On the role of helper lipids in lipid nanoparticle formulations of siRNA

Nanocarrier-mediated siRNA delivery: a new approach for the treatment of traumatic brain injury-related Alzheimer's disease

Traumatic brain injury and Alzheimer's disease share pathological similarities, including neuronal loss, amyloid-β deposition, tau hyperphosphorylation, blood-brain barrier dysfunction, neuroinflammation, and cognitive deficits. Furthermore, traumatic brain injury can exacerbate Alzheimer's disease-like pathologies, potentially leading to the development of Alzheimer's disease. Nanocarriers offer a potential solution by facilitating the delivery of small interfering RNAs across the blood-brain barrier for the targeted silencing of key pathological genes implicated in traumatic brain injury and Alzheimer's disease. Unlike traditional approaches to neuroregeneration, this is a molecular-targeted strategy, thus avoiding non-specific drug actions. This review focuses on the use of nanocarrier systems for the efficient and precise delivery of siRNAs, discussing the advantages, challenges, and future directions. In principle, siRNAs have the potential to target all genes and non-targetable proteins, holding significant promise for treating various diseases. Among the various therapeutic approaches currently available for neurological diseases, siRNA gene silencing can precisely "turn off" the expression of any gene at the genetic level, thus radically inhibiting disease progression; however, a significant challenge lies in delivering siRNAs across the blood-brain barrier. Nanoparticles have received increasing attention as an innovative drug delivery tool for the treatment of brain diseases. They are considered a potential therapeutic strategy with the advantages of being able to cross the blood-brain barrier, targeted drug delivery, enhanced drug stability, and multifunctional therapy. The use of nanoparticles to deliver specific modified siRNAs to the injured brain is gradually being recognized as a feasible and effective approach. Although this strategy is still in the preclinical exploration stage, it is expected to achieve clinical translation in the future, creating a new field of molecular targeted therapy and precision medicine for the treatment of Alzheimer's disease associated with traumatic brain injury.

Facile lipid nanoparticle size engineering approach via controllable fusion induced by depletion forces

Lipid nanoparticles (LNPs) are among the most promising drug delivery carriers in research and development, with one major clinical application being messenger RNA (mRNA) vaccine. Current LNP production methods have the limit of generating low polydispersity index (PDI; PDI < 0.1) only for relatively small particles (<100 nm). It is known that larger LNPs have desirable properties, for example, particles with diameters in the 100 to 200 nm range have good immunogenicity. Yet, these larger particles' large PDI limits their clinical translation because of concerns about manufacturing reproducibility and possible side effects. We report here a facile approach to produce large and monodisperse (100-200 nm, PDI < 0.1) LNPs. The approach is based on adding 10 kDa polyethylene glycol (PEG) to a solution containing smaller LNPs. We show that PEG-induced depletion forces lead to the fusion of LNPs to form particles of approximately double the original size while keeping the same starting PDI. We discuss the fusion mechanism and show the parameters it depends on. In particular, we show that the fusion leads to a decrease in the fraction of empty LNPs. We show that the purification for PEG after fusion is simple and complete, thus, we believe that this is a method for the production of large LNP with low PDI that has a lot of potential to find industrial use.

Targeted delivery systems of siRNA based on ionizable lipid nanoparticles and cationic polymer vectors

As an emerging therapeutic tool, small interfering RNA (siRNA) had the capability to down-regulate nearly all human mRNAs via sequence-specific gene silencing. Numerous studies have demonstrated the substantial potential of siRNA in the treatment of broad classes of diseases. With the discovery and development of various delivery systems and chemical modifications, six siRNA-based drugs have been approved by 2024. The utilization of siRNA-based therapeutics has significantly propelled efforts to combat a wide array of previously incurable diseases and advanced at a rapid pace, particularly with the help of potent targeted delivery systems. Despite encountering several extracellular and intracellular challenges, the efficiency of siRNA delivery has been gradually enhanced. Currently, targeted strategies aimed at improving potency and reducing toxicity played a crucial role in the druggability of siRNA. This review focused on recent advancements on ionizable lipid nanoparticles (LNPs) and cationic polymer (CP) vectors applied for targeted siRNA delivery. Based on various types of targeted modifications, we primarily described delivery systems modified with receptor ligands, peptides, antibodies, aptamers and amino acids. Finally, we discussed the challenges and opportunities associated with siRNA delivery systems based on ionizable LNPs and CPs vectors.

