Toxicity of cationic lipids and cationic polymers in gene delivery

Phospholipid conjugate for intracellular delivery of peptide nucleic acids

Peptide nucleic acids (PNAs) have a number of attractive features that have made them an ideal choice for antisense and antigene-based tools, probes, and drugs, but their poor membrane permeability has limited their application as therapeutic or diagnostic agents. Herein, we report a general method for the synthesis of phospholipid-PNAs (LP-PNAs) and compare the effect of noncleavable lipids and bioreductively cleavable lipids (L and LSS) and phospholipid (LP) on the splice-correcting bioactivity of a PNA bearing the cell penetrating Arg9 group (PNA-R9). While the three constructs show similar and increasing bioactivity at 1-3 microM, the activity of LP-PNA-R9 continues to increase from 4-6 microM, while the activity of L-PNA-R9 remains constant and that of LSS-PNA-R9 decreases rapidly in parallel with their relative cytotoxicity. The activity of both LP-PNA-R9 and L-PNA-R9 dramatically increased in the presence of chloroquine, as expected for an endocytotic entry mechanism. The constructs were also found to have CMC values of 1.0 and 4.5 microM, respectively, in 150 mM NaCl, pH 7 water, suggesting that micelle formation may play a hitherto unrecognized role in modulating toxicity and/or facilitating endocytosis.

Chitosan-modified poly(D,L-lactide-co-glycolide) nanospheres for improving siRNA delivery and gene-silencing effects

Chitosan (CS) surface-modified poly(d,l-lactide-co-glycolide) (PLGA) nanospheres (NS) for a siRNA delivery system were evaluated in vitro. siRNA-loaded PLGA NS were prepared by an emulsion solvent diffusion (ESD) method, and the physicochemical properties of NS were investigated. The level of targeted protein expression and siRNA uptake were examined in A549 cells. CS-modified PLGA NS exhibited much higher encapsulation efficiency than unmodified PLGA NS (plain-PLGA NS). CS-modified PLGA NS showed a positive zeta potential, while plain-PLGA NS were negatively charged. siRNA uptake studies by observation with confocal leaser scanning microscopy (CLSM) indicated that siRNA-loaded CS-modified PLGA NS were more effectively taken up by the cells than plain-PLGA NS. The efficiencies of different siRNA preparations were compared at the level of targeted protein expression. The gene-silencing efficiency of CS-modified PLGA NS was higher and more prolonged than those of plain-PLGA NS and naked siRNA. This result correlated with the CLSM studies, which may have been due to higher cellular uptake of CS-modified PLGA NS due to electrostatic interactions. It was concluded that CS-modified PLGA NS containing siRNA could provide an effective siRNA delivery system.

Synthesis and biological applications of imidazolium-based polymerized ionic liquid as a gene delivery vector

The encouraging results of preliminary toxicological studies on imidazolium-based ionic liquids provide good opportunities for the development of ionic liquids in biomedical applications. In this work, the polymerized ionic liquid poly[3-butyl-1-vinylimidazolium L-proline salt] has been synthesized as a gene vector. The interaction of poly[3-butyl-1-vinylimidazolium L-proline salt] with DNA was studied by agarose gel electrophoresis. The cell viability was determined through PI (propidium iodine) staining and flow cytometry, showing marginal toxicity toward the cells examined. The transfection efficiency was evaluated through the in vitro transfection experiment. The results indicated that the imidazolium cation had a high binding ability to DNA, and the condensed DNA in the complexes could be effectively protected against enzymatic degradation. Poly[3-butyl-1-vinylimidazolium L-proline salt] could further transfer the reporter gene into the HeLa cell and successfully mediate the gene expression without the aid of additional agent.

Intracellular small interfering RNA delivery using genetically engineered double-stranded RNA binding protein domain

BACKGROUND

A variety of synthetic carriers, such as cationic polymers and lipids, have been used as nonviral carriers for small interfering RNA (siRNA) delivery. Although siRNA polyplexes and lipoplexes exhibited good gene silencing efficiencies, they often showed serious cytotoxicities, which are not useful for clinical applications. A double-stranded RNA binding cellular protein with highly specific siRNA binding property and noncytotoxicity was used for siRNA delivery.

METHODS

A double-stranded RNA binding domain (dsRBD) of human double-stranded RNA activated protein kinase R was genetically produced and utilized to complex siRNA for intracellular delivery. For characterization of the siRNA/dsRBD complexes, decomplexation assay and RNase protection assay were performed. Cytotoxicity and target gene inhibition ability were also examined using human carcinoma cell lines.

RESULTS

The recombinantly produced polypeptide dsRBD exhibited its inherent binding activity for siRNA without sequence specificity, and the siRNA/dsRBD complexes protected siRNA from degradation by ribonucleases. Green fluorescent protein (GFP) siRNA/dsRBD complexes showed prominent down-regulation of a target GFP gene, when an endosomal escape function was supplemented by addition of a fusogenic peptide, KALA, in the formulation.

CONCLUSIONS

The results suggest that dsRBD-based protein carriers could be successfully applied for a wide range of therapeutic siRNAs for intracellular gene inhibition without showing any cytotoxicity.

