Structural variation of cationic lipids: minimum requirement for improved oligonucleotide delivery into cells

Biocompatible Cationic Lipoamino Acids as Counterions for Oral Administration of API-Ionic Liquids

Purpose

The use of ionic liquids (ILs) in drug delivery has focused attention on non-toxic IL counterions. Cationic lipids can be used to form ILs with weakly acidic drugs to enhance drug loading in lipid-based formulations (LBFs). However, cationic lipids are typically toxic. Here we explore the use of lipoaminoacids (LAAs) as cationic IL counterions that degrade or digest in vivo to non-toxic components.

Methods

LAAs were synthesised via esterification of amino acids with fatty alcohols to produce potentially digestible cationic LAAs. The LAAs were employed to form ILs with tolfenamic acid (Tol) and the Tol ILs loaded into LBF and examined in vitro and in vivo.

Results

Cationic LAAs complexed with Tol to generate lipophilic Tol ILs with high drug loading in LBFs. Assessment of the LAA under simulated digestion conditions revealed that they were susceptible to enzymatic degradation under intestinal conditions, forming biocompatible FAs and amino acids. In vitro dispersion and digestion studies of Tol ILs revealed that formulations containing digestible Tol ILs were able to maintain drug dispersion and solubilisation whilst the LAA were breaking down under digesting conditions. Finally, in vivo oral bioavailability studies demonstrated that oral delivery of a LBF containing a Tol IL comprising a digestible cationic lipid counterion was able to successfully support effective oral delivery of Tol.

Conclusions

Digestible LAA cationic lipids are potential IL counterions for weakly acidic drug molecules and digest in situ to form non-toxic breakdown products.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-022-03305-y.

Effects of Surface Charge, PEGylation and Functionalization with Dipalmitoylphosphatidyldiglycerol on Liposome-Cell Interactions and Local Drug Delivery to Solid Tumors via Thermosensitive Liposomes

Purpose

Previous studies demonstrated the possibility of targeting tumor-angiogenic endothelial cells with positively charged nanocarriers, such as cationic liposomes. We investigated the active targeting potential of positively charged nanoparticles in combination with the heat-induced drug release function of thermosensitive liposomes (TSL). This novel dual-targeted approach via cationic TSL (CTSL) was thoroughly explored using either a novel synthetic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphodiglycerol (DPPG₂) or a conventional polyethylene glycol (PEG) surface modification. Anionic particles containing either DPPG₂ or PEG were also included in the study to highlight difference in tumor enrichment driven by surface charge. With this study, we aim to provide a deep insight into the main differences between DPPG₂- and PEG-functionalized liposomes, focusing on the delivery of a well-known cytotoxic drug (doxorubicin; DOX) in combination with local hyperthermia (HT, 41–43°C).

Materials and Methods

DPPG₂- and PEG-based cationic TSLs (PG₂-CTSL/PEG-CTSL) were thoroughly analyzed for size, surface charge, and heat-triggered DOX release. Cancer cell targeting and DOX delivery was evaluated by FACS, fluorescence imaging, and HPLC. In vivo particle behavior was analyzed by assessing DOX biodistribution with local HT application in tumor-bearing animals.

Results

The absence of PEG in PG₂-CTSL promoted more efficient liposome–cell interactions, resulting in a higher DOX delivery and cancer cell toxicity compared with PEG-CTSL. By exploiting the dual-targeting function of CTSLs, we were able to selectively trigger DOX release in the intracellular compartment by HT. When tested in vivo, local HT promoted an increase in intratumoral DOX levels for all (C)TSLs tested, with DOX enrichment factors ranging from 3 to 14-fold depending on the type of formulation.

Conclusion

Cationic particles showed lower hemocompatibility than their anionic counterparts, which was partially mitigated when PEG was grafted on the liposome surface. DPPG₂-based anionic TSL showed optimal local drug delivery compared to all other formulations tested, demonstrating the potential advantages of using DPPG₂ lipid in designing liposomes for tumor-targeted applications.

Preparation, Physicochemical Properties, and Transfection Activities of Tartaric Acid-Based Cationic Lipids as Effective Nonviral Gene Delivery Vectors

In this work two novel cationic lipids using natural tartaric acid as linking backbone were synthesized. These cationic lipids were simply constructed by tartaric acid backbone using head group 6-aminocaproic acid and saturated hydrocarbon chains dodecanol (T-C12-AH) or hexadecanol (T-C16-AH). The physicochemical properties, gel electrophoresis, transfection activities, and cytotoxicity of cationic liposomes were tested. The optimum formulation for T-C12-AH and T-C16-AH was at cationic lipid/dioleoylphosphatidylethanolamine (DOPE) molar ratio of 1 : 0.5 and 1 : 2, respectively, and N/P charge molar ratio of 1 : 1 and 1 : 1, respectively. Under optimized conditions, T-C12-AH and T-C16-AH showed effective gene transfection capabilities, superior or comparable to that of commercially available transfecting reagent 3β-[N-(N',N'-dimethylaminoethyl)carbamoyl]cholesterol (DC-Chol) and N-[2,3-dioleoyloxypropyl]-N,N,N-trimethylammonium chloride (DOTAP). The results demonstrated that the two novel tartaric acid-based cationic lipids exhibited low toxicity and efficient transfection performance, offering an excellent prospect as nonviral vectors for gene delivery.

