Modeling cytoplasmic release of encapsulated oligonucleotides from cationic liposomes

Interaction Kinetics of Individual mRNA-Containing Lipid Nanoparticles with an Endosomal Membrane Mimic: Dependence on pH, Protein Corona Formation, and Lipoprotein Depletion

Lipid nanoparticles (LNPs) have emerged as potent carriers for mRNA delivery, but several challenges remain before this approach can offer broad clinical translation of mRNA therapeutics. To improve their efficacy, a better understanding is required regarding how LNPs are trapped and processed at the anionic endosomal membrane prior to mRNA release. We used surface-sensitive fluorescence microscopy with single LNP resolution to investigate the pH dependency of the binding kinetics of ionizable lipid-containing LNPs to a supported endosomal model membrane. A sharp increase of LNP binding was observed when the pH was lowered from 6 to 5, accompanied by stepwise large-scale LNP disintegration. For LNPs preincubated in serum, protein corona formation shifted the onset of LNP binding and subsequent disintegration to lower pH, an effect that was less pronounced for lipoprotein-depleted serum. The LNP binding to the endosomal membrane mimic was observed to eventually become severely limited by suppression of the driving force for the formation of multivalent bonds during LNP attachment or, more specifically, by charge neutralization of anionic lipids in the model membrane due to their association with cationic lipids from earlier attached LNPs upon their disintegration. Cell uptake experiments demonstrated marginal differences in LNP uptake in untreated and lipoprotein-depleted serum, whereas lipoprotein-depleted serum increased mRNA-controlled protein (eGFP) production substantially. This complies with model membrane data and suggests that protein corona formation on the surface of the LNPs influences the nature of the interaction between LNPs and endosomal membranes.

Co-condensation synthesis of well-defined mesoporous silica nanoparticles: effect of surface chemical modification on plasmid DNA condensation and transfection

Chemically modified mesoporous silica nanoparticles (MSNs) are of interest due to their chemical and thermal stability with adjustable morphology and porosity; therefore, it was aimed to develop and compare the MCM-41 MSNs functionalised with imidazole groups (MCM-41-Im) to unmodified (MCM-41-OH) and primary amine functionalised (MCM-41-NH₂) MSNs for experimental gene delivery. The results show efficient transfection of the complexes of the plasmid and either MCM-41-NH₂ or MCM-41-Im. Furthermore, following transfection of HeLa cells using MCM-41-Im, an enhanced GFP expression was achieved consistent with the noticeable DNase1 protection and endosomal escape properties of MCM-41-Im using carboxyfluorescein tracer.

IN VITRO RELEASE KINETICS MODEL FITTING OF LIPOSOMES: AN INSIGHT

Liposomes are emerging cargoes for bioactive delivery owing to their widely accepted biocompatible and biodegradable nature. It is always a challenge to control the release of payload for effective delivery to the site of interest. Over the couple of decennia, mathematical modeling of release process is a need of time whether the drug remains in the circulation or reaches at the target site. For establishing a better in vitro - in vivo correlation, release kinetics models viz. Peppas, Higuchi, Weibull, Zero Order and First order including mechanistic models like All-or-None, Toroidal, and Biomembrane models etc. are continuously exploited to predict drug release profile. Most of these models rely on the diffusion equations based on the composition of liposomes and conditions of release. Here, we summarized the crucial reports exploring these models and associated interventions to know the underlying physicochemical release phenomenon. Such mathematical model fitting can be a promising approach to deduce release/delivery process to help in designing the safe and efficacious ("Smart") liposomes.