Preparation and characterization of poly(DL-lactide-co-glycolide) nanoparticles for siRNA delivery

Synthetic short interfering RNA (siRNA) is promising for specific and efficient knockdown of disease-related genes. However, in vivo application of siRNA requires an effective delivery system. Commonly used siRNA carriers are based on polycations, which form electrostatic complexes with siRNA. Such poly- or lipoplexes are of limited use in vivo due to severe problems associated with toxicity, serum instability and non-specific immune-responses. The aim of the present study was to prepare uniformly sized nanoparticles (NPs) with a high load of siRNA by use of the safe and biodegradable poly-(DL-lactide-co-glycolide) (PLGA) polymer without including polycations. The siRNA was encapsulated in the core of NPs by the double emulsion solvent evaporation method. To optimize the NP formulation, the effects of important formulation and processing parameters were investigated systematically. Generally, spherical siRNA-loaded NPs (<300 nm, PDI<0.2, zeta potential -40 mV) were obtained. An encapsulation efficiency of up to 57% was achieved by adjusting the inner water phase volume, the PLGA concentration, the first emulsification sonication time, and stabilization of the water-oil interface with serum albumin. The integrity of siRNA was preserved during the preparation. Preparation of core-loaded siRNA-NPs based on PLGA and no cationic excipient seems possible and promising for delivery of siRNA.

Gene delivery via DNA incorporation within a biomimetic apatite coating

Integrating inductivity with conductivity in a material may advance tissue engineering. An organic/inorganic hybrid was developed by incorporating plasmid DNA encoding for the beta-gal gene complexed with Lipofectamine 2000 (DNA-Lipoplex) within apatite via coprecipitation. It was hypothesized that this system will result in enhanced transfection efficiency compared to DNA-Lipoplexes adsorbed to the mineral surface and DNA coprecipitated without Lipofectamine 2000. PLGA films were cast onto glass slips and apatite and DNA were coprecipitated in modified simulated body fluid (mSBF). DNA-Lipoplex presence in mineral, DNA-Lipoplex stability (vs. coprecipitation time), and transfection efficiency (determined with C3H10T1/2 cells) as a function of coprecipitation time, DNA-Lipoplex concentration, and DNA incorporation method were studied. DNA-Lipoplex presence and spatial distribution on apatite were confirmed through fluorescence. Transfection efficiency was highest for 6h of DNA-Lipoplex coprecipitation. Differences in transfection efficiency were found between the DNA concentrations, with the highest efficiency for coprecipitation being 40 microg/ml (p < or = 0.009 relative to other coprecipitation concentrations). Significant differences in transfection efficiency existed between incorporation methods (p < 0.05) with the highest efficiency for DNA-Lipoplex coprecipitation. This hybrid material system not only integrates inductivity provided by the DNA and conductivity provided by the apatite, but it also has significant implications in non-viral gene delivery due to its ability to increase transfection efficiency.

The role of nanoparticle concentration-dependent induction of cellular stress in the internalization of non-toxic cationic magnetoliposomes

Magnetoliposomes (MLs), built up of ultrasmall iron oxide cores each individually surrounded by a lipid bilayer, have emerged as highly biocompatible nanoparticles and promising tools in many biomedical applications. To improve cell uptake, cationic amphiphiles are inserted into the ML coat, but this often induces cytotoxic effects. In the present work, we synthesized and tested a cationic peptide-lipid conjugate (dipalmitoylphosphatidylethanolamine-succinyl-tetralysine [DPPE-succ-(Lys)4]) which is entirely composed of biodegradable moieties and specifically designed to exert minimal cytotoxic effects. Uptake studies with both murine 3T3 fibroblasts and C17.2 neural progenitor cells shows 95.63 +/- 5.83 pg Fe and 87.46 +/- 5.62 pg Fe per cell after 24 h, respectively, for 16.66% DPPE-succ-(Lys)4-containing MLs, with no effect on cell viability. However, these high intracellular nanoparticle concentrations transiently affect actin cytoskeleton architecture, formation of focal adhesion complexes and cell proliferation, returning to control levels after approximately 7 days post ML-incubation in both cell types. This study points out the great need for thorough characterization of cell-nanoparticle interactions as subtle time-dependent effects are hard to monitor and commonly used viability and functionality assays are not sufficient to address the broad spectrum of possible interferences of the nanoparticle with normal cell functioning.

Development of a genetically engineered biomimetic vector for targeted gene transfer to breast cancer cells

A biomimetic vector was genetically engineered to contain at precise locations (a) an adenovirus mu peptide to condense pDNA into nanosize particles, (b) a synthetic cyclic peptide to target breast cancer cells and enhance internalization of nanoparticles, (c) a pH-responsive synthetic fusogenic peptide to disrupt endosome membranes and facilitate escape of the nanoparticles into the cytosol, and (d) a nuclear localization signal from human immunodeficiency virus for microtubule mediated transfer of genetic material to the nucleus. The vector was characterized using physicochemical and biological assays to demonstrate the functionality of each motif in the vector backbone. The results demonstrated that the vector is able to condense plasmid DNA into nanosize particles (<100 nm), protect pDNA from serum endonucleases, target ZR-75-1 breast cancer cells and internalize, efficiently disrupt endosome membranes, exploit microtubules to reach nucleus and mediate gene expression. The therapeutic potential of the vector was evaluated by complexing with plasmid DNA encoding TRAIL (pTRAIL) and transfecting ZR-75-1 cells. The results demonstrated that up to 62% of the ZR-75-1 breast cancer cells can be killed after administration of pTRAIL in complex with the vector.

Effect of head size in head-tail-type polycations on their in vitro performances as nonviral gene vectors

Three kinds of head-tail-type block copolymers composed of polyamidoamine (PAMAM) dendron heads and poly(L-lysine) (PLL) tail blocks (PAMAM dendron-PLL), having PAMAM dendrons with different generations (G2.5-PLL, G3.5-PLL and G4.5-PLL) were synthesized. Some of the dendron heads were located at polyplex surface, and G2.5-PLL and G3.5-PLL could form small polyplexes (less than 150 nm in size). G2.5-PLL and G3.5-PLL polyplexes were taken up into the cells more effectively. PAMAM dendron-PLL that had a larger dendron head could show a more-effective buffering effect. The in vitro performance of the PAMAM dendron-PLL polyplexes was controlled by the balance of cellular uptake and endosomal escape by a buffering effect.

