Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry

Objective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH) following Phase

Cationic liposomenucleic acid nanoparticle assemblies with applications in gene delivery and gene silencing

Cationic liposomes (CLs) are synthetic carriers of nucleic acids in gene delivery and gene silencing therapeutics. The introduction will describe the structures of distinct liquid crystalline phases of CL-nucleic acid complexes, which were revealed in earlier synchrotron small-angle X-ray scattering experiments. When mixed with plasmid DNA, CLs containing lipids with distinct shapes spontaneously undergo topological transitions into self-assembled lamellar, inverse hexagonal, and hexagonal CL-DNA phases. CLs containing cubic phase lipids are observed to readily mix with short interfering RNA (siRNA) molecules creating double gyroid CL-siRNA phases for gene silencing. Custom synthesis of multivalent lipids and a range of novel polyethylene glycol (PEG)-lipids with attached targeting ligands and hydrolysable moieties have led to functionalized equilibrium nanoparticles (NPs) optimized for cell targeting, uptake or endosomal escape. Very recent experiments are described with surface-functionalized PEGylated CL-DNA NPs, including fluorescence microscopy colocalization with members of the Rab family of GTPases, which directly reveal interactions with cell membranes and NP pathways. In vitro optimization of CL-DNA and CL-siRNA NPs with relevant primary cancer cells is expected to impact nucleic acid therapeutics in vivo. This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'

Quantitative Intracellular Localization of Cationic Lipid–Nucleic Acid Nanoparticles with Fluorescence Microscopy

Current activity in developing synthetic carriers of nucleic acids (NA) and small molecule drugs for therapeutic applications is unprecedented. One promising class of synthetic vectors for the delivery of therapeutic NA is PEGylated cationic liposome (CL)-NA nanoparticles (NPs). Chemically modified PEG-lipids can be used to surface-functionalize lipid-NA nanoparticles, allowing researchers to design active nanoparticles that can overcome the various intracellular and extracellular barriers to efficient delivery. Optimization of these functionalized vectors requires a comprehensive understanding of their intracellular pathways. In this chapter we present two distinct methods for investigating the intracellular activity of PEGylated CL-NA NPs using quantitative analysis with fluorescence microscopy.The first method, spatial localization, describes how to prepare fluorescently labeled CL-NA NPs, perform fluorescence microscopy and properly analyze the data to measure the intracellular distribution of nanoparticles and fluorescent signal. We provide software which allows data from multiple cells to be averaged together and yield statistically significant results. The second method, fluorescence colocalization, describes how to label endocytic organelles via Rab-GFPs and generate micrographs for software-assisted NP-endocytic marker colocalization measurements. These tools will allow researchers to study the endosomal trafficking of CL-NA NPs which can guide their design and improve their efficiency

The Influence of Multivalent Charge and PEGylation on Shape Transitions in Fluid Lipid Assemblies: From Vesicles to Discs, Rods, and Spheres

Lipids, and cationic lipids in particular, are of interest as delivery vectors for hydrophobic drugs such as the cancer therapeutic paclitaxel, and the structures of lipid assemblies affect their efficacy. We investigated the effect of incorporating the multivalent cationic lipid MVL5 (+5 e ) and poly(ethylene glycol)-lipids (PEG-lipids), alone and in combination, on the structure of fluid-phase lipid assemblies of the charge-neutral lipid 1,2-dioleoyl- sn -glycero-phosphocholine (DOPC). This allowed us to elucidate lipid–liposome structure correlations in sonicated formulations with high charge density, which are not accessible with univalent lipids such as the well-studied DOTAP (+1 e ). Cryogenic TEM allowed us to determine the structure of the lipid assemblies, revealing diverse combinations of vesicles and disc-shaped, worm-like, and spherical micelles. Remarkably, MVL5 forms an essentially pure phase of disc micelles at 50 mol% MVL5. At higher (75 mol%) content of MVL5, short and intermediate-length worm-like micellar rods were observed and, in ternary mixtures with PEG-lipid, longer and highly flexible worm-like micelles formed. Independent of their length, the worm-like micelles coexisted with spherical micelles. In stark contrast, DOTAP forms mixtures of vesicles, disc micelles and spherical micelles at all studied compositions, even when combined with PEG-lipids. The observed similarities and differences in the effects of charge (multivalent versus univalent) and high curvature (multivalent charge versus PEG-lipid) on assembly structure provide insights into parameters that control the size of fluid lipid nanodiscs, relevant for future applications

