A Direct Comparison of in Vitro and in Vivo Nucleic Acid Delivery Mediated by Hundreds of Nanoparticles Reveals a Weak Correlation

Passive, active and endogenous organ-targeted lipid and polymer nanoparticles for delivery of genetic drugs

Genetic drugs based on nucleic acid biomolecules are a rapidly emerging class of medicines that directly reprogramme the central dogma of biology to prevent and treat disease. However, multiple biological barriers normally impede the intracellular delivery of nucleic acids, necessitating the use of a delivery system. Lipid and polymer nanoparticles represent leading approaches for the clinical translation of genetic drugs. These systems circumnavigate biological barriers and facilitate the intracellular delivery of nucleic acids in the correct cells of the target organ using passive, active and endogenous targeting mechanisms. In this Review, we highlight the constituent materials of these advanced nanoparticles, their nucleic acid cargoes and how they journey through the body. We discuss targeting principles for liver delivery, as it is the organ most successfully targeted by intravenously administered nanoparticles to date, followed by the expansion of these concepts to extrahepatic (non-liver) delivery. Ultimately, this Review connects emerging materials and biological insights playing key roles in targeting specific organs and cells in vivo.

Substituting racemic ionizable lipids with stereopure ionizable lipids can increase mRNA delivery

Lipid nanoparticles (LNPs) have delivered siRNA and mRNA drugs in humans, underscoring the potential impact of improving the therapeutic window of next-generation LNPs. To increase the LNP therapeutic window, we applied lessons from small-molecule chemistry to ionizable lipid design. Specifically, given that stereochemistry often influences small-molecule safety and pharmacokinetics, we hypothesized that the stereochemistry of lipids within an LNP would influence mRNA delivery. We tested this hypothesis in vivo using 128 novel LNPs that included stereopure derivatives of C12-200, an ionizable lipid that when formulated into LNPs delivers RNA in mice and non-human primates but is not used clinically due to its poor tolerability. We found that a novel C12-200-S LNP delivered up to 2.8-fold and 6.1-fold more mRNA in vivo than its racemic and C12-200-R controls, respectively. To identify the potential causes leading to increased delivery, we quantified LNP biophysical traits and concluded that these did not change with stereochemistry. Instead, we found that stereopure LNPs were better tolerated than racemic LNPs in vivo. These data suggest that LNP-mediated mRNA delivery can be improved by designing LNPs to include stereopure ionizable lipids.

The Extent to Which Lipid Nanoparticles Require Apolipoprotein E and Low-Density Lipoprotein Receptor for Delivery Changes with Ionizable Lipid Structure

Lipid nanoparticles (LNPs) have delivered therapeutic RNA to hepatocytes in humans. Adsorption of apolipoprotein E (ApoE) onto these clinical LNP-mRNA drugs has been shown to facilitate hepatocyte entry via the low-density lipoprotein receptor (LDLR). Since ApoE-LDLR trafficking is conserved in mice, non-human primates, and humans, characterizing this mechanism eased clinical transition. Recently, LNPs have delivered mRNA to non-hepatocytes in mice and non-human primates, suggesting they can target new cell types via ApoE- and LDLR-independent pathways. To test this hypothesis, we quantified how 60 LNPs delivered mRNA with cell type resolution in wild-type mice and three knockout mouse strains related to lipid trafficking: ApoE^-/-, LDLR^-/-, and PCSK9^-/-. These data suggest that the hydrophobic tail length of diketopiperazine-based lipids can be changed to drive ApoE- and LDLR-independent delivery in vivo. More broadly, the results support the hypothesis that endogenous LNP trafficking can be tuned by modifying lipid chemistry.

Lipid Nanoparticle Composition Drives mRNA Delivery to the Placenta

Ionizable lipid nanoparticles (LNPs) have gained attention as mRNA delivery platforms for vaccination against COVID-19 and for protein replacement therapies. LNPs enhance mRNA stability, circulation time, cellular uptake, and preferential delivery to specific tissues compared to mRNA with no carrier platform. However, LNPs have yet to be developed for safe and effective mRNA delivery to the placenta as a method to treat placental dysfunction. Here, we develop LNPs that enable high levels of mRNA delivery to trophoblasts in vitro and to the placenta in vivo with no toxicity. We conducted a Design of Experiments to explore how LNP composition, including the type and molar ratio of each lipid component, drives trophoblast and placental delivery. Our data revealed that a specific combination of ionizable lipid and phospholipid in the LNP design yields high transfection efficiency in vitro . Further, we present one LNP platform that exhibits highest delivery of placental growth factor mRNA to the placenta in pregnant mice, which demonstrates induced protein synthesis and secretion of a therapeutic protein. Lastly, our high-performing LNPs have no toxicity to both the pregnant mice and fetuses. Our results demonstrate the feasibility of LNPs as a platform for mRNA delivery to the placenta. Our top LNPs may provide a therapeutic platform to treat diseases that originate from placental dysfunction during pregnancy.

Approaches towards biomaterial-mediated gene editing for cancer immunotherapy

Gene therapies are transforming treatment modalities for many human diseases and disorders, including those in ophthalmology, oncology, and nephrology. To maximize the clinical efficacy and safety of these treatments, consideration of both delivery materials and cargos is critical. In consideration of the former, a large effort has been placed on transitioning away from potentially immunoreactive and toxic viral delivery mechanisms towards safer and highly tunable nonviral delivery mechanisms, including polymeric, lipid-based, and inorganic carriers. This change of paradigm does not come without obstacles, as efficient non-viral delivery is challenging, particularly to immune cells, and has yet to see clinical translation breakthroughs for gene editing. This mini-review describes notable examples of biomaterial-based gene delivery to immune cells, with emphasis on recent in vivo successes. In consideration of delivery cargos, clustered regularly interspaced palindromic repeat (CRISPR) technology is reviewed and its great promise in the field of immune cell gene editing is described. This mini-review describes how leading non-viral delivery materials and CRISPR technology can be integrated together to advance its clinical potential for therapeutic gene transfer to immune cells to treat cancer.

Engineering Self-Assembling Protein Nanoparticles for Therapeutic Delivery

Despite remarkable advances over the past several decades, many therapeutic nanomaterials fail to overcome major in vivo delivery barriers. Controlling immunogenicity, optimizing biodistribution, and engineering environmental responsiveness are key outstanding delivery problems for most nanotherapeutics. However, notable exceptions exist including some lipid and polymeric nanoparticles, some virus-based nanoparticles, and nanoparticle vaccines where immunogenicity is desired. Self-assembling protein nanoparticles offer a powerful blend of modularity and precise designability to the field, and have the potential to solve many of the major barriers to delivery. In this review, we provide a brief overview of key designable features of protein nanoparticles and their implications for therapeutic delivery applications. We anticipate that protein nanoparticles will rapidly grow in their prevalence and impact as clinically relevant delivery platforms.

