Incorporation of DOPE into Lipoplexes formed from a Ferrocenyl Lipid leads to Inverse Hexagonal Nanostructures that allow Redox-Based Control of Transfection in High Serum

Messenger RNA Lipid-Based Nanoparticles: Optimization of Formulations in the Lab

Among the large variety of messenger RNA (mRNA) delivery systems, those developed with lipid-based formulations were the most widely used and efficient. In our lab, we produced different mRNA formulations made with liposomes, hybrid lipid polymer, and lipid nanoparticles. Our formulations were made with lipids bearing imidazole groups that trigger the endosomal escape of nanoparticles once protonated inside the mild acidic milieu of endosomes upon their cell uptake. Herein, we describe protocols that we used to produce, optimize, and characterize those formulations. The transfection efficiency is influenced by various factors including the physicochemical parameters of the nanoparticles, their efficiency to be internalized in cells, and their intracellular routing as well as their capacity to induce immune system sensors. We provide details on how to quantify the amount of mRNA nanoparticles uptake by cells and evaluate the acidity of the intracellular compartments where they are located, to investigate the endosomal escape, and to assess the activation of innate immune sensors as phosphorylation of PKR hampering mRNA translation.

mRNA Lipoplexes with Cationic and Ionizable α-Amino-lipophosphonates: Membrane Fusion, Transfection, mRNA Translation and Conformation

Cationic liposomes are attractive carriers for mRNA delivery. Here, mRNA lipoplexes (LX) were prepared with the cationic lipids α-aminolipophosphonate (3b) or imidazolium lipophosphoramidate (2) associated with various α-aminolipophosphonates co-lipids comprising protonable groups (imidazole or pyridine) and DOPE. Physicochemical parameters of liposomes and their membrane fusion activity were measured. LXs comprising either 3b- or 2- allowed transfection of ~25% and 40% of dendritic cells with low cytotoxicity, respectively; the efficiency increased up to 80% when 2 was combined with the imidazole-based co-lipid 1. The transfections were high with 3b/1, 3b/DOPE, 2/1 and 2/DOPE LXs. We observed that the transfection level was not well correlated with the acid-mediated membrane fusion activity of liposomes supposed to destabilize endosomes. The mRNA release from LXs and its translation capacity after release were studied for the most efficient LXs. The results showed that the more mRNA was condensed, the poorer the translation efficiency after release was. In contrast to DNA, circular dichroism performed on mRNA complexed with 2/DOPE revealed the presence of denatured mRNA in LXs explaining this lack of translation efficiency. This is an important parameter that should be stressed for the preparation of mRNA LXs with a conserved mRNA translation activity.

Redox-Triggered Disassembly of Nanosized Liposomes Containing Ferrocene-Appended Amphiphiles

We report a redox-responsive liposomal system capable of oxidatively triggered disassembly. We describe the synthesis, electrochemical characterization, and incorporation into vesicles of an alternative redox lipid with significantly improved synthetic efficiency and scalability compared to a ferrocene-appended phospholipid previously employed by our group in giant vesicles. The redox-triggered disassembly of both redox lipids is examined in nanosized liposomes as well as the influence of cholesterol mole fraction on liposome disassembly and suitability of various chemical oxidants for  in vitro disassembly experiments. Electronic structure density functional theory calculations of membrane-embedded ferrocenes are provided to characterize the role of charge redistribution in the initial stages of the disassembly process.

Small Angle X-ray and Neutron Scattering: Powerful Tools for Studying the Structure of Drug-Loaded Liposomes

Nanovectors, such as liposomes, micelles and lipid nanoparticles, are recognized as efficient platforms for delivering therapeutic agents, especially those with low solubility in water. Besides being safe and non-toxic, drug carriers with improved performance should meet the requirements of (i) appropriate size and shape and (ii) cargo upload/release with unmodified properties. Structural issues are of primary importance to control the mechanism of action of loaded vectors. Overall properties, such as mean diameter and surface charge, can be obtained using bench instruments (Dynamic Light Scattering and Zeta potential). However, techniques with higher space and time resolution are needed for in-depth structural characterization. Small-angle X-ray (SAXS) and neutron (SANS) scattering techniques provide information at the nanoscale and have therefore been largely used to investigate nanovectors loaded with drugs or other biologically relevant molecules. Here we revise recent applications of these complementary scattering techniques in the field of drug delivery in pharmaceutics and medicine with a focus to liposomal carriers. In particular, we highlight those aspects that can be more commonly accessed by the interested users.