Cryo-TEM Reveals the Influence of Multivalent Charge and PEGylation on Shape Transitions in Fluid Lipid Assemblies: From Vesicles to Discs, Rods, and Spheres

Lipids, and cationic lipids in particular are of interest as delivery vectors for hydrophobic drugs such as the cancer therapeutic paclitaxel, and the structures of lipid assemblies affect their efficacy. We investigated the effect of incorporating the multivalent cationic lipid MVL5 (+5e) and poly(ethylene glycol)-lipids (PEG-lipids), alone and in combination, on the structure of fluid-phase lipid assemblies of the charge-neutral lipid 1,2-dioleoyl-sn-glycero-phosphocholine (DOPC). This allowed us to elucidate lipid-assembly structure correlations in sonicated formulations with high charge density, which are not accessible with univalent lipids such as the well-studied DOTAP (+1e). Cryogenic transmission electron microscopy (cryo-TEM) allowed us to determine the structure of the lipid assemblies, revealing diverse combinations of vesicles and disc-shaped, worm-like, and spherical micelles. Remarkably, MVL5 forms an essentially pure phase of disc micelles at 50 mol % MVL5. At a higher (75 mol %) content of MVL5, short- and intermediate-length worm-like micellar rods were observed, and in ternary mixtures with PEG-lipid, longer and highly flexible worm-like micelles formed. Independent of their length, the worm-like micelles coexisted with spherical micelles. In stark contrast, DOTAP forms mixtures of vesicles, disc micelles, and spherical micelles at all studied compositions, even when combined with PEG-lipids. The observed similarities and differences in the effects of charge (multivalent versus univalent) and high curvature (multivalent charge versus PEG-lipid) on the assembly structure provide insights into parameters that control the size of fluid lipid nanodiscs, relevant for future applications

Highly Efficient Gene Silencing Activity of siRNA Embedded in a Nanostructured Gyroid Cubic Lipid Matrix

RNA interference (RNAi) is an evolutionarily conserved sequence-specific post-transcriptional gene silencing pathway with wide-ranging applications in functional genomics, therapeutics, and biotechnology. Cationic liposome-small interfering RNA (CL-siRNA) complexes have emerged as vectors of choice for delivery of siRNA, which mediates RNAi. However, siRNA delivery by CL-siRNA complexes is often inefficient and accompanied by lipid toxicity. We report the development of CL-siRNA complexes with a novel cubic phase nanostructure, which exhibit efficient silencing at low toxicity. The inverse bicontinuous gyroid cubic nanostructure was unequivocally established from synchrotron X-ray scattering data, while fluorescence microscopy revealed colocalization of lipid and siRNA in complexes. We attribute the efficient silencing to enhanced fusion of complex and endosomal membranes, facilitated by the cubic phase membrane's positive Gaussian modulus, which may enable spontaneous formation of transient pores. The findings underscore the importance of understanding membrane-mediated interactions between CL-siRNA complex nanostructure and cell components in developing CL-based gene silencing vectors

Block liposome and nanotube formation is a general phenomenon of two-component membranes containing multivalent lipids

We report a study on the formation of block liposomes (BLs) and nanotubes from membranes comprised of mixtures of membrane curvature-stabilizing multivalent cationic lipids MVL3(3+) and MVL5(5+) with neutral 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC). In conjunction with prior work on MVLBG2(16+), our experiments suggest that BL and nanotube formation is a general phenomenon in membranes containing multivalent lipids, thus enhancing the relevance of BLs for applications such as gene/drug storage and delivery or templating