Delivery of RNAs to Specific Organs by Lipid Nanoparticles for Gene Therapy

Gene therapy holds great promise in the treatment of genetic diseases. It is now possible to make DNA modifications using the CRISPR system. However, a major problem remains: the delivery of these CRISPR-derived technologies to specific organs. Lipid nanoparticles (LNPs) have emerged as a very promising delivery method. However, when delivering LNPs intravenously, most of the cargo is trapped by the liver. Alternatively, injecting them directly into organs, such as the brain, requires more invasive procedures. Therefore, developing more specific LNPs is crucial for their future clinical use. Modifying the composition of the lipids in the LNPs allows more specific deliveries of the LNPs to some organs. In this review, we have identified the most effective compositions and proportions of lipids for LNPs to target specific organs, such as the brain, lungs, muscles, heart, liver, spleen, and bones.

FASTAptameR 2.0: A web tool for combinatorial sequence selections

Combinatorial selections are powerful strategies for identifying biopolymers with specific biological, biomedical, or chemical characteristics. Unfortunately, most available software tools for high-throughput sequencing analysis have high entrance barriers for many users because they require extensive programming expertise. FASTAptameR 2.0 is an R-based reimplementation of FASTAptamer designed to minimize this barrier while maintaining the ability to answer complex sequence-level and population-level questions. This open-source toolkit features a user-friendly web tool, interactive graphics, up to 100 times faster clustering, an expanded module set, and an extensive user guide. FASTAptameR 2.0 accepts diverse input polymer types and can be applied to any sequence-encoded selection.

Piperazine-derived lipid nanoparticles deliver mRNA to immune cells in vivo

In humans, lipid nanoparticles (LNPs) have safely delivered therapeutic RNA to hepatocytes after systemic administration and to antigen-presenting cells after intramuscular injection. However, systemic RNA delivery to non-hepatocytes remains challenging, especially without targeting ligands such as antibodies, peptides, or aptamers. Here we report that piperazine-containing ionizable lipids (Pi-Lipids) preferentially deliver mRNA to immune cells in vivo without targeting ligands. After synthesizing and characterizing Pi-Lipids, we use high-throughput DNA barcoding to quantify how 65 chemically distinct LNPs functionally delivered mRNA (i.e., mRNA translated into functional, gene-editing protein) in 14 cell types directly in vivo. By analyzing the relationships between lipid structure and cellular targeting, we identify lipid traits that increase delivery in vivo. In addition, we characterize Pi-A10, an LNP that preferentially delivers mRNA to the liver and splenic immune cells at the clinically relevant dose of 0.3 mg/kg. These data demonstrate that high-throughput in vivo studies can identify nanoparticles with natural non-hepatocyte tropism and support the hypothesis that lipids with bioactive small-molecule motifs can deliver mRNA in vivo.

Nanoparticle single-cell multiomic readouts reveal that cell heterogeneity influences lipid nanoparticle-mediated messenger RNA delivery

Cells that were previously described as homogeneous are composed of subsets with distinct transcriptional states. However, it remains unclear whether this cell heterogeneity influences the efficiency with which lipid nanoparticles (LNPs) deliver messenger RNA therapies in vivo. To test the hypothesis that cell heterogeneity influences LNP-mediated mRNA delivery, we report here a new multiomic nanoparticle delivery system called single-cell nanoparticle targeting-sequencing (SENT-seq). SENT-seq quantifies how dozens of LNPs deliver DNA barcodes and mRNA into cells, the subsequent protein production and the transcriptome, with single-cell resolution. Using SENT-seq, we have identified cell subtypes that exhibit particularly high or low LNP uptake as well as genes associated with those subtypes. The data suggest that cell subsets have distinct responses to LNPs that may affect mRNA therapies.

Lipid-peptide nanocomplexes for mRNA delivery in vitro and in vivo

Despite recent advances in the field of mRNA therapy, the lack of safe and efficacious delivery vehicles with pharmaceutically developable properties remains a major limitation. Here, we describe the systematic optimisation of lipid-peptide nanocomplexes for the delivery of mRNA in two murine cancer cell types, B16-F10 melanoma and CT26 colon carcinoma as well as NCI-H358 human lung bronchoalveolar cells. Different combinations of lipids and peptides were screened from an original lipid-peptide nanocomplex formulation for improved luciferase mRNA transfection in vitro by a multi-factorial screening approach. This led to the identification of key structural elements within the nanocomplex associated with substantial improvements in mRNA transfection efficiency included alkyl tail length of the cationic lipid, the fusogenic phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and cholesterol. The peptide component (K₁₆GACYGLPHKFCG) was further improved by the inclusion of a linker, RVRR, that is cleavable by the endosomal enzymes cathepsin B and furin, and a hydrophobic motif (X-S-X) between the mRNA packaging (K₁₆) and receptor targeting domains (CYGLPHKFCG). Nanocomplex transfections of a murine B16-F10 melanoma tumour supported the inclusion of cholesterol for optimal transfection in vivo as well as in vitro. In vitro transfections were also performed with mRNA encoding interleukin-15 as a potential immunotherapy agent and again, the optimised formulation with the key structural elements demonstrated significantly higher expression than the original formulation. Physicochemical characterisation of the nanocomplexes over time indicated that the optimal formulation retained biophysical properties such as size, charge and mRNA complexation efficiency for 14 days upon storage at 4 °C without the need for additional stabilising agents. In summary, we have developed an efficacious lipid-peptide nanocomplex with promising pharmaceutical development properties for the delivery of therapeutic mRNA.

Universal Barcoding Predicts In Vivo ApoE-Independent Lipid Nanoparticle Delivery

To predict whether preclinical lipid nanoparticle (LNP) delivery will translate in humans, it is necessary to understand whether the mechanism used by LNPs to enter cells is conserved across species. In mice, non-human primates, and humans, LNPs deliver RNA to hepatocytes by adsorbing apolipoprotein E (ApoE), which binds low-density lipoprotein receptor (LDLR). A growing number of LNPs can deliver RNA to nonhepatocytes, suggesting that ApoE- and LDLR-independent interactions could affect LNP tropism. To evaluate this hypothesis, we developed a universal DNA barcoding system that quantifies how chemically distinct LNPs deliver small interfering RNA in any mouse model, including genetic knockouts. We quantified how 98 different LNPs targeted 11 cell types in wildtype, LDLR^-/-, very low-density lipoprotein receptor, and ApoE^-/- mice, studying how these genes, which traffic endogenous lipids, affected LNP delivery. These data identified a novel, stereopure LNP that targets Kupffer cells, endothelial cells, and hepatocytes in an ApoE-independent manner. These results suggest that non-ApoE interactions can affect the tropism of LNP-RNA drugs.

Materiomically Designed Polymeric Vehicles for Nucleic Acids: Quo Vadis?

