Cellular environment-responsive nanomaterials for use in gene and siRNA delivery: molecular design for biomembrane destabilization and intracellular collapse

Delivering mRNA to Secondary Lymphoid Tissues by Phosphatidylserine-Loaded Lipid Nanoparticles

Lipid nanoparticles (LNPs) are one of the most successful technologies in messenger RNA (mRNA) delivery. While the liver is the most frequent target for LNP delivery of mRNA, technologies for delivering mRNA molecules to extrahepatic tissues are also important. Herein, it is reported on the development of an LNP that targets secondary lymphoid tissues. New types of alcohol-soluble phosphatidylserine (PS) derivatives are designed as materials that target immune cells and then incorporated into LNPs using a microfluidic technique with a high degree of scalability and reproducibility. The resulting LNP that contained the synthesized PS delivered mRNA to the spleen much more efficiently compared to a control LNP. A sub-organ analysis revealed that the PS-loaded LNP is extensively taken up by tissue-resident macrophages in the red pulp and the marginal zone of the spleen. Thus, the PS-loaded LNP reported in this study will be a promising strategy for clinical applications that involve delivering mRNA to the spleen.

Effects on Metabolism in Astrocytes Caused by cGAMP, Which Imitates the Initial Stage of Brain Metastasis

The second messenger 2'3'-cyclic-GMP-AMP (cGAMP) is thought to be transmitted from brain carcinomas to astrocytes via gap junctions, which functions to promote metastasis in the brain parenchyma. In the current study, we established a method to introduce cGAMP into astrocytes, which simulates the state of astrocytes that have been invaded by cGAMP around tumors. Astrocytes incorporating cGAMP were analyzed by metabolomics, which demonstrated that cGAMP increased glutamate production and astrocyte secretion. The same trend was observed for γ-aminobutyric acid (GABA). Conversely, glutamine production and secretion were decreased by cGAMP treatment. Due to the fundamental role of astrocytes in regulation of the glutamine-glutamate cycle, such metabolic changes may represent a potential mechanism and therapeutic target for alteration of the central nervous system (CNS) environment and the malignant transformation of brain carcinomas.

Delivery of Oligonucleotides Using a Self-Degradable Lipid-Like Material

The world-first success of lipid nanoparticle (LNP)-based siRNA therapeutics (ONPATTRO^®) promises to accelerate developments in siRNA therapeutics/gene therapy using LNP-type drug delivery systems (DDS). In this study, we explore the optimal composition of an LNP containing a self-degradable material (ssPalmO-Phe) for the delivery of oligonucleotides. siRNA or antisense oligonucleotides (ASO) were encapsulated in LNP with different lipid compositions. The hepatic knockdown efficiency of the target genes and liver toxicity were evaluated. The optimal compositions for the siRNA were different from those for ASO, and different from those for mRNA that were reported in a previous study. Extracellular stability, endosomal escape and cellular uptake appear to be the key processes for the successful delivery of mRNA, siRNA and ASO, respectively. Moreover, the compositions of the LNPs likely contribute to their toxicity. The lipid composition of the LNP needs to be optimized depending on the type of nucleic acids under consideration if the applications of LNPs are to be further expanded.

Understanding In Vivo Fate of Nucleic Acid and Gene Medicines for the Rational Design of Drugs

Nucleic acid and genetic medicines are increasingly being developed, owing to their potential to treat a variety of intractable diseases. A comprehensive understanding of the in vivo fate of these agents is vital for the rational design, discovery, and fast and straightforward development of the drugs. In case of intravascular administration of nucleic acids and genetic medicines, interaction with blood components, especially plasma proteins, is unavoidable. However, on the flip side, such interaction can be utilized wisely to manipulate the pharmacokinetics of the agents. In other words, plasma protein binding can help in suppressing the elimination of nucleic acids from the blood stream and deliver naked oligonucleotides and gene carriers into target cells. To control the distribution of these agents in the body, the ligand conjugation method is widely applied. It is also important to understand intracellular localization. In this context, endocytosis pathway, endosomal escape, and nuclear transport should be considered and discussed. Encapsulated nucleic acids and genes must be dissociated from the carriers to exert their activity. In this review, we summarize the in vivo fate of nucleic acid and gene medicines and provide guidelines for the rational design of drugs.

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.

Coupling Self-Assembly Mechanisms to Fabricate Molecularly and Electrically Responsive Films

Biomacromolecules often possess information to self-assemble through low energy competing interactions which can make self-assembly responsive to environmental cues and can also confer dynamic properties. Here, we coupled self-assembling systems to create biofunctional multilayer films that can be cued to disassemble through either molecular or electrical signals. To create functional multilayers, we: (i) electrodeposited the pH-responsive self-assembling aminopolysaccharide chitosan, (ii) allowed the lectin Concanavalin A (ConA) to bind to the chitosan-coated electrode (presumably through electrostatic interactions), (iii) performed layer-by-layer self-assembly by sequential contacting with glycogen and ConA, and (iv) conferred biological (i.e., enzymatic) function by assembling glycoprotein (i.e., enzymes) to the ConA-terminated multilayer. Because the ConA tetramer dissociates at low pH, this multilayer can be triggered to disassemble by acidification. We demonstrate two approaches to induce acidification: (i) glucose oxidase can induce multilayer disassembly in response to molecular cues, and (ii) anodic reactions can induce multilayer disassembly in response to electrical cues.

Interaction of pH-responsive polyanions with phospholipid membranes

The behavior of two acrylate polymers, with carboxylic acid side groups, was investigated with regard to their pH-responsive interaction with phospholipid membranes.

Redox-Mediated Disassembly to Build Activatable Trimodal Probe for Molecular Imaging of Biothiols

Activatable multimodal probes that show enhancement of multiplex imaging signals upon interaction with their specific molecular target have become powerful tools for rapid and precise imaging of biological processes. Herein, we report a stimuli-responsive disassembly approach to construct a redox-activatable fluorescence/¹⁹F-MRS/¹H-MRI triple-functional probe 1. The small molecule probe 1 itself has a high propensity to self-assemble into nanoparticles with quenched fluorescence, attenuated ¹⁹F-MRS signal, and high ¹H-MRI contrast. Biothiols that are abundant in reducing biological environment were able to cleave the disulfide bond in probe 1 to induce disassembly of the nanoparticles and lead to fluorescence activation (∼70-fold), ¹⁹F-MRS signal amplification (∼30-fold) and significant r₁ relaxivity reduction (∼68% at 0.5 T). Molecular imaging of reducing environment in live cells and in vivo was realized using probe 1. This approach could facilitate the development of other stimuli-responsive trimodal probes for molecular imaging.