Efficient Gene Silencing by Self-Assembled Complexes of siRNA and Symmetrical Fatty Acid Amides of Spermine

Transdermal delivery of ultradeformable cationic liposomes complexed with miR211-5p (UCL-211) stabilizes BRAFV600E+ melanocytic nevi

Small non-coding RNAs (e.g., siRNA, miRNA) are involved in a variety of melanocyte-associated skin conditions and act as drivers for alterations in gene expression within melanocytes. These molecular changes can potentially affect the cellular stability of melanocytes and promote their oncogenic transformation. Thus, small RNAs can be considered as therapeutic targets for these conditions, however, their transdermal delivery to the melanocytes through the epidermal barrier is challenging. We synthesized and extensively evaluated ultradeformable cationic liposome (UCLs) carriers complexed with synthetic microRNAs (miR211-5p; UCL-211) for transdermal delivery to melanocytes. UCL-211 complexes were characterized for their physicochemical properties, encapsulation efficiency, and deformability, which revealed a significant advantage over conventional liposomal carriers. Increased expression of miR211-5p stabilizes melanocytic nevi and keeps them in a growth-arrested state. We did a comprehensive assessment of cellular delivery, and biological activity of the miR211-5p carried by UCL-211 in vitro and their permeation through the epidermis of intact skin using ex vivo human skin tissue explants. We also demonstrated, in vivo, that transdermal delivery of miR211-5p by topical application of UCL-211 stabilized BRAFV600E+ nevi melanocytes in a benign nevi state.

T14diLys/DOPE Liposomes: An Innovative Option for siRNA-Based Gene Knockdown?

BACKGROUND/OBJECTIVES

Bringing small interfering RNA (siRNA) into the cell cytosol to achieve specific gene silencing is an attractive but also very challenging option for improved therapies. The first step for successful siRNA delivery is the complexation with a permanent cationic or ionizable compound. This protects the negatively charged siRNA and enables transfection through the cell membrane. The current study explores the performance of the innovative, ionizable lipid 2-Tetradecylhexadecanoic acid-(2-bis{[2-(2,6-diamino-1-oxohexyl)amino]ethyl}aminoethyl)-amide (T14diLys), in combination with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), for siRNA delivery and the impact of the production method (sonication vs. extrusion) on the particle properties.

METHODS

Liposomes were produced either with sonication or extrusion and characterized. The extruded liposomes were combined with siRNA at different N/P ratios and investigated in terms of size zeta potential, encapsulation efficiency, lipoplex stability against RNase A, and knockdown efficiency using enhanced green fluorescent protein (eGFP)-marked colon adenocarcinoma cells.

RESULTS

The liposomes prepared by extrusion were smaller and had a narrower size distribution than the sonicated ones. The combination of siRNA and liposomes at a nitrogen-to-phosphate (N/P) ratio of 5 had optimal particle properties, high encapsulation efficiency, and lipoplex stability. Gene knockdown tests confirmed this assumption.

CONCLUSIONS

Liposomes produced with extrusion were more reproducible and provided enhanced particle properties. The physicochemical characterization and in vitro experiments showed that an N/P ratio of 5 was the most promising ratio for siRNA delivery.

Transdermal Delivery of Ultradeformable Cationic Liposomes Complexed with miR211-5p (UCL-211) Stabilizes BRAFV600E+ Melanocytic Nevi

Small non-coding RNAs (e.g. siRNA, miRNA) are involved in a variety of melanocyte-associated skin conditions and act as drivers for alterations in gene expression within melanocytes. These molecular changes can potentially affect the cellular stability of melanocytes and promote their oncogenic transformation. Thus, small RNAs can be considered as therapeutic targets for these conditions, however, their topical delivery to the melanocytes through the epidermal barrier is challenging. We synthesized and extensively evaluated ultradeformable cationic liposome (UCLs) carriers complexed with synthetic microRNAs (miR211-5p; UCL-211) for transdermal delivery to melanocytes. UCL-211 complexes were characterized for their physicochemical properties, encapsulation efficiency, and deformability, which revealed a significant advantage over conventional liposomal carriers. Increased expression of miR211-5p stabilizes melanocytic nevi and keeps them in growth-arrested state. We did a comprehensive assessment of cellular delivery, and biological activity of the miR211-5p carried by UCL-211 in vitro and their permeation through the epidermis of intact skin using ex vivo human skin tissue explants. We also demonstrated, in vivo, that topical delivery of miR211-5p by UCL-211 stabilized BRAFV600E+ nevi melanocytes in a benign nevi state.

