidermal growth factor receptor (EGFR)-targeted polyplexes (EGF+ polyplexes) were engineered in our laboratory for tumor-directed transfer and expression of DNA. Here, we further analyzed specificity and kinetics of EGFR-mediated cellular uptake of these polyplexes. Similar to our previous results, EGF+ polyplexes significantly enhanced the transfection efficiency as compared to polyplexes without EGF (EGF- polyplexes) in HUH-7 hepatoma cells and Renca-EGFR renal carcinoma cells. EGF+ polyplexes rapidly associated with the cells within 30 min of exposure, and binding of EGF+ polyplexes to the cells after 4 h was significantly higher than that of EGF- polyplexes. In the presence of free EGF, both cell association and transfection efficiency of EGF+ polyplexes were markedly reduced indicating that these effects were primarily mediated via ligand receptor interaction. Fluorescence microscopy revealed that the cell-associated EGF+ polyplexes aggregated to micrometer sized clusters, resembling typical clustering of receptors upon ligand binding. In conclusion, EGFR-targeting enhances transfection efficiency due to accelerated and increased cell association followed by aggregation of the bound EGF+ polyplexes.

Local, non-viral IL-12 gene therapy using a water soluble lipopolymer as carrier system combined with systemic paclitaxel for cancer treatment

Development of improved gene transfer methods is needed for gene therapy to achieve its clinical potential. The use of biocompatible polymeric gene carriers has shown effectiveness in overcoming the current problems associated with viral vectors in safety, immunogenicity and mutagenesis. Previous work has demonstrated that repeated, local, non-viral interleukin-12 (IL-12) gene delivery successfully slows down tumor progression, while improving immunogenicity. Combining IL-12 gene delivery with systemic paclitaxel (PCT) chemotherapy as a treatment for various subcutaneous mouse mammary carcinomas, we used PCT with either a biodegradable polymeric solubilizer, HySolv or Cremophor EL for systemic treatment and injected water soluble lipopolymer (WSLP)/plasmid-encoding IL-12 gene (p2CMVmIL-12) complexes local once every week. The amount of lung metastases being essential for survival as well as subcutaneous tumor volume were compared against untreated controls. We showed inhibition of tumor growth and decreased lung metastases in the combined WSLP/p2CMVmIL-12/HySolv group compared to the controls and the PCT only treated groups. Compared to Cremophor, HySolv performed better alone or in combination with IL-12. Using polymeric vectors as gene carrier systems in combination with improved systemic therapies provide evidence for the efficacy and feasibility of polymer-based drug delivery systems. Especially local cytokine gene delivery showed augmentation of systemic chemotherapy while reducing the hosts risk for further systemic toxicity.

Silencing viruses by RNA interference

Post-transcriptional gene silencing (PTGS) makes possible new approaches for studying the various steps of the viral cycle. Plus-strand RNA viruses appear to be attractive targets for small interfering RNAs (siRNAs), as their genome functions as both mRNA and replication template. PTGS creates an alternative to classic reverse genetics for viruses with either negative-strand or double-stranded RNA genomes and for those with a large genome. PTGS allows modification of the expression of a given cellular gene as a means to elucidate its role in the viral cycle and in virus-host cell interactions, and to investigate cellular pathways involved in viral pathogenesis. It also allows the creation of new animal models of human diseases. In addition, PTGS already appears to be a promising new therapeutic tool to fight viral multiplication and dissemination through the host and to prevent inflammation and virus-induced pathogenesis, including virus-induced tumorigenesis.

Cytokine therapy for craniosynostosis

The birth prevalence of craniosynostosis (premature suture fusion) is 300-500 per 1,000,000 live births. Surgical management involves the release of the synostosed suture. In many cases, however, the suturectomy site rapidly reossifies, further restricts the growing brain and alters craniofacial growth. This resynostosis requires additional surgery, which increases patient morbidity and mortality. New findings in bone biology and molecular pathways involved with suture fusion, combined with novel tissue engineering techniques, may allow the design of targeted and complementary therapies to decrease complications inherent in high-risk surgical procedures. This paper selectively reviews recent advances in i) identifying genetic mutations and the aetiopathogenesis of a number of craniosynostotic conditions; ii) cranial suture biology and molecular biochemical pathways involved in suture fusion; and iii) the design, development and application of various vehicles and tissue engineered constructs to deliver cytokines and genes to cranial sutures. Such biologically based therapies may be used as surgical adjuncts to rescue fusing sutures or help manage postoperative resynostosis.

