Gene transfer into hepatoma cells mediated by galactose-modified alpha-helical peptides

Peptides, polypeptides and peptide–polymer hybrids as nucleic acid carriers

Peptide, polypeptide and polymer–peptide hybrid based nucleic acid therapeutics (NAT).

Galactose-decorated light-responsive hydrogelator precursors for selectively killing cancer cells

A multi-functional gelator precursor with high photosensitivity is rationally designed for selectively inhibiting liver cancer cells.

Asialoglycoprotein Receptor-Mediated Gene Delivery to Hepatocytes Using Galactosylated Polymers

Highly efficient, specific, and nontoxic gene delivery vector is required for gene therapy to the liver. Hepatocytes exclusively express asialoglycoprotein receptor (ASGPR), which can recognize and bind to galactose or N-acetylgalactosamine. Galactosylated polymers are therefore explored for targeted gene delivery to the liver. A library of safe and stable galactose-based glycopolymers that can specifically deliver genes to hepatocytes were synthesized having different architectures, compositions, and molecular weights via the reversible addition-fragmentation chain transfer process. The physical and chemical properties of these polymers have a great impact on gene delivery efficacy into hepatocytes, as such block copolymers are found to form more stable complexes with plasmid and have high gene delivery efficiency into ASGPR expressing hepatocytes. Transfection efficiency and uptake of polyplexes with these polymers decreased significantly by preincubation of hepatocytes with free asialofetuin or by adding free asialofetuin together with polyplexes into hepatocytes. The results confirmed that polyplexes with these polymers were taken up specifically by hepatocytes via ASGPR-mediated endocytosis. The results from transfection efficiency and uptake of these polymers in cells without ASGPR, such as SK Hep1 and HeLa cells, further support this mechanism. Since in vitro cytotoxicity assays prove these glycopolymers to be nontoxic, they may be useful for delivery of clinically important genes specifically to the liver.

Active radar guides missile to its target: receptor-based targeted treatment of hepatocellular carcinoma by nanoparticulate systems

Patients with hepatocellular carcinoma (HCC) usually present at advanced stages and do not benefit from surgical resection, so drug therapy should deserve a prominent place in unresectable HCC treatment. But chemotherapy agents, such as doxorubicin, cisplatin, and paclitaxel, frequently encounter important problems such as low specificity and non-selective biodistribution. Recently, the development of nanotechnology led to significant breakthroughs to overcome these problems. Decorating the surfaces of nanoparticulate-based drug carriers with homing devices has demonstrated its potential in concentrating chemotherapy agents specifically to HCC cells. In this paper, we reviewed the current status of active targeting strategies for nanoparticulate systems based on various receptors such as asialoglycoprotein receptor, transferrin receptor, epidermal growth factor receptor, folate receptor, integrin, and CD44, which are abundantly expressed on the surfaces of hepatocytes or liver cancer cells. Furthermore, we pointed out their merits and defects and provided theoretical references for further research.

Insight into the role of physicochemical parameters in a novel series of amphipathic peptides for efficient DNA delivery

Amphipathic peptides constitute a class of molecules with the potential to develop as efficient and safer alternatives to viral and other nonviral vectors for intracellular delivery of therapeutics. These peptides can be useful for nucleic acid delivery and hence promise to have pharmaceutical application, particularly in gene therapy. In order to design novel amphipathic peptides and improve their efficiency of therapeutic cargo delivery, one needs to understand the role of the physicochemical properties of the peptide. There are very few reports in the literature where the physicochemical properties of the peptide have been correlated with efficiency of plasmid DNA delivery. In the present work we hunted out a naturally occurring amphipathic peptide termed Mgpe-1 (derived from HUMAN Protein phosphatase 1E) as a possible novel DNA delivery agent. We systematically altered the physicochemical parameters of this peptide to further enhance its DNA delivery efficiency. We changed its amphipathicity (from secondary to primary), the total charge (from +6 to +9), hydrophobicity, and the amino acid composition (lysine and serines to arginine; substitution of tryptophan) and studied which of these alterations affect DNA delivery efficiency. Our results showed that although Mgpe-1 exhibited very strong cellular uptake, its plasmid DNA delivery efficiency was poor. The presence of nine arginines improved the DNA delivery efficiency, and the effect was observed in both the primary and the secondary amphipathic variants. We further observed that the presence of tryptophan was important but not essential and the effect of its removal was stronger in the case of the secondary amphipathic peptide. However, increase in total hydrophobicity of the peptide led to a fall in transfection efficiency in the primary amphipathic peptide whereas the secondary amphipathic peptide having the same chemical composition was almost unaffected by this change. The primary amphipathic peptides with high positive charge and low hydrophobicity formed colloidally stable polyplexes with DNA and avoided a major impediment in DNA delivery, namely, the aggregation of polyplexes and cytotoxicity. The secondary amphipathic variants by virtue of the positional arrangement of the amino acids led to formation of polyplexes with partly hydrophilic surfaces which prevented aggregation and controlled particle size irrespective of the hydrophobicity. Two variants in the series Mgpe-3 and Mgpe-4 having nine positive charges with less hydrophobicity showed high transfection efficiency in multiple cell lines along with serum stability and much less cytotoxicity and promise to be novel and efficient DNA delivery vectors.