Delivery of nucleic acids via disulfide-based carrier systems

Nucleic acids are not only expected to assume a pivotal position as "drugs" in the treatment of genetic and acquired diseases, but could also act as molecular cues to control the microenvironment during tissue regeneration. Despite this promise, the efficient delivery of nucleic acids to their side of action is still the major hurdle. One among many prerequisites for a successful carrier system for nucleic acids is high stability in the extracellular environment, accompanied by an efficient release of the cargo in the intracellular compartment. A promising strategy to create such an interactive delivery system is to exploit the redox gradient between the extra- and intracellular compartments. In this review, emphasis is placed on the biological rationale for the synthesis of redox sensitive, disulfide-based carrier systems, as well as the extra- and intracellular processing of macromolecules containing disulfide bonds. Moreover, the basic synthetic approaches for introducing disulfide bonds into carrier molecules, together with examples that demonstrate the benefit of disulfides at the individual stages of nucleic acid delivery, will be presented.

Controlled delivery of antisense oligonucleotides: a brief review of current strategies

Antisense therapy has been investigated extensively over the past two decades, either experimentally for gene functional research or clinically as therapeutic agents owing to the conceptual simplicity, ease of design and low cost. The concept of this therapeutic approach is promising because short antisense oligonucleotides (ASOs) can be delivered into target cells for specific hybridisation with target mRNA, resulting in the inhibition of the expression of pathogenic genes. However, the efficient delivery of the ASO molecules into target cells remains challenging; this bottleneck together with several other technical hurdles need to be overcome before this approach becomes effective and widely adopted. A variety of vectors such as lipids, polymers, peptides and nanoparticles have been explored. This review outlines the recent advances of the non-viral ASO delivery strategies. Several recent scientific studies, including authors' contributions, have been selected to highlight the technical aspects of ASO delivery.

Characterization, in vitro cytotoxicity assessment, and in vivo visualization of multimodal, RITC-labeled, silica-coated magnetic nanoparticles for labeling human cord blood-derived mesenchymal stem cells

Live imaging is a powerful technique that can be used to characterize the fate and location of stem cells in animal models. Here we investigated the characteristics and in vitro cytotoxicity of human mesenchymal stem cells (MSCs) labeled with silica-coated magnetic nanoparticles incorporating rhodamine B isothiocyanate, MNPs@SiO2(RITC). We also conducted various in vivo-uptake tests with nanoparticle-labeled human MSCs. MNPs@SiO2(RITC) showed photostability against ultraviolet light exposure and were nontoxic to human MSCs, based on the MTT, apoptosis, and cell cycle arrest assays. In addition, MNPs@SiO2(RITC) did not affect the surface phenotype or morphology of human MSCs. We also demonstrated that MNPs@SiO2(RITC) have stable retention properties in MSCs in vitro. Furthermore, using optical and magnetic resonance imaging, we successfully detected a visible signal from labeled human MSCs that were transplanted into NOD.CB17-Prkdc(SCID) (NOD-SCID) mice. These results demonstrate that MNPs@SiO2(RITC) are biocompatible and useful tools for human MSC labeling and bioimaging.

FROM THE CLINICAL EDITOR

The characteristics and in vitro cytotoxicity of human mesenchymal stem cells (MSCs) labeled with silica-coated magnetic nanoparticles incorporating rhodamine B isothiocyanate, RITC were investigated in this study. RITC showed photostability against ultraviolet light exposure and was nontoxic to human MSCs. Using both optical and magnetic resonance imaging, successful detection of signal from labeled human MSCs transplanted into mice is demonstrated.

siRNA delivery systems for cancer treatment

With increasing knowledge on the molecular mechanisms of endogenous RNA interference, small interfering RNAs (siRNAs) have been emerging as innovative nucleic acid medicines for treatment of incurable diseases such as cancers. Although several siRNA candidates for the treatment of ocular and respiratory diseases are undergoing clinical trials, there are challenges inherent in the further development of siRNAs for anti-cancer therapeutics, because systemic administration will be required in most cases. In addition to nonspecific off-target and immune stimulation problems, appropriate delivery remains a major hurdle. The technologies developed for delivery of nucleic acid medicines such as plasmid DNA and antisense oligonucleotides have paved the way to rapid progress for in vivo delivery of siRNAs. Here, we review various in vivo delivery strategies including chemical modification, conjugation, lipid-based techniques, polymer-based nanosystems, and physical methods. Moreover, the current progress in siRNA delivery systems for gynecologic, liver, lung, and prostate cancers is discussed.

Polyethylene glycol-complexed cationic liposome for enhanced cellular uptake and anticancer activity

Liposomes as one of the efficient drug carriers have some shortcomings such as their relatively short blood circulation time, fast clearance from human body by reticuloendothelial system (RES) and limited intracellular uptake to target cells. In this study, polyethylene glycol (PEG)-complexed cationic liposomes (PCL) were prepared by ionic complex of cationically charged liposomes with carboxylated polyethylene glycol (mPEG-COOH). The cationic liposomes had approximately 98.6+/-1.0 nm of mean particle diameter and 45.5+/-1.1 mV of zeta potential value. While, the PCL had 110.1+/-1.2 nm of mean particle diameter and 18.4+/-0.8 mV of zeta potential value as a result of the ionic complex of mPEG-COOH with cationic liposomes. Loading efficiency of model drug, doxorubicin, into cationic liposomes or PCL was about 96.0+/-0.7%. Results of intracellular uptake evaluated by flow cytometry and fluorescence microscopy studies showed higher intracellular uptake of PCL than that of Doxil. In addition, in vitro cytotoxicity of PCL was comparable to cationic liposomes. In pharmacokinetic study in rats, PCL showed slightly lower plasma level of DOX than that of Doxil. In vivo antitumor activity of DOX-loaded PCL was comparable to that of Doxil against human SKOV-3 ovarian adenocarcinoma xenograft rat model. Consequently, the PCL, of which surface was complexed with PEG by ionic complex may be applicable as drug delivery carriers for increasing therapeutic efficacy of anticancer drugs.