Design and synthesis of hybrid compounds as novel drugs and medicines

The development of highly effective conjugate chemistry approaches is a way to improve the quality of drugs and of medicines. The aim of this paper is to highlight and review such hybrid compounds and the strategies underpinning their design. A variety of unique hybrid compounds provide an excellent toolkit for novel biological activity, e.g. anticancer and non-viral gene therapy (NVGT), and as templates for killing bacteria and preventing antibiotic drug resistance. First we discuss the anticancer potential of hybrid compounds, containing daunorubicin, benzyl- or tetrahydroisoquinoline-coumarin, and cytotoxic NSAID-pyrrolizidine/indolizine hybrids, then NVGT cationic lipid-based delivery agents, where steroids or long chain fatty acids as the lipid moiety are bound to polyamines as the cationic moiety. These polyamines can be linear as in spermidine or spermine, or on a polycyclic sugar template, aminoglycosides kanamycin and neomycin B, the latter substituted with six amino groups. They are highly efficient for the delivery of both fluorescent DNA and siRNA. Molecular precedents can be found for the design of hybrid compounds in the natural world, e.g., squalamine, the first representative of a previously unknown class of natural antibiotics of animal origin. These polyamine-bile acid (e.g. cholic acid type) conjugates display many exciting biological activities with the bile acids acting as a lipidic region and spermidine as the polycationic region. Analogues of squalamine can act as vectors in NVGT. Their natural role is as antibiotics. Novel antibacterial materials are urgently needed as recalcitrant bacterial infection is a worldwide problem for human health. Ribosome inhibitors founded upon dimers of tobramycin or neomycin, bound as ethers by a 1,6-hexyl linker or a more complex diether-disulfide linker, improved upon the antibiotic activity of aminoglycoside monomers by 20- to 1200-fold. Other hybrids, linked by click chemistry, conjugated ciprofloxacin to neomycin, trimethoprim, or tedizolid, which is now in clinical trials.

Lipids and Lipid Derivatives for RNA Delivery

RNA-based therapeutics have shown great promise in treating a broad spectrum of diseases through various mechanisms including knockdown of pathological genes, expression of therapeutic proteins, and programmed gene editing. Due to the inherent instability and negative-charges of RNA molecules, RNA-based therapeutics can make the most use of delivery systems to overcome biological barriers and to release the RNA payload into the cytosol. Among different types of delivery systems, lipid-based RNA delivery systems, particularly lipid nanoparticles (LNPs), have been extensively studied due to their unique properties, such as simple chemical synthesis of lipid components, scalable manufacturing processes of LNPs, and wide packaging capability. LNPs represent the most widely used delivery systems for RNA-based therapeutics, as evidenced by the clinical approvals of three LNP-RNA formulations, patisiran, BNT162b2, and mRNA-1273. This review covers recent advances of lipids, lipid derivatives, and lipid-derived macromolecules used in RNA delivery over the past several decades. We focus mainly on their chemical structures, synthetic routes, characterization, formulation methods, and structure-activity relationships. We also briefly describe the current status of representative preclinical studies and clinical trials and highlight future opportunities and challenges.

Delivery of small interfering RNAs by nanovesicles for cancer therapy

Small interfering ribonucleic acids (siRNAs) are originally recognized as an intermediate of the RNA interference (RNAi) pathway. They can inhibit or silence various cellular pathways by knocking down specific messenger RNA molecules. In cancer cells, siRNAs can suppress the expression of several multidrug-resistant genes, leading to the increased deposition of chemotherapeutic drugs at the tumor site. siRNA therapy can be used to selectively increase apoptosis of cancer cells or activate an immune response to the cancer. However, delivering siRNAs to the targeted location is the main limitation in achieving safe and effective delivery of siRNAs. This review highlights some representative examples of nonviral delivery systems, especially nanovesicles such as exosomes, liposomes, and niosomes. Nanovesicles can improve the delivery of siRNAs by increasing their intracellular delivery, and they have demonstrated excellent potential for cancer therapy. This review focuses on recent discoveries of siRNA targets for cancer therapy and the use of siRNAs to successfully silence these targets. In addition, this review summarizes the recent progress in designing nanovesicles (liposomes or niosomes) for siRNA delivery to cancer cells and the effects of a combination of anticancer drugs and siRNA therapy in cancer therapy.

