A hepatic pDNA delivery system based on an intracellular environment sensitive vitamin E-scaffold lipid-like material with the aid of an anti-inflammatory drug

Lipid-nanoparticle-enabled nucleic acid therapeutics for liver disorders

Inherited genetic disorders of the liver pose a significant public health burden. Liver transplantation is often limited by the availability of donor livers and the exorbitant costs of immunosuppressive therapy. To overcome these limitations, nucleic acid therapy provides a hopeful alternative that enables gene repair, gene supplementation, and gene silencing with suitable vectors. Though viral vectors are the most efficient and preferred for gene therapy, pre-existing immunity debilitating immune responses limit their use. As a potential alternative, lipid nanoparticle-mediated vectors are being explored to deliver multiple nucleic acid forms, including pDNA, mRNA, siRNA, and proteins. Herein, we discuss the broader applications of lipid nanoparticles, from protein replacement therapy to restoring the disease mechanism through nucleic acid delivery and gene editing, as well as multiple preclinical and clinical studies as a potential alternative to liver transplantation.

An overview of lipid constituents in lipid nanoparticle mRNA delivery systems

mRNA therapeutics have shown great potential for a broad spectrum of disease treatment. However, the challenges of mRNA's inherent instability and difficulty in cellular entry have hindered its progress in the biomedical field. To address the cellular barriers and deliver mRNA to cells of interest, various delivery systems are designed. Among these, lipid nanoparticles (LNPs) stand out as the most extensively used mRNA delivery systems, particularly following the clinical approvals of corona virus disease 2019 (COVID-19) mRNA vaccines. LNPs are comprised of ionizable cationic lipids, phospholipids, cholesterol, and polyethylene glycol derived lipids (PEG-lipids). In this review, we primarily summarize the recent advancements of the LNP mRNA delivery technology, focusing on the structures of four lipid constituents and their biomedical applications. We delve into structure-activity relationships of the lipids, while also exploring the future prospects and challenges in developing more efficacious mRNA delivery systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Lipid-Based Structures Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Lipid Nanoparticle-Mediated Delivery of CRISPR-Cas9 Against Rubicon Ameliorates NAFLD by Modulating CD36 Along with Glycerophospholipid Metabolism

Non-alcoholic fatty liver disease (NAFLD) is a prominent cause of various chronic metabolic hepatic diseases with limited therapeutics. Rubicon, an essential regulator in lysosomal degradation, is reported to exacerbate hepatic steatosis in NAFLD mice and patients, indicating its probability of being a therapeutic target for NAFLD treatment. In this study, the therapeutic potential of Rubicon blockage is investigated. Lipid nanoparticles carrying Rubicon-specific CRISPR-Cas9 components exhibited liver accumulation, cell internalization, and Rubicon knockdown. A single administration of the nanoparticles results in attenuated lipid deposition and hepatic steatosis, with lower circulating lipid levels and decreased adipocyte size in NAFLD mice. Furthermore, the increase of phosphatidylcholine and phosphatidylethanolamine levels can be observed in the NAFLD mice livers after Rubicon silencing, along with regulatory effects on metabolism-related genes such as CD36, Gpcpd1, Chka, and Lpin2. The results indicate that knockdown of Rubicon improves glycerophospholipid metabolism and thereby ameliorates the NAFLD progression, which provides a potential strategy for NAFLD therapy via the restoration of Rubicon.

Zwitterionic materials for nucleic acid delivery and therapeutic applications

Nucleic acid therapeutics have demonstrated substantial potential in combating various diseases. However, challenges persist, particularly in the delivery of multifunctional nucleic acids. To address this issue, numerous gene delivery vectors have been developed to fully unlock the potential of gene therapy. The advancement of innovative materials with exceptional delivery properties is critical to propel the clinical translation of nucleic acid drugs. Cationic vector materials have received extensive attention, while zwitterionic materials remain relatively underappreciated in delivery. In this review, we outline a diverse range of zwitterionic material nucleic acid carriers, predominantly encompassing zwitterionic lipids, polymers and peptides. Their respective chemical structures, synthesis approaches, properties, advantages, and therapeutic applications are summarized and discussed. Furthermore, we highlight the challenges and future opportunities associated with the development of zwitterionic vector materials. This review will aid to understand the zwitterionic materials in aiding gene delivery, contributing to the continual progress of nucleic acid therapeutics.

