Amino Acid-Based Cationic Lipids With α -Tocopherol Hydrophobic Tail for Efficient Gene Delivery

Biodegradable Cationic and Ionizable Cationic Lipids: A Roadmap for Safer Pharmaceutical Excipients

Cationic and ionizable cationic lipids are broadly applied as auxiliary agents, but their use is associated with adverse effects. If these excipients are rapidly degraded to endogenously occurring metabolites such as amino acids and fatty acids, their toxic potential can be minimized. So far, synthesized and evaluated biodegradable cationic and ionizable cationic lipids already showed promising results in terms of functionality and safety. Within this review, an overview about the different types of such biodegradable lipids, the available building blocks, their synthesis and cleavage by endogenous enzymes is provided. Moreover, the relationship between the structure of the lipids and their toxicity is described. Their application in drug delivery systems is critically discussed and placed in context with the lead compounds used in mRNA vaccines. Moreover, their use as preservatives is reviewed, guidance for their design is provided, and an outlook on future developments is given.

Reducible amino acid based cationic lipids with a naphthalimide moiety as non-viral gene vehicles

Three basic amino acid–based cationic lipids bearing a fluorescent naphthalimide moiety and a reducible disulfide linkage are synthesized and applied as non-viral gene vehicles. Their DNA interactions are investigated by agarose-gel retardant and ethidium bromide replacement assays. The sizes and zeta potentials of the liposome/DNA complexes are measured by dynamic light scattering. The cytotoxicities of the liposome/DNA complexes are examined using HeLa and 7702 cell lines by MTT assays. The glutathione-responsive DNA release process is studied through time-dependent fluorescence assays. Luciferase gene expression showed the transfection efficiency of the liposome is dramatically increased in the presence of 10% serum. Confocal laser scanning microscopy studies corroborated that the liposome/DNA complexes are successfully uptaken into HeLa cells. These results demonstrate the promising use of amino acids and naphthalimide-containing lipids for safe and efficient gene delivery.

Cimetidine-Based Cationic Amphiphiles for In Vitro Gene Delivery Targetable to Colon Cancer

Cimetidine, a histamine-2 (H2) receptor antagonist, has been found to have anticancer properties against a number of cancer-type cells. In this report, we have demonstrated that cimetidine can acts as a hydrophilic domain in cationic lipids and targetable to the gastric system by carrying reporter genes and therapeutic genes through in vitro transfection. Two lipids, namely, Toc-Cim and Chol-Cim consisting cimetidine as the main head group and hydrophobic moieties as alpha-tocopherol or cholesterol, respectively, were designed and synthesized. 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) is a well-known co-lipid employed to produce liposomes as uniform vesicles. The liposomes and lipoplexes were structurally and functionally evaluated for global surface charges and hydrodynamic diameters, and results found that both liposome and lipoplex size and surface charges are optimal to screen the transfection potentials. DNA-binding studies were analyzed as complete binding at all formulated N/P ratios. The liposomes and lipoplexes of both the lipids Toc-Cim and Chol-Cim show minimal cytotoxicity even though at higher concentrations. The results of the transfection experiments revealed that tocopherol-based cationic lipids (Toc-Cim) show finer transfection efficacy with optimized N/P ratios (2:1 and 4:1) in the colon cancer cell line. Toc-Cim lipoplexes show higher cellular uptake compare to Chol-Cim in the colon cancer cell line at 2:1 and 4:1 N/P ratios. Toc-Cim and Chol-Cim lipids showed highly compatible serum, examined up to 50% of the serum concentration. To evaluate the apoptotic cell death in CT-26 cells, exposed to Toc-Cim:p53 and Chol-Cim:p53 lipoplexes at 2:1 N/P ratios, superior results showed with Toc-Cim:p53. An effect of TP53 protein expression in CT-26 cell lines assayed by western blot, transfected with Toc-Cim:p53 and Chol-Cim:p53 lipoplexes, demonstrated the superior efficacy of Toc-Cim. All of the findings suggest that Toc-Cim lipid is relatively secure and is an effective transfection agent to colon cancer gene delivery.

Physical-Chemical Characterization of Bilayer Membranes Derived from (±) α-Tocopherol-Based Gemini Lipids and Their Interaction with Phosphatidylcholine Bilayers and Lipoplex Formation with Plasmid DNA

Membrane formation and aggregation properties of two series of (±) α-tocopherol-based cationic gemini lipids without and with hydroxyl functionalities at the headgroup region (TnS n = 3, 4, 5, 6, 8, and 12; THnS n = 4, 5, 6, 8, and 12) with varying polymethylene spacer lengths were investigated extensively while comparing with the corresponding properties of the monomeric counterparts (TM and THM). Liposomal suspensions of each cationic lipid were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), zeta potential measurements, and small-angle X-ray diffraction studies. The length of the spacer and the presence of hydroxyl functionalities at the headgroup region strongly contribute to the aggregation behavior of these gemini lipids in water. The interaction of each tocopherol lipid with a model phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC)-derived vesicles, was thoroughly examined by differential scanning calorimetry (DSC) and 1,6-diphenyl-1,3,5-hexatriene (DPH)-doped fluorescence anisotropy measurements. The binding efficiency of the cationic tocopherol liposomes with plasmid DNA (pDNA) was followed by an ethidium bromide (EB) exclusion assay and zeta potential measurements, whereas negatively charged micellar sodium dodecyl sulfate (SDS)-mediated release of the pDNA from various preformed pDNA-liposomal complexes (lipoplex) was studied by an ethidium bromide (EB) reintercalation assay. The structural transformation of pDNA upon complexation with liposome was characterized using circular dichroism (CD) spectroscopic measurements. Gemini lipid-pDNA interactions depend on both the presence of hydroxyl functionalities at the headgroups and the length of the spacer chain between the headgroups. Succinctly, we performed a detailed physical-chemical characterization of the membranes formed from cationic monomeric and gemini lipids bearing tocopherol as their hydrophobic backbone and describe the role of inserting the -OH group at the headgroup of such lipids.