Comparative in silico-in vivo evaluation of ASGP-R ligands for hepatic targeting of curcumin Gantrez nanoparticles

The present study aims to design hepatic targeted curcumin (CUR) nanoparticles using Gantrez (GZ) as a polymer. Three carbohydrate-based hepatocyte asialoglycoprotein receptor (ASGP-R) ligands were selected for the study, namely kappa carrageenan (KC), arabinogalactan (AG), and pullulan (P). AG and KC are galactose based while P is a glucose-based polymer. CUR-GZ nanoparticles were prepared by nanoprecipitation and anchored with the ligands by nonspecific adsorption onto preformed nanoparticles. The change in zeta potential values confirmed adsorption of the ligands. Docking simulation was evaluated as a tool to predict ligand ASGP-R interactions, using grid-based ligand docking with energies (Glide). Monomers and dimers were used as representative units of polymer for docking analysis. The binding of ASGP-R was validated using D-galactose as monomer. The interaction of the ligands with the receptor was evaluated based on Glide scores and E model values, both for monomers and dimers. The data of the docking study based on Glide scores and E model values suggested higher affinity of AG and P to the ASGP-R, compared to KC. At 1 h, following intravenous administration of the nanoparticles to rats, the in vivo hepatic accumulation in the order CUR-GZAG > CUR-GZKC > CUR-GZP correlated with the docking data based on Glide scores. However, at the end of 6 h, pullulan exhibited maximum hepatic accumulation and arabinogalactan minimum accumulation (p < 0.05). Nevertheless, as predicted by docking analysis, arabinogalactan and pullulan revealed maximum hepatic accumulation. Docking analysis using dimers as representative stereochemical units of polymers provides a good indication of ligand receptor affinity. Docking analysis provides a useful tool for the preliminary screening of ligands for hepatic targeting.

Hepatocyte-targeting gene transfer mediated by galactosylated poly(ethylene glycol)-graft-polyethylenimine derivative

Biscarbamate cross-linked polyethylenimine derivative (PEI-Et) has been reported as a novel nonviral vector for efficient and safe gene transfer in our previous work. However, it had no cell-specificity. To achieve specific delivery of genes to hepatocytes, galactosylated poly(ethylene glycol)-graft-polyethylenimine derivative (GPE) was prepared through modification of PEI-Et with poly(ethylene glycol) and lactobionic acid, bearing a galactose group as a hepatocyte-targeting moiety. The composition of GPE was characterized by proton nuclear magnetic resonance. The weight-average molecular weight of GPE measured with a gel permeation chromatography instrument was 9489 Da, with a polydispersity of 1.44. GPE could effectively condense plasmid DNA (pDNA) into nanoparticles. Gel retardation assay showed that GPE/pDNA complexes were completely formed at weigh ratios (w/w) over 3. The particle size of GPE/pDNA complexes was 79-100 nm and zeta potential was 6-15 mV, values which were appropriate for cellular uptake. The morphology of GPE/pDNA complexes under atomic force microscopy appeared spherical and uniform in size, with diameters of 53-65 nm. GPE displayed much higher transfection efficiency than commercially available PEI 25 kDa in BRL-3A cell lines. Importantly, GPE showed good hepatocyte specificity. Also, the polymer exhibited significantly lower cytotoxicity compared to PEI 25 kDa at the same concentration or weight ratio in BRL-3A cell lines. To sum up, our results indicated that GPE might carry great potential in safe and efficient hepatocyte-targeting gene delivery.

Diaminododecane-based cationic bolaamphiphile as a non-viral gene delivery carrier

The advancement in gene therapy relies upon the discovery of safe and efficient delivery agents and methods. In this study, we report the design and synthesis of a cationic bolaamphiphile as a non-viral gene delivery agent. The bolaamphiphile is composed of 1,12-diaminododecane as the central hydrophobic unit linked to the hydrophilic pentaethylenehexamine via thioether-based glycidyl units. This bolaamphiphile condensed DNA efficiently into nanoparticles of sizes around 150-200 nm with positive zeta potential of 30-35 mV. In vitro luciferase expression levels and percentage of GFP expressing cells induced by the bolaamphiphile/DNA complexes were higher than those mediated by the often used "golden" standard of non-viral systems, polyethyleneimine (PEI, branched, 25 kDa) at its optimal N/P ratio in HEK293, HepG2, NIH3T3, HeLa and 4T1 cells. In vitro cytotoxicity testing revealed that the DNA complexes fabricated from this cationic bolaamphiphile displayed marginal toxicity towards all the cell lines tested. In addition, in vivo transfection studies carried out in a 4T1 mouse breast cancer model showed that the cationic bolaamphiphile delivered DNA more efficiently than PEI. This cationic bolaamphiphile may make a promising gene delivery vector for future gene therapy.