Intracellular Drug Delivery Process of Am80-Encapsulated Lipid Nanoparticles Aiming for Alveolar Regeneration

Chronic obstructive pulmonary disease (COPD) results in obstructive ventilatory impairment caused by emphysema, and current treatment is limited to symptomatic therapy or lung transplantation. Therefore, the development of new treatments to repair alveolar destruction is especially urgent. Our previous study revealed that 1.0 mg/kg of synthetic retinoid Am80 had a repair effect on collapsed alveoli in a mouse model of elastase-induced emphysema. From these results, however, the clinical dose calculated in accordance with FDA guidance is estimated to be 5.0 mg/60 kg, and it is desirable to further reduce the dose to allow the formulation of a powder inhaler for clinical application. To efficiently deliver Am80 to the retinoic acid receptor in the cell nucleus, which is the site of action, we focused on SS-cleavable proton-activated lipid-like material O-Phentyl-P4C2COATSOME^®SS-OP, hereinafter referred to as "SS-OP"). In this study, we investigated the cellular uptake and intracellular drug delivery process of Am80-encapsulated SS-OP nanoparticles to elucidate the mechanism of Am80 by nanoparticulation. Am80-encapsulated SS-OP nanoparticles were taken up into the cells via ApoE, and then Am80 was efficiently delivered into the nucleus via RARα. These results indicated the usefulness of SS-OP nanoparticles as drug delivery system carriers of Am80 for COPD treatment.

Coatsome-replicon vehicles: Self-replicating RNA vaccines against infectious diseases

Herein, we provide the first description of a synthetic delivery method for self-replicating replicon RNAs (RepRNA) derived from classical swine fever virus (CSFV) using a Coatsome-replicon vehicle based on Coatsome® SS technologies. This results in an unprecedented efficacy when compared to well-established polyplexes, with up to ∼65 fold-increase of the synthesis of RepRNA-encoded gene of interest (GOI). We demonstrated the efficacy of such Coatsome-replicon vehicles for RepRNA-mediated induction of CD8 T-cell responses in mice. Moreover, we provide new insights on physical properties of the RepRNA, showing that the removal of all CSFV structural protein genes has a positive effect on the translation of the GOI. Finally, we successfully engineered RepRNA constructs encoding a porcine reproductive and respiratory syndrome virus (PRRSV) antigen, providing an example of antigen expression with potential application to combat viral diseases. The versatility and simplicity of modifying and manufacturing these Coatsome-replicon vehicle formulations represents a major asset to tackle foreseeable emerging pandemics.

Modulating intracellular pathways to improve non-viral delivery of RNA therapeutics

RNA therapeutics (e.g. siRNA, oligonucleotides, mRNA, etc.) show great potential for the treatment of a myriad of diseases. However, to reach their site of action in the cytosol or nucleus of target cells, multiple intra- and extracellular barriers have to be surmounted. Several non-viral delivery systems, such as nanoparticles and conjugates, have been successfully developed to meet this requirement. Unfortunately, despite these clear advances, state-of-the-art delivery agents still suffer from relatively low intracellular delivery efficiencies. Notably, our current understanding of the intracellular delivery process is largely oversimplified. Gaining mechanistic insight into how RNA formulations are processed by cells will fuel rational design of the next generation of delivery carriers. In addition, identifying which intracellular pathways contribute to productive RNA delivery could provide opportunities to boost the delivery performance of existing nanoformulations. In this review, we discuss both established as well as emerging techniques that can be used to assess the impact of different intracellular barriers on RNA transfection performance. Next, we highlight how several modulators, including small molecules but also genetic perturbation technologies, can boost RNA delivery by intervening at differing stages of the intracellular delivery process, such as cellular uptake, intracellular trafficking, endosomal escape, autophagy and exocytosis.