Lipid nanoparticle (LNP) mediated mRNA delivery in neurodegenerative diseases

Neurodegenerative diseases (NDD) are characterized by the progressive loss of neurons and the impairment of cellular functions. Messenger RNA (mRNA) has emerged as a promising therapy for treating NDD, as it can encode missing or dysfunctional proteins and anti-inflammatory cytokines or neuroprotective proteins to halt the progression of these diseases. However, effective mRNA delivery to the central nervous system (CNS) remains a significant challenge due to the limited penetration of the blood-brain barrier (BBB). Lipid nanoparticles (LNPs) offer an efficient solution by encapsulating and protecting mRNA, facilitating transfection and intracellular delivery. This review discusses the pathophysiological mechanisms of neurological disorders, including Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS), Huntington's disease (HD), ischemic stroke, spinal cord injury, and Friedreich's ataxia. Additionally, it explores the potential of LNP-mediated mRNA delivery as a therapeutic strategy for these diseases. Various approaches to overcoming BBB-related challenges and enhancing the delivery and efficacy of mRNA-LNPs are discussed, including non-invasive methods with strong potential for clinical translation. With advancements in artificial intelligence (AI)-guided mRNA and LNP design, targeted delivery, gene editing, and CAR-T cell therapy, mRNA-LNPs could significantly transform the treatment landscape for NDD, paving the way for future clinical applications.

Regulating mRNA endosomal escape through lipid rafts: A review

Messenger RNA (mRNA) therapeutics, enabled by lipid nanoparticles (LNPs) delivery systems, have revolutionized modern medicine by facilitating the delivery of genetic cargo to target cells. However, the efficient release of mRNA from LNPs within the endosomal pathways into the cytosol remains a major bottleneck in this field. Revisiting the formulation and function of mRNA-LNPs, it has been found that lipid rafts formed by cholesterol and distearoylphosphatidylcholine during the self-assembly process plan an essential role in the intracellular delivery and endosomal escape of mRNA-LNPs. These lipid rafts enhance the rigidity and stability of LNPs, facilitating mRNA encapsulation and closely contributing to improved intracellular delivery efficiency. By adjusting the composition or behavior of lipid rafts within LNPs-such as substituting cholesterol or altering the lipid phase-endosomal membranes can be destabilized, facilitating the escape of mRNA into the cytoplasm. This approach provides a promising strategy for rational design of mRNA delivery system and optimization of LNPs formulation. Additionally, methods for studying the mRNA escape process are summarized, as they serve as the foundation for achieving reliable and reproducible results.

More than a delivery system: the evolving role of lipid-based nanoparticles

Lipid-based nanoparticles, including liposomes and lipid nanoparticles (LNPs), make up an important class of drug delivery systems. Their modularity enables encapsulation of a wide range of therapeutic cargoes, their ease of functionalization allows for incorporation of targeting motifs and anti-fouling coatings, and their scalability facilitates rapid translation to the clinic. While the discovery and early understanding of lipid-based nanoparticles is heavily rooted in biology, formulation development has largely focused on materials properties, such as how liposome and lipid nanoparticle composition can be altered to maximize drug loading, stability and circulation. To achieve targeted delivery and enable improved accumulation of therapeutics at target tissues or disease sites, emphasis is typically placed on the use of external modifications, such as peptide, protein, and polymer motifs. However, these approaches can increase the complexity of the nanocarrier and complicate scale up. In this review, we focus on how our understanding of lipid structure and function in biological contexts can be used to design intrinsically functional and targeted nanocarriers. We highlight formulation-based strategies, such as the incorporation of bioactive lipids, that have been used to modulate liposome and lipid nanoparticle properties and improve their functionality while retaining simple nanocarrier designs. We also highlight classes of naturally occurring lipids, their functions, and how they have been incorporated into lipid-based nanoparticles. We will additionally position these approaches into the historical context of both liposome and LNP development.

