Coupling of RAFT polymerization and chemoselective post-modifications of elastin-like polypeptides for the synthesis of gene delivery hybrid vectors

Hybrid cationic ELPs for nucleic acids transport and delivery were synthetized through the coupling of RAFT polymerization and biorthogonal chemistry of ELPs, introducing a specific number of positive charges to the ELP backbone.

Enhanced antitumor efficacy of arginine modified amphiphilic nanoparticles co-delivering doxorubicin and iSur-pDNA via the multiple synergistic effect

Arginine and α-tocopherol succinate (α-TOS) double grafted N-trimethyl chitosan chloride (TMC) nanoparticles (TAS NPs) were designed and developed for effective co-delivery of doxorubicin (DOX) and Survivin shRNA-expressing pDNA (iSur-pDNA). With DOX loading into the hydrophobic core and iSur-pDNA combining to the hydrophilic shell, TAS/DOX/pDNA NPs demonstrated favorable structural stability and sustained release properties in vitro. With the special non-clathrin-dependent endocytosis, TAS/DOX/pDNA NPs presented higher cellular uptake and mainly distributed in ER and Golgi rather than lysosomes following internalization. The in vitro nuclear localization, gene silencing efficiency, cell apoptosis, and growth inhibition of tumor cells were significantly promoted by arginine modification. In the tumor-bearing mice model, TAS/DOX/pDNA NPs possessed the maximum antitumor efficiency as compared with single delivery of DOX or iSur-pDNA. Particularly, blank TAS NPs were selectively be toxic to tumor cells as evidenced by their capabilities to inhibit proliferation and induce apoptosis of tumor cells. The promising tumor treatment of TAS/DOX/pDNA NPs via a multiple synergistic manner arising from DOX and pDNA as well as the vectors would provide a potential strategy for a dual-delivery system to improve their therapeutic efficacies.

Characterization of Protamine as a Transfection Accelerator for Gene Delivery

Protamine is an FDA-approved compound with a documented safety profile that facilitates efficient plasmid condensation for gene delivery by various types of cationic liposomes. It also improves adenoviral vector-mediated gene transfer as a transfection accelerator. However, there is no consensus as to the mechanism of protamine on gene delivery into cells. To analyze the uptake and subcellular distribution, plasmid and protamine were labeled with FITC and Texas-Red, respectively. Although the uptake of FITC-labeled plasmid/protamine complexes into the cells was the same as that of free FITC-labeled plasmid in HeLa, SOJ and A549 cells, they improved the transfection efficiency by several orders of magnitude. Moreover, we found that protamine derived from different sources (salmon, herring and trout sperm) had different transfection efficiencies; however, the gene transfer efficiency with protamine was lower than with optimized poly(L-lysine) and DEAE-Dextran. There were likely two main reasons: firstly, the uptake of plasmid mediated by protamine was complete within the first 10min because the particle size increased as time passed, and secondly, the plasmid/protamine complexes were not released from endosomal membrane. These results indicate that as a transfection accelerator from an appropriate protamine source, with controlled particle size and facile release from endosomes would lead to successful gene delivery with protamine.

Exploring advantages/disadvantages and improvements in overcoming gene delivery barriers of amino acid modified trimethylated chitosan

PURPOSE

Present study aimed at exploring advantages/disadvantages of amino acid modified trimethylated chitosan in conquering multiple gene delivery obstacles and thus providing comprehensive understandings for improved transfection efficiency.

METHODS

Arginine, cysteine, and histidine modified trimethyl chitosan were synthesized and employed to self-assemble with plasmid DNA (pDNA) to form nanocomplexes, namely TRNC, TCNC, and THNC, respectively. They were assessed by structural stability, cellular uptake, endosomal escape, release behavior, nuclear localization, and in vitro and in vivo transfection efficiencies. Besides, sodium tripolyphosphate (TPP) was added into TRNC to compromise certain disadvantageous attributes for pDNA delivery.

RESULTS

Optimal endosomal escape ability failed to bring in satisfactory transfection efficiency of THNC due to drawbacks in structural stability, cellular uptake, pDNA liberation, and nuclear distribution. TCNC evoked the most potent gene expression owing to multiple advantages including sufficient stability, preferable uptake, efficient pDNA release, and high nucleic accumulation. Undesirable stability and insufficient pDNA release adversely affected TRNC-mediated gene transfer. However, incorporation of TPP could improve such disadvantages and consequently resulted in enhanced transfection efficiencies.

CONCLUSIONS

Coordination of multiple contributing effects to conquer all delivery obstacles was necessitated for improved transfection efficiency, which would provide insights into rational design of gene delivery vehicles.