Double-tailed lipid modification as a promising candidate for oligonucleotide delivery in mammalian cells

BACKGROUND

The potential use of nucleic acids as therapeutic drugs has triggered the quest for oligonucleotide conjugates with enhanced cellular permeability. To this end, the biophysical aspects of previously reported potential lipid oligodeoxyribonucleotide conjugates were studied including its membrane-binding properties and cellular uptake.

METHODS

These conjugates were fully characterized by MALDI-TOF mass spectrometry and HPLC chromatography. Their ability to insert into lipid model membrane systems was evaluated by Langmuir balance and confocal microscopy followed by the study of the internalization of a lipid oligodeoxyribonucleotide conjugate bearing a double-tail lipid modification (C28) into different cell lines by confocal microscopy and flow cytometry. This compound was also compared with other lipid containing conjugates and with the classical lipoplex formulation using Transfectin as transfection reagent.

RESULTS

This double-tail lipid modification showed better incorporation into both lipid model membranes and cell systems. Indeed, this lipid conjugation was capable of inserting the oligodeoxyribonucleotide into both liquid-disordered and liquid-ordered domains of model lipid bilayer systems and produced an enhancement of oligodeoxyribonucleotide uptake in cells, even better than the effect caused by lipoplexes. In addition, in β2 integrin (CR3) expressing cells this receptor was directly involved in the enhanced internalization of this compound.

CONCLUSIONS

All these features confirm that the dual lipid modification (C28) is an excellent modification for enhancing nucleic acid delivery without altering their binding properties.

GENERAL SIGNIFICANCE

Compared to the commercial lipoplex approach, oligodeoxyribonucleotide conjugation with C28 dual lipid modification seems to be promising to improve oligonucleotide delivery in mammalian cells.

Asymmetrical N4,N9-diacyl spermines: SAR studies of nonviral lipopolyamine vectors for efficient siRNA delivery with silencing of EGFP reporter gene

Our aim is to study the effects of varying the two acyl moieties in synthesized N(4),N(9)-diacyl spermines on siRNA formulations and their delivery efficiency in cell lines. Six novel asymmetrical lipopolyamines, [N(4)-cholesteryloxy-3-carbonyl-N(9)-oleoyl-, N(4)-decanoyl-N(9)-oleoyl-, N(4)-decanoyl-N(9)-stearoyl-, N(4)-lithocholoyl-N(9)-oleoyl-, N(4)-myristoleoyl-N(9)-myristoyl-, and N(4)-oleoyl-N(9)-stearoyl]-1,12-diamino-4,9-diazadodecane, were assessed for their abilities to bind to siRNA, studied using a RiboGreen intercalation assay, and to form nanoparticles. Their siRNA delivery efficiencies were quantified in FEK4 primary skin cells and in an immortalized cancer cell line (HtTA) using a fluorescein-tagged siRNA, and compared with formulations of N(4),N(9)-dioleoyl-1,12-diamino-4,9-diazadodecane and of a leading transfecting agent, TransIT-TKO. Transfection was measured in terms of siRNA delivery and silencing of EGFP reporter gene in HeLa cells. By incorporating two different acyl moieties, changing their length and oxidation level in a controlled manner, we show efficient fluorescein-tagged siRNA formulation, delivery, and knock-down of EGFP reporter gene. N(4)-Oleoyl-N(9)-stearoyl spermine and N(4)-myristoleoyl-N(9)-myristoyl spermine are effective siRNA delivery vectors typically resulting in 89% cell delivery and gene silencing to 34% in the presence of serum, comparable with the results obtained with TransIT-TKO; adding a second lipid chain is better than incorporating a steroid moiety.

Novel cholesterol-based cationic lipids for gene delivery

Gene therapy based on gene delivery is a promising strategy for the treatment of human disease. Here we present data on structure/biological activity of new biodegradable cholesterol-based cationic lipids with various heterocyclic cationic head groups and linker types. Enhanced accumulation of nucleic acids in the cells mediated by the lipids was demonstrated by fluorescent microscopy and flow cytometry. Light scattering and atomic force microscopy were used to find structure/transfection activity correlations for the lipids. We found that the ability of the lipids to stimulate intracellular accumulation of the oligodeoxyribonucleotides and plasmid DNA correlates well with their ability to form in solution lipid/NA complexes of sizes that do not exceed 100 nm. Screening of the lipids revealed the most promising transfection agents both in terms of low toxicity and efficient delivery: cholesterol-based lipids with positively charged pyridine and methyl imidazole head groups and either the ester or carbamate linker.

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.