Rational design of anti-inflammatory lipid nanoparticles for mRNA delivery

Lipid nanoparticles (LNPs) play a crucial role in delivering messenger RNA (mRNA) therapeutics for clinical applications, including COVID-19 mRNA vaccines. While mRNA can be chemically modified to become immune-silent and increase protein expression, LNPs can still trigger innate immune responses and cause inflammation-related adverse effects. Inflammation can in turn suppress mRNA translation and reduce the therapeutic effect. Dexamethasone (Dex) is a widely used anti-inflammatory corticosteroid medication that is structurally similar to cholesterol, a key component of LNPs. Here, we developed LNP formulations with anti-inflammatory properties by partially substituting cholesterol with Dex as a means to reduce inflammation. We demonstrated that Dex-incorporated LNPs effectively abrogated the induction of tumor necrosis factor alpha (TNF-ɑ) in vitro and significantly reduced its expression in vivo. Reduction of inflammation using this strategy improved in vivo mRNA expression in mice by 1.5-fold. Thus, we envision that our Dex-incorporated LNPs could potentially be used to broadly to reduce the inflammatory responses of LNPs and enhance protein expression of a range of mRNA therapeutics.

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.

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.

The biological applications of DNA nanomaterials: current challenges and future directions

DNA, a genetic material, has been employed in different scientific directions for various biological applications as driven by DNA nanotechnology in the past decades, including tissue regeneration, disease prevention, inflammation inhibition, bioimaging, biosensing, diagnosis, antitumor drug delivery, and therapeutics. With the rapid progress in DNA nanotechnology, multitudinous DNA nanomaterials have been designed with different shape and size based on the classic Watson-Crick base-pairing for molecular self-assembly. Some DNA materials could functionally change cell biological behaviors, such as cell migration, cell proliferation, cell differentiation, autophagy, and anti-inflammatory effects. Some single-stranded DNAs (ssDNAs) or RNAs with secondary structures via self-pairing, named aptamer, possess the ability of targeting, which are selected by systematic evolution of ligands by exponential enrichment (SELEX) and applied for tumor targeted diagnosis and treatment. Some DNA nanomaterials with three-dimensional (3D) nanostructures and stable structures are investigated as drug carrier systems to delivery multiple antitumor medicine or gene therapeutic agents. While the functional DNA nanostructures have promoted the development of the DNA nanotechnology with innovative designs and preparation strategies, and also proved with great potential in the biological and medical use, there is still a long way to go for the eventual application of DNA materials in real life. Here in this review, we conducted a comprehensive survey of the structural development history of various DNA nanomaterials, introduced the principles of different DNA nanomaterials, summarized their biological applications in different fields, and discussed the current challenges and further directions that could help to achieve their applications in the future.

Development of an SS-Cleavable pH-Activated Lipid-Like Material (ssPalm) as a Nucleic Acid Delivery Device

Gene and nucleic acid-based medication is an ultimate strategy in the field of personalized medicine. A gene or short interference RNA (siRNA) molecule needs to be delivered to the appropriate organelle (i.e., nucleus and cytoplasm, respectively). We recently focused on improving the intrinsic activity of my original material (ssPalm) in terms of endosomal/lysosomal membrane destabilization activity by chemically modifying the tertiary amine structure. In parallel, I have been expanding the range of applications of ssPalms. The first application is a DNA or RNA vaccine. My crucial finding is that the vitamin E-scaffold ssPalm (ssPalmE) is highly immune-stimulative when combined with DNA. Thereafter, I redesigned the hydrophobic scaffold structure, and found that an oleic acid-scaffold ssPalm (ssPalmO) can confer anti-inflammatory characteristics. Based on this result, I further upgraded the ssPalmO, by inserting a newly designed linker with self-degradable properties.