Oral delivery of shRNA and siRNA via multifunctional polymeric nanoparticles for synergistic cancer therapy

Galactose modified trimethyl chitosan-cysteine (GTC) conjugates with various galactose grafting densities were developed for oral delivery of Survivin shRNA-expression pDNA (iSur-pDNA) and vascular endothelial growth factor (VEGF) siRNA (siVEGF) in the synergistic and targeted treatment of hepatoma. iSur-pDNA and siVEGF loaded GTC nanoparticles (NPs) were prepared via electrostatic complexation and showed desirable stability in physiological fluids and improved intestinal permeation compared to naked genes. Galactose grafting density of GTC NPs significantly affected their in vitro and in vivo antitumor activities. GTC NPs with moderate galactose grafting density, termed GTC2 NPs, were superior in facilitating cellular uptake, promoting nuclear distribution, and silencing target genes, leading to notable inhibition of cell growth. In tumor-bearing mice, orally delivered GTC2 NPs could effectively accumulate in the tumor tissues and silence the expression of Survivin and VEGF, evoking increased apoptosis, inhibited angiogenesis, and thus the most efficient tumor regression. Moreover, compared with single gene delivery, co-delivery of iSur-pDNA and siVEGF showed synergistic effects on inhibiting in vitro cell proliferation and in vivo tumor growth. This study could serve as an effective approach for synergistic cancer therapy via oral gene delivery, and highlighted the importance of ligand grafting density in the rational design of targeted nanocarriers.

Gene delivery using biodegradable polyelectrolyte microcapsules prepared through the layer-by-layer technique

Biodegradable and non-biodegradable microcapsules were prepared via the layer-by-layer (LbL) technique consisting of the polyelectrolyte pairs of dextran sulphate/poly-L-arginine and poly(styrene sulfonate)/poly(allylamine hydrochloride), respectively, in an attempt to encapsulate plasmid DNA (pDNA) for efficient transfection into NIH 3T3 cells. Results indicated the retention of bioactivity in the encased pDNA, as well as a correlation between the level of in vitro gene expression and biodegradability properties of polyelectrolyte. Furthermore, the incorporation of iron oxide nanoparticles within the polyelectrolyte layers significantly improved the in vitro transfection efficiency of the microcapsules. As a novel pDNA delivery system, the reported biodegradable microcapsules provide useful insight into plasmid-based vaccination and where there is a prerequisite to deliver genes into cells capable of phagocytosis.

Self-assembly of polyamines as a facile approach to fabricate permeability tunable polymeric shells for biomolecular encapsulation

In this article, the self-assembly of polyamines as a facile approach to fabricate permeability tunable polymeric shells for encapsulation of relatively low molecular weight (LM(w)) hydrophilic biomacromolecules (M(w) ≈ 4000 Da) is presented. The entire process is performed in organic solvents within 2 to 4 h to allow for nearly 100% encapsulation yield. The polymeric shells are fabricated by a two-step process: 1) The self-assembly of polyamines (nonionized poly(allylamine) (niPA) or branched nonionized polyethyleneimine (niPEI)) within porous agarose microbeads via an inwards buildup self-assembly process. 2) Stabilization of assembled polyamines either via covalent (cross-linkers) or ionic bonding (complex with nonionized poly(styrene sulfonic acid) (niPSS)). Stable and distinct polymeric shells are formed in both cases. The shell thickness is demonstrated to be tunable within a range of 1 to 14 μm; and as the inwards buildup self-assembly technique is not a self-limiting process, shells with broader thicknesses can be achieved. Also, it is demonstrated that the polymer density of the shell can be tuned. Depending on the fabrication parameters, the resulting polymeric shells have been demonstrated to have different permeability characteristics for relatively LM(W) dextran (M(W) ≈ 4000 Da). For example, niPEI shells are observed to have a higher permeability than niPA shells. Therefore, polymeric capsules can be fabricated via this facile approach for either retention of relatively LM(w) hydrophilic biomacromolecules or designed to passively or responsively release the biomacromolecule payload. This two-step shell fabrication process represent an alternative and facile approach for the fabrication of self-assembled polymeric shells in the fields of capsule-based reactors/sensors and drugs/gene delivery where relatively LM(w) macromolecules are concerned.

Formulation of chitosan-TPP-pDNA nanocapsules for gene therapy applications

The encapsulation of DNA inside nanoparticles meant for gene delivery applications is a challenging process where several parameters need to be modulated in order to design nanocapsules with specific tailored characteristics. The purpose of this study was to investigate and improve the formulation parameters of plasmid DNA (pDNA) loaded in chitosan nanocapsules using tripolyphosphate (TPP) as polyanionic crosslinker. Nanocapsule morphology and encapsulation efficiency were analyzed as a function of chitosan degree of deacetylation and chitosan-TPP ratio. The manipulation of these parameters influenced not only the particle size but also the encapsulation and release of pDNA. Consequently the transfection efficiency of the nanoparticulated systems was also enhanced with the optimization of the particle characteristics. Overall, the differently formulated nanoparticulated systems possess singular properties that can be employed according to the desired gene delivery application.

