In Vitro Gene Transfer Efficacies of N,N-Dialkylpyrrolidinium Chlorides: A Structure−Activity Investigation

Biomimetic noncationic lipid nanoparticles for mRNA delivery

Although the tremendous progress has been made for mRNA delivery based on classical cationic carriers, the excess cationic charge density of lipids was necessary to compress mRNA through electrostatic interaction, and with it comes inevitably adverse events including the highly inflammatory and cytotoxic effects. How to develop the disruptive technologies to overcome cationic nature of lipids remains a major challenge for safe and efficient mRNA delivery. Here, we prepared noncationic thiourea lipids nanoparticles (NC-TNP) to compress mRNA by strong hydrogen bonds interaction between thiourea groups of NC-TNP and the phosphate groups of mRNA, abandoning the hidebound and traditional electrostatic force to construct mRNA-cationic lipids formulation. NC-TNP was a delivery system for mRNA with simple, convenient, and repeatable preparation technology and showed negligible inflammatory and cytotoxicity side effects. Furthermore, we found that NC-TNP could escape the recycling pathway to inhibit the egress of internalized nanoparticles from the intracellular compartment to the extracellular milieu which was a common fact in mRNA-LNP (lipid nanoparticles) formulation. Therefore, NC-TNP-encapsulated mRNA showed higher gene transfection efficiency in vitro and in vivo than mRNA-LNP formulation. Unexpectedly, NC-TNP showed spleen targeting delivery ability with higher accumulation ratio (spleen/liver), compared with traditional LNP. Spleen-targeting NC-TNP with mRNA exhibited high mRNA-encoded antigen expression in spleen and elicited robust immune responses. Overall, our work establishes a proof of concept for the construction of a noncationic system for mRNA delivery with good inflammatory safety profiles, high gene transfection efficiency, and spleen-targeting delivery to induce permanent and robust humoral and cell-mediated immunity for disease treatments.

Topical delivery of anti-TNFα siRNA and capsaicin via novel lipid-polymer hybrid nanoparticles efficiently inhibits skin inflammation in vivo

The barrier properties of the skin pose a significant but not insurmountable obstacle for development of new effective anti-inflammatory therapies. The objective of this study was to design and evaluate therapeutic efficacy of anti-nociception agent Capsaicin (Cap) and anti-TNFα siRNA (siTNFα) encapsulated cyclic cationic head lipid-polymer hybrid nanocarriers (CyLiPns) against chronic skin inflammatory diseases. Physico-chemical characterizations including hydrodynamic size, surface potential and entrapment efficacies of CyLiPns were found to be 163±9nm, 35.14±8.23mV and 92% for Cap, respectively. In vitro skin distribution studies revealed that CyLiPns could effectively deliver FITC-siRNA up to 360μm skin depth. Further, enhanced (p<0.001) Cap permeation from CyLiPns was observed compared to Capsaicin-Solution and Capzasin-HP. Therapeutic efficacies of CyLiPns were assessed using imiquamod-induced psoriatic plaque like model. CyLiPns carrying both Cap and siTNFα showed significant reduced expression of TNFα, NF-κB, IL-17, IL-23 and Ki-67 genes compared to either drugs alone (p<0.05) and were in close comparison with Topgraf®. Collectively these findings support our notion that novel cationic lipid-polymer hybrid nanoparticles can efficiently carry siTNFα and Cap into deeper dermal milieu and Cap with a combination of siTNFα shows synergism in treating skin inflammation.

Strategies for the preparation of synthetic transfection vectors

In the late 1980s independent work by Felgner and Behr pioneered the use of cationic materials to complex and deliver nucleic acids into eukaryotic cells. Since this time, a vast number of synthetic transfection vectors, which are typically divided into two main "transfectors", have been developed namely: (1) cationic lipids and (2) polycationic polymers. In this chapter the main synthetic approaches used for the synthesis of these compounds will be reviewed with particular attention paid to: cationic lipids and dendrimers. This review is aimed primarily at the younger audience of doctoral students and non-specialist readers.

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.

Cationic glycolipids with cyclic and open galactose head groups for the selective targeting of genes to mouse liver

Toward probing an hitherto unexplored structure-activity issue namely, the relative in vitro and in vivo efficacies of cationic glycolipids with cyclic and acyclic sugar heads for targeting of genes to liver, we have designed and synthesized two novel series of cationic glycolipids with cyclic (lipids 1-5) and open d-galactose heads (lipids 6-10) containing varying spacer arm lengths in between the sugar and positively charged nitrogen atoms. Among the cyclic glycolipids, lipid 3 with six methylene units spacer in between the quaternary nitrogen atom and among the glycolipids with the open-sugar heads, lipid 6 with only two methylene units spacer were found to be the most efficacious in targeting genes to cultured HepG2 (human hepatocarcinoma cells) and primary hepatocytes. Findings in the fluorescence resonance energy transfer (FRET) studies revealed biomembrane fusibilities as important physico-chemical parameters behind the varying spacer arm dependencies in the two series. Importantly, both the serum compatible glycolipids 3 &6 were found to be equally efficacious in selectively targeting genes to mouse livers under systemic settings. The significantly reduced efficiencies of the glycolipids 3 &6 in transfecting primary hepatocytes as well as mice pretreated with asialofetuin (the ligands of asialoglycoprotein receptors) support the notion that the cellular uptake of the lipoplexes prepared from both the open and the cyclic sugar-head series is mediated via asialoglycoprotein receptor. In summary, our present findings demonstrate for the first time that cationic glycolipids with cyclic sugar-head require longer spacer arms than their acyclic sugar-head counterparts for efficient gene transfection and both the series hold equal promise for selective gene targeting to liver under systemic settings.