siRNA-mediated integrin-linked kinase suppression: nonspecific effects of siRNA/cationic liposome complexes trigger changes in the expression of phosphorylated-AKT and mTOR independently of ILK silencing

Short interfering RNA targeting ILK (ILK siRNA) could be used to treat patients with cancers where constitutive activation of the AKT/PI3K pathway is prominent (e.g., those cancers lack functional PTEN). It is generally believed that siRNA therapeutics will require the use of delivery systems and lipid-based formulations containing cationic lipids (CLs) are a viable option. However, CLs are known to be toxic and exposure to CLs can influence cell survival pathways. This study characterized how CLs combine with ILK siRNA to influence the AKT/PI3K pathway. Using PTEN-negative cell lines (PC3 castration-insensitive prostate cancer cells and U251 glioma cancer cells), the influence of CLs on the downstream consequences of ILK silencing was determined. When comparing nucleofection (an electroporation method that does not require the use of CLs) and CLs as means to deliver ILK siRNA, a 12- to 30-fold increase in siRNA delivery was achieved when using a CL formulation, yet ILK suppression was less efficient. Importantly, time-dependent signaling consequences associated with ILK silencing, including suppression of phosphorylated (serine 473)-AKT and changes in mTOR expression, were observed independently of ILK suppression when the target cells were exposed to cationic lipids following nucleofection-based delivery of ILK siRNA.

Delivery of RNA interference therapeutics using polycation-based nanoparticles

RNAi-based therapies are dependent on extracellular and intracellular delivery of RNA molecules for enabling target interaction. Polycation-based nanoparticles (or polyplexes) formed by self-assembly with RNA can be used to modulate pharmacokinetics and intracellular trafficking to improve the therapeutic efficacy of RNAi-based therapeutics. This review describes the application of polyplexes for extracellular and intracellular delivery of synthetic RNA molecules. Focus is given to routes of administration and silencing effects in animal disease models. The inclusion of functional components into the nanoparticle for controlling cellular trafficking and RNA release is discussed. This work highlights the versatile nature of polycation-based nanoparticles to fulfil the delivery requirements for RNA molecules with flexibility in design to evolve alongside an expanding repertoire of RNAi-based drugs.

siRNA vs. shRNA: similarities and differences

RNA interference (RNAi) is a natural process through which expression of a targeted gene can be knocked down with high specificity and selectivity. Using available technology and bioinformatics investigators will soon be able to identify relevant bio molecular tumor network hubs as potential key targets for knockdown approaches. Methods of mediating the RNAi effect involve small interfering RNA (siRNA), short hairpin RNA (shRNA) and bi-functional shRNA. The simplicity of siRNA manufacturing and transient nature of the effect per dose are optimally suited for certain medical disorders (i.e. viral injections). However, using the endogenous processing machinery, optimized shRNA constructs allow for high potency and sustainable effects using low copy numbers resulting in less off-target effects, particularly if embedded in a miRNA scaffold. Bi-functional design may further enhance potency and safety of RNAi-based therapeutics. Remaining challenges include tumor selective delivery vehicles and more complete evaluation of the scope and scale of off-target effects. This review will compare siRNA, shRNA and bi-functional shRNA.

Cationic liposomes as carriers for aerosolized formulations of an anionic drug: safety and efficacy study

This study tests the hypothesis that pegylated cationic liposomes are a viable carrier for inhalable formulations of low molecular weight heparin, an anionic drug. Cationic liposomal formulations of low molecular weight heparin were prepared by the hydration method using 1,2-dioleoyl-3-trimethylammonium-propane (chloride salt), cholesterol and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol)-2000]. The formulations were characterized for particle size, entrapment efficiency, pulmonary absorption and pharmacological efficacy. For absorption studies, the formulations were administered to anesthetized male Sprague-Dawley rats via the pulmonary route and drug absorption was monitored by measuring plasma anti-factor Xa activity. The pharmacological efficacy of the formulations was studied in rodent models of pulmonary embolism and deep vein thrombosis. The mean particle size of the liposomes was 104.8+/-20.7 nm and the drug entrapment efficiency was 90.3+/-0.1%. The half-life of the cationic liposomal formulation was 10.6+/-0.2h, a 2.2-fold increase compared to low molecular weight heparin formulated in saline, and the relative bioavailability was approximately 73.4+/-19.1% when compared to subcutaneously administered drug. A once-every-other-day inhaled dose of the formulation showed similar efficacy in reducing thrombus weight as a once-daily dose of subcutaneously administered drug. Likewise, cationic liposomal formulations administered via the pulmonary route 6h prior to embolization in the lungs showed a thrombolytic effect comparable to that of low molecular weight heparin administered subcutaneously 2h before embolization. Histological examination of lung tissue and measurement of injury markers in bronchoalveolar lavage fluid suggest that the formulations did not produce extensive damage. The results demonstrate that pegylated cationic liposomes could be a viable carrier for an inhalable formulation of low molecular weight heparin.