Lipophilic Polyamines as Promising Components of Liposomal Gene Delivery Systems

Gene therapy requires an effective and safe delivery vehicle for nucleic acids. In the case of non-viral vehicles, including cationic liposomes, the structure of compounds composing them determines the efficiency a lot. Currently, cationic amphiphiles are the most frequently used compounds in liposomal formulations. In their structure, which is a combination of hydrophobic and cationic domains and includes spacer groups, each component contributes to the resulting delivery efficiency. This review focuses on polycationic and disulfide amphiphiles as prospective cationic amphiphiles for gene therapy and includes a discussion of the mutual influence of structural components.

Arginine-tocopherol bioconjugated lipid vesicles for selective pTRAIL delivery and subsequent apoptosis induction in glioblastoma cells

The incorporation of specific therapeutic gene into glioblastoma offers potent therapeutic strategy to treat the disease. Non-viral gene delivery vectors are of particular interest due to their tuneable transfection efficiency and easy scale-up. Herein, we demonstrate successful delivery of plasmid encoding tumor necrosis factor (TNF)-related apoptosis-inducing ligand (pTRAIL) using arginine-conjugated tocopherol lipid (AT) nanovesicles into glioblastoma cell lines. Another cationic lipid, glycine-conjugated tocopherol lipid (GT) having glycine in the head group region is also synthesized as a control lipid. Both lipid-derived liposomes effectively condensed the pDNA and the corresponding biomacromolecular assemblies (lipoplexes) are efficiently transfected into different cell lines. AT-based liposomes exhibit higher transfection efficacy in various cell lines, particularly selective in glioma cell lines. At an optimized N/P ratio, both the liposomal formulations show low cytotoxicity. AT-based lipoplexes have superior cellular uptake in U87 than the control lipid GT. The expression of TRAIL protein regulated death receptor and apoptosis signaling pathway is assayed by western blot using transfection of AT-based/pTRAIL into U87 cell lines. Induction of apoptosis in U87 cells exposed to AT-based/pTRAIL plasmid is evaluated by MTT assay as well as Annexin V-propidium iodide dual-staining assay. All results indicate that the developed AT-based/pTRAIL system offers a potentially safe and efficient therapeutic strategy for glioblastoma gene therapy.

A review on cationic lipids with different linkers for gene delivery

Cationic lipids have become known as one of the most versatile tools for the delivery of DNA, RNA and many other therapeutic molecules, and are especially attractive because they can be easily designed, synthesized and characterized. Most of cationic lipids share the common structure of cationic head groups and hydrophobic portions with linker bonds between both domains. The linker bond is an important determinant of the chemical stability and biodegradability of cationic lipid, and further governs its transfection efficiency and cytotoxicity. Based on the structures of linker bonds, they can be grouped into many types, such as ether, ester, amide, carbamate, disulfide, urea, acylhydrazone, phosphate, and other unusual types (carnitine, vinyl ether, ketal, glutamic acid, aspartic acid, malonic acid diamide and dihydroxybenzene). This review summarizes some research results concerning the nature (such as the structure and orientation of linker groups) and density (such as the spacing and the number of linker groups) of linker bond for improving the chemical stability, biodegradability, transfection efficiency and cytotoxicity of cationic lipid to overcome the critical barriers of in vitro and in vivo transfection.

Transfection efficiencies of α-tocopherylated cationic gemini lipids with hydroxyethyl bearing headgroups under high serum conditions

Liposomal gene transfection under high serum conditions.

pH and reduction dual-responsive dipeptide cationic lipids with α-tocopherol hydrophobic tail for efficient gene delivery

A series of tocopherol-based cationic lipid 3a-3f bearing a pH-sensitive imidazole moiety in the dipeptide headgroup and a reduction-responsive disulfide linkage were designed and synthesized. Acid-base titration of these lipids showed good buffering capacities. The liposomes formed from 3 and co-lipid 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) could efficiently bind and condense DNA into nanoparticles. Gel binding and HPLC assays confirmed the encapsulated DNA could release from lipoplexes 3 upon addition of 10 mM glutathione (GSH). MTT assays in HEK 293 cells demonstrated that lipoplexes 3 had low cytotoxicity. The in vitro gene transfection studies showed cationic dipeptide headgroups clearly affected the transfection efficiency (TE), and arginine-histidine based dipeptide lipid 3f give the best TE, which was 30.4 times higher than Lipofectamine 3000 in the presence of 10% serum. Cell-uptake assays indicated that basic amino acid containing dipeptide cationic lipids exhibited more efficient cell uptake than serine and aromatic amino acids based dipeptide lipids. Confocal laser scanning microscopy (CLSM) studies corroborated that 3 could efficiently deliver and release DNA into the nuclei of HeLa cells. These results suggest that tocopherol-based dipeptide cationic lipids with pH and reduction dual-sensitive characteristics might be promising non-viral gene delivery vectors.