Structural rearrangements and chemical modifications in known cell penetrating peptide strongly enhance DNA delivery efficiency

Amphipathic peptides with unusual cellular translocation properties have been used as carriers of different biomolecules. However, the parameters which control the delivery efficiency of a particular cargo by a peptide and the selectivity of cargo delivery are not very well understood. In this work, we have used the known cell penetrating peptide pVEC (derived from VE-cadherin) and systematically changed its amphipathicity (from primary to secondary) as well as the total charge and studied whether these changes influence the plasmid DNA condensation ability, cellular uptake of the peptide-DNA complexes and in turn the efficiency of DNA delivery of the peptide. Our results show that although the efficiency of DNA delivery of pVEC is poor, modification of the same peptide to create a combination of nine arginines along with secondary amphipathicity improves its plasmid DNA delivery efficiency, particularly in presence of an endosomotropic agent like chloroquine. In addition, presence of histidines along with 9 arginines and secondary amphipathicity shows efficient DNA delivery with low toxicity even in absence of chloroquine in multiple cell lines. We attribute these enhancements in transfection efficiency to the differences in the mechanism of complex formation by the different variants of the parent peptide which in turn are related to the chemical nature of the peptide itself. These results exhibit the importance of understanding the physicochemical parameters of the carrier and complex in modulating gene delivery efficiency. Such studies can be helpful in improving peptide design for delivery of different cargo molecules.

Preparation of galactosylated chitosan/tripolyphosphate nanoparticles and application as a gene carrier for targeting SMMC7721 cells

Nanoparticles composed of galactosylated chitosan (GC) and tripolyphosphate (TPP) were prepared and their application as potential gene carriers for targeting SMMC7721 cells was investigated. The results showed that at certain pH (5.5-6.2) of GC solutions, small and stable nanoparticles were obtained at an optimal weight ratio of 5:1 (GC/TPP). Transmission electron microscope (TEM) revealed formation of spherical particles. The optimal pH of cell culture environment for transfection was from 6.4 to 6.7, which was the same pH as the polymer complex formation of GC/TPP solutions. The charge ratio of GC/TPP to DNA (N/P) at 10:1, 20:1 and 30:1 were checked for transfection and under optimized conditions, the GC/TPP-DNA nanoparticles successfully transfected 6.8% of the SMMC7721 cells as represented by overexpression of enhanced green fluorescent protein (EGFP), which showed a much more higher efficiency when compared to 0.6% of GC/DNA transfection under the same conditions. The presented results indicate that the GC/TPP nanoparticles might be very attractive to be used as a gene delivery carrier for hepatocyte targeting, thus warranting further in vivo or clinical investigations.

Recent developments in carbohydrate-decorated targeted drug/gene delivery

Targeted delivery of a drug or gene to its site of action has clear therapeutic advantages by maximizing its therapeutic efficiency and minimizing its systemic toxicity. Generally, targeted drug or gene delivery is performed by loading a macromolecular carrier with an appropriate drug or gene, and by targeting the drug/gene carrier to specific cell or tissue with the help of specific targeting ligand. The emergence of glycobiology, glycotechnology, and glycomics and their continual adaptation by pharmaceutical scientists have opened exciting avenue of medicinal applications of carbohydrates. Among them, the biocompatibility and specific receptor recognition ability confer the ability of carbohydrates as potential targeting ligands for targeted drug and gene delivery applications. This review summarizes recent progress of carbohydrate-decorated targeted drug/gene delivery applications.

In vivo targeted gene delivery by cationic nanoparticles for treatment of hepatocellular carcinoma

BACKGROUND

Transgene expression in vivo for therapeutic purposes will require methods that allow for efficient gene transfer into cells. Although current vector technologies are being improved, the development of novel vector systems with improved targeting specificity, higher transduction efficiencies and improved safety is necessary.

METHODS

Asialoglycoprotein receptor-targeted cationic nanoparticles for interleukin (IL)-12 encapsulation (NP1) or adsorption (NP2) have been formulated by blending poly(D,L-lactic-co-glycolic) acid (PLGA) (50 : 50) with the cationic lipid 1,2-dioleoyl-3-(trimethylammonium) propane (DOTAP) and the ligand asialofetuin (AF), by using a modified solvent evaporation process.