Modulated cellular delivery of anti-VEGF siRNA (bevasiranib) by incorporating supramolecular assemblies of hydrophobically modified polyamidoamine dendrimer in stealth liposomes

A novel lipopolymer based system was designed and characterized for cellular delivery of anti-VEGF siRNA in SKBR-3 breast tumor cell line. Polyamidoamine (PAMAM) dendrimers of low generations (G1, G2 and G3) were incorporated into polyethylene glycol (PEG)-stabilized liposomes by following the consecutive steps: (a) synthesis of the cholesterol conjugates (40% molar ratio of cholesterol to primary amines of PAMAM), (b) incorporation of the conjugates in liposome by lipid mixing and (c) microencapsulation of the siRNA using the ethanol drop method. The cholesterol conjugates of PAMAM dendrimers (G1-Chol40%, G2-Chol40% and G3-Chol40%) formed self assembly with low CMC values (<11μg/ml). Not only did G2-Chol40% show the highest lipid mixing among the cholesterol conjugates, but also, had the lowest leakage of encapsulated carboxyfluorescein tracer. Various N(amine))/L(lipid)/P(phosphate) mole ratios were investigated for siRNA condensation by ethidium bromide dye exclusion assay. The optimum N/L/P ratio of 20:33:10 was chosen for microencapsulation of anti-VEGF siRNA by ethanol drop method, showing particle size of 130nm, zeta-potential of +4mV, siRNA loading efficiency and capacity of 96% and 13wt%, and high stability against heparin sulfate (extracellular matrix). TEM shows uniform and discrete oligo- or multi-lamellar vesicular structures. The liposome incorporating G2-Chol40% was successfully internalized into SKBR-3 cells mainly through clathrin-mediated endocytosis, which was able to escape from endosomes and showed a significantly higher sequence-specific inhibition of VEGF expression and cell growth than the respective G2-Chol40%/siRNA dendriplexes. Importantly, the cytotoxicity decreased with incorporation of G2-Chol40% in the liposomes.

Cholesterol-based cationic liposome increases dsRNA protection of yellow head virus infection in Penaeus vannamei

Protection of shrimp from yellow head virus (YHV) infection has been demonstrated by injection and oral delivery of dsRNA-YHV protease gene (dsYHV) or shrimp endogenous gene (dsRab7). However, to achieve complete viral suppression and to prolong dsRNA activity, the development of an effective dsRNA delivery system is required. In this study, four cationic liposomes were synthesized and tested for their ability to increase dsRNA efficiency. The results demonstrated that entrapping dsYHV in a cholesterol-based cationic liposome gave the best protection against YHV infection when compared with other cationic lipids. The cholesterol-based cationic liposome-dsYHV (Chol-dsYHV) complex conferred YHV protection in a dose-dependent manner. Injection with Chol-dsYHV at 0.05μg dsYHV/g shrimp could give comparable level of YHV protection to the injection with 1.25μg naked dsYHV/g shrimp. The shrimp injected with Chol- dsYHV at 1.25μg dsRNA/g shrimp showed only 50% mortality at 60days post injection whereas the naked dsYHV at the same concentration gave 90% mortality. Thus, the liposome-entrapped dsYHV could lower an effective dsRNA concentration in viral protection and prolong dsRNA activity. In addition, encapsulating dsRab7 in the cholesterol-based cationic liposome could protect the dsRab7 from enzymatic digestion, and continuous feeding the shrimp with the diet formulated with the liposome-entrapped dsRab7 for 4days in the total of 960μg dsRab7/g shrimp could enhance YHV protection efficiency compared with the naked dsRab7. Our studies reveal that cholesterol-based cationic liposome is a promising dsRNA carrier to enhance dsRNA efficiency in both injection and oral delivery systems.

Synthesis and characterization of a PAMAM dendrimer nanocarrier functionalized by SRL peptide for targeted gene delivery to the brain

Blood-brain barrier inhibits most of drugs and genetic materials from reaching the brain. So, developing high efficiency carriers for gene and drug delivery to the brain, is the challenging area in pharmaceutical sciences. This investigation aimed to target DNA to brain using Serine-Arginine-Leucine (SRL) functionalized PAMAM dendrimers as a novel gene delivery system. The SRL peptide was linked on G4 PAMAM dendrimers using bifunctional PEG. DNA was then loaded in these functionalized nanoparticles and their physicochemical properties and cellular uptake/distribution evaluated by AFM, NMR, FTIR and fluorescence and confocal microscopy. Also, biodistribution and brain localization of nanoparticles were studied after IV injection of nanoparticles into rat tail. Unmodified nanoparticles were used as control in all evaluations. In vitro studies showed that SRL-modified nanoparticles have good transfection efficacy and low toxicity. Results also showed that SRL is a LRP ligand and SRL-modified nanoparticles internalized by clathrin/caveolin energy-dependent endocytosis to brain capillary endothelial cells. After intravenous administration, the SRL-modified nanoparticles were able to cross the blood-brain barrier and enter the brain parenchyma. Our result showed that, SRL-modified nanoparticles provide a safe and effective nanocarrier for brain gene delivery.