Synthesis of biodegradable multi-block copolymers of poly(L-lysine) and poly(ethylene glycol) as a non-viral gene carrier

Biodegradable and non-toxic multi-block copolymers based on poly(L-lysine) and poly(ethylene glycol) were synthesized. Synthesized copolymers showed almost negligible cytotoxicity above 95% cell viability and transfection efficiency compared to the PLL homopolymer with molecular weight of 25,700. Biodegradation under physiological conditions revealed that the molecular weight of copolymers decreased to 20% of the initial molecular weight within 72 h. Transfection efficiencies of copolymers were not affected by the presence of serum, while that of PLL homopolymer decreased to the level of naked DNA in the presence of serum. Based on the results, the new copolymers are believed to be a potentially efficient carrier for the delivery of bioactive agents.

Photochemically enhanced gene delivery of EGF receptor-targeted DNA polyplexes

Epidermal growth factor receptor (EGFR) targeted DNA polyplexes, containing polyethylenimine (PEI) conjugated with EGF protein as cell-binding ligand for endocytosis and polyethylene glycol (PEG) for masking the polyplex surface charge, mediated a 3- to 30-fold higher luciferase gene expression in HUH7, HepG2 and A431 cell transfections than analogous untargeted PEG-PEI polyplexes. Transfection levels can be further enhanced by treatment of cells with amphiphilic photosensitizers followed by illumination. In this process photosensitizers localized in membranes of endocytic vesicles are activated by light, resulting in the destruction of endocytic membrane structures and releasing co-endocytosed polyplexes into the cell cytosol. Photochemical enhanced gene expression was observed in all cell lines, with the magnitude of enhancement depending on the particular PEI polyplex formulation and cell line, ranging between 2- and 600-fold. Importantly, improved gene transfer retained EGF receptor specificity, as demonstrated by comparison with ligand-free polyplexes and by receptor antibody or ligand competition experiments. These results suggest that this combined procedure enables a dual mode of targeting polyplexes: biological targeting via EGFR interaction, combined with physical targeting with light to direct a photochemical delivery of therapeutic genes to a desired location.

Terplex Gene Delivery System

Polymeric gene delivery systems have been developed to overcome problems caused by viral carriers. They are low cytotoxic, have no size limit, are convenient in handling, of low cost and reproducible. A Terplex gene delivery system consisting of plasmid DNA, low density lipoprotein and hydropholized poly-L-lysine was designed and characterized. The plasmid DNA, when formulated with stearyl PLL and LDL, forms a stable and hydrophobicity/charge-balanced Terplex system of optimal size for efficient cellular uptake. DNA is still intact after the Terplex formation. This information is expected to be utilized for the development of improved transfection vector for in vivo gene therapy. Terplex DNA complex showed significantly longer retention in the vascular space than naked DNA. This system was used in the augmentation of myocardial transfection at an infarction site with the VEGF gene.

Biocompatible polymer enhances thein vitro andin vivo transfection efficiency of HVJ envelope vector

BACKGROUND

Vector development is critical for the advancement of human gene therapy. However, the use of viral vectors raises many safety concerns and most non-viral methods are less efficient for gene transfer. One of the breakthroughs in vector technology is the combination of the vector with various polymers.

METHODS

HVJ (hemagglutinating virus of Japan) envelope vector (HVJ-E) has been developed as a versatile gene transfer vector. In this study, we combined HVJ-E with cationized gelatin to make it a more powerful tool and assessed its transfection efficiency in vitro and in vivo. In addition, we investigated the mechanism of the gene transfer by means of the inhibition of fusion or endocytosis.

RESULTS

The combination of both protamine sulfate and cationized gelatin with HVJ-E, referred to as PS-CG-HVJ-E, further enhanced the in vitro transfection efficiency. In CT26 cells, the luciferase gene expression of PS-CG-HVJ-E was approximately 10 times higher than that of the combination of protamine sulfate with HVJ-E or the combination of cationized gelatin with HVJ-E, referred to as PS-HVJ-E or CG-HVJ-E, respectively. Furthermore, the luciferase gene expression in liver mediated by intravenous administration of CG-HVJ-E was much higher than the luciferase gene expression mediated by PS-HVJ-E or PS-CG-HVJ-E and approximately 100 times higher than that mediated by HVJ-E alone.

CONCLUSIONS

Cationized gelatin-conjugated HVJ-E enhanced gene transfection efficiency both in vitro and in vivo. These results suggest that low molecular weight cationized gelatin may be appropriate for complex formation with various envelope viruses, such as retrovirus, herpes virus and HIV.