RESULTS

We present a novel targeted lipopolymeric vector, which improves significantly the levels of luciferase gene expression in the liver upon i.v. administration. Targeted-NP2 particles showed a five- and 12-fold higher transfection activity in the liver compared to non-targeted (plain) complexes or naked pCMV DNA, respectively. On the other hand, BNL tumor-bearing animals treated with AF-NP1 containing the therapeutic gene IL-12, showed tumor growth inhibition, leading to a complete tumor regression in 75% of the treated mice, without signs of recurrence. High levels of IL-12 and interferon-gamma were detected in the sera of treated animals. Mice survival also improved considerably. Tumor treatment with AF-NP2 formulations lead only to a retardation in the tumor growth.

CONCLUSIONS

In the present study, we have developed an efficient targeted non-viral vector for IL-12 gene transfer in hepatocellular carcinoma in vivo, by employing non-toxic cationic PLGA/DOTAP/AF nanoparticles. These results demonstrate for the first time that this cationic system could be used successfully and safely for delivery of therapeutic genes with antitumor activity into liver tumors with targeting specificity.

Galactosylated multimodular lipoplexes for specific gene transfer into primary hepatocytes

BACKGROUND

Numerous synthetic cationic vectors have been synthesized and are successfully used for in vitro gene transfer but an excess of positive charges can lead to cytotoxicity and does not enable specific transfection.

METHODS

We decided to develop alternative molecular systems consisting of neutral, colloidally stable bioassemblies equipped with ligands for specific cell targeting. Consequently, we directed our efforts toward the development of a multimodular non-viral gene delivery system consisting of a condensed core of DNA with cationic liposomes of bis(guanidinium)-tren-cholesterol and an external corona of poly(ethylene oxide) stretches harbored by the steric stabilizers used to stabilize lipoplexes colloidally. A ligand capable of cell targeting by receptor-mediated endocytosis was covalently linked at the poly(ethylene oxide) extremity of steric stabilizers. Steric stabilizers were functionalized by a one-step enzymatic galactosylation to develop new supramolecular assemblies of lipoplexes able to target asialoglycoprotein receptors located on primary hepatocytes.

RESULTS

Cryo-TEM and fluorescence experiments showed that DNA was condensed within lamellar complexes whose size ranged between 100 to 300 nm in diameter. Bis(guanidinium)-tren-cholesterol-DNA lipoplexes, colloidally stabilized by galactosylated steric stabilizers at a galactosylated steric stabilizer/DNA ratio of 300, led to specific transfection of primary hepatocytes whereas ungalactosylated steric stabilizer did not transfect.

CONCLUSIONS

Our findings confirm the receptor-mediated endocytosis pathway of galactosylated multimodular lipoplexes. Thus, we conclude that the fabrication of a multimodular assembly harboring a ligand without non-specific interaction with cell membranes is possible and a highly promising system to transfect other primary or cultured cells specifically through a receptor-dependent mechanism.

Mechanisms of co-modified liver-targeting liposomes as gene delivery carriers based on cellular uptake and antigens inhibition effect

In order to deliver antisense oligonucleotides (asODN) into hepatocytes orientedly in the treatment of hepatitis B virus (HBV) infection, the liver-targeting cationic liposomes was developed as a gene carrier, which was co-modified with the ligand of the asialoglycoprotein receptor (ASGPR), beta-sitosterol-beta-d-glucoside (sito-G) and the nonionic surfactant, Brij 35. Flow cytometry (FCM) analysis and enzyme-linked immunosorbent assay (ELISA) showed that the asODN-encapsulating cationic liposomes exhibited high transfection efficiency and strong antigens inhibition effect in primary rat hepatocytes and HepG2.2.15 cells, respectively. With the help of several inhibitors acting on different steps during the targeting lipofection, the cellular uptake mechanisms of the co-modified liver-targeting cationic liposomes were investigated through antigens inhibition effect assay and confocal laser scanning microscopy (CLSM) analysis. The cellular uptake with high transfection efficiency seemed to involve both endocytosis and membrane fusion. The ligand sito-G was confirmed to be able to enhance ASGPR-mediated endocytosis, the nonionic surfactant Brij 35 seemed to be able to facilitate membrane fusion, and the co-modification resulted in the most efficient transfection but no enhanced cytotoxicity. These results suggested that the co-modified liver-targeting cationic liposomes would be a specific and effective carrier to transfer asODN into hepatocytes infected with HBV orientedly.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update covering the period 1999-2000

This review describes the use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates and continues coverage of the field from the previous review published in 1999 (D. J. Harvey, Matrix-assisted laser desorption/ionization mass spectrometry of carbohydrates, 1999, Mass Spectrom Rev, 18:349-451) for the period 1999-2000. As MALDI mass spectrometry is acquiring the status of a mature technique in this field, there has been a greater emphasis on applications rather than to method development as opposed to the previous review. The present review covers applications to plant-derived carbohydrates, N- and O-linked glycans from glycoproteins, glycated proteins, mucins, glycosaminoglycans, bacterial glycolipids, glycosphingolipids, glycoglycerolipids and related compounds, and glycosides. Applications of MALDI mass spectrometry to the study of enzymes acting on carbohydrates (glycosyltransferases and glycosidases) and to the synthesis of carbohydrates, are also covered.