Improving cellular uptake and in vivo tumor suppression efficacy of liposomal oligonucleotides by urea as a chemical penetration enhancer

BACKGROUND

Liposomes are among the most widely used carriers for the delivery of antisense oligonucleotides (AsODNs) to intracellular targets. Although different strategies have been employed, the question of how to improve liposomal uptake and enhance the release of AsODN into cytoplasm still remains to be answered with respect to the use of a safe, easy and economic method. In the present study, the possibility of enhancing such processes at cellular and animal levels using urea as a penetration enhancer was investigated.

METHODS

To perform this investigation, a cationic liposome containing an AsODN against protein kinase (PKC)-α was prepared, and the effect of urea on its cellular internalization and the related sequence-specific inhibition of gene expression in human lung adenocarcinoma A549 cells were investigated by flow cytometry and the reverse transcriptase-polymerase chain reaction, respectively. In in vivo studies, a xenograft lung tumor was established in nude mice by A549 cells and the enhancement effect of urea toward the effects of liposomal AsODN on tumor growth was investigated.

RESULTS

Cellular studies revealed that urea treatment increases liposomal uptake and the release of AsODN into the cytoplasm by approximately 40%. Sequence-specific inhibition of target gene PKC-α expression was also increased by approximately two-fold by urea at 200-300 nM AsODN. In animal studies, urea significantly decreased the tumor volume (approximately 40%) and increased its doubling time from approximately 13 days to 17 days.

CONCLUSIONS

Urea, and possibly other membrane fluidizers, could be regarded as penetration enhancers for liposomal AsODN delivery and may improve the therapeutic effect of these gene-therapy vectors at both cellular and animal levels.

Cationic liposomal vaccine adjuvants in animal challenge models: overview and current clinical status

Cationic liposome formulations can function as efficient vaccine adjuvants. However, due to the highly diverse nature of lipids, cationic liposomes have different physical-chemical characteristics that influence their adjuvant mechanisms and their relevance for use in different vaccines. These characteristics can be further manipulated by incorporation of additional lipids or stabilizers, and inclusion of carefully selected immunostimulators is a feasible strategy when tailoring cationic liposomal adjuvants for specific disease targets. Thus, cationic liposomes present a plasticity, which makes them promising adjuvants for future vaccines. This versatility has also led to a vast amount of literature on different experimental liposomal formulations in combination with a wide range of immunostimulators. Here, we have compiled information about the animal challenge models and administration routes that have been used to study vaccine adjuvants based on cationic liposomes and provide an overview of the applicability, progress and clinical status of cationic liposomal vaccine adjuvants.

The delineation of the morphology of charged liposomal vectors via a fractal analysis in aqueous and biological media: physicochemical and self-assembly studies