Low molecular weight chitosan in DNA vaccine delivery via mucosa

It is acknowledged that low molecular weight chitosan (LMWC) is advantageous over high molecular weight chitosan (HMWC) in the biodegradability. In this report, the potential of LMWC in DNA vaccine delivery via mucosa was evaluated. Firstly, the effects of molecular weight of chitosan on the physicochemical properties and in vitro transfection efficiency of chitosan/DNA polyplexes were investigated. Secondly, the capabilities of the polyplexes based on LMWC to elicit serum IgG antibodies and to attenuate the development of atherosclerosis after intranasal vaccination were compared with the polyplexes based on HMWC in the rabbit model. Finally, the intramucosal transport of the double-labeled polyplexes was observed by confocal microscopy. The results indicated that LMWC had lower binding affinity to DNA and mediated higher transfection efficiency. Intranasal vaccination with LMWC/DNA polyplexes could elicit significant systemic immune responses, modulate the plasma lipoprotein profile and attenuate the progression of atherosclerosis. Those aspects were comparable to those obtained by HMWC/DNA polyplexes. As revealed by confocal images, LMWC/DNA polyplexes remained stable during interaction with the nasal mucosa, and were internalized by nasal epithelial cells, which was similar to the case of HMWC/DNA polyplexes. In conclusion, LMWCs have potential applications in DNA vaccine delivery via mucosa.

Design of novel polysaccharidic nanostructures for gene delivery

The goal of the present work was to develop a new synthetic nanosystem for gene delivery. For this purpose, we chose two polysaccharides, hyaluronic acid (HA) and chitosan (CS), as the main components of the nanocarrier. Nanoparticles with different hyaluronate:chitosan (HA:CS) mass ratios (0.5:1 and 1:1) and different polymer molecular weights (hyaluronate 170 (HA) or <10 kDa (HAO) and chitosan 125 (CS) or 10-12 (CSO) kDa) could be obtained using an ionic crosslinking method. These nanoparticles were loaded with pDNA and characterized for their size, zeta potential and pDNA association efficiency. Moreover, their toxicity and ability to transfect the model plasmid pEGFP-C1 were evaluated in the cell line HEK 293, as well as their intracellular fate. The results showed that HA:CS nanoparticles have a small size in the range of 110-230 nm, a positive zeta potential of +10 to +32 mV and a very high pDNA association efficiency of 87-99% (w/w). On the other hand, nanoparticles exhibited low cell toxicity and transfection levels up to 25% GFP expressing HEK 293 cells, lasting for the whole observation period of 10 days. We also provide basic information about the role of both polymers, HA and CS, and the effect of their molecular weight on the effectiveness of the resulting DNA nanocarrier, being the highest transfection levels observed with HAO:CSO 1:1 nanoparticles. In conclusion, HA:CS nanoparticles are promising carriers for gene delivery.

N,N,N-Trimethylchitosan Chloride as a Gene Vector: Synthesis and Application

N,N,N-Trimethylchitosan chloride with different degrees of quaternization has been synthesized and characterized by (1)H NMR spectroscopy. The particle size ranges from 150 to 600 nm, which is dependent on the N/P ratio and is less influenced by the degree of quaternization. The majority of the particles have a spherical morphology. The zeta potential of the particles increases with the N/P ratio and the quaternization degree of TMC. Short-term contact experiments show good biocompatibility of TMC, but long-term contact experiments reveal its high toxicity. This study suggests that TMC is a promising gene carrier, but further modification is still required to improve its cytocompatibility.

PLGA:poloxamer and PLGA:poloxamine blend nanostructures as carriers for nasal gene delivery

We have recently reported the formation of a new type of nanoparticles consisting of blends of poly (lactic-co-glycolic acid) (PLGA) and polyethylene oxide (PEO) derivatives, which exhibit the capacity to associate and release plasmid DNA in a controlled manner. In the present work our goal was to investigate the ability of these nanoparticles to overcome cellular and mucosal barriers (i.e. nasal mucosa) and thus, to work as gene delivery carriers. First, we studied the in vitro cellular uptake (HEK 293 cell line) of FITC-labelled plasmid DNA nanoencapsulated in PLGA: Pluronic F68 and PLGA: Tetronic T904 particles by confocal microscopy. Second, we investigated the uptake of rhodamine-labelled nanoparticles by the nasal mucosa following intranasal administration to mice. Third, we monitored the immune response generated by the nanoparticles containing a beta-galactosidase encoding gene, following nasal administration to mice, using the ELISA technique. The results of the in vitro cell culture studies showed the ability of these new nanoparticles to enter the cells and transport the associated DNA molecule across the cell membrane. Moreover, the results obtained following in vivo administration of the fluorescent nanoparticles evidenced their capability to overcome the nasal mucosal barrier. Finally, the results of the immunisation studies showed that DNA-loaded nanoparticles elicit a fast and strong response, significantly more pronounced than that corresponding to the naked plasmid DNA for up to 6 weeks. Overall, these results suggest that these new nanoparticles have a potential as carriers for the delivery of DNA across the nasal mucosa.