Cationic liposomes as non-viral carriers of gene medicines: resolved issues, open questions, and future promises

The clinical success of gene therapy is critically dependent on the development of efficient and safe gene delivery reagents, popularly known as "transfection vectors." The transfection vectors commonly used in gene therapy are mainly of two types: viral and non-viral. The efficiencies of viral transfection vectors are, in general, superior to their non-viral counterparts. However, the myriads of potentially adverse immunogenic aftermaths associated with the use of viral vectors are increasingly making the non-viral gene delivery reagents as the vectors of choice. Among the existing arsenal of non-viral gene delivery reagents, the distinct advantages associated with the use of cationic transfection lipids include their: (a) robust manufacture; (b) ease in handling and preparation techniques; (c) ability to inject large lipid:DNA complexes; and (d) low immunogenic response. The present review highlights the major achievements in the area of designing efficacious cationic transfection lipids, some of the more recent advances in the field of cationic liposomes-mediated gene transfer and targeted gene delivery, some unresolved issues and challenges in liposomal gene delivery, and future promises of cationic liposomes as gene-carriers in non-viral gene therapy.

Synthesis and Gene Transfer Activities of Novel Serum Compatible Cholesterol-Based Gemini Lipids Possessing Oxyethylene-Type Spacers

Four novel cholesterol-based gemini cationic lipids differing in the length of oxyethylene-type spacers [-CH2-(CH2-O-CH2)n-CH2-] between each ammonium headgroup have been synthesized. These formed stable suspensions in aqueous media. Cationic liposomes were prepared from each of these lipids individually and as mixtures of cationic lipid and DOPE. These were used as nonviral gene delivery agents. All the cholesterol-based gemini lipids induced better transfection activity than their monomeric counterpart. Inclusion of DOPE in co-liposomal formulation of the cationic gemini lipid potentiates their gene transfer activity significantly. A major characteristic feature of these oxyethylene spacer based cholesterol gemini lipids was that serum does not inhibit the transfection activity of these gemini lipids, whereas the transfection activity of their monomeric counterpart decreased drastically in the presence of serum. One of the cholesterol-based gemini lipids 2a possessing a -CH2-CH2-O-CH2-CH2- spacer showed the highest transfection activity.

Design, synthesis, and evaluation of enhanced DNA binding new lipopolythioureas

Nonviral gene delivery is limited to a large extent by the cationic nature of most of the chemical vector. We have shown that lipopolythioureas interact with DNA. However, lipopolythioureas were not very efficient at transfecting cells, probably due to reduced interaction between the noncationic synthetic lipid and the cell membrane. Here, we report that liposomes made from a new thiourea lipid, DPPC, and a lipid bearing an RGD ligand allowed very efficient entry of the lipopolythioureas into integrin alpha(v)beta(3) expressing cells. In addition, we show that a stable interaction between DNA and lipopolythiourea could be obtain with two thiourea groups. Moreover, the addition of a hydrophilic terminus improves the formulation of these new DNA binding agents.

In vitro gene transfer efficacies and serum compatibility profiles of novel mono-, di-, and tri-histidinylated cationic transfection lipids: a structure-activity investigation

Recently, we demonstrated that covalent grafting of an endosome-disrupting single histidine functionality in the headgroup region imparts high gene transfer properties to cationic amphiphiles (Kumar, V. V., et al. Gene Ther. 2003, 10, 1206-1215). However, whether covalent attachment of multiple histidine functionalities in the headgroup region are capable of further enhancing the gene transfer efficacies of cationic amphiphiles remains to be explored. To this end, herein, we report on the design, syntheses, physicochemical characterizations, in vitro gene transfer properties, and serum compatibilities of three novel nontoxic cationic transfection amphiphiles containing mono-, di-, and tri-histidine functionalities in their headgroup regions (lipids 1-3) in multiple cultured cells. Significantly, findings in both the reporter gene expression assay and the whole cell histochemical X-gal staining assay support the notion that there is no linear correlation between the in vitro transfection efficacies and the number of histidine functionalities in the polar headgroup regions for histidinylated cationic amphiphiles. The relative gene transfer efficiencies, as well as the serum compatibilities, of the present histidinylated cationic amphiphiles were found to be strikingly dependent on the medium of lipoplex formation. Most importantly, high serum compatibilities (up to 50% added serum) of the lipoplexes of lipids 1 and 3 make them promising nonviral transfection vectors for future systemic applications.

Lipophilic Pyrylium Salts in the Synthesis of Efficient Pyridinium-Based Cationic Lipids, Gemini Surfactants, and Lipophilic Oligomers for Gene Delivery

Several new classes of pyridinium cationic lipids were synthesized and tested as gene delivery agents. They were obtained through a procedure that generates simultaneously the heterocyclic ring and the positively charged nitrogen atom, using lipophilic pyrylium salts as key intermediates that react with primary amines, yielding pyridinium salts. The choice of the appropriately substituted primary amine, diamine or polyamine, allows the design of the shape of the final lipids, gemini surfactants, or lipophilic polycations. We report also a comprehensive structure-activity relationship study that identified the most efficient structural variables at the levels of the hydrophobic anchor, linker, and counterion for these classes of pyridinium cationic lipids. This study was also aimed at finding the best liposomal formulation for the new transfection agents.