Peptide dendrimers

Dendrimers are branched structures and represent a fast growing field covering many areas of chemistry. Various types of dendrimers differing in composition and structure are mentioned, together with their practical use spanning from catalysis, transport vehicles to synthetic vaccines. The main stress is given to peptide dendrimers, namely, multiple antigenic peptides (MAPs). Their synthesis, physicochemical properties, biological activities, etc. have been described with many examples. MAPs can be used as diagnostics, mimetics, for complexation of different cations, as vaccines against parasites, bacteria, viruses, etc.

pDNA loaded calcium phosphate nanoparticles: highly efficient non-viral vector for gene delivery

Nanoparticles of calcium phosphate encapsulating plasmid DNA (pDNA) of size 100-120 nm in diameter were prepared. XRD studies of these nanoparticles showed them to be crystalline in nature having hydroxyapatite structure. The maximum loading of pDNA and its release from nanoparticles were studied using gel electrophoresis. The time dependent size measurement of these particles demonstrated that these particles show strong aggregational behaviour in aqueous dispersion. Calcium phosphate nanoparticles were found to be dissolved even in low acidic buffer (pH 5.0) releasing the pDNA, which suggested that DNA release from these particles in the endosomal compartment was possible. In vitro transfection efficiency of these calcium phosphate nanoparticles was found to be higher than that of the commercial transfecting reagent Polyfect.

Unilateral Kidney-Selective Gene Transfer Following the Administration of Naked Plasmid DNA to the Kidney Surface in Mice

We developed a gene transfer following the administration of naked plasmid DNA (pDNA) to the kidney surface in mice, and found that the luciferase levels produced in the applied kidney were significantly higher than those produced in another kidney. In contrast, stable renal gene expression was not observed in the case of intraperitoneal or intravenous administration of pDNA. The level of gene expression after instillation of pDNA to the kidney surface reached maximum at 12 h and gradually diminished thereafter. The production of luciferase was saturated at 5 microg of pDNA, and was not affected by instillation volume. Furthermore, pDNA uptake from the kidney surface was proved by in situ experiments using a glass-made diffusion cell. We demonstrated a novel unilateral kidney-selective gene transfer following the administration of naked pDNA to the kidney surface in mice.

Targeting of Polyplexes: Toward Synthetic Virus Vector Systems

Dominating issues in gene vector optimization are specific in recognizing the target cells and exploiting the proper intracellular trafficking routes. Any progress in this area will result in improved specific gene transfer, reduce the required therapeutic vector doses and, in consequence, lower the overall toxicity to the host. To provide polyplexes with the ability to distinguish between non-target and target cells, cell-binding ligands have been incorporated which recognize target-specific cellular receptors. In addition, polyplex domains with unspecific binding capacity (such as surface charges) have to be shielded or removed. Cell-binding ligands can be small molecules, vitamins, carbohydrates, peptides or proteins such as growth factors or antibodies. Such ligands have been incorporated into polyplexes after chemical conjugation to cationic polymers. The choice of the ligand and physical properties of the DNA formulation strongly influence extracellular routing (circulation in blood, tissue distribution), uptake and intracellular delivery of polyplexes. Recent efforts are discussed that aim at the development of polyplexes into virus-like supramolecular complexes; such particles should undergo structural changes compatible with extracellular and intracellular targeting.

Novel cationic pentablock copolymers as non-viral vectors for gene therapy

New cationic pentablock copolymers of poly(diethylaminoethylmethacrylate) (PDEAEM), poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO)--PDEAEM-b-PEO-b-PPO-b-PEO-b-PDEAEM--synthesized in our laboratory were investigated for their potential as non-viral vectors for gene therapy. Agarose gel studies showed that the copolymers effectively condensed plasmid DNA to form polyplexes, and also protected plasmids against nuclease degradation. Light scattering and transmission electron microscopy were used to analyze the apparent size, molecular weight and morphology of these polyplexes. Lactate dehydrogenase assay was employed to find the cytotoxicity limits of the polymers and polyplexes on a human ovarian cancer cell line. The polymers showed much less cytotoxicity than commercially available ExGen 500 (linear polyethyleneimine). By changing the relative lengths of the blocks in the copolymers, it was found that the cytotoxicity of these copolymers could be tailored. The micellar structures of these copolymers in aqueous solutions and their pH-sensitive protonation were added advantages. In vitro transfection efficiencies of the polymers using green fluorescent protein (pEGFP-N1) and luciferase (pRL-CMV) reporter genes were found comparable to ExGen 500. Besides, aqueous solutions of these pentablock copolymers have been shown to exhibit thermodynamic phase transitions and thermoreversible gelation, a quality that could allow subcutaneous/intramuscular injections of these polymers for controlled gene delivery over time.