Despite rapid advances in molecular biology, particularly in site-specific genome editing technologies, such as CRISPR/Cas9 and base editing, financial and logistical challenges hinder a broad population from accessing and benefiting from gene therapy. To improve the affordability and scalability of gene therapy, we need to deploy chemically defined, economical, and scalable materials, such as synthetic polymers. For polymers to deliver nucleic acids efficaciously to targeted cells, they must optimally combine design attributes, such as architecture, length, composition, spatial distribution of monomers, basicity, hydrophilic-hydrophobic phase balance, or protonation degree. Designing polymeric vectors for specific nucleic acid payloads is a multivariate optimization problem wherein even minuscule deviations from the optimum are poorly tolerated. To explore the multivariate polymer design space rapidly, efficiently, and fruitfully, we must integrate parallelized polymer synthesis, high-throughput biological screening, and statistical modeling. Although materiomics approaches promise to streamline polymeric vector development, several methodological ambiguities must be resolved. For instance, establishing a flexible polymer ontology that accommodates recent synthetic advances, enforcing uniform polymer characterization and data reporting standards, and implementing multiplexed in vitro and in vivo screening studies require considerable planning, coordination, and effort. This contribution will acquaint readers with the challenges associated with materiomics approaches to polymeric gene delivery and offers guidelines for overcoming these challenges. Here, we summarize recent developments in combinatorial polymer synthesis, high-throughput screening of polymeric vectors, omics-based approaches to polymer design, barcoding schemes for pooled in vitro and in vivo screening, and identify materiomics-inspired research directions that will realize the long-unfulfilled clinical potential of polymeric carriers in gene therapy.

Correction of Beta-Thalassemia IVS-II-654 Mutation in a Mouse Model Using Prime Editing

Prime editing was used to insert and correct various pathogenic mutations except for beta-thalassemia variants, which disrupt functional beta-globin and prevent hemoglobin assembly in erythrocytes. This study investigated the effect of gene correction using prime editor version 3 (PE3) in a mouse model with the human beta-thalassemia IVS-II-654 mutation (C > T). The T conversion generates a 5′ donor site at intron 2 of the beta-globin gene resulting in aberrant splicing of pre-mRNA, which affects beta-globin expression. We microinjected PE3 components (pegRNA, nick sgRNA, and PE2 mRNA) into the zygotes from IVS-II-654 mice to generate mutation-edited mice. Genome sequencing of the IVS-II-654 site showed that PE3 installed the correction (T > C), with an editing efficiency of 14.29%. Reverse transcription-PCR analysis showed that the PE3-induced conversion restored normal splicing of beta-globin mRNA. Subsequent comprehensive phenotypic analysis of thalassemia symptoms, including anemic hematological parameters, anisocytosis, splenomegaly, cardiac hypertrophy, extramedullary hematopoiesis, and iron overload, showed that the corrected IVS-II-654 mice had a normal phenotype identical to the wild type mice. Off-target analysis of pegRNA and nick sgRNA additionally showed the genomic safety of PE3. These results suggest that correction of beta-thalassemia mutation by PE3 may be a straightforward therapeutic strategy for this disease.

Drug delivery systems for RNA therapeutics

RNA-based gene therapy requires therapeutic RNA to function inside target cells without eliciting unwanted immune responses. RNA can be ferried into cells using non-viral drug delivery systems, which circumvent the limitations of viral delivery vectors. Here, we review the growing number of RNA therapeutic classes, their molecular mechanisms of action, and the design considerations for their respective delivery platforms. We describe polymer-based, lipid-based, and conjugate-based drug delivery systems, differentiating between those that passively and those that actively target specific cell types. Finally, we describe the path from preclinical drug delivery research to clinical approval, highlighting opportunities to improve the efficiency with which new drug delivery systems are discovered.

Anionic Lipid Nanoparticles Preferentially Deliver mRNA to the Hepatic Reticuloendothelial System

Lipid nanoparticles (LNPs) are the leading nonviral technologies for the delivery of exogenous RNA to target cells in vivo. As systemic delivery platforms, these technologies are exemplified by Onpattro, an approved LNP-based RNA interference therapy, administered intravenously and targeted to parenchymal liver cells. The discovery of systemically administered LNP technologies capable of preferential RNA delivery beyond hepatocytes has, however, proven more challenging. Here, preceded by comprehensive mechanistic understanding of in vivo nanoparticle biodistribution and bodily clearance, an LNP-based messenger RNA (mRNA) delivery platform is rationally designed to preferentially target the hepatic reticuloendothelial system (RES). Evaluated in embryonic zebrafish, validated in mice, and directly compared to LNP-mRNA systems based on the lipid composition of Onpattro, RES-targeted LNPs significantly enhance mRNA expression both globally within the liver and specifically within hepatic RES cell types. Hepatic RES targeting requires just a single lipid change within the formulation of Onpattro to switch LNP surface charge from neutral to anionic. This technology not only provides new opportunities to treat liver-specific and systemic diseases in which RES cell types play a key role but, more importantly, exemplifies that rational design of advanced RNA therapies must be preceded by a robust understanding of the dominant nano-biointeractions involved.

The Cure VCP Scientific Conference 2021: Molecular and clinical insights into neurodegeneration and myopathy linked to multisystem proteinopathy-1 (MSP-1)

The 2021 VCP Scientific Conference took place virtually from September 9–10, 2021. This conference, planned and organized by the nonprofit patient advocacy group Cure VCP Disease, Inc. (https://www.curevcp.org), was the first VCP focused meeting since the 215th ENMC International Workshop VCP-related multi-system proteinopathy in 2016 (Evangelista et al., 2016). Mutations in VCP cause a complex and heterogenous disease termed inclusion body myopathy (IBM) with Paget’s disease of the bone (PDB) and frontotemporal dementia (FTD) (IBMPFD), or multisystem proteinopathy 1 (MSP-1) Kimonis (n.d.), Kovach et al. (2001), Kimonis et al. (2000). In addition, VCP mutations also cause other age-related neurodegenerative disorders including amyptrophic lateral sclerosis (ALS), Parkinsonism, Charcot-Marie type II-B, vacuolar tauopathy among others (Korb et al., 2022). The objectives of this conference were as follows: (1) to provide a forum that facilitates sharing of published and unpublished information on physiological roles of p97/VCP, and on how mutations of VCP lead to diseases; (2) to bolster understanding of mechanisms involved in p97/VCP-relevant diseases and to enable identification of therapeutics to treat these conditions; (3) to identify gaps and barriers of further discoveries and translational research in the p97/VCP field; (4) to set a concrete basic and translational research agenda for future studies including crucial discussions on biomarker discoveries and patient longitudinal studies to facilitate near-term clinical trials; (5) to accelerate cross-disciplinary research collaborations among p97/VCP researchers; (6) to enable attendees to learn about new tools and reagents with the potential to facilitate p97/VCP research; (7) to assist trainees in propelling their research and to foster mentorship from leaders in the field; and (8) to promote diversity and inclusion of under-represented minorities in p97/VCP research as diversity is critically important for strong scientific research. Given the range of topics, the VCP Scientific Conference brought together over one hundred and forty individuals representing a diverse group of research scientists, trainees, medical practitioners, industry representatives, and patient advocates. Twenty-five institutions with individuals from thirteen countries attended this virtual meeting. In this report, we summarize the major topics presented at this conference by a range of experts.