The present study deals with the physicochemical characterization of DPPC:DPPG (9:1 molar ratio) and DPPC:DODAP (9:1 molar ratio) liposomes, and the determination of their fractal dimension in HPLC-grade water, PBS and in FBS. Light scattering techniques were used in order to extract information on the structure, morphology, size and surface charge of liposomes in an ageing study and their structural response to changes in concentration and temperature. Fluorescence spectroscopy showed that the microviscosity of cationic liposomes changed by an increase of temperature. The fractal dimension, d(f), was found equal to 1.8 for reconstituted DPPC:DPPG (9:1) and DPPC:DODAP (9:1) liposomes in aqueous media. Aggregation of reconstituted DPPC:DPPG (9:1) and DPPC:DODAP (9:1) liposomes in FBS was observed. Their fractal dimensions were 1.46 and 2.45, respectively. The first order aggregation kinetics of DPPC:DODAP (9:1) liposomes in the presence of serum proteins was determined; the aggregates of cationic liposomes with serum components remained stable during 20 days with fractal dimension 2.5. The responsiveness of cationic liposomes to changes in temperature in the three dispersion media has revealed the self-assembly and the morphological complexity of cationic vectors. Finally, we suggest that these studies could be used for developing effective advanced drug delivery nano-systems (aDDnSs) based on their fractal characteristics which effectively draw their morphological profile.

Convenient targeting of stealth siRNA-lipoplexes to cells with chelator lipid-anchored molecules

A major obstacle for the use of siRNAs as novel therapeutics is the requirement for functional delivery to specific cells in vivo. siRNA delivery by cationic agents is generally non-specific and a convenient targeting strategy has been lacking. This work explored the potential for using the chelator lipid 3(nitrilotriacetic acid)-ditetradecylamine (NTA(3)-DTDA) with neutral stealth liposomes to target siRNA to cells. A novel method for incorporating siRNAs into lipoplexes was developed which utilised helper lipids and the ionisable lipid 1,2-dioleoyl-3-dimethylammonium-propane (DODAP). This approach results in an efficient (>50%) incorporation of siRNA into lipoplexes, which when incorporated with Ni-NTA(3)-DTDA and engrafted with a His-tagged form of murine CD4 can target siRNA to murine A20 B cells, in vitro. Also, siRNA-lipoplexes engrafted with His-tagged peptides that target receptors on HEK-293 cells, or the receptor for tumour necrosis factor alpha expressed on the murine dendritic cell line DC2.4, could target siRNA and silence the expression of enhanced green fluorescence protein (EGFP). siRNA-lipoplexes produced by this method are approximately 240 nm dia, exhibit low zeta-potential (-1 mV), and target cells in serum-containing media. The results show that NTA(3)-DTDA can be used to target siRNA-lipoplexes to cells, and could provide a convenient approach for targeting siRNA to cells in vivo for therapeutic applications.

Topical delivery of interleukin-13 antisense oligonucleotides with cationic elastic liposome for the treatment of atopic dermatitis

BACKGROUND

Interleukin (IL)-13, overproduced in the skin of atopic dermatitis (AD), has been shown to play an essential role in the pathogenesis of the disease. Thus, inhibition of IL-13 production should provide a key step to alleviate disease conditions of the atopic skin. In the present study, IL-13 antisense oligonucleotide (ASO) was designed and formulated with cationic elastic liposome (cEL) to improve transdermal delivery.

METHODS

ASOs were generated against murine IL-13 mRNA (+4 to + 23) and complexed with cEL. Physicochemical properties of IL-13 ASO/cEL complex were examined by DNA retardation and DNase I protection assay. An in vitro inhibition study was performed in T-helper 2 (Th2) cells and cytotoxicity was tested by the XTT assay. The in vivo effect of IL-13 ASO/cEL complex was tested in a murine model of AD.

RESULTS

In vitro, the IL-13 ASO/cEL complex showed dose- and ratio-dependent inhibition of IL-13 secretion in Th2 cells. At the IL-13 ASO/cEL ratio of 6, maximum inhibition of IL-13 secretion was observed. When applied to the ovalbumin-sensitized murine model of AD, topically administered IL-13 ASO/cEL complex dramatically suppressed IL-13 production (by up to 70% of the control) in the affected skin region. In addition, the levels of IL-4 and IL-5 were also significantly reduced. Moreover, IL-13 ASO/cEL-treated AD mice showed reduced infiltration of inflammatory cells into the epidermal and dermal areas, with concomitant reduction of skin thickness.

CONCLUSIONS

These data suggests that IL-13 ASO/cEL complex can provide a potential therapeutic tool for the treatment of AD and also be applied to other immune diseases associated with the production of Il-13.