Synthesis of a novel archaeal tetraether-type lipid containing a diorthoester group as a helper lipid for gene delivery

Archaeal ether lipids improve internalization and transfection with mRNA lipid nanoparticles

Neutral and positively charged archaeal ether lipids (AEL) have been studied for their utilization as novel delivery systems for pDNA, showing efficient immune response with a strong memory effect while lacking noticeable toxicity. Recent technological advances placed mRNA lipid nanoparticles (LNPs) at the forefront of next-generation delivery systems; however, no study has examined AELs in mRNA delivery yet. In this study, we investigated either a crude lipid extract or the purified tetraether lipid caldarchaeol from Sulfolobus acidocaldarius as potential novel excipients for mRNA LNPs. Depending on their molar share in the respective LNP, particle uptake, and mRNA expression levels could be increased by up to 10-fold in in vitro transfection experiments using both primary cell sources (HSMM) and established cell lines (Caco-2, C2C12) compared to a well-known reference formulation. This increased efficiency might be linked to a substantial effect on endosomal escape, indicating fusogenic and lyotropic features of AELs. This study shows the high value of archaeal ether lipids for mRNA delivery and provides a solid foundation for future in vivo experiments and further research.

Hemiacetal-linked pH-sensitive PEG-lipids for non-viral gene delivery

Cationic lipid–DNA complexes containing a novel hemiacetal PEG-lipid for endosomal escape were characterized in terms of pH-response, stability, and biological activity.

Liposomal nanoparticles based on steroids and isoprenoids for nonviral gene delivery

Natural lipid molecules are an essential part of life as they constitute the membrane of cells and organelle. In most of these cases, the hydrophobicity of natural lipids is contributed by alkyl chains. Although natural lipids with a nonfatty acid hydrophobic backbone are quite rare, steroids and isoprenoids have been strong candidates as part of a lipid. Over the years, these natural molecules (steroid and isoprenoids) have been used to make either lipid-based nanoparticle or functionalize in such a way that it could form nano assembly alone for therapeutic delivery. Here we mainly focus on the synthetic functionalized version of these natural molecules which forms cationic liposomal nanoparticles (LipoNPs). These cationic LipoNPs were further used to deliver various negatively charged genetic materials in the form of pDNA, siRNA, mRNA (nucleic acids), and so on. This article is categorized under: Biology-Inspired Nanomaterials > Lipid-Based Structures.

Fusion of Bipolar Tetraether Lipid Membranes Without Enhanced Leakage of Small Molecules

A major challenge in liposomal research is to minimize the leakage of encapsulated cargo from either uncontrolled passive permeability across the liposomal membrane or upon fusion with other membranes. We previously showed that liposomes made from pure Archaea-inspired bipolar tetraether lipids exhibit exceptionally low permeability of encapsulated small molecules due to their capability to form more tightly packed membranes compared to typical monopolar lipids. Here, we demonstrate that liposomes made of synthetic bipolar tetraether lipids can also undergo membrane fusion, which is commonly accompanied by content leakage of liposomes when using typical bilayer-forming lipids. Importantly, we demonstrate calcium-mediated fusion events between liposome made of glycerolmonoalkyl glycerol tetraether lipids with phosphatidic acid headgroups (GMGTPA) occur without liposome content release, which contrasts with liposomes made of bilayer-forming EggPA lipids that displayed ~80% of content release under the same fusogenic conditions. NMR spectroscopy studies of a deuterated analog of GMGTPA lipids reveal the presence of multiple rigid and dynamic conformations, which provide evidence for the possibility of these lipids to form intermediate states typically associated with membrane fusion events. The results support that biomimetic GMGT lipids possess several attractive properties (e.g., low permeability and non-leaky fusion capability) for further development in liposome-based technologies.

Thiol-Triggered Release of Intraliposomal Content from Liposomes Made of Extremophile-Inspired Tetraether Lipids

Liposomal drug-delivery systems have been used for delivery of drugs to targeted tissues while reducing unwanted side effects. DOXIL, for instance, is a liposomal formulation of the anticancer agent doxorubicin (DOX) that has been used to address problems associated with nonspecific toxicity of free DOX. However, while this liposomal formulation allows for a more-stable circulation of doxorubicin in the body compared to free drug, the efficacy for cancer therapy is reduced in comparison with systemic injections of free drug. A robust liposomal system that can be triggered to release DOX in cancer cells could mitigate problems associated with reduced drug efficacy. In this work, we present a serum-stable, cholesterol-integrated tetraether lipid comprising of a cleavable disulfide bond, {GcGT(S-S)PC-CH}, that is designed to respond to the reducing environment of the cell to trigger the release intraliposomal content upon cellular uptake by cancer cells. A cell viability assay revealed that DOX- loaded liposomes composed of pure GcGT(S-S)PC-CH lipids were ∼20 times more toxic than DOXIL, with an IC₅₀ value comparable to that of free DOX. The low inherent membrane-leakage properties of GcGT(S-S)PC-CH liposomes in the presence of serum, combined with an intracellular triggered release of encapsulated cargo, represents a promising approach for developing improved drug-delivery formulations for the treatment of cancer and possibly other diseases.

Engineering liposomal nanoparticles for targeted gene therapy

Recent mechanistic studies have attempted to deepen our understanding of the process by which liposome-mediated delivery of genetic material occurs. Understanding the interactions between lipid nanoparticles and cells is still largely elusive. Liposome-mediated delivery of genetic material faces systemic obstacles alongside entry into the cell, endosomal escape, lysosomal degradation and nuclear uptake. Rational design approaches for targeted delivery have been developed to reduce off-target effects and enhance transfection. These strategies, which have included the modification of lipid nanoparticles with target-specific ligands to enhance intracellular uptake, have shown significant promise at the proof-of-concept stage. Control of physical and chemical specifications of liposome composition, which includes lipid-to-DNA charge, size, presence of ester bonds, chain length and nature of ligand complexation, is integral to the performance of targeted liposomes as genetic delivery agents. Clinical advances are expected to rely on such systems in the therapeutic application of liposome nanoparticle-based gene therapy. Here, we discuss the latest breakthroughs in the development of targeted liposome-based agents for the delivery of genetic material, paying particular attention to new ligand and cationic lipid design as well as recent in vivo advances.