Cetuximab-siRNA Conjugate Linked Through Cationized Gelatin Knocks Down KRAS G12C Mutation in NSCLC Sensitizing the Cells Toward Gefitinib

Delivery of small-interfering RNA (siRNA) has been of great interest in the past decade for effective gene silencing. To overcome synthetic and regulatory challenges posed by nanoparticle-mediated siRNA delivery, antibody–siRNA conjugate (ARC) platform is emerging as a potential siRNA delivery system suitable for clinical translation. Herein, we have developed a delivery technology based on the ARC platform for stable delivery of siRNA called as Gelatin-Antibody Delivery System (GADS). In GADS, positively charged gelatin acts as a linker between antibody–siRNA and enables the endosomal escape of siRNA for gene silencing postcellular internalization. For proof of concept, we synthesized a scalable GADS conjugate comprising of Cetuximab (CTB), cationized gelatin (cGel) and NSCLC KRAS_G12C-specific siRNA. CTB was chemically conjugated to cGel through an amide link to form the CTB–cGel complex. Thereafter, siRNA was chemically conjugated to the cGel moiety of the complex through the thioether link to form CTB–cGel–siRNA conjugate. RP-HPLC analysis was used to monitor the reaction while gel retardation assay was used to determine siRNA loading capacity. SPR analysis showed the preservation of ligand binding affinity of antibody conjugates with K_D of ∼0.3 nM. Furthermore, cellular internalization study using florescent microscopy revealed receptor-mediated endocytosis. The conjugate targeted EGFR receptor of KRAS mutant NSCLC to specifically knockdown G12C mutation. The oncogene knockdown sensitized the cells toward small molecule inhibitor—Gefitinib causing ∼70% loss in cell viability. Western blot analysis revealed significant downregulation for various RAS downstream proteins postoncogene knockdown. Comparison of the efficiency of GADS vis-à-vis positive siRNA control and CRISPR–Cas9-based knockout of KRAS Exon 2 in the NCI-H23 NSCLC cell line suggests GADS as a potential technology for clinical translation of gene therapy.

Cationic Single-Chained Surfactants with a Functional Group at the End of the Hydrophobic Tail DNA Compacting Efficiency

The interaction between calf-thymus DNA, ctDNA, and various single-chained surfactants with different functional groups at the end of hydrophobic tail was studied with the goal of investigating the influence of the functional group nature on surfactant DNA compacting efficiency. The surfactants investigated were dodecyltriethylammonium bromide (DTEABr), triethyl(1-phenoxydodecyl)ammonium bromide (12PhBr), triethyl(2-naphthoxydodecyl)ammonium bromide (12NBr) and 11-(isonicotinoyloxy)-N,N,N-triethyl-1-undecanaminium bromide (11PyBr). Results made evident that the surfactants' tendencies to self-aggregation is the key factor determining their efficiency to compact the nucleic acid. Subsequently, DOPE/12NBr/pEGFP-C1 lipoplexes, with different cationic surfactant molar fractions (α) and mass ratios (L/D), were prepared and characterized. DOPE is a zwitterionic phospholipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine, and the plasmid pEGFP-C1 carries a GFP coding sequence with the necessary regulatory elements for constitutive expression of the gene in human cells. 12NBr was chosen because it was the most efficient DNA compacting agent among the surfactants investigated. Finally, the cytotoxicity and transfection efficiency (TE) of DOPE/12NBr/pDNA lipoplexes, with different compositions, were investigated.

Self-assembly of poly(allylamine)/siRNA nanoparticles, their intracellular fate and siRNA delivery

Silencing RNA (siRNA) technologies attract significant interest as a therapeutic tool for a large number of diseases. However, the medical translation of this technology is hampered by the lack of effective delivery vehicles for siRNAs in cytosol that prevent their degradation in the bloodstream. The use of molecular complexes based on polyamines have great potential for siRNA delivery as polyamines can protect the siRNA during circulation and at the same time favor siRNA translocation in cytosol. Here, nanoparticles are prepared by complexation of poly(allylamine hydrochloride) (PAH) and siRNA varying the ratio of nitrogen groups from PAH to phosphate groups from siRNA (N/P ratio). Nanoparticles are characterized by transmission electron microscopy and dynamic light scattering. The stability of complexes of green rhodamine labelled PAH (G-PAH) and Cy5 labelled siRNA (R-siRNA) at different pHs and in cell media is studied by fluorescence cross-correlation spectroscopy (FCCS). FCCS studies show that the nanoparticles are stable at physiological pH and in cell media but they disassemble at acidic pH. An optimal N/P ratio of 2 is identified in terms of stability in media, degradation at endosomal pH and toxicity. The intracellular fate of the complexes is studied following uptake in A549 cells. The cross-correlation between G-PAH and R-siRNA decreases substantially 24 h after uptake, while diffusion times of siRNA decrease indicating that the complexes disassemble, liberating the siRNAs. The release of siRNAs into the cytosol is confirmed with parallel confocal laser scanning microscopy. Flow cytometry studies show that PAH/siRNA nanoparticles are effective at silencing green fluorescent protein expression at low N/P ratios at which polyethylenimine/siRNA shows no significant silencing.