Polyethylenimine with acid-labile linkages as a biodegradable gene carrier

Polyethylenimine (PEI) is a gene carrier with high transfection efficiency. However, PEI has high cytotoxicity, which depends on its molecular weight. To reduce the cytotoxicity, degradable PEIs with acid-labile imine linkers were synthesized with low molecular weight PEI1.8K (1.8 kDa) and glutadialdehyde. The molecular weights of the synthesized acid-labile PEIs were 23.7 and 13 kDa, respectively. The half-life of the acid-labile PEI was 1.1 h at pH 4.5 and 118 h at pH 7.4, suggesting that the acid-labile PEI may be rapidly degraded into nontoxic low molecular weight PEI in acidic endosome. In a gel retardation assay, plasmid DNA (pDNA) was completely retarded at a 3:1 N/P (nitrogen of polymer/phosphate of DNA) ratio. The zeta potential of the polyplexes was in the range of 46.1 to 50.9 mV and the particle size was in the range of 131.8 to 164.6 nm. In vitro transfection assay showed that the transfection efficiency of the acid-labile PEIs was comparable to that of PEI25K. In toxicity assay, the acid-labile PEI was much less toxic than PEI25K, due to the degradation of acid-labile linkage. Therefore, the acid-labile PEIs may be useful for the development of a nontoxic polymeric gene carrier.

Novel dextran–spermine conjugates as transfecting agents: comparing water-soluble and micellar polymers

Recently, a novel cationic polymer, dextran-spermine (D-SPM) was developed for gene delivery. An efficient transfection was obtained using this polycation for a variety of genes and cell lines in serum-free or serum-poor medium. However, transfection using the water-soluble D-SPM-based polyplexes decreased with increasing serum concentration in cell culture in a concentration-dependent manner, reaching 95% inhibition at 50% serum in the cell growth medium. In order to overcome this obstacle, oleyl derivatives of D-SPM (which form micelles in aqueous phase) were synthesized at 1, 10, and 20 mol% of oleyl moiety to polymer epsilon-NH2 to form N-oleyl-D-SPM (ODS). Polyplexes based on ODS transfected well in medium containing 50% serum. Comparison with polyplexes based on well-established polymers (branched and linear polyethyleneimine) and with DOTAP/Cholesterol lipoplexes showed that regarding beta-galactosidase transgene expression level and cytotoxicity in tissue culture, the D-SPM and ODS compare well with the above polyplexes and lipoplexes. Intracellular trafficking using FITC-labeled ODS and Rhodamine-labeled pGeneGrip plasmid cloned with hBMP2 monitored by confocal microscopy revealed that during the transfection process the fluorescent-labeled polymer concentrates in the Golgi apparatus and around the nucleus, while the cell cytoplasm was free of fluorescent particles, suggesting that the polyplexes move in the cell toward the nucleus by vesicular transport through the cytoplasm and not by a random diffusion. We found that the plasmids penetrate the cell nucleus without the polymer. Preliminary results in zebra fish and mice demonstrate the potential of ODS to serve as an efficient nonviral vector for in vivo transfection.

Effective transfection of rabies DNA vaccine in cell culture using an artificial lipoprotein carrier system

PURPOSE

To evaluate the transfection efficiency in cell culture of rabies plasmid DNA vaccine carried by a novel artificial lipoprotein system.

METHODS

Phospholipid nanoemulsions resembling the lipid core of natural lipoproteins were prepared. The artificial lipoprotein carrier system for DNA was constructed by assembling of the nanoemulsion (NE)-palmitoyl-poly-L-lysine (p-PLL)-rabies DNA complex. Agarose gel electrophoresis, zeta potential, and mobility measurement were conducted to determine the surface charge balance in various complex compositions. Transfection and transfection efficiency were examined by fluorescence microscopy and flow cytometry, respectively.

RESULTS

The artificial lipoprotein system was successfully constructed and the rabies DNA vaccine was effectively transfected in glioma cell line SF-767. The amount of p-PLL incorporated into the artificial lipoprotein formulations had a significant effect on transfection efficiency. The new system also proved to be more efficient in cellular transfection of rabies DNA vaccine than the commercial lipofectamine formulation.

CONCLUSIONS

Effective transfection of rabies DNA vaccine in cell culture can be achieved using the novel artificial lipoprotein carrier system, and the charge balance of the NE-p-PLL-DNA complex appears an important factor.