Performance of nanoparticles for biomedical applications: The in vitro/in vivo discrepancy

Nanomedicine has a great potential to revolutionize the therapeutic landscape. However, up-to-date results obtained from in vitro experiments predict the in vivo performance of nanoparticles weakly or not at all. There is a need for in vitro experiments that better resemble the in vivo reality. As a result, animal experiments can be reduced, and potent in vivo candidates will not be missed. It is important to gain a deeper knowledge about nanoparticle characteristics in physiological environment. In this context, the protein corona plays a crucial role. Its formation process including driving forces, kinetics, and influencing factors has to be explored in more detail. There exist different methods for the investigation of the protein corona and its impact on physico-chemical and biological properties of nanoparticles, which are compiled and critically reflected in this review article. The obtained information about the protein corona can be exploited to optimize nanoparticles for in vivo application. Still the translation from in vitro to in vivo remains challenging. Functional in vitro screening under physiological conditions such as in full serum, in 3D multicellular spheroids/organoids, or under flow conditions is recommended. Innovative in vivo screening using barcoded nanoparticles can simultaneously test more than hundred samples regarding biodistribution and functional delivery within a single mouse.

Physiology, pathology and the biomolecular corona: the confounding factors in nanomedicine design

The biomolecular corona that forms on nanomedicines in different physiological and pathological environments confers a new biological identity. How the recipient biological system's state can potentially affect nanomedicine corona formation, and how this can be modulated, remains obscure. With this perspective, this review summarizes the current knowledge about the content of biological fluids in various compartments and how they can be affected by pathological states, thus impacting biomolecular corona formation. The content of representative biological fluids is explored, and the urgency of integrating corona formation, as an essential component of nanomedicine designs for effective cargo delivery, is highlighted.

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.

Power in Numbers: Harnessing Combinatorial and Integrated Screens to Advance Nanomedicine

Nanocarriers have significant potential to advance personalized medicine through targeted drug delivery. However, to date, efforts to improve nanoparticle accumulation at target disease sites have largely failed to translate clinically, stemming from an incomplete understanding of nano-bio interactions. While progress has been made to evaluate the effects of specific physical and chemical nanoparticle properties on trafficking and uptake, there is much to be gained from controlling these properties singularly and in combination to determine their interactions with different cell types. We and others have recently begun leveraging library-based nanoparticle screens to study structure-function relationships of lipid- and polymer-based drug delivery systems to guide nanoparticle design. These combinatorial screening efforts are showing promise in leading to the successful identification of critical characteristics that yield improved and specific accumulation at target sites. However, there is a crucial need to equally consider the influence of biological complexity on nanoparticle delivery, particularly in the context of clinical translation. For example, tissue and cellular heterogeneity presents an additional dimension to nanoparticle trafficking, uptake, and accumulation; applying imaging and screening tools as well as bioinformatics may further expand our understanding of how nanoparticles engage with cells and tissues. Given recent advances in the fields of omics and machine learning, there is substantial promise to revolutionize nanocarrier development through the use of integrated screens, harnessing the combinatorial parameter space afforded both by nanoparticle libraries and clinically annotated biological data sets in combination with high throughput in vivo studies.

High-throughput and high-content bioassay enables tuning of polyester nanoparticles for cellular uptake, endosomal escape, and systemic in vivo delivery of mRNA

Nanoparticle-based mRNA therapeutics hold great promise, but cellular internalization and endosomal escape remain key barriers for cytosolic delivery. We developed a dual nanoparticle uptake and endosomal disruption assay using high-throughput and high-content image-based screening. Using a genetically encoded Galectin 8 fluorescent fusion protein sensor, endosomal disruption could be detected via sensor clustering on damaged endosomal membranes. Simultaneously, nucleic acid endocytosis was quantified using fluorescently tagged mRNA. We used an array of biodegradable poly(beta-amino ester)s as well as Lipofectamine and PEI to demonstrate that this assay has higher predictive capacity for mRNA delivery compared to conventional polymer and nanoparticle physiochemical characteristics. Top nanoparticle formulations enabled safe and efficacious mRNA expression in multiple tissues following intravenous injection, demonstrating that the in vitro screening method is also predictive of in vivo performance. Efficacious nonviral systemic delivery of mRNA with biodegradable particles opens up new avenues for genetic medicine and human health.

A scalable and robust cationic lipid/polymer hybrid nanoparticle platform for mRNA delivery

mRNA based gene therapies hold the potential to treat multiple diseases with significant advantages over DNA based therapies, including rapid protein expression and minimized risk of mutagenesis. However, successful delivery of mRNA remains challenging, and clinical translation of mRNA therapeutics has been limited. This study investigated the use of a lipid/polymer hybrid (LPH) nanocarrier for mRNA, designed to address key delivery challenges and shuttle mRNA to targeted tissues. LPH nanocarriers were synthesized using a scalable microfluidic process with a variety of material compositions and mRNA loading strategies. Results show that a combination of permanently ionized and transiently, pH-dependent ionizable cationic lipids had a synergistic effect upon on mRNA gene translation, when compared to each lipid independently. Upon intravenous administration, particles with adsorbed mRNA outperformed particles with encapsulated mRNA for protein expression in the lungs and the spleen despite significant LPH nanoparticle localization to the liver. In contrast, encapsulated particles had higher localized expression when injected intramuscularly with protein expression detectable out to 12 days post injection. Intramuscular administration of particles with OVA mRNA resulted in robust humoral immune response with encapsulated outperforming adsorbed particles in terms of antibody titers at 28 days. These results demonstrate LPH nanocarriers have great potential as a vehicle for mRNA delivery and expression in tissues and that tissue expression and longevity can be influenced by LPH composition and route of administration.