Efficacious redox-responsive gene delivery in serum by ferrocenylated monomeric and dimeric cationic cholesterols

New redox-active monomeric and dimeric ferrocenylated cationic cholesterols for gene transfection.

Influence of the Phase State of Self-Assembling Redox Mediators on their Electrochemical Activity

Self-assembling redox mediators have the potential to be broadly useful in a range of interfacial electrochemical contexts because the oxidation state and state of assembly of the mediator are closely coupled. In this paper, we report an investigation of the self-assembly of single- and double-tailed ferrocenyl amphiphiles (FTMA and BFDMA, respectively) at the surfaces of Pt electrodes and the impact of the dynamic assembled state of the amphiphiles on their rate of oxidation. We conclude that frozen aggregates of BFDMA adsorb to the surfaces of the Pt electrodes, and that slow dynamics of reorganization BFDMA within these aggregates limits the rate of electrooxidation of BFDMA. In contrast, FTMA, while forming assemblies on the surfaces of Pt electrodes, is characterized by fast reorganization dynamics and a corresponding rate of oxidation that is an order of magnitude greater than BFDMA.

Tumor priming enhances siRNA delivery and transfection in intraperitoneal tumors

Cancers originating from the digestive system account for 290,000 or ~20% of all new cancer cases annually in the US. We previously developed paclitaxel-loaded tumor-penetrating microparticles (TPM) for intraperitoneal (IP) treatment of peritoneal tumors (Lu et al., 2008; Tsai et al., 2007; Tsai et al., 2013). TPM is undergoing NIH-supported IND-enabling studies for clinical evaluation. The present study evaluated the hypothesis that TPM, via inducing apoptosis and expanding the interstitial space, promotes the delivery and transfection of lipid vectors containing siRNA. The in vivo model was the metastatic human Hs766T pancreatic tumor that, upon IP injection, produced widely distributed solid tumors and ascites in the peritoneal cavity in 100% of animals. The target gene was survivin, an anti-apoptotic protein induced by chemotherapy and associated with metastases and poor prognosis of patients with gastric and colorectal cancers. The siRNA carrier was pegylated liposomes comprising cationic and neutral lipids plus a fusogenic lipid (PCat). PCat-loaded with survivin siRNA (PCat-siSurvivin) was active in cultured cells (decreased survivin mRNA and protein levels, reduced cell clonogenicity, enhanced paclitaxel activity), but lost its activity in vivo; this difference is consistent with the well-known problem of inadequate delivery and transfection of siRNA in vivo. In comparison, single agent TPM prolonged animal survival and, as expected, induced survivin expression in tumors. Addition of PCat-siSurvivin reversed the TPM-induced survivin expression and enhanced the antitumor activity of TPM. The finding that in vivo survivin knockdown by PCat-siSurvivin was successful only when it was given in combination with TPM provides the proof-of-concept that tumor priming promotes the delivery and transfection of liposomal siRNA. The data further suggest the TPM/PCat-siSurvivin combination as a potentially useful chemo-gene therapy for peritoneal cancer.

Redox-based control of the transformation and activation of siRNA complexes in extracellular environments using ferrocenyl lipids

We report physical characterization and biological evaluation of complexes of small interfering RNA (siRNA) formed using a cationic lipid [bis(11-ferrocenylundecyl)dimethylammonium bromide (BFDMA)] containing redox-active ferrocenyl groups at the end of each hydrophobic tail. We demonstrate that control over the redox state of BFDMA can be used to influence key physical properties and control the activities of lipoplexes formed using siRNA-based constructs. Specifically, lipoplexes of siRNA and reduced BFDMA lead to high levels of sequence-specific gene silencing in cells, but lipoplexes formed using oxidized BFDMA do not. Lipoplexes of oxidized BFDMA can be activated in situ to induce high levels of silencing by addition of a chemical reducing agent, demonstrating a basis for external control over the activation/delivery of siRNA in cellular environments. Differences in activity arise from the inability of oxidized BFDMA to promote efficient internalization of siRNA; these differences also correlated to significant differences in the nanostructures of these lipoplexes (determined by cryo-TEM) and their ζ potentials as a function of oxidation state. These results are considered in view of recent studies characterizing the nanostructures, properties, and behaviors of lipoplexes formed using BFDMA and macromolecular plasmid DNA. We find that several key structural features and aspects of redox control observed for lipoplexes of plasmid DNA are maintained in complexes formed using smaller and more rigid siRNA. The ability to transform BFDMA in complex media presents opportunities to exert control over the nanostructures and behaviors of siRNA lipoplexes in ways not possible using conventional lipids. The approaches reported here could thus prove useful in both fundamental and applied contexts.