Synthesis and use of pHEMA microbeads with human EA.hy 926 endothelial cells

Cancer has become a major problem in public health and the resulting bone metastases a worsening factor. Facing it, different strategies have been proposed and mechanisms involved in tumor angiogenesis are being studied. Enhanced permeability retention (EPR) effect is a key step in designing new anticancer drugs. We have prepared poly 2-hydroxyethyl methacrylate (pHEMA) microbeads to target human endothelial EA.hy 926 cells, a cell line derived from human umbilical vein endothelial cells. Microbeads were synthesized by emulsion precipitation method and carried positive or negative charges. EA.hy 926 cells were cultured in 24-well plates and microbeads were deposited on cells at various times. Scanning and transmission electron microscopy, flow cytometry, confocal microscopy, and three-dimensional (3D) reconstruction were used to characterize microbeads and their location outside and inside cells. Microbeads were uptaken by endothelial cells with a better internalization for negatively charged microbeads. 3D reconstruction of confocal optical sections clearly evidenced the uptake and internalization of microbeads by endothelial cells. pHEMA microbeads could represent potential drug carrier in tumor model of metastases.

Modulation of water exchange in Eu(III) DOTA-tetraamide complexes: considerations for in vivo imaging of PARACEST agents

Modulation of water exchange in lanthanide(III)-DOTA type complexes has drawn considerable attention over the past two decades, particularly because of their application as contrast agents for magnetic resonance imaging. LnDOTA-tetraamide complexes display unusually slow water exchange kinetics and this chemical property offers an opportunity to use these complexes as a new type of contrast agent based upon the chemical exchange saturation transfer (CEST) mechanism. Six new DOTA-tetraamide ligands having side-chain amide arms with varying hydrophobicity and polarity were prepared and the water exchange characteristic of complexes formed with europium(III) complexes were investigated. The results show that introduction of steric bulk into the amide side-chain arms of the europium(III) complexes not only favors formation of the mono-capped twisted square antiprism coordination isomers, the isomer that is generally less favourable for CEST, but also accelerates water exchange in the mono-capped square antiprism isomers. However, converting single methyl groups on these bulky arms to carboxyl or carboxyl ethyl esters results in a rather dramatic decrease in water exchange rates, about 50-fold. Thus, steric bulk, polarity and hydrophobicity of the amide side-chains each contribute to organization of water molecules in the second hydration sphere of the europium(III) ion and this in turn controls water exchange in these complexes.

Anionic amino acid-derived cationic lipid for siRNA delivery

Viable siRNA therapeutic strategies require the concurrent development of effective and safe delivery systems. Here, we described the synthesis of a new cationic lipid, N,N''-dioleylglutamide (DG), and evaluated DG-based liposomes as an siRNA delivery system. DG, an amino acid derivative, was synthesized by peptide bond linkage of oleylamine to each carboxylic acid group of glutamic acid. Gel retardation assays showed that DG-based cationic liposomes and siRNA began to form complexes from the N/P ratio of 1.8. The viability of A549, HeLa and WM266.4 cells was significantly higher after treatment with DG-based liposomes than with Lipofectamine 2000 and cationic 3beta-[N-(N',N'-dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol)-based liposomes. The DG-based cationic liposomes could effectively deliver a fluorescent model siRNA into A549, HeLa, and WM266.4 human cancer cell lines, showing at least 2-fold higher fluorescence mean intensity values than did Lipofectamine 2000. When survivin-specific siRNA was delivered to cells in lipoplexes, survivin mRNA levels were reduced by DG-based liposomes to the higher extent than Lipofectamine 2000 and DC-Chol-based liposomes. When red fluorescent protein (RFP)-expressing cells were treated with RFP-specific siRNA (siRFP), RFP expression significantly decreased in cells treated with DG-based liposomes. Molecular imaging revealed that intratumoral injection of siRFP and DG-based liposome complexes significantly reduced fluorescence in RFP-expressing tumor tissues in mice. These results suggest that DG-based cationic liposomes would be of value for cellular delivery and in vivo local delivery of siRNA.

Pharmacokinetics and bone formation by BMP-2 entrapped in polyethylenimine-coated albumin nanoparticles

The osteoinductive growth factor, bone morphogenetic protein-2 (BMP-2), is capable of inducing de novo bone formation after implantation. A nanoparticulate (NP) system was developed for BMP-2 delivery based on NPs fabricated from bovine serum albumin (BSA) and stabilized by polyethylenimine (PEI) coating. In this study, the pharmacokinetics and osteoinductivity of BMP-2 delivered with different BSA NP formulations were determined by subcutaneous implantation in rats. A 7-day pharmacokinetics study showed that PEI coating on NPs effectively reduced the initial burst release of BMP-2 and prolonged the BMP-2 retention at implantation site. However, the uncoated BMP-2 NPs (BMP-2 loading of 1.44% w/w) were able to induce a robust ectopic bone formation, while no bone formation was found by the BMP-2 NPs coated with PEI. The toxicity of the PEI used for NP coating was determined to be the reason for lack of osteoinduction. Increasing BMP-2 loading (up to 5.76% w/w) was then employed to formulate NPs with lower PEI content; the higher BMP-2 loading was found to better promote induction of de novo bone. Our findings indicated that PEI coating on BSA NPs was effective for controlling BMP-2 release from NPs, but the toxicity of cationic PEI was a concern for the osteoinductive activity, which should be alleviated by further optimization of NP formulations.

Effect of acyl chain length on transfection efficiency and toxicity of polyethylenimine

Polyethylenimine (PEI) is an efficient nonviral gene delivery vector because of its high buffering capacity and DNA condensation ability. In our study, the amino groups on the polymeric backbone were acylated using acetic or propionic anhydride to alter the protonation behaviour and the hydrophilic/hydrophobic balance of the polymer. The concentration of acylated primary amines was determined using trinitrobenzene sulphonic acid assay. Results showed that our modified polymers had lower buffering capacities in solutions compared to PEI. The polymers were complexed with plasmid encoding enhanced green fluorescent protein at three different ratios (1:1, 1:2 and 1:10 w/w DNA to polymer) to form polyplexes and their toxicities and transfection efficiencies were evaluated in HEK 293 cells. Acylation reduced the number of primary amines on the polymer and the surface charge, improving haemocompatibility and reducing cytotoxicity. The reduction in the concentration of amino groups helped to optimise DNA compaction and facilitated polyplex dissociation in the cell, which increased transfection efficiency of the modified polymers compared to the parent polymer. Polymers with buffering capacities greater than 50% and less than 80% relative to PEI, showed higher transfection efficiencies than PEI. The propionic anhydride modified polymers had appropriate interactions with DNA which provided both DNA compaction and polyplex dissociation. These systems interacted better with the cell membrane because of their slightly higher lipophilicity and formed polyplexes which were less cytotoxic than polyplexes of acetic anhydride modified polymers. Among the vectors tested, 1:0.3 mol/mol PEI:propionic anhydride in a 1:2 w/w DNA:polymer composition provided the best transfection system with improved transfection efficiency and reduced cytotoxicity.