Non-liver mRNA Delivery

mRNA drugs can preempt infectious disease and treat Mendelian disorders, such as sickle cell anemia, muscular dystrophy, and cystic fibrosis, as well as autoimmunity and cancer. The three major therapeutic areas for which mRNA delivery is currently being explored are antigen production, including the COVID-19 vaccine, protein replacement therapy, and genome engineering. It was demonstrated 30 years ago that introducing in vitro transcribed mRNA intramuscularly results in detectable protein expression for specific antigens protecting against the likes of influenza and cancer. Utilizing mRNA as a therapeutic modality, however, is challenging. mRNA is large and anionic and, as a result, cannot passively diffuse across the negatively charged plasma membrane. In addition, RNases present in the bloodstream and tissues rapidly degrade mRNA, and its administration induces the innate immune response. In consequence, lipid-, polymer-, dendrimer-, and natural membrane-based mRNA drug delivery systems have been developed to deliver mRNA to target cells. Significant efforts and investments have been made to translate some of these systems into the clinic. Specifically, systemically administered lipid nanoparticles (LNPs) have delivered mRNA to the liver, and intramuscularly administered LNPs have delivered mRNA to immune cells to protect against coronavirus disease of 2019. However, clinically relevant delivery in non-liver tissues such as the spleen, lungs, heart, eye, central nervous system, and lymphatics requires improved drug delivery systems.In this Account, we provide an overview of key advances that have led us to Food and Drug Administration approval for the Pfizer/BioNTech mRNA-based vaccine against SARS-CoV-2 and Emergency Use Authorization for the Moderna mRNA-based vaccine against the same disease, and we explain how these developments will contribute to the clinical translation of mRNA therapeutics targeted outside of the liver. We first focus on the chemical modifications and sequence optimization that can improve the potency of mRNA, resulting in greatly improved pharmacokinetics. After detailing what makes an ideal mRNA payload, we review drug delivery systems used to deliver the payload into target cells. We describe efforts to reduce clearance by the liver, a key obstacle to the development of non-liver therapies. We then consider recent examples of nanoparticles that have delivered mRNA to non-liver tissues. Finally, we discuss current clinical mRNA programs, focusing on the COVID vaccines and highlighting lessons that may be applied to future mRNA drugs.

RGD peptide-based lipids for targeted mRNA delivery and gene editing applications

mRNA therapeutics are promising platforms for protein replacement therapies and gene editing technologies. When delivered via non-viral gene delivery systems, such as lipid nanoparticles (LNPs), mRNA therapeutics are easy to produce and show low toxicity and immunogenicity. However, LNPs show limited delivery efficiency and tissue specificity in certain applications. To overcome this, we designed RGD peptide (Arg-Gly-Asp) based ionizable lipids, which can be formulated into LNPs for integrin binding on cells and targeted mRNA delivery. RGD-LNPs were formulated using microfluidic devices and screened in vitro for size, mRNA encapsulation efficiency, transfection efficiency, and cell viability. A lead candidate, 1A RGD-based hybrid LNP, showed effective mRNA encapsulation and transfection, and was selected for further testing, including the co-delivery of Cas9 mRNA and sgRNA for gene editing applications. In vitro, 1A RGD-based hybrid LNP outperformed a non-targeted control LNP and showed GFP knockout efficiencies up to 90%. Further, the improved cellular uptake was reversed in the presence of soluble RGD, supporting the hypothesis that this improved uptake is RGD-dependent. In vivo, 1A RGD-based hybrid LNPs showed comparable mRNA delivery to the liver and spleen, when compared to a non-targeted control, and had increased expression in the whole body. Overall, this RGD-based hybrid LNP system is a promising platform for targeted mRNA delivery, which may allow for mRNA-based protein replacement and gene editing in a more efficient and specific manner with reduced off-target effects.

We developed RGD peptide based ionizable lipids, which can be formulated into LNPs for integrin-dependent targeted mRNA delivery and gene editing applications.

Obstacles and opportunities in a forward vision for cancer nanomedicine

Cancer nanomedicines were initially envisioned as magic bullets, travelling through the circulation to target tumours while sparing healthy tissues the toxicity of classic chemotherapy. While a limited number of nanomedicine therapies have resulted, the disappointing news is that major obstacles were overlooked in the nanoparticle's journey. However, some of these challenges may be turned into opportunities. Here, we discuss biological barriers to cancer nanomedicines and elaborate on two directions that the field is currently exploring to meet its initial expectations. The first strategy entails re-engineering cancer nanomedicines to prevent undesired interactions en route to the tumour. The second aims instead to leverage these obstacles into out-of-the-box diagnostic and therapeutic applications of nanomedicines, for cancer and beyond. Both paths require, among other developments, a deeper understanding of nano-bio interactions. We offer a forward look at how classic cancer nanomedicine may overcome its limitations while contributing to other areas of research.

Optimization of lipid nanoparticles for the delivery of nebulized therapeutic mRNA to the lungs

Lipid nanoparticles (LNPs) for the efficient delivery of drugs need to be designed for the particular administration route and type of drug. Here we report the design of LNPs for the efficient delivery of therapeutic RNAs to the lung via nebulization. We optimized the composition, molar ratios and structure of LNPs made of lipids, neutral or cationic helper lipids and poly(ethylene glycol) (PEG) by evaluating the performance of LNPs belonging to six clusters occupying extremes in chemical space, and then pooling the lead clusters and expanding their diversity. We found that a low (high) molar ratio of PEG improves the performance of LNPs with neutral (cationic) helper lipids, an identified and optimal LNP for low-dose messenger RNA delivery. Nebulized delivery of an mRNA encoding a broadly neutralizing antibody targeting haemagglutinin via the optimized LNP protected mice from a lethal challenge of the H1N1 subtype of influenza A virus, and delivered mRNA more efficiently than LNPs previously optimized for systemic delivery. A cluster approach to LNP design may facilitate the optimization of LNPs for other administration routes and therapeutics.

High-throughput screening of nanoparticles in drug delivery

The use of pharmacologically active compounds to manage and treat diseases is of utmost relevance in clinical practice. It is well recognized that spatial-temporal control over the delivery of these biomolecules will greatly impact their pharmacokinetic profile and ultimately their therapeutic effect. Nanoparticles (NPs) prepared from different materials have been tested successfully in the clinic for the delivery of several biomolecules including non-coding RNAs (siRNA and miRNA) and mRNAs. Indeed, the recent success of mRNA vaccines is in part due to progress in the delivery systems (NP based) that have been developed for many years. In most cases, the identification of the best formulation was done by testing a small number of novel formulations or by modification of pre-existing ones. Unfortunately, this is a low throughput and time-consuming process that hinders the identification of formulations with the highest potential. Alternatively, high-throughput combinatorial design of NP libraries may allow the rapid identification of formulations with the required release and cell/tissue targeting profile for a given application. Combinatorial approaches offer several advantages over conventional methods since they allow the incorporation of multiple components with varied chemical properties into materials, such as polymers or lipid-like materials, that will subsequently form NPs by self-assembly or chemical conjugation processes. The current review highlights the impact of high-throughput in the development of more efficient drug delivery systems with enhanced targeting and release kinetics. It also describes the current challenges in this research area as well as future directions.

Therapeutic RNA Delivery for COVID and Other Diseases

RNA can alter the expression of endogenous genes and can be used to express therapeutic proteins. As a result, RNA-based therapies have recently mitigated disease in patients. Yet most potential RNA therapies cannot currently be developed, in large part because delivering therapeutic quantities of RNA drugs to diseased cells remains difficult. Here, recent studies focused on the biological hurdles that make in vivo drug delivery challenging are described. Then RNA drugs that have overcome these challenges in humans, focusing on siRNA to treat liver disease and mRNA to vaccinate against COVID, are discussed. Finally, research centered on improving drug delivery to new tissues is highlighted, including the development of high-throughput in vivo nanoparticle DNA barcoding assays capable of testing over 100 distinct nanoparticles in a single animal.