Asialoglycoprotein-receptor-targeted hepatocyte imaging using 99mTc galactosylated chitosan

This study investigated the usefulness of 99mTc hydrazinonicotinamide-galactosylated chitosan (HGC) in hepatocyte imaging. HGC was obtained by coupling the galactose moiety of both lactobionic acid and succinimidyl 6-hydrazinonicotinate hydrochloride (succinimidyl HYNIC). The coupled product was then radiolabeled with 99mTc using stannous chloride and tricine as reducing agent and coligand, respectively. Labeling efficiency was >90% both in room temperature and in serum up to 24 h after injection. The hepatic uptake properties of 99mTc HGC were studied in Balb/C mice. 99mTc HGC and 99mTc hydrazinonicotinamide chitosan (HC) were intravenously injected into mice, with receptor binding identified by coinjection with 9 and 14 mg of free galactose. Images were acquired with a gamma-camera. After injection via the tail vein of the mice, 99mTc HGC showed high selectivity for the liver, while 99mTc HC without a galactose group showed low liver uptake. In addition, the hepatic uptake of 99mTc HGC was blocked by coinjection of free galactose. Tissue distribution was determined at three different times (10, 60 and 120 min). The liver accumulated 13.16+/-2.72%, 16.11+/-5.70% and 16.55+/-2.28% of the injected dose per gram at 10, 60 and 120 min after injection, respectively. 99mTc HGC showed specific and rapid targeting of hepatocytes. It is a promising receptor-specific radiopharmaceutical with potential applications in liver imaging for the evaluation of hepatocytic function.

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.

Enhancing effects of galactosylated dendrimer/alpha-cyclodextrin conjugates on gene transfer efficiency

To improve in vitro gene transfer efficiency and/or achieve cell-specific gene delivery of polyamidoamine (PAMAM) starburst dendrimer (generation 2, G2) conjugate with alpha-cyclodextrin (alpha-CDE conjugate (G2)), we prepared alpha-CDE conjugate bearing galactose (Gal-alpha-CDE conjugates) with the various degrees of substitution of the galactose moiety (DSG) as a novel non-viral vector. The agarose gel electrophoretic studies revealed that Gal-alpha-CDE conjugates formed complexes with plasmid DNA (pDNA) and protected the degradation of pDNA by DNase I, but these effects impaired as the DSG value increased. Dendrimer and alpha-CDE conjugate exerted pDNA condensation through the complexation, but Gal-alpha-CDE conjugates did not. Gal-alpha-CDE conjugate (DSG 4) was found to have much higher gene transfer activity than dendrimer, alpha-CDE conjugate and Gal-alpha-CDE conjugates (DSG 8, 15) in HepG2, NIH3T3 and A549 cells, which are independent of the expression of the asialoglycoprotein receptor. Transfection activity of Gal-alpha-CDE conjugate (DSG 4) was insensitive to the existence of competitors (asialofetuin and galactose) and serum. In addition, no cytotoxicity after transfection of the complex of pDNA with Gal-alpha-CDE conjugate (DSG 4) was observed. These results suggest the potential use of Gal-alpha-CDE conjugate (DSG 4) as a non-viral vector in various cells.

Cytosolic soluble proteins induce DNA release from DNA--gene carrier complexes

In nonviral transfection systems, the gene carrier/DNA complex must undergo several steps for successful transgene expression. DNA release from the complex is one important step. However, the detailed mechanism of intracellular processes involved in DNA release is not well understood. In this study, to clarify the dissociation of the complex in the cytosol, we investigated whether the DNA release was caused by addition of a cytosolic fraction prepared from mouse liver to the complex. When Lipofectamine (a liposome-type gene carrier) was used as a complex forming reagent with DNA, the cytosolic fraction caused no DNA release from the complex. In contrast, when dendritic poly(L-lysine) and jetPEI (polymer-type gene carriers) were used, DNA release was observed when the complex formed at a low cation/anion ratio. This result showed that a DNA releasing factor was present in the cytosolic fraction, suggesting that in the cytosol the DNA was spontaneously released from a gene carrier/DNA complex when the carrier was a polymer-type gene carrier. Furthermore, this DNA releasing ability of the cytosolic fraction was protease sensitive.