Optimizing Peptide-Conjugated Lipid Nanoparticles for Efficient siRNA Delivery across the Blood-Brain Barrier and Treatment of Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is a WHO grade 4 glioma and the most common malignant primary brain tumor. Addressing the clinical management of GBM presents an exceptionally daunting and intricate challenge, particularly in overcoming the blood-brain barrier (BBB) to deliver effective therapies to the brain. Nanotechnology-based drug delivery systems have exhibited considerable promise in tackling this aggressive brain cancer. However, the BBB remains a key challenge in achieving effective brain delivery of nanocarriers. Here, we have optimized a lipid nanoparticle (LNP) formulation (C2) and modified the LNP with Angiopep-2 peptide, which exhibits the most significant improvements in blood-brain barrier penetration and brain accumulation (about 2.23% injection dose). Using the Ang-2-coupled C2 LNP formulation, we researched the therapeutic effect of Polo-like Kinase 1(PLK1)-targeted siRNA delivery to treat a mouse model of GBM. The optimized LNP formulation was demonstrated to significantly inhibit mouse GBM growth and extend the median survival of mice (2.18-fold). This work demonstrates the efficacy of a brain-targeted siRNA delivery system in GBM treatment. As the understanding of the role of RNAs in GBM deepens and innovative delivery methods are continually developed and refined, RNA-based therapies could emerge as a crucial breakthrough in the advancement of brain tumor treatment.

Lipid Nanoparticles and PEG: Time Frame of Immune Checkpoint Blockade Can Be Controlled by Adjusting the Rate of Cellular Uptake of Nanoparticles

The engineerability of lipid nanoparticles (LNPs) and their ability to deliver nucleic acids make LNPs attractive tools for cancer immunotherapy. LNP-based gene delivery can be employed for various approaches in cancer immunotherapy, including encoding tumor-associated antigens and silencing of negative immune checkpoint proteins. For example, LNPs carrying small interfering RNAs can offer several advantages, including sustained and durable inhibition of an immune checkpoint protein. Due to their tunable design, modifying the lipid composition of LNPs can regulate the rate of their uptake by immune cells and the rate of gene silencing. Controlling the kinetics of LNP uptake provides additional flexibility and strategies to generate appropriate immunomodulation in the tumor microenvironment. Here, we evaluated the effects of polyethylene glycol (PEG) content ranging from 0.5 to 6 mol % on the cellular uptake of LNPs by immune cells and gene silencing of PD-L1 after intratumoral administration. We evaluated the cellular uptake and PD-L1 blockade in vitro in cell studies and in vivo using the YUMM1.7 melanoma tumor model. Cell studies showed that the rate of cell uptake was inversely correlated to an increasing mol % of PEG in a linear relationship. In the in vivo studies, 0.5% PEG LNP initiated an immediate effect in the tumor with a significant decrease in the PD-L1 expression of immune cells observed within 24 h. In comparison, the gene silencing effect of 6% PEG LNP was delayed, with a significant decrease of PD-L1 expression in immune cell subsets being observed 72 h after administration. Notably, performance of the 6% PEG LNP at 72 h was comparable to that of the 0.5% PEG LNP at 24 h. Overall, this study suggests that PEG modifications and intratumoral administration of LNPs can be a promising strategy for an effective antitumor immune response.

Molecular Insight into Lipid Nanoparticle Assembly from NMR Spectroscopy and Molecular Dynamics Simulation

Lipid nanoparticles (LNPs) have emerged as the premier drug delivery system for oligonucleotide vaccines and therapeutics in recent years. Despite their prosperous advancement in research and clinical applications, there is a significant lack of mechanistic understanding of the assembly of lipid particles at the molecular level. In our study, we utilized a combination of solution and solid-state NMR, together with molecular dynamics simulations, to elucidate local structures and interactions of chemical components across multiple motional regimes. Our results comprehensively evaluated the impact of formulation components and engineering process factors on the particle formation and identified the interplay of phospholipids (DSPC), poly(ethylene glycol) (PEG) lipid conjugates, and cholesterol in governing the particle size and lipid dynamics from a structural perspective, using static 31P NMR techniques. These studies provide novel insights into the impact of particle engineering on the molecular properties of the LNP envelope membrane. Additionally, molecular interactions and compositional distribution play a critical role in particle engineering and the consequent stability and potency. In this study, we have identified intermolecular contacts among the lipid components using one-dimensional 1H-13C cross-polarization magic angle spinning experiments, 1H relaxation measurements, and two-dimensional 1H-1H correlation methods, providing a structural basis for the lipid assembly. Interestingly, the cationic and ionizable lipids, conventionally regarded as stabilizing agents primarily located within the core of LNPs, were found to interact with PEG lipids and coexist in the outer layer of the particles. We suggest that LNPs examined here are comprised of an outer layer rich in lipid components surrounding a core region. Our high-resolution findings offer insightful structural and dynamic details pertaining to the individual chemical components in the lipid particles and their interactions influence lipid complex structure and stability in particle engineering.