Internalisation and Biological Activity of Nucleic Acids Delivering Cell-Penetrating Peptide Nanoparticles Is Controlled by the Biomolecular Corona

Nucleic acid molecules can be transferred into cells to alter gene expression and, thus, alleviate certain pathological conditions. Cell-penetrating peptides (CPPs) are vectors that can be used for transfecting nucleic acids as well as many other compounds. CPPs associate nucleic acids non-covalently, forming stable nanoparticles and providing efficient transfection of cells in vitro. However, in vivo, expected efficiency is achieved only in rare cases. One of the reasons for this discrepancy is the formation of protein corona around nanoparticles, once they are exposed to a biological environment, e.g., blood stream. In this study, we compared protein corona of CPP-nucleic acid nanoparticles formed in the presence of bovine, murine and human serum. We used Western blot and mass-spectrometry to identify the major constituents of protein corona forming around nanoparticles, showing that proteins involved in transport, haemostasis and complement system are its major components. We investigated physical features of nanoparticles and measured their biological efficiency in splice-correction assay. We showed that protein corona constituents might alter the fate of nanoparticles in vivo, e.g., by subjecting them to phagocytosis. We demonstrated that composition of protein corona of nanoparticles is species-specific that leads to dissimilar transfection efficiency and should be considered while developing delivery systems for nucleic acids.

Non-adhesive and highly stable biodegradable nanoparticles that provide widespread and safe transgene expression in orthotopic brain tumors

Several generations of poly(β-amino ester) (PBAE) polymers have been developed for efficient cellular transfection. However, PBAE-based gene vectors, similar to other cationic materials, cannot readily provide widespread gene transfer in the brain due to adhesive interactions with the extracellular matrix (ECM). We thus engineered eight vector candidates using previously identified lead PBAE polymer variants but endowed them with non-adhesive surface coatings to facilitate their spread through brain ECM. Specifically, we screened for the ability to provide widespread gene transfer in tumor spheroids and healthy mouse brains. We then confirmed that a lead formulation provided widespread transgene expression in orthotopically established brain tumor models with an excellent in vivo safety profile. Lastly, we developed a method to store it long-term while fully retaining its brain-penetrating property. This new platform provides a broad utility in evaluating novel genetic targets for gene therapy of brain tumors and neurological disorders in preclinical and clinical settings. Graphical abstract We engineered biodegradable DNA-loaded brain-penetrating nanoparticles (DNA-BPN) possessing small particle diameters (< 70 nm) and non-adhesive surface coatings to facilitate their spread through brain tumor extracellular matrix (ECM). These DNA-BPN provide widespread gene transfer in models recapitulating the ECM barrier, including three-dimensional multicellular tumor spheroids and mice with orthotopically established brain tumor.

Intracellular Routing and Recognition of Lipid-Based mRNA Nanoparticles

Messenger RNA (mRNA) is being extensively used in gene therapy and vaccination due to its safety over DNA, in the following ways: its lack of integration risk, cytoplasmic expression, and transient expression compatible with fine regulations. However, clinical applications of mRNA are limited by its fast degradation by nucleases, and the activation of detrimental immune responses. Advances in mRNA applications, with the recent approval of COVID-19 vaccines, were fueled by optimization of the mRNA sequence and the development of mRNA delivery systems. Although delivery systems and mRNA sequence optimization have been abundantly reviewed, understanding of the intracellular processing of mRNA is mandatory to improve its applications. We will focus on lipid nanoparticles (LNPs) as they are the most advanced nanocarriers for the delivery of mRNA. Here, we will review how mRNA therapeutic potency can be affected by its interactions with cellular proteins and intracellular distribution.

Virus Eradication and Synthetic Biology: Changes with SARS-CoV-2?

The eradication of infectious diseases has been achieved only once in history, in 1980, with smallpox. Since 1988, significant effort has been made to eliminate poliomyelitis viruses, but eradication is still just out of reach. As the goal of viral disease eradication approaches, the ability to recreate historically eradicated viruses using synthetic biology has the potential to jeopardize the long-term sustainability of eradication. However, the emergence of the severe acute respiratory syndrome-coronavirus (SARS-CoV)-2 pandemic has highlighted our ability to swiftly and resolutely respond to a potential outbreak. This virus has been synthetized faster than any other in the past and is resulting in vaccines before most attenuated candidates reach clinical trials. Here, synthetic biology has the opportunity to demonstrate its truest potential to the public and solidify a footing in the world of vaccines.

Self-assembled mRNA vaccines

mRNA vaccines have evolved from being a mere curiosity to emerging as COVID-19 vaccine front-runners. Recent advancements in the field of RNA technology, vaccinology, and nanotechnology have generated interest in delivering safe and effective mRNA therapeutics. In this review, we discuss design and self-assembly of mRNA vaccines. Self-assembly, a spontaneous organization of individual molecules, allows for design of nanoparticles with customizable properties. We highlight the materials commonly utilized to deliver mRNA, their physicochemical characteristics, and other relevant considerations, such as mRNA optimization, routes of administration, cellular fate, and immune activation, that are important for successful mRNA vaccination. We also examine the COVID-19 mRNA vaccines currently in clinical trials. mRNA vaccines are ready for the clinic, showing tremendous promise in the COVID-19 vaccine race, and have pushed the boundaries of gene therapy.

Novel lipid combination for delivery of plasmid DNA to immune cells in the spleen

This study reports on the development of a novel lipid combination that permits the efficient and highly selective delivery of plasmid DNA (pDNA) to immune cells in the spleen. Using DODAP, an ionizable lipid that was previously thought to be inefficient for gene delivery, we show for the first time, that this ignored lipid can be successfully used for efficient and targeted gene delivery in vivo, but only when combined with DOPE, a specific helper lipid. Using certain DODAP and DOPE ratios resulted in the formation of lipid nanoparticles (LNPs) with a ~ 1000-fold higher gene expression, and this expression was specific for the spleen, making it the most spleen-selective system for transfection using pDNA. The developed DODAP/DOPE-LNPs target immune cells in the spleen via receptors for complement C3 and this pathway is critical for efficient gene expression. We hypothesize that the high spleen transfection activity of DODAP/DOPE-LNPs is caused by the promotion of gene expression associated with B cell activation via complement receptors. LNPs encapsulating tumor-antigen encoding pDNA showed both prophylactic and therapeutic anti-tumor effects. The optimized LNPs resulted in the production of different cytokines and antigen-specific antibodies as well as exerting antigen-specific cytotoxic effects. This study revives the use of DODAP in gene delivery and highlights the importance of using appropriate lipid combinations for delivering genes to specific cells.