Galactosylated chitosan/DNA nanoparticles prepared using water-soluble chitosan as a gene carrier

Water-soluble chitosan (WSC) was used to increase the stability of chitosan in water and decrease the cytotoxicity induced by acetic acid. Lactobionic acid (LA) bearing galactose group was coupled with WSC for hepatocytes specificity. The composition of galactose in galactosylated chitosan (GC) was determined by NMR spectroscopy. The GC was complexed with plasmid DNA in various GC/DNA (N/P) charge ratios and the resulting complex was characterized by dynamic light scattering, gel retardation, and turbidity to determine the particle sizes, complex formation, and complex stability, respectively. Cytotoxicity and transfection efficiency of GC were also studied in cultured HepG2 human hepatoblastoma cell line and HeLa human cervix epithelial carcinoma cells. The complete GC/DNA complex was formed at the charge ratio of 5 and the GC/DNA complex to DNase I resistance was obtained. Particle sizes decreased with increasing charge ratio of GC to DNA and had a minimum value around 120 nm at the charge ratio of 5. And no significant difference in particle sizes from the charge ratio of 5-20 was found. The suspension of GC/DNA complexes exhibited no significant change in turbidity at the charge ratios of 10, indicating the complete shielding of DNA charge. Cytotoxicity study showed that GC prepared by the water-soluble chitosan had no cytotoxic effects on cells. And transfection efficiency into HepG2, which has asialoglycoprotein receptors (ASGP-R), was higher than that into HeLa without ASGP-R.

An overview of current delivery systems in cancer gene therapy

The main objective in gene therapy is the development of efficient, non-toxic gene carriers that can encapsulate and deliver foreign genetic materials into specific cell types such as cancerous cells. During the past two decades, enormous research in the area of gene delivery has been conducted worldwide, in particular for cancer gene therapy application. Viral vectors are biological systems derived from naturally evolved viruses capable of transferring their genetic materials into the host cells. Many viruses including retrovirus, adenovirus, herpes simplex virus (HSV), adeno-associated virus (AAV) and pox virus have been modified to eliminate their toxicity and maintain their high gene transfer capability. The limitations associated with viral vectors, however, in terms of their safety, particularly immunogenicity, and in terms of their limited capacity of transgenic materials, have encouraged researchers to increasingly focus on non-viral vectors as an alternative to viral vectors. Non-viral vectors are generally cationic in nature. They include cationic polymers such as poly(ethylenimine) (PEI) and poly(L-lysine) (PLL), cationic peptides and cationic liposomes. The newly described liposomal preparation LPD (liposomes/protamine/DNA), for example, has shown superiority over conventional liposomes/DNA complexes (lipoplexes). Although non-viral vectors are less efficient than viral ones, they have the advantages of safety, simplicity of preparation and high gene encapsulation capability. This article reviews the most recent studies highlighting the advantages and the limitations of various types of gene delivery systems used in cancer gene therapy.

Targeted gene delivery into HepG2 cells using complexes containing DNA, cationized asialoorosomucoid and activated cationic liposomes

Unilamellar activated cationic liposomes containing 3beta[N-(N',N'-dimethylaminopropane)-carbamoyl] cholesterol, dioleoyl phosphatidylethanolamine (DOPE) and the N-hydroxysuccinimide ester of cholesteryl hemisuccinate (4:5:1, molar ratio) have been prepared and their DNA-binding capacity has been assessed in a gel retardation assay. Ternary complexes composed of activated cationic liposomes, carbodiimide-cationized asialoorosomucoid (Me+AOM) and pRSVL plasmid DNA were assembled for receptor-mediated DNA delivery into cells expressing the asialoglycoprotein receptor (ASGP-R). Binding of complexes in which Me+AOM was replaced by fluoresceinated Me+AOM (FMe+AOM) to the human hepatocellular cell line HepG2 at 4 degrees C was severely reduced by co-incubation with asialoorosomucoid (AOM). Moreover, assemblies containing liposomes, pRSVL DNA and Me+AOM (8:1:4, w/w/w) promoted high levels of luciferase activity in this cell line (1.3 x 10(7) relative light units/mg soluble cell protein). Assays conducted in the presence of a hundred-fold excess of the ligand AOM afforded considerably lower levels of transfection (2.5 x 10(5) relative light units/mg soluble cell protein). In contrast, the highest level of luciferase activity achieved with liposome, pRSVL DNA, AOM complexes was only a quarter of the best levels obtained with liposome, pRSVL DNA, Me+AOM assemblies. These findings strongly support the notion that complexes gain entry into hepatocyte-derived cells by ASGP-R mediation and that they are potentially useful gene carriers to liver hepatocytes.