Use of siRNAs to prevent and treat influenza virus infection

Influenza virus causes one of the most prevalent infections in humans. In a typical year, 10-20% of the population in the United States are infected by influenza virus, resulting in up to 40,000 deaths. Current vaccines can prevent illness in approximately 70-80% of healthy individuals under age 65, but the protection rate is much lower in those most susceptible to infection, namely infants, the elderly, and immunocompromised individuals. Although four antiviral drugs have been approved in the United States for treatment and/or prophylaxis of influenza, their use is limited because of concerns about side effects, compliance, and the possible emergence of resistant virus. We found that short interfering RNAs (siRNAs) specific for conserved regions of the influenza virus genome are potent inhibitors of influenza virus replication in both cell lines and embryonated chicken eggs. In this review, we discuss the potential value of siRNAs for preventing and treating influenza virus infections in humans and the challenges that have to be overcome to realize their potential.

Liver site-specific gene transfer following the administration of naked plasmid DNA to the liver surface in mice

The present study was undertaken to investigate liver site-specific gene transfer following the administration of naked plasmid DNA (pDNA) to the liver surface in mice. We examined whether genes could be delivered to the liver site specifically by utilizing the glass-made diffusion cell that is able to limit the contact dimension between the liver surface and pDNA solution administered. Gene expression was detected at the site of diffusion cell attachment (site 1) and was significantly higher than in other liver sites and tissues. Moreover, gene expression was also detected at deeper site from the liver surface (noncontact side with pDNA solution). The level of gene expression at site 1 did not change significantly with pDNA treatment for 10, 30, and 60 min. In conclusion, we demonstrated that naked pDNA administered to the liver surface in mice was taken up from its surface, and subsequently the protein encoded by pDNA could be produced site specifically.

Strategies to improve DNA polyplexes for in vivo gene transfer: will "artificial viruses" be the answer?

For the purpose of introducing nucleic acids into cells, cationic polymers have been steadily improved as gene carriers. This has resulted in improved polymer-based gene transfer formulations, termed polyplexes, which efficiently transfect cell cultures and also have shown encouraging gene transfer potential in in vivo administration. Targeted delivery to liver, lung, tumor, or other tissues has been achieved in experimental animals by localized or systemic application. Therapeutic effect has been demonstrated, although efficiencies are still too low to justify clinical use. The limitations of first-generation polymeric carriers (modest activity and significant toxicity) have been addressed by developments of new biodegradable polycations, incorporation of targeting and intracellular transport functions, and polyplex formulations that avoid unspecific adverse interactions with the host. A key future step will be the development of polyplexes into artificial viruses, with virus-like entry functions presented by smart polymers and polymer conjugates. These polymers have to sense their biologic microenvironment, respond in a more dynamic manner to alterations in pH, ionic or redox environment, undergoing programmed structural changes compatible with the different gene delivery steps.

Efficient gene delivery by urocanic acid-modified chitosan

Nonviral delivery systems for gene therapy have been increasingly proposed as safer alternatives to viral vectors. Chitosan is considered to be a good candidate for the gene delivery system since it is already known as a biocompatible, biodegradable, and low toxic material with high cationic charge potential. However, the use of chitosan for gene delivery is limited due to low transfection efficiency. To enhance the transfection efficiency, water-soluble chitosan (WSC) was coupled with urocanic acid (UA) bearing imidazole ring which can play the crucial role in endosomal rupture through proton sponge mechanism. The urocanic acid-modified chitosan (UAC) was complexed with DNA, and UAC/DNA complexes were characterized. The sizes of UAC/DNA complexes under physiological condition (109-342 nm) were almost same as those of chitosan-DNA complexes. UAC also showed good DNA binding ability, high protection of DNA from nuclease attack, and low cytotoxicity. The transfection efficiency of chitosan into 293T cells was much enhanced after coupling with UA and increased with an increase of UA contents in the UAC.

Molecularly designed water soluble, intelligent, nanosize polymeric carriers

Intelligent polymers, also referred as "stimuli-responsive polymers" undergo strong property changes (in shape, surface characteristics, solubility, etc.) when only small changes in their environment (changes in temperature, pH, ionic strength light, electrical and magnetic field, etc.). They have been used in several novel applications, drug delivery systems, tissue engineering scaffolds, bioseparation, biomimetic actuators, etc. The most popular member of these type of polymers is poly(N-isopropylacrylamide) (poly(NIPA)) which exhibits temperature-sensitive character, in which the polymer chains change from water-soluble coils to water-insoluble globules in aqueous solution as temperature increases above the lower critical solution temperature (LCST) of the polymer. Copolymerization of NIPA with acrylic acid (AAc) allows the synthesis of both pH and temperature-responsive copolymers. This paper summarizes some of our related studies in which NIPA and its copolymers were synthesized and used as intelligent carriers in diverse applications.