Optimizing synthetic nucleic acid and protein nanocarriers: The chemical evolution approach

Optimizing synthetic nanocarriers is like searching for a needle in a haystack. How to find the most suitable carrier for intracellular delivery of a specified macromolecular nanoagent for a given disease target location? Here, we review different synthetic 'chemical evolution' strategies that have been pursued. Libraries of nanocarriers have been generated either by unbiased combinatorial chemistry or by variation and novel combination of known functional delivery elements. As in natural evolution, definition of nanocarriers as sequences, as barcode or design principle, may fuel chemical evolution. Screening in appropriate test system may not only provide delivery candidates, but also a refined understanding of cellular delivery including novel, unpredictable mechanisms. Combined with rational design and computational algorithms, candidates can be further optimized in subsequent evolution cycles into nanocarriers with improved safety and efficacy. Optimization of nanocarriers differs for various cargos, as illustrated for plasmid DNA, siRNA, mRNA, proteins, or genome-editing nucleases.

Non-Viral Targeted Nucleic Acid Delivery: Apply Sequences for Optimization

In nature, genomes have been optimized by the evolution of their nucleic acid sequences. The design of peptide-like carriers as synthetic sequences provides a strategy for optimizing multifunctional targeted nucleic acid delivery in an iterative process. The optimization of sequence-defined nanocarriers differs for different nucleic acid cargos as well as their specific applications. Supramolecular self-assembly enriched the development of a virus-inspired non-viral nucleic acid delivery system. Incorporation of DNA barcodes presents a complementary approach of applying sequences for nanocarrier optimization. This strategy may greatly help to identify nucleic acid carriers that can overcome pharmacological barriers and facilitate targeted delivery in vivo. Barcode sequences enable simultaneous evaluation of multiple nucleic acid nanocarriers in a single test organism for in vivo biodistribution as well as in vivo bioactivity.

The Opposing Effect of Type I IFN on the T Cell Response by Non-modified mRNA-Lipoplex Vaccines Is Determined by the Route of Administration

mRNA-lipoplex vaccines are currently being explored in phase II clinical trials for the treatment of patients with advanced solid tumors. Mechanistically, these mRNA-lipoplex vaccines are characterized by the induction of type I interferon (IFN) centered innate responses. Earlier studies have identified type I IFNs as major regulators of the T cell response instigated by mRNA-lipoplex vaccines. However, stimulatory or, in contrast, profound inhibitory effects of type I IFNs were described depending on the study. In this mouse study, we demonstrated that the opposing roles of type I IFN signaling on the magnitude of the vaccine-evoked T cell responses is dependent on the route of mRNA-lipoplex administration and is regulated at the level of the T cells rather than indirectly through modulation of dendritic cell function. This study helps to understand the double-edged sword character of type I IFN induction upon mRNA-based vaccine treatment and may contribute to a more rational design of mRNA vaccination regimens.

Treating Cystic Fibrosis with mRNA and CRISPR

Less than 20% of the protein coding genome is thought to be targetable using small molecules. mRNA therapies are not limited in the same way since in theory, they can silence or edit any gene by encoding CRISPR nucleases, or alternatively, produce any missing protein. Yet not all mRNA therapies are equally likely to succeed. Over the past several years, an increasing number of clinical trials with siRNA- and antisense oligonucleotide-based drugs have revealed three key concepts that will likely extend to mRNA therapies delivered by nonviral systems. First, scientists have come to understand that some genes make better targets for RNA therapies than others. Second, scientists have learned that the type and position of chemical modifications made to an RNA drug can alter its therapeutic window, toxicity, and bioavailability. Third, scientists have found that safe and targeted drug delivery vehicles are required to ferry mRNA therapies into diseased cells. In this study, we apply these learnings to cystic fibrosis (CF). We also describe lessons learned from a subset of CF gene therapies that have already been tested in patients. Finally, we highlight the scientific advances that are still required for nonviral mRNA- or CRISPR-based drugs to treat CF successfully in patients.

Nanoparticles containing constrained phospholipids deliver mRNA to liver immune cells in vivo without targeting ligands

Once inside the cytoplasm of a cell, mRNA can be used to treat disease by upregulating the expression of any gene. Lipid nanoparticles (LNPs) can deliver mRNA to hepatocytes in humans, yet systemic non-hepatocyte delivery at clinical doses remains difficult. We noted that LNPs have historically been formulated with phospholipids containing unconstrained alkyl tails. Based on evidence that constrained adamantyl groups have unique properties that can improve small molecule drug delivery, we hypothesized that a phospholipid containing an adamantyl group would facilitate mRNA delivery in vivo. We quantified how 109 LNPs containing "constrained phospholipids" delivered mRNA to 16 cell types in mice, then using a DNA barcoding-based analytical pipeline, related phospholipid structure to in vivo delivery. By analyzing delivery mediated by constrained phospholipids, we identified a novel LNP that delivers mRNA to immune cells at 0.5 mg/kg. Unlike many previous LNPs, these (a) did not preferentially target hepatocytes and (b) delivered mRNA to immune cells without targeting ligands. These data suggest constrained phospholipids may be useful LNP components.

The Biomolecular Corona of Lipid Nanoparticles for Gene Therapy

Gene therapy holds great potential for treating almost any disease by gene silencing, protein expression, or gene correction. To efficiently deliver the nucleic acid payload to its target tissue, the genetic material needs to be combined with a delivery platform. Lipid nanoparticles (LNPs) have proven to be excellent delivery vectors for gene therapy and are increasingly entering into routine clinical practice. Over the past two decades, the optimization of LNP formulations for nucleic acid delivery has led to a well-established body of knowledge culminating in the first-ever RNA interference therapeutic using LNP technology, i.e., Onpattro, and many more in clinical development to deliver various nucleic acid payloads. Screening a lipid library in vivo for optimal gene silencing potency in hepatocytes resulted in the identification of the Onpattro formulation. Subsequent studies discovered that the key to Onpattro's liver tropism is its ability to form a specific "biomolecular corona". In fact, apolipoprotein E (ApoE), among other proteins, adsorbed to the LNP surface enables specific hepatocyte targeting. This proof-of-principle example demonstrates the use of the biomolecular corona for targeting specific receptors and cells, thereby opening up the road to rationally designing LNPs. To date, however, only a few studies have explored in detail the corona of LNPs, and how to efficiently modulate the corona remains poorly understood. In this review, we summarize recent discoveries about the biomolecular corona, expanding the knowledge gained with other nanoparticles to LNPs for nucleic acid delivery. In particular, we address how particle stability, biodistribution, and targeting of LNPs can be influenced by the biological environment. Onpattro is used as a case study to describe both the successful development of an LNP formulation for gene therapy and the key influence of the biological environment. Moreover, we outline the techniques available to isolate and analyze the corona of LNPs, and we highlight their advantages and drawbacks. Finally, we discuss possible implications of the biomolecular corona for LNP delivery and we examine the potential of exploiting the corona as a targeting strategy beyond the liver to develop next-generation gene therapies.