Co-delivery Systems of Multiple Drugs Using Nanotechnology for Future Cancer Therapy

Cancer treatments have improved significantly during the last decade but are not yet satisfactory. Combination therapy is often administered to improve efficacy and safety. Drug delivery systems can also improve efficacy and safety. To control the spatiotemporal distribution of drugs, nanotechnology involving liposomes, solid lipid nanoparticles, and polymeric micelles has been developed. Co-delivery systems of multiple drugs are a promising approach to combat cancer. Synergistic effects and reduced side effects are expected from the use of co-delivery systems. In this review, we summarize various co-delivery systems for multiple drugs, including small-molecule drugs, nucleic acids, genes, and proteins. Co-delivery of drugs with different properties is relatively difficult, but some researchers have succeeded in developing such co-delivery systems. Environment-responsive carrier designs can control the release of cargos. Although their preparation is more complicated than that of mono-delivery systems, co-delivery systems can simplify clinical procedures and improve patient QOL.

Development of lipid-like materials for RNA delivery based on intracellular environment-responsive membrane destabilization and spontaneous collapse

Messenger RNA and small interfering RNA are attractive modalities for curing diseases by complementation or knock-down of proteins. For success of these RNAs, a drug delivery system (DDS) is required to control a pharmacokinetics, to enhance cellular uptake, to overcome biological membranes, and to release the cargo into the cytoplasm. Based on past research, developing nanoparticles that are neutrally charged have been the mainstream of their development. Also, the materials are further mounted with pH- and/or reducing environment-responsive units. In this review, we summarize progress made in the molecular design of these materials. We also focus on the importance of the hydrophobic scaffold for tissue/cell targeting, intracellular trafficking, and immune responses. As a practical example, the design concept of the SS-cleavable and pH-activated lipid-like material (ssPalm) and subsequent molecular modification tailored to the RNA-based medical application is discussed.

Vitamin E Scaffolds of pH-Responsive Lipid Nanoparticles as DNA Vaccines in Cancer and Protozoan Infection

DNA vaccinations are promising strategies for treating diseases that require cellular immunity (i.e., cancer and protozoan infection). Here, we report on the use of a liposomal nanocarrier (lipid nanoparticles (LNPs)) composed of an SS-cleavable and pH-activated lipidlike material (ssPalm) as an in vivo DNA vaccine. After subcutaneous administration, the LNPs containing an ssPalmE, an ssPalm with vitamin E scaffolds, elicited a higher gene expression activity in comparison with the other LNPs composed of the ssPalms with different hydrophobic scaffolds. Immunization with the ssPalmE-LNPs encapsulating plasmid DNA that encodes ovalbumin (OVA, a model tumor antigen) or profilin (TgPF, a potent antigen of Toxoplasma gondii) induced substantial antitumor or antiprotozoan effects, respectively. Flow cytometry analysis of the cells that had taken up the LNPs in draining lymph nodes (dLNs) showed that the ssPalmE-LNPs were largely taken up by macrophages and a small number of dendritic cells. We found that the transient deletion of CD169⁺ macrophages, a subpopulation of macrophages that play a key role in cancer immunity, unexpectedly enhanced the activity of the DNA vaccine. These data suggest that the ssPalmE-LNPs are effective DNA vaccine carriers, and a strategy for avoiding their being trapped by CD169⁺ macrophages will be a promising approach for developing next-generation DNA vaccines.

Development of a lipoplex-type mRNA carrier composed of an ionizable lipid with a vitamin E scaffold and the KALA peptide for use as an ex vivo dendritic cell-based cancer vaccine