Stable polyplexes based on arginine-containing oligopeptides for in vivo gene delivery

In this study, we investigated to what extent the stability and transduction capacity of polyplexed DNA can be improved by optimizing the condensing peptide sequence. We have synthesized a small library of cationic peptides, at which the lysine/arginine ratio and the cation charge were varied. All peptides were able to compact DNA, at which polyplexes of short lysine-rich sequences were considerably larger than those of elongated or arginine-rich peptides (GM102 and GM202). In addition, the arginine-rich peptides GM102 and GM202 rendered the polyplexes resistant to plasma incubation or DNase I-mediated digestion. While all peptides were found to improve the transfection efficiency in HepG2 cells, only the GM102- and GM202-derived polyplexes could be specifically targeted to HepG2 cells by incorporation of a ligand-derivatized YKAK(8)WK peptide. We propose that GM102 and GM202 combine the advantage of small condensing peptides to give small-sized polyplexes with the superior stability of condensing polymers, which makes GM102 and GM202 excellent candidates for future in vivo gene therapy studies.

Improvement of hepatocyte-specific gene expression by a targeted colchicine prodrug

Colchicine, an established tubulin inhibitor, interferes with the trafficking of endocytotic vesicles and thereby promotes the escape of lysosome-entrapped compounds. To improve its potency and cell specificity, a targeted prodrug of colchicine was synthesized by conjugation to a high-affinity ligand (di-N(alpha),N(epsilon)-(5-(2-acetamido-2-deoxy-beta-D-galactopyranosyloxy)pentanomido)lysine, K(GalNAc)(2)) for the asialoglycoprotein receptor on parenchymal liver cells. The resulting colchicine-K(GalNAc)(2) conjugate bound to this receptor with an affinity of 4.5 nM. Confocal microscopy studies confirmed rapid uptake and receptor dependency of a prodrug conjugated with fluorescein isothiocyanate. Colchicine-K(GalNAc)(2) substantially increased the transfection efficiency of polyplexed DNA in parenchymal liver cells in a concentration- and receptor-dependent fashion. Colchicine-K(GalNAc)(2) was found to enhance the transfection efficiency by 50-fold at 1 nM, whereas the parental colchicine was ineffective. In conclusion, this nontoxic colchicine-K(GalNAc)(2) conjugate can be a useful tool to improve the transfection efficiency of hepatic nonviral gene transfer vehicles.

Visualization of transfection of hepatocytes by galactosylated chitosan-graft-poly(ethylene glycol)/DNA complexes by confocal laser scanning microscopy

Dual-labeled galactosylated chitosan-graft-poly(ethylene glycol) (PEG) (GCP)/DNA complexes were prepared and their hepatocyte-specific delivery and cellular distribution were investigated by confocal laser scanning microscopy (CLSM). The complexes were transfected into hepatocyte through specific interaction of galactose moiety of the GCP and asialoglycoprotein receptors (ASGPR) of the hepatocytes. The GCP/DNA complexes taken up by the hepatocytes were rapidly released into the cytoplasm, but nuclear trafficking of the released complexes was slow and rate-limiting process. The more efficient transfection of the complex occurred in the human-derived HepG2 cells than in primary hepatocytes.

Artificial viruses and their application to gene delivery. Size-controlled gene coating with glycocluster nanoparticles

Number- and size-controlled macromolecular associations are common in biology with viruses as a typical example. We report here a novel example of artificial viruses, in which the double-helical DNA is coated with 4-nm sized neutral glycocluster nanoparticles (GNPs) with a coating stoichiometry of approximately 2 GNPs per helical pitch (10 base pairs), where GNP arises from micellization of a cone-shaped, quadruple-chain glycocluster amphiphile having eight saccharide moieties with beta-glucoside termini on the calix[4]resorcarene macrocycle. The resulting "glycoviruses" are compactly packed (54 nm in the case of 7040 base-pair plasmid pCMVluc), are well charge-shielded (zeta congruent with approximately 0 mV), and effectively transfect cell cultures without notable cytotoxicity. The use of artificial viral vectors thus allows a new (nonamine/noncationic/nonpolymeric) access to gene delivery, a potential but still tough subject which has been studied extensively over the last 15 years by using viral or amine-based cationic vectors. The remarkable adhesion-manipulation ability of saccharide clusters also provides a strategy of bottom-up construction of nanometric or mesoscopic sizes.

Non-viral and hybrid vectors in human gene therapy: an update

Non-viral DNA vectors have several advantages over viral vectors. For example, virus production is expensive and there are safety concerns regarding viral manipulations. In addition, the size of the delivered plasmid is limited by the size of the viral capsid, whereas this is not a problem with non-viral vectors. The major disadvantage of using non-viral DNA delivery vectors, compared with their viral counterparts, is the low transfection efficiency. This has resulted in low levels of usage in clinical trials. Consequently, the majority of research into non-viral gene therapy has been focused on developing more efficient vectors.