Increased PIP3 activity blocks nanoparticle mRNA delivery

The biological pathways that affect drug delivery in vivo remain poorly understood. We hypothesized that altering cell metabolism with phosphatidylinositol (3,4,5)-triphosphate (PIP3), a bioactive lipid upstream of the metabolic pathway PI3K (phosphatidylinositol 3-kinase)/AKT/ mTOR (mammalian target of rapamycin) would transiently increase protein translated by nanoparticle-delivered messenger RNA (mRNA) since these pathways increase growth and proliferation. Instead, we found that PIP3 blocked delivery of clinically-relevant lipid nanoparticles (LNPs) across multiple cell types in vitro and in vivo. PIP3-driven reductions in LNP delivery were not caused by toxicity, cell uptake, or endosomal escape. Interestingly, RNA sequencing and metabolomics analyses suggested an increase in basal metabolic rate. Higher transcriptional activity and mitochondrial expansion led us to formulate two competing hypotheses that explain the reductions in LNP-mediated mRNA delivery. First, PIP3 induced consumption of limited cellular resources, "drowning out" exogenously-delivered mRNA. Second, PIP3 triggers a catabolic response that leads to protein degradation and decreased translation.

Deconvoluting Lipid Nanoparticle Structure for Messenger RNA Delivery

Lipid nanoparticle (LNP) packaged mRNA vaccines have been deployed against infectious diseases such as COVID-19, yet their structural features remain unclear. Cholesterol, a major constituent within LNPs, contributes to their morphology that influences gene delivery. Herein, we examine the structure of LNPs containing cholesterol derivatives using electron microscopy, differential scanning calorimetry, and membrane fluidity assays. LNPs formulated with C24 alkyl derivatives of cholesterol show a polymorphic shape and various degrees of multilamellarity and lipid partitioning, likely due to phase separation. The addition of methyl and ethyl groups to the C24 alkyl tail of the cholesterol backbone induces multilamellarity (>50% increase compared to cholesterol), while the addition of a double bond induces lipid partitioning (>90% increase compared to cholesterol). LNPs with multilamellar and faceted structures, as well as a lamellar lipid phase, showed higher gene transfection. Unraveling the structure of mRNA-LNPs can enable their rational design toward enhanced gene delivery.

Deconvoluting Lipid Nanoparticle Structure for Messenger RNA Delivery

Lipid nanoparticle (LNP) packaged mRNA vaccines have been deployed against infectious diseases such as COVID-19, yet their structural features remain unclear. Cholesterol, a major constituent within LNPs, contributes to their morphology that influences gene delivery. Herein, we examine the structure of LNPs containing cholesterol derivatives using electron microscopy, differential scanning calorimetry, and membrane fluidity assays. LNPs formulated with C24 alkyl derivatives of cholesterol show a polymorphic shape and various degrees of multilamellarity and lipid partitioning, likely due to phase separation. The addition of methyl and ethyl groups to the C24 alkyl tail of the cholesterol backbone induces multilamellarity (>50% increase compared to cholesterol), while the addition of a double bond induces lipid partitioning (>90% increase compared to cholesterol). LNPs with multilamellar and faceted structures, as well as a lamellar lipid phase, showed higher gene transfection. Unraveling the structure of mRNA-LNPs can enable their rational design toward enhanced gene delivery.

Naturally Derived Membrane Lipids Impact Nanoparticle-Based Messenger RNA Delivery

Introduction

Lipid based nanoparticles (LNPs) are clinically successful vectors for hepatic delivery of nucleic acids. These systems are being developed for non-hepatic delivery of mRNA for the treatment of diseases like cystic fibrosis or retinal degeneration as well as infectious diseases. Localized delivery to the lungs requires aerosolization. We hypothesized that structural lipids within LNPs would provide features of integrity which can be tuned for attributes required for efficient hepatic and non-hepatic gene delivery. Herein, we explored whether naturally occurring lipids that originate from the cell membrane of plants and microorganisms enhance mRNA-based gene transfection in vitro and in vivo and whether they assist in maintaining mRNA activity after nebulization.

Methods

We substituted DSPC, a structural lipid used in a conventional LNP formulation, to a series of naturally occurring membrane lipids. We measured the effect of these membrane lipids on size, encapsulation efficiency and their impact on transfection efficiency. We further characterized LNPs after nebulization and measured whether they retained their transfection efficiency.

Results

One plant-derived structural lipid, DGTS, led to a significant improvement in liver transfection of mRNA. DGTS LNPs had similar transfection ability when administered in the nasal cavity to conventional LNPs. In contrast, we found that DGTS LNPs had reduced transfection efficiency in cells pre-and post-nebulization while maintaining size and encapsulation similar to DSPC LNPs.

Conclusions

We found that structural lipids provide differential mRNA-based activities in vitro and in vivo which also depend on the mode of administration. Understanding influence of structural lipids on nanoparticle morphology and structure can lead to engineering potent materials for mRNA-based gene therapy applications.

Comprehensive approach of hybrid nanoplatforms in drug delivery and theranostics to combat cancer

To date, various chemically synthesized and biosynthesized nanoparticles, or hybrid nanosystems and/or nanoplatforms, have been developed under the umbrella of nanomedicine. These can be introduced into the body orally, nasally, intratumorally or intravenously. Successfully translating hybrid nanoplatforms from preclinical proof-of-concept to therapeutic value in the clinic is challenging. Having made significant advances with drug delivery technologies, we must learn from other areas of oncology drug development, where patient stratification and target-driven design have improved patient outcomes. This review aims to identify gaps in our understanding of the current strengths of nanomedicine platforms in drug delivery and cancer theranostics. We report on the current approaches of nanomedicine at preclinical and clinical stages.

The Application of Tetrahedral Framework Nucleic Acids as a Drug Carrier in Biomedicine Fields

In recent years, tetrahedral Framework Nucleic Acids(tFNAs) have become a hot topic in the field of DNA nanostructures because of their stable structures, nanoscale size, superior mechanical properties and convenient synthesis with high yield. tFNAs are considered promising drug delivery carriers because they can pass through the cellular membrane without any help and they have a good biocompatibility and biodegradability. Besides, they have rich modification sites, they can be modified by kinds of functional groups. The functionalization molecules can be modified on the vertexes, embedded between the double-stranded DNA of the tetrahedron edges, hanged on the edges, or encapsulated in the cage-like structure of the tetrahedron. The structure of tetrahedron can also be intelligently controlled through smart design, such as integrating DNA hairpin loop structure onto the edges. Nowadays, DNA tetrahedron will have a broader development prospect in the application of drug transport carriers and intelligent drug carriers. Therefore, DNA material is a new carrier material with great advantages and has a very broad application prospect in the construction of an intelligent drug transport system.