Propidium Iodide and PicoGreen as Dyes for the DNA Fluorescence Correlation Spectroscopy Measurements

Many experimental designs, in which nucleic acid conformational changes are of interest, require reliable fluorescence labeling. The appropriate fluorescence probe should have suitable optical properties and, more importantly, should not interfere with the investigated processes. In order to avoid chemical modifications the fluorescence label needs to be associated with nucleic acid via weak non-covalent interactions. There are a number of fluorescent probes that change their fluorescent properties (i.e. their quantum yield and/or spectral characteristics) upon association with nucleic acid. Such probes are frequently used to detect, visualize and follow processes involving nucleic acid and its conformational changes. In order to obtain reliable data regarding macromolecule or aggregate topology a detailed knowledge of probe-nucleic acid interactions on the molecular level is needed. In this paper we show that the association of propidium iodide with DNA alters its conformation and that it selectively labels plasmid fragments and/or its subpopulations in a concentration-dependent meaner. Another dye, PicoGreen, exhibits better properties. It labels nucleic acid uniformly and without any concentration-dependent artifacts.

Specific 3′-Terminal Modification of DNA with a Novel Nucleoside Analogue that Allows a Covalent Linkage of a Nuclear Localization Signal and Enhancement of DNA Stability

We report a straightforward method for the site-specific modification of long double-stranded DNA by using a maleimide adduct of deoxycytidine. This novel nucleoside analogue was efficiently incorporated at the 3'-termini of DNA by terminal deoxynucleotidyl transferase (TdT). Thiol-containing compounds can be covalently linked to the maleimide moieties. We added a nuclear localization signal peptide to the 3'-terminal of a 350 bp-long DNA that encoded short-hairpin RNA, and these modifications resulted in the enhancement of silencing activity by RNA interference. This enhancement is mainly attributed to increased stability of the template DNA.

Galactosylated chitosan (GC)-graft-poly(vinyl pyrrolidone) (PVP) as hepatocyte-targeting DNA carrier:in vitro transfection

Galactosylated chitosan-graft-poly(vinyl pyrrolidone) (GCPVP) was synthesized and characterized for hepatocyte-targeting gene carrier. GCPVP itself as well as GCPVP/DNA complex had negligible cytotoxicity regardless of the concentration of GCPVP and the charge ratio, but GCPVP/DNA complex had slightly cytotoxic effect on HepG2 cells only in the case of the higher charge ratio and 20 mM of Ca2+ concentration used. Through the confocal laser scanning microscopy, it is shown that the endocytosis by interaction between galactose ligands of GCPVP and ASGPR of the hepatocytes was the major route of transfection of GCPVP/F-plasmid complexes.

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.

Mechanism of cell transfection with plasmid/chitosan complexes

Chitosan is useful as a non-viral vector for gene delivery. Although there are several reports supporting the use of chitosan for gene delivery, studies regarding effects on transfection and the chitosan-specific transfection mechanism remain insufficient. In this report, the level of expression with plasmid/chitosan was observed to be no less than that with plasmid/lipofectin complexes in SOJ cells. The transfection mechanism of plasmid/chitosan complexes as well as the relationship between transfection activity and cell uptake was analyzed by using fluorescein isothiocyanate-labeled plasmid and Texas Red-labeled chitosan. In regard to effects on transfection, there were several factors to affect transfection activity and cell uptake, for example: the molecular mass of chitosan, stoichiometry of complex, as well as serum concentration and pH of transfection medium. The level of transfection with plasmid/chitosan complexes was found to be highest when the molecular mass of chitosan was 40 or 84 kDa, ratio of chitosan nitrogen to DNA phosphate (N/P ratio) was 5, and transfection medium contained 10% serum at pH 7.0. We also investigated the transfection mechanism, and found that plasmid/chitosan complexes most likely condense to form large aggregates (5-8 microm), which absorb to the cell surface. After this, plasmid/chitosan complexes are endocytosed, and possibly released from endosomes due to swelling of lysosomal in addition to swelling of plasmid/chitosan complex, causing the endosome to rupture. Finally, complexes were also observed to accumulate in the nucleus using a confocal laser scanning microscope.