Targeted lysosome disruptive elements for improvement of parenchymal liver cell-specific gene delivery

The transfection ability of nonviral gene therapy vehicles is generally hampered by untimely lysosomal degradation of internalized DNA. In this study we describe the development of a targeted lysosome disruptive element to facilitate the escape of DNA from the lysosomal compartment, thus enhancing the transfection efficacy, in a cell-specific fashion. Two peptides (INF7 and JTS-1) were tested for their capacity to disrupt liposomes. In contrast to JTS-1, INF7 induced rapid cholesterol-independent leakage (EC(50), 1.3 microm). INF7 was therefore selected for coupling to a high affinity ligand for the asialoglycoprotein receptor (ASGPr), K(GalNAc)(2), to im- prove its uptake by parenchymal liver cells. Although the parent peptide disrupted both cholesterol-rich and -poor liposomes, the conjugate, INF7-K(GalNAc)(2), only induced leakage of cholesterol-poor liposomes. Given that endosomal membranes of eukaryotic cells contain <5% cholesterol, this implies that the conjugate will display a higher selectivity toward endosomal membranes. Although both INF7 and INF7-K(GalNAc)(2) were found to increase the transfection efficiency on polyplex-mediated gene transfer to parenchymal liver cells by 30-fold, only INF7-K(GalNAc)(2) appeared to do so in an ASGPr-specific manner. In mice, INF7-K(GalNAc)(2) was specifically targeted to the liver, whereas INF7 was distributed evenly over various organs. In summary, we have prepared a nontoxic cell-specific lysosome disruptive element that improves gene delivery to parenchymal liver cells via the ASGPr. Its high cell specificity and preference to lyse intracellular membranes make this conjugate a promising lead in hepatocyte-specific drug/gene delivery protocols.

Mimovirus: a novel form of vaccine that induces hepatitis B virus-specific cytotoxic T-lymphocyte responses in vivo

CD8(+) cytotoxic T lymphocytes (CTLs) are now recognized as important mediators of immunity against intracellular pathogens, including human immunodeficiency virus and tumors. How to efficiently evoke antigen-specific CTL responses in vivo has become a crucial problem in the development of modern vaccines. Here, we developed a completely novel CTL vaccine-mimovirus, which is a kind of virus-size particulate antigen delivery system. It was formed by the self-assembly of a cationic peptide containing 18 lysines and a CTL-epitope peptide of HBsAg(28-39), with a plasmid encoding mouse interleukin-12 (IL-12) through electrostatic interactions. We examined the formation of mimovirus by DNA retardation assay, DNase I protection assay, and transmission electron microscopy and demonstrated that mimovirus could efficiently transfer the plasmid encoding IL-12 into mammalian cells such as P815 cells in vitro. Furthermore, it was proved that mimovirus could induce an HBsAg(28-39)-specific CTL response in vivo. Considering its effectiveness, flexibility, and defined composition, mimovirus is potentially a novel system for vaccination against intracellular pathogens and tumors.

Synthesis of galactosyl compounds for targeted gene delivery

Cell-specific DNA delivery offers a great potential for targeted gene therapy. Toward this end, we have synthesized a series of compounds carrying galactose residues as a targeting ligand for asialoglycoprotein receptors of hepatocytes and primary amine groups as a functional domain for DNA binding. Biological activity of these galactosyl compounds in DNA delivery was evaluated in HepG2 and BL-6 cells and compared with respect to the number of galactose residues as well as primary amine groups in each molecule. Transfection experiments using a firefly luciferase gene as a reporter revealed that compounds with multivalent binding properties were more active in DNA delivery. An optimal transfection activity in HepG2 cells requires seven primary amine groups and a minimum of two galactose residues in each molecule. The transfection activity of compounds carrying multi-galactose residues can be inhibited by asialofetuin, a natural substrate for asialoglycoprotein receptors of hepatocytes, suggesting that gene transfer by these galactosyl compounds is asialoglycoprotein receptor-mediated. These results provide direct evidence in support of our new strategy for the use of small and synthetic compounds for cell specific and targeted gene delivery.

Identification of the molecular interaction site of amyloid beta peptide by using a fluorescence assay

Beta-amyloid peptides (Abeta) are the main protein components of neuritic plaques and are important in the pathogenesis of Alzheimer's disease. It is reported that Abeta itself is not toxic; however, it becomes toxic to neuronal cells once it has aggregated into amyloid fibrils by peptide-peptide interactions. In this study, to specify the molecular mechanism of aggregation, a novel fluorescence assay was designed. For this purpose, possible partial peptides (38 types of 5-mer) were synthesized on solid-phase. The molecular interactions were examined by a fluorescence probe possessing Lys-Leu-Val-Phe-Phe (KLVFF) as a molecular recognition site. KLVFF is known to be a minimum sequence for formation of the Abeta aggregate. A specific interaction was observed between labeled and immobilized KLVFF. It suggests that the aggregation of Abeta was controlled by the recognition of KLVFF itself by hydrophobic and electrostatic interactions.