Intravaginal gene silencing using biodegradable polymer nanoparticles densely loaded with small-interfering RNA

Vaginal instillation of small-interfering RNA (siRNA) using liposomes has led to silencing of endogenous genes in the genital tract and protection against challenge from infectious disease. Although siRNA lipoplexes are easily formulated, several of the most effective transfection agents available commercially may be toxic to the mucosal epithelia and none are able to provide controlled or sustained release. Here, we demonstrate an alternative approach using nanoparticles composed entirely of FDA-approved materials. To render these materials effective for gene silencing, we developed novel approaches to load them with high amounts of siRNA. A single dose of siRNA-loaded nanoparticles to the mouse female reproductive tract caused efficient and sustained gene silencing. Knockdown of gene expression was observed proximal (in the vaginal lumen) and distal (in the uterine horns) to the site of topical delivery. In addition, nanoparticles penetrated deep into the epithelial tissue. This is the first report demonstrating that biodegradable polymer nanoparticles are effective delivery vehicles for siRNA to the vaginal mucosa.

Use of liposomes as drug delivery vehicles for treatment of melanoma

Melanoma is a progressive disease that claims many lives each year due to lack of therapeutics effective for the long-term treatment of patients. Currently, the best treatment option is early detection followed by surgical removal. Better melanoma therapies that are effectively delivered to tumors with minimal toxicity for patients are urgently needed. Nanotechnologies provide one approach to encapsulate therapeutic agents leading to improvements in circulation time, enhanced tumor uptake, avoidance of the reticulo-endothelial system, and minimization of toxicity. Liposomes in particular are a promising nanotechnology that can be used for more effective delivery of therapeutic agents to treat melanoma. Liposomes delivering chemotherapies, siRNA, asODNs, DNA, and radioactive particles are just some of the promising new nanotechnology based therapies under development for the treatment of melanoma that are discussed in this review.

Molecular mechanism of caspase-3-induced gene expression of polyplexes formed from polycations grafted with cationic substrate peptides

We previously reported a novel disease-site-specific gene targeting system that can release plasmid DNA (pDNA) from polymeric carriers responding to abnormally activated signal proteins in disease cells. In this study, the molecular mechanism of the gene targeting system responding to Caspase-3 activity was studied in detail. The polymeric carrier used was composed of a neutral main chain polymer and a grafted oligocationic peptide which contains the substrate sequence of Caspase-3. The polyplex formed from the polymeric carrier and pDNA was stable in physiological saline solution and protected from access of RNA polymerase and the transcriptional factors. These results indicate that the polyplex adopts a core-shell-like structure with a polyion complex core surrounded by neutral main chain polymers. In spite of the inert character of the polyplex to transcription, the polyplex afforded the access of Caspase-3 to the substrate peptide because the electrostatic interaction between each peptide and DNA is essentially weak. After the Caspase-3 reaction, the polyplex was weakened and then became available as a template for transcription.

Relevance of the colloidal stability of chitosan/PLGA nanoparticles on their cytotoxicity profile

The application of nanoparticles on a sub-cellular level necessitates an in depth study of their biocompatibility. However, complete characterization of the particles under the physiological conditions relevant for biological evaluation is still lacking. Our goal is therefore to evaluate the possible toxicity aspects of chitosan-modified PLGA nanoparticles on different cell lines and relate them to the parameters affecting the colloidal stability of the nanoparticles. The impacts of different factors such as nanoparticle concentration, exposure time, chitosan content in the particles and pH fluctuations on the cell viability were investigated. Meanwhile, the colloidal stability of the particles in cell culture media was checked by measuring their size and charge as well as visualizing the particles in media by scanning force microscopy (SFM). A slight shift in the pH of the culture medium to the acidic side allows the protonation of chitosan; thus the increased positive surface charge induced membrane damage ( approximately 50% increase in LDH released). Besides, cell viability is reduced by 15% in the absence of serum; serum in the culture medium forms a protective shell around the particles; such interaction influences the surface charge of the particles and was found to be a function of chitosan content in the particles. In conclusion, there is an undeniable impact of cell type, medium, presence/absence of serum on the colloidal state of the particles that consequently influence their interaction with the cells.

Biosynthesis and characterization of a novel genetically engineered polymer for targeted gene transfer to cancer cells

A novel multi-domain biopolymer was designed and genetically engineered with the purpose to target and transfect cancer cells. The biopolymer contains at precise locations: 1) repeating units of arginine and histidine to condense pDNA and lyse endosome membranes, 2) a HER2 targeting affibody to target cancer cells, 3) a pH responsive fusogenic peptide to destabilize endosome membranes and enhance endosomolytic activity of histidine residues, and 4) a nuclear localization signal to enhance translocation of pDNA towards the cell nucleus. The results demonstrated that the biopolymer was able to condense pDNA into nanosize particles, protect pDNA from serum endonucleases, target HER2 positive cancer cells but not HER2 negative ones, efficiently disrupt endosomes, and effectively reach the cell nucleus of target cells to mediate gene expression. To reduce potential toxicity and enhance biodegradability, the biopolymer was designed to be susceptible to digestion by endogenous furin enzymes inside the cells. The results revealed no significant biopolymer related toxicity as determined by impact on cell viability.