Transfection of Antisense Oligonucleotides Mediated by Cationic Vesicles Based on Non-Ionic Surfactant and Polycations Bearing Quaternary Ammonium Moieties

Three different ionene polymers with varying quaternary ammonium moieties were used as a proof of concept for the formulation of antisense oligonucleotides, which are capable of inhibiting Renilla luciferase messenger ribonucleic acid (mRNA). Cationic vesicles, consisting of cationic polymer, antisense oligonucleotide (Luc) and non-ionic surfactant polysorbate 80, were investigated regarding their ζ potential, cytotoxicity and transfection efficiency. Deoxyribonucleic acid- (DNA) forming complexes in the presence of cationic vesicles were also investigated in terms of small-angle X-ray scattering (SAXS). The studied cationic vesicles showed very little, if any, toxicity against HeLa cells. Transfection abilities proved to vary strongly depending on the present quaternary ammonium moiety.

The influence of novel gemini surfactants containing cycloalkyl side-chains on the structural phases of DNA in solution

Very important to gene therapy is the delivery system of the nucleic acids (called a vector), which will enhance the efficiency of the transport of new DNA into cells whilst protecting against damage. A promising alternative to the currently used viral vectors are the systems based on amphiphilic compounds - lipoplexes. Among them, gemini surfactants, which consist of two hydrophobic chains and two cationic heads connected by a linker - spacer group, appear to be promising candidates. The subject of this study involves two gemini surfactants, alkoxy derivatives of bis-imidazolium quaternary salts, differing in the length of their spacer groups and how they interact with two types of salmon sperm DNA (low and high molecular weight (MW)) or plasmid DNA (pDNA). The mixtures of gemini surfactants with nucleic acids of differing p/n ratios (positive-to-negative charge ratio) were characterised by small angle X-ray scattering (SAXS) of synchrotron radiation, dynamic light scattering (DLS), circular dichroism (CD) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and gel electrophoresis techniques. This analysis allows for the selection of the most suitable and promising candidates for non-viral vectors in gene therapy, determination of the conditions needed to form stable complexes, identification of conformational changes in the DNA molecules upon interactions with gemini surfactants and in some cases, determination of the structures formed in these lipoplexes.

Quantitative silencing of EGFP reporter gene by self-assembled siRNA lipoplexes of LinOS and cholesterol