Splenic B cell-targeting lipid nanoparticles for safe and effective mRNA vaccine delivery

mRNA-loaded lipid nanoparticles (LNPs) have emerged as a potent and versatile platform that underpins the success of mRNA vaccines, but guidelines for designing safe and effective formulations with minimal off-target effects remain unclear. In this study, we focused on a rational design for a novel ionizable lipid library that is based on ionizable tri-oleoyl-tris (iTOT) compounds with a high yield via a simple 2-step synthesis. To further enhance the efficacy and safety of this potent library for vaccine applications, we identified the optimal composition for a vaccine by focusing on the molar ratio of specific lipid excipients in the formulation. This composition brought about a shift in delivery to the spleen, and the LNP formulation, which contained 15 mol% DSPC (15%DSPC-LNPs), was thoroughly taken up by both B cells and other splenic immune cells. This formulation requires neither additional lipid components nor targeting ligand modifications, and it is accompanied by antigen-specific cytotoxic T lymphocyte responses. The rigid, hydrophobic, and charge-neutral surface of 15%DSPC-LNPs minimizes apolipoprotein E-dependent hepatic uptake and maximizes complement receptor-mediated B-cell targeting. Furthermore, as an intramuscularly administered vaccine, 15%DSPC-LNPs induce antigen-specific immune responses and, importantly, results in significantly lower levels of hepatotoxicity compared with that of the mRNA vaccine formulations currently being marketed. In summary, this study demonstrated how the passive targeting of mRNA-LNPs to organs and cells could be regulated by designing novel ionizable lipids combined with adjusting the relative proportions of lipid components. The results of this study also emphasize how selective mRNA delivery to the spleen could avoid the liver, which highlights a promising strategy for the development of safe and effective vaccines.

Formulation and Characterization of Novel Ionizable and Cationic Lipid Nanoparticles for the Delivery of Splice-Switching Oligonucleotides

Despite increasing knowledge about the mechanistic aspects of lipid nanoparticles (LNPs) as oligonucleotide carriers, the structure-function relationship in LNPs has been generally overlooked. Understanding this correlation is critical in the rational design of LNPs. Here, a materials characterization approach is utilized, applying structural information from small-angle X-ray scattering experiments to design novel LNPs focusing on distinct lipid organizations with a minimal compositional variation. The lipid phase structures are characterized in these LNPs and their corresponding bulk lipid mixtures with small-angle scattering techniques, and the LNP-cell interactions in vitro with respect to cytotoxicity, hemolysis, cargo delivery, cell uptake, and lysosomal swelling. An LNP is identified that outperforms Onpattro lipid composition using lipid components and molar ratios which differ from the gold standard clinical LNPs. The base structure of these LNPs has an inverse micellar phase organization, whereas the LNPs with inverted hexagonal phases are not functional, suggesting that this phase formation may not be needed for LNP-mediated oligonucleotide delivery. The importance of stabilizer choice for the LNP function is demonstrated and super-resolution microscopy highlights the complexity of the delivery mechanisms, where lysosomal swelling for the majority of LNPs is observed. This study highlights the importance of advanced characterization for the rational design of LNPs to enable the study of structure-function relationships.

Antibody-Nanoparticle Conjugates in Therapy: Combining the Best of Two Worlds

Monoclonal antibodies (mAbs) and antibody fragments have revolutionized medicine as highly specific binding agents and inhibitors. At the same time, several types of nanomaterials, including liposomes, lipid nanoparticles (NPs), polymersomes, metal and metal oxide NPs, and protein nanostructures, are increasingly utilized and explored for therapeutic potential due to their versatility, chemical and physical properties, and tunability. However, nanomaterials alone often lack specificity, leading to relatively low efficacy and/or high toxicity. To address this problem, a rapidly emerging area is antibody-nanomaterial conjugates (ANCs), which combine the precise targeting specificity of antibodies with the effector functionality of the nanomaterial. In this review, we give a brief introduction to mAbs and major conjugation techniques, describe major classes of nanomaterials being studied for therapeutic potential, and review the literature on ANCs of each class. Special focus is given to emerging applications including ANCs addressing the blood-brain barrier, ANCs delivering nucleic acids, and light-activated ANCs. While many disease targets are related to cancer, ANCs are also under development to address autoimmune, neurological, and infectious diseases. While important challenges remain, ANCs are poised to become a next-generation therapeutic technology.