DNA alters the bilayer structure of cationic lipid diC14-amidine: a spin label study

Cationic lipids-DNA complexes (lipoplexes) have been used for delivery of nucleic acids into cells in vitro and in vivo. Despite the fact that, over the last decade, significant progress in the understanding of the cellular pathways and mechanisms involved in lipoplexes-mediated gene transfection have been achieved, a convincing relationship between the structure of lipoplexes and their in vivo and in vitro transfection activity is still missing. How does DNA affect the lipid packing and what are the consequences for transfection efficiency is the point we want to address here. We investigated the bilayer organization in cationic liposomes by electron spin resonance (ESR). Phospholipids spin labeled at the 5th and 16th carbon atoms were incorporated into the DNA/diC14-amidine complex. Our data demonstrate that electrostatic interactions involved in the formation of DNA-cationic lipid complex modify the packing of the cationic lipid membrane. DNA rigidifies the amidine fluid bilayer and fluidizes the amidine rigid bilayer just below the gel-fluid transition temperature. These effects were not observed with single nucleotides and are clearly related to the repetitive charged motif present in the DNA chain and not to a charge-charge interaction. These modifications of the initial lipid packing of the cationic lipid may reorient its cellular pathway towards different routes. A better knowledge of the cationic lipid packing before and after interaction with DNA may therefore contribute to the design of lipoplexes capable to reach specific cellular targets.

Very long chain N4, N9 -diacyl spermines: non-viral lipopolyamine vectors for efficient plasmid DNA and siRNA delivery

PURPOSE

To study the effect of increasing the chain length over C-18 and varying the oxidation level in synthesized N4, N9-diacyl spermines on DNA and siRNA formulation, and then to compare their transfection efficiency in cell lines

METHODS

The five novel very long chain N4, N9-diacyl polyamines: N4, N9-[diarachidoyl, diarachidonoyl, dieicosenoyl, dierucoyl and dinervonoyl]-1,12-diamino-4,9-diazadodecane were synthesized. The abilities of these novel compounds to condense DNA and to form nanoparticles were studied using ethidium bromide fluorescence quenching and nanoparticle characterization techniques. Transfection efficiency was studied in FEK4 primary skin cells and in an immortalized cancer cell line (HtTA), and compared with the non-liposomal transfection formulation Lipogen, N4, N9-dioleoyl-1,12-diamino-4,9-diazadodecane. Also, the abilities of these compounds to condense siRNA and to form nanoparticles were studied using a RiboGreen intercalation assay and their abilities to deliver siRNA into cells were studied in FEK4 and HtTA cells using fluorescein-labelled Label IT(R) RNAi Delivery Control, a sequenced 21-mer from Mirus.

RESULTS

We show efficient pEGFP and siRNA formulation and delivery to primary skin and cancer cell lines.

CONCLUSIONS

Adding two C20 or C22 chains, both mono-cis-unsaturated, N4, N9-dieicosenoyl spermine and N4, N9-dierucoyl spermine, gave efficient siRNA delivery vectors, even in the presence of serum, comparable to TransIT-TKO and with excellent cell viability.

Cationic liposomal lipids: from gene carriers to cell signaling

Cationic lipids are positively charged amphiphilic molecules which, for most of them, form positively charged liposomes, sometimes in combination with a neutral helper lipid. Such liposomes are mainly used as efficient DNA, RNA or protein carriers for gene therapy or immunization trials. Over the past decade, significant progress has been made in the understanding of the cellular pathways and mechanisms involved in lipoplex-mediated gene transfection but the interaction of cationic lipids with cell components and the consequences of such an interaction on cell physiology remains poorly described. The data reported in the present review provide evidence that cationic lipids are not just carriers for molecular delivery into cells but do modify cellular pathways and stimulate immune or anti-inflammatory responses. Considering the wide number of cationic lipids currently available and the variety of cellular components that could be involved, it is likely that only a few cationic lipid-dependent functions have been identified so far.

Importance of divalent cations in nanolipoplex gene delivery

Gene therapy is a promising therapeutic strategy to combat genetic or acquired diseases at their root cause rather than just treating symptoms. It is well recognised that there is an urgent need for non-toxic and efficient gene delivery vectors to fully exploit the current potential of gene therapy in molecular medicine. Cell-specific targeting of bioactive nucleotides is a prerequisite to attain the concentration of nucleic acids required for therapeutic efficacy in the target tissue. Many metal ions such as Mg2+, Mn2+, Ba2+ and, most importantly, Ca2+ have been demonstrated to have significant roles in gene delivery. These inorganic cations show low toxicity, good biocompatibility and promise for controlled delivery properties, thus presenting a new alternative to toxic and immunogenic carriers. Recently, inorganic nanoparticles alone, or in combination with a colloidal particulate system such as nanoliposome, an advanced approach to gene delivery, were found to exert a positive effect on gene transfer. In this report, the role of the divalent cations in nucleic acid delivery, particularly with respect to the potential improvement of transfection efficiency of nanolipoplexes, is reviewed.