Nonviral siRNA vectors prepared by the direct mixing of siRNA and mixtures of an asymmetric N(4),N(9)-diacyl spermine conjugate, N(4)-linoleoyl-N(9)-oleoyl-1,12-diamino-4,9-diazadodecane (LinOS), with either cholesterol or DOPE, at various molar ratios of the neutral lipids, are reported. The effects of varying the lipid formulation and changing the N/P charge ratio on the intracellular delivery of siRNA to HeLa cells and on the siRNA-mediated gene silencing of a stably expressed reporter gene (EGFP) were evaluated. The presence of either cholesterol or DOPE in the mixture resulted in a marked increase in the delivery of the siRNA as well as enhanced EGFP silencing as evaluated by FACS. A LinOS/Chol 1:2 mixture resulted in the highest siRNA delivery and the most efficient EGFP silencing (reduced to 20%) at N/P = 3.0. Lowering the amount of siRNA from 15 pmol to 3.75 pmol, thus increasing the N/P charge ratio to 11.9, resulted in decreasing the amount of delivered siRNA, while the efficiency of gene silencing was comparable to that obtained with 15 pmol (N/P = 3.0) of siRNA. Mixtures of symmetrical N(4),N(9)-dioleoyl spermine (DOS) with cholesterol at 1:2 molar ratio showed less siRNA delivery than with LinOS/Chol at N/P = 3.0 (15 pmol of siRNA), and comparable delivery at N/P = 11.9 (3.75 pmol of siRNA). The EGFP silencing was comparable with LinOS and with DOS when mixed with cholesterol 1:2 (lipoplexes prepared with 15 pmol of siRNA), but LinOS mixtures showed better EGFP silencing when the siRNA was reduced to 3.75 pmol. Lipoplex particle size determination by DLS of cholesterol mixtures was 106-118 nm, compared to 194-356 nm for lipoplexes prepared with the spermine conjugates only, and to 685 nm for the LinOS/DOPE 1:1 mixture. Confocal microscopy showed successful siRNA delivery of red tagged siRNA and quantitative EGFP knockdown in HeLa EGFP cells; Z-stack photomicrographs showed that the delivered siRNA is distributed intracellularly. Cryo-TEM of siRNA LinOS/Chol 1:2 lipoplexes shows the formation of multilamellar spheres with a size of ∼100 nm, in good agreement with the particle size measured by DLS. The constant distance between lamellar repeats is ∼6 nm, with the electron-dense layers fitting a monolayer of siRNA. AlamarBlue cell viability assay showed that the lipoplexes resulted in cell viability ≥81%, with LinOS/Chol 1:2 mixtures resulting in cell viabilities of 89% and 94% at siRNA 15 nM and 3.75 nM respectively. These results show that lipoplexes of siRNA and LinOS/Chol mixtures prepared by the direct mixing of the lipid mixture and siRNA, without any preceding preformulation steps, result in enhanced siRNA delivery and EGFP knockdown, with excellent cell viability. Thus, LinOS/Chol 1:2 mixture is a promising candidate as a nontoxic nonviral siRNA vector.

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.

Efficient silencing of EGFP reporter gene with siRNA delivered by asymmetrical N4,N9-diacyl spermines

It is important to obtain structure-activity relationship (SAR) data across cationic lipids for the self-assembly and nonviral intracellular delivery of siRNA. The aims of this work are to carry out a SAR study on the efficiency of asymmetrical N(4),N(9)-diacyl spermines in siRNA delivery and EGFP reporter gene silencing, with comparisons to selected mixtures composed of symmetrical N(4),N(9)-diacyl spermines. Another important aim of these studies is to quantify the changes in cell viability, assayed with alamarBlue, as a function of lipid structure. Therefore, we have designed, synthesized, purified, and assayed novel cationic lipids that are asymmetrical lipopolyamines based on spermine. Flow cytometry and fluorescence microscopy in an EGFP stably transfected HeLa cell line, measuring both delivery of fluorescently tagged siRNAs and silencing the EGFP signal, allowed quantitation of the differences between asymmetrical cationic lipids, mixtures of their symmetrical counterparts, and comparison with commercial nonviral delivery agents. Intracellular delivery of siRNA and gene silencing by siRNA differ with different hydrophobic domains. In these asymmetrical N(4),N(9)-diacyl spermines, lipids that enhance siRNA uptake do not necessarily enhance siRNA-induced inhibition of gene expression: C18 and longer saturated chains promote uptake, while more unsaturated C18 chains promote gene silencing. These properties are efficiently demonstrated in a new nontoxic cationic lipid siRNA vector, N(4)-linoleoyl-N(9)-oleoyl-1,12-diamino-4,9-diazadodecane (LinOS), which is also shown to be comparable with or superior to TransIT-TKO and Lipofectamine 2000.

Self-Assembled Lipoplexes of Short Interfering RNA (siRNA) Using Spermine-Based Fatty Acid Amide Guanidines: Effect on Gene Silencing Efficiency

Four guanidine derivatives of N4,N9-diacylated spermine have been designed, synthesized, and characterized. These guanidine-containing cationic lipids bound siRNA and formed nanoparticles. Two cationic lipids with C18 unsaturated chains, N1,N12-diamidino-N4,N9-dioleoylspermine and N1,N12-diamidino-N4-linoleoyl-N9-oleoylspermine, were more efficient in terms of GFP expression reduction compared to the other cationic lipids with shorter C12 (12:0) and very long C22 (22:1) chains. N1,N12-Diamidino-N4-linoleoyl-N9-oleoylspermine siRNA lipoplexes resulted in GFP reduction (26%) in the presence of serum, and cell viability (64%). These data are comparable to those obtained with TransIT TKO. Thus, cationic lipid guanidines based on N4,N9-diacylated spermines are good candidates for non-viral delivery of siRNA to HeLa cells using self-assembled lipoplexes.