Addressing the problem of cationic lipid-mediated toxicity: the magnetoliposome model

The high biocompatibility and versatile nature of liposomes made these particles keystone components in many hot-topic research areas. For transfection and cell labelling purposes, synthetic cationic lipids are often added, but in most studies, little attention has been paid to their cytotoxic effects. In the present work, cationic magnetoliposomes (MLs), i.e. iron oxide cores enwrapped by a phospholipid bilayer (dimyristoylphosphatidylcholine or sphingomyelin) doped with cationic lipids (1,2-distearoyl-3-trimethylammonium propane), serve as a model to examine cationic lipid toxicity. Mechanisms of cytotoxic effects were found to be either dependent or independent of actual particle internalisation according to data obtained in the absence or presence of several endocytosis inhibitors. The former seem to be caused by the generation of reactive oxygen species (ROS) leading to a Ca2+ influx at high ROS levels. The latter are due to a destabilisation of the cell plasma membrane upon transfer of the cationic lipid from the ML bilayer into the plasma membrane. However, these adverse effects can be diminished by the use of a ROS scavenger, a Ca(2+)-channel blocker or by modulating the liposome size, lipid bilayer constitution or by stabilising the membrane by anchoring it on a solid core. Careful attention must be paid in terms of assessing cell viability as the effects are highly time dependent and the data suggest the incompatibility of using the well-known MTT assay when high levels of ROS species are generated.

Cellular delivery and biological activity of antisense oligonucleotides conjugated to a targeted protein carrier

Targeted delivery can potentially improve the pharmacological effects of antisense and siRNA oligonucleotides. Here, we describe a novel bioconjugation approach to the delivery of splice-shifting antisense oligonucleotides (SSOs). The SSOs are linked to albumin via reversible S-S bonds. The albumin is also conjugated with poly(ethylene glycol) (PEG) chains that terminate in an RGD ligand that selectively binds the alphavbeta3 integrin. As a test system, we utilized human melanoma cells that express the alphavbeta3 integrin and that also contain a luciferase reporter gene that can be induced by delivery of SSOs to the cell nucleus. The RGD-PEG-SSO-albumin conjugates were endocytosed by the cells in an RGD-dependent manner; using confocal fluorescence microscopy, evidence was obtained that the SSOs accumulate in the nucleus. The conjugates were able to robustly induce luciferase expression at concentrations in the 25-200 nM range. At these levels, little short-term or long-term toxicity was observed. Thus, the RGD-PEG-albumin conjugates may provide an effective tool for targeted delivery of oligonucleotides to certain cells and tissues.

A designer biomimetic vector with a chimeric architecture for targeted gene transfer

Designer biomimetic vectors are genetically engineered biomacromolecules that are designed to mimic viral characteristics in order to overcome the cellular barriers associated with the targeted gene transfer. The vector in this study was genetically engineered to contain at precise locations: a) four tandem repeating units of N-terminal domain of histone H2A to condense DNA into stable nanosize particles suitable for cellular uptake, b) a model targeting motif to target HER2 and enhance internalization of nanoparticles, and c) a pH-responsive synthetic fusogenic peptide to disrupt endosome membranes and promote escape of the nanoparticles into the cytosol. The results demonstrate that a fully functional, multi-domain, designer vector can be engineered to target cells with high specificity, overcome the biological barriers associated with targeted gene transfer, and mediate efficient gene transfer.

Knocking down barriers: advances in siRNA delivery

In the 10 years that have passed since the Nobel prize-winning discovery of RNA interference (RNAi), billions of dollars have been invested in the therapeutic application of gene silencing in humans. Today, there are promising data from ongoing clinical trials for the treatment of age-related macular degeneration and respiratory syncytial virus. Despite these early successes, however, the widespread use of RNAi therapeutics for disease prevention and treatment requires the development of clinically suitable, safe and effective drug delivery vehicles. Here, we provide an update on the progress of RNAi therapeutics and highlight novel synthetic materials for the encapsulation and intracellular delivery of nucleic acids.

Knocking down barriers: advances in siRNA delivery

RNA interference (RNAi) is a fundamental pathway in eukaryotic cells by which sequence-specific small interfering RNA (siRNA) is able to silence genes through the destruction of complementary mRNA. RNAi is an important therapeutic tool that can be used to silence aberrant endogenous genes or to knockdown genes essential to the proliferation of infectious organisms.

Delivery remains the central challenge to the therapeutic application of RNAi technology. Before siRNA can take effect in the cytoplasm of a target cell, it must be transported through the body to the target site without undergoing clearance or degradation.

Currently, the most effective synthetic, non-viral delivery agents of siRNA are lipids, lipid-like materials and polymers.

Various cationic agents including stable nucleic acid–lipid particles, lipidoids, cyclodextrin polymers and polyethyleneimine polymers have been used to achieve the successful systemic delivery of siRNA in mammals without inducing significant toxicity.

Direct conjugation of delivery agents to siRNA can facilitate delivery. For example, cholesterol-modified siRNA enables targeting to the liver.

RNAi therapeutics have progressed to the clinic, where studies are being conducted to determine siRNA efficacy in treating several diseases, including age-related macular degeneration and respiratory syncytial virus.

Moving forward, it will be important to pay close attention to the potential nonspecific immunostimulatory effects of siRNA. Modifications to siRNA can be used to minimize stimulation of the immune system, and an increased emphasis must be placed on performing proper controls to ensure that therapeutic effects are sequence-specific.