A dendritic cells (DCs)-based vaccine (DC-vaccine) system is an attractive technology for eliciting antigen-specific immune responses that can protect subjects from infectious diseases and for curing various types of cancers. For the insertion of a foreign antigen to DCs, the transfection of an antigen-coding mRNA to the cells is a promising approach. In order to introduce an antigen, a carrier for mRNA transfection is required, since the mRNA molecule per se is unstable in serum-containing medium. We previously reported on an ionizable lipid-like material with vitamin E-scaffolds (ssPalmE) as a material for a lipid nanoparticle (LNP)-based carrier for nucleic acids. In the present study, we report on the development of a lipoplex-type mRNA carrier for use as a DC-vaccine by using a combination of an ssPalmE-LNP and an α-helical cationic peptide "KALA" (ssPalmE-KALA). The transfection of mRNAs complexed with the ssPalmE-KALA achieved a significantly higher protein expression and the production of proinflammatory cytokines from murine bone marrow derived DCs (BMDCs) in comparison with a lipoplex that was prepared with an ssPalm with fatty acid-scaffolds (myristic acid; ssPalmM-KALA). A cellular uptake process and a pH-responsive membrane-destabilization activity cannot explain the preferred protein expression and immune-stimulation caused by the ssPalmE-KALA. Proteomic analyses suggest that transfection with the ssPalmM-KALA stimulates a down-regulatory pathway of translation, while the transfection with the ssPalmE-KALA does not stimulate it. In the vaccination with the BMDCs that were preliminarily transfected with an ovalbumin (OVA)-encoding mRNA elicited the induction OVA specific cytotoxic T-lymphocyte activity in vivo. In parallel, the vaccination induced significant prophylactic anti-tumor effects against a model tumor that stably expressed the OVA protein. Based on the above findings, the ssPalmE-KALA appears to be a potent ex vivo DCs-based RNA vaccine platform.

Inhibition of the Inflammatory Pathway Enhances Both the in Vitro and in Vivo Transfection Activity of Exogenous in Vitro-Transcribed mRNAs Delivered by Lipid Nanoparticles

While the use of in vitro-transcribed mRNA (IVT-mRNA) in therapeutics is a rapidly expanding area, the transfection of the exogenous IVT-mRNA is accompanied by a risk of immune activation. This immunological defense mechanism suppresses cellular translation process and can reduce transfection efficiency to a considerable extent. In the present study, we investigated the in vitro effects of Integrated Stress Response Inhibitor (ISRIB), and dexamethasone, a steroidal anti-inflammatory drug, on the transfection activity of a lipid nanoparticle (LNP) that was composed of ionizable lipids and IVT-mRNA. In the case of transfection to mouse embryonic fibroblast (MEF) cells, ISRIB mainly enhanced the transfection activity at an early stage of transfection (0-6 h). In contrast, dexamethasone caused an increase in transfection activity at intermediate-late stages of transfection (4-48 h). We also investigated the in vivo effects of dexamethasone using an LNP on that the IVT-mRNA and lipid-conjugated dexamethasone (Dex-Pal) were co-loaded. The intravenous administration of the LNP successfully enhanced the protein expression in a mouse liver by up to 6.6-fold. Collectively, the co-delivery of an anti-inflammatory drug is a promising approach for enhancing transfection efficiency of IVT-mRNA.

The delivery of mRNA to colon inflammatory lesions by lipid-nano-particles containing environmentally-sensitive lipid-like materials with oleic acid scaffolds

An mRNA gene therapy represents a potentially promising therapeutic for curing inflammatory diseases. The transient nature of the gene expression of mRNA would be expected to be beneficial for avoiding undesired side effects. Since the mRNA is a vulnerable molecule, a development of a carrier that can deliver the mRNA to the cytoplasm has a high priority. We report herein on the development of a system for delivering mRNA to the inflammatory lesion in a dextran sulfate sodium (DSS)-induced colitis model. We modulated molecular structures of an ionizable lipid, an SS-cleavable and pH-activated lipid-like material (ssPalm). Among the fatty acids investigated, oleic acid scaffolds (ssPalmO) appeared to be more biocompatible than either myristic acid or linoleic acid scaffolds with the colitis model. The structural modification of the hydrophilic head groups from linear tertiary amines to piperazine rings (ssPalmO-Paz4-C2) resulted in a more than 10-fold higher increasing in the transgene activity in inflammatory colon. The most notable observation is that the transgene activity in the inflammatory colon is significantly higher than that in liver, the major clearance organ of lipid nanoparticles. Collectively, the ssPalmO-Paz4-C2 represents a promising material for the delivery of an mRNA to inflammatory lesions.