Lipid-siRNA Organization Modulates the Intracellular Dynamics of Lipid Nanoparticles

Lipid nanoparticles (LNPs) are widely used for delivering therapeutic nucleic acids, yet the relationship between their internal structure and intracellular behavior, particularly before RNA release, remains unclear. Here, we elucidate how lipid-siRNA organization within LNPs can modulate their intracellular delivery dynamics. We use cryo-electron microscopy and photochemical assays to reveal that increased siRNA loading can reduce helper lipids' distribution to the LNP surface, while siRNA consistently localizes near the surface. These alterations in lipid-siRNA organization affect LNP membrane fluidity, enhancing LNP fusion with cellular membranes and promoting cytosolic siRNA delivery, primarily via macropinocytosis. Using photosensitive lipids and live cell imaging, we demonstrate that lipid-siRNA organization regulates LNP responsiveness to external stimuli, significantly affecting siRNA endosomal escape efficiency upon light activation. We further confirm this observation using convex lens-induced confinement microscopy and single-particle imaging. Overall, our findings provide critical insights into how lipid-siRNA organization shapes LNP intracellular dynamics, offering rational design principles for optimizing LNP-based RNA therapeutics.

Targeting Neuroinflammation in Central Nervous System Diseases by Oral Delivery of Lipid Nanoparticles

Neuroinflammation within the central nervous system (CNS) is a primary characteristic of CNS diseases, such as Parkinson's disease, Alzheimer's disease (AD), amyotrophic lateral sclerosis, and mental disorders. The excessive activation of immune cells results in the massive release of pro-inflammatory cytokines, which subsequently induce neuronal death and accelerate the progression of neurodegeneration. Therefore, mitigating excessive neuroinflammation has emerged as a promising strategy for the treatment of CNS diseases. Despite advancements in drug discovery and the development of novel therapeutics, the effective delivery of these agents to the CNS remains a serious challenge due to the restrictive nature of the blood-brain barrier (BBB). This underscores the need to develop a novel drug delivery system. Recent studies have identified oral lipid nanoparticles (LNPs) as a promising approach to efficiently deliver drugs across the BBB and treat neurological diseases. This review aims to comprehensively summarize the recent advancements in the development of LNPs designed for the controlled delivery and therapeutic modulation of CNS diseases through oral administration. Furthermore, this review addresses the mechanisms by which these LNPs overcome biological barriers and evaluate their clinical implications and therapeutic efficacy in the context of oral drug delivery systems. Specifically, it focuses on LNP formulations that facilitate oral administration, exploring their potential to enhance bioavailability, improve targeting precision, and alleviate or manage the symptoms associated with a range of CNS diseases.

Lipid Nanoparticles for mRNA Delivery in Cancer Immunotherapy

Cancer immunotherapy is poised to be one of the major modalities for cancer treatment. Messenger RNA (mRNA) has emerged as a versatile and promising platform for the development of effective cancer immunotherapy. Delivery systems for mRNA therapeutics are pivotal for their optimal therapeutic efficacy and minimal adverse side effects. Lipid nanoparticles (LNPs) have demonstrated a great success for mRNA delivery. Numerous LNPs have been designed and optimized to enhance mRNA stability, facilitate transfection, and ensure intracellular delivery for subsequent processing. Nevertheless, challenges remain to, for example, improve the efficiency of endosomal escape and passive targeting. This review highlights key advancements in the development of mRNA LNPs for cancer immunotherapy. We delve into the design of LNPs for mRNA delivery, encompassing the chemical structures, characterization, and structure-activity relationships (SAR) of LNP compositions. We discuss the key factors influencing the transfection efficiency, passive targeting, and tropism of mRNA-loaded LNPs. We also review the preclinical and clinical applications of mRNA LNPs in cancer immunotherapy. This review can enhance our understanding in the design and application of LNPs for mRNA delivery in cancer immunotherapy.

AI-driven innovations in smart multifunctional nanocarriers for drug and gene delivery: A mini-review

The convergence of artificial intelligence (AI) and nanomedicine has revolutionized the design of smart multifunctional