RNA interference holds vast potential as a therapeutic strategy for both disease prevention and treatment, but its use has so far been hampered by a lack of safe and effective delivery techniques. In their Review, Anderson and colleagues discuss the challenges associated with small interfering RNA delivery and highlight promising novel synthetic delivery agents.

In the 10 years that have passed since the Nobel prize-winning discovery of RNA interference (RNAi), billions of dollars have been invested in the therapeutic application of gene silencing in humans. Today, there are promising data from ongoing clinical trials for the treatment of age-related macular degeneration and respiratory syncytial virus. Despite these early successes, however, the widespread use of RNAi therapeutics for disease prevention and treatment requires the development of clinically suitable, safe and effective drug delivery vehicles. Here, we provide an update on the progress of RNAi therapeutics and highlight novel synthetic materials for the encapsulation and intracellular delivery of nucleic acids.

The combination of stabilized plasmid lipid particles and lipid nanoparticle encapsulated CpG containing oligodeoxynucleotides as a systemic genetic vaccine

BACKGROUND

DNA vaccines offer unique potential for generating protective and therapeutic immunity against infectious and malignant diseases. Unfortunately, rapid degradation and poor cellular uptake has significantly limited the efficacy of 'naked' plasmid DNA vaccines. We have previously described stabilized plasmid lipid particles (SPLP) as effective nonviral gene delivery vehicles for the transfection of tumours at distal sites following intravenous administration. Based on their low toxicity and favourable transfection profile following systemic administration, we investigate SPLP as gene delivery vehicles for the generation of a systemically administered genetic vaccine.

METHODS

The uptake of SPLP and their ability to transfect splenic antigen presenting cells (APC) following systemic administration is assessed through fluorescently-labelled SPLP in combination with phenotype markers and a very sensitive flow cytometry-based assay for the detection of the transgene, beta-galactosidase. The priming of antigen-specific adaptive and humoural immune responses following vaccination with SPLP alone or in combination with liposomal nanoparticle encapsulated CpG-ODN containing oligodeoxynucleotides (LN CpG-ODN) is characterized through the use of antigen-specific cytotoxicity assays, interferon-gamma secretion assays and enzyme-linked immunosorbant assay.

RESULTS

We demonstrate that SPLP are taken up by and transfect APC in the spleen following intravenous administration and that, in the presence of a strong immunostimulatory signal provided by LN CpG-ODN, are able to prime transgene-specific humoural and cellular immune responses.

CONCLUSIONS

SPLP represent an effective candidate for the nonviral delivery of a systemic genetic vaccine when combined with additional immune stimulation provided by LN CpG-ODN.

Effect of chain length on physicochemical properties and cytotoxicity of cationic vesicles composed of phosphatidylcholines and dialkyldimethylammonium bromides

This study investigated the physicochemical characteristics of cationic vesicles that were prepared from two phosphatidylcholines and three dialkyldimethylammonium bromides (DXDAB) with differing in dialkyl chain lengths, ranging from 2-C(14) to 2-C(18), by measuring particle size and zeta potential. The dependence of particle size, zeta potential and short-storage stability of mixed phosphatidylcholine/DXDAB vesicles on the chain length and composition were also elucidated. Transmission electron microscopy analysis verified that vesicles were formed as a phosphatidylcholine film to which DXDAB was added in a phosphate buffer saline (PBS, pH 7.4). Furthermore, the toxicity to the human keratinocytes (HaCaT) and squamous cell carcinomas (SCC25) cells that were incubated with these vesicles, evaluated by a cell viability assay, increased with the percentage of DXDAB that was incorporated and was inversely proportional to the chain length of DXDAB. The morphological features (round shape, chromatin condensation and apoptosis bodies) and results of flow cytometry analysis (increased sub-G(1) fraction) confirmed the induction of apoptosis in HaCaT and SCC25 cells by cationic vesicles. Apoptosis caused by cationic vesicles without the addition of any drugs was observed for the first time in HaCaT and SCC25 cells. The results of this investigation suggest that cytotoxicity is related to the zeta potential of the cationic vesicles.

Comparison of the efficiency and toxicity of sonoporation with branched polyethylenimine-mediated gene transfection in various cultured cell lines

OBJECTIVE

The objective of this study is to evaluate transfection efficiency and safety for gene delivery by sonoporation in comparison with cationic polymer gene carrier branched polyethylenimine (BPEI).

METHODS

The cDNA expressing VEGF(165) was cloned under chicken beta-actin promoter. The plasmid DNA was transfected into the CHO, HEK293, and NIH3T3 cells using microbubble-based sonoporation and BPEI (25 kDa) under various conditions. Enzyme-linked immunosorbent assay (ELISA) was used to determine the expressed protein level. Cytotoxicities of transfection methods were compared by Cell Counting Kit-8.

RESULTS

At 1 MHz intensity, transfection efficiency of sonoporation was enhanced by microbubble concentration with no detrimental effects. By contrast, BPEI exacerbated cell viability, despite its high transgene expression efficiency.

CONCLUSION

Sonoporation gene therapy might be the safest technique to be used in actual clinical practice.

Determining the cytotoxicity of catanionic surfactant mixtures on HeLa cells

The cytotoxicity of commonly used synthetic surfactants and catanionic mixtures of those was evaluated using MTT on HeLa cells. The 50% inhibition concentration (IC(50)) for MTT reduction was calculated. The effect on chain length increase and inclusion of polyoxyethylene groups on the toxicity was tested on single surfactant systems. A general trend of increasing toxicity with increasing chain length and the presence of polyoxyethylene groups was observed. The measured IC(50) values of catanionic systems lie between those of participating surfactants. The increase in toxicity as the cationic surfactant is added to the anionic one is however not linear. A steep decrease of the IC(50) values (and therefore increase in the toxic properties) is observed immediately already at low concentrations of the cationic surfactants. This behavior is analogous to the enzyme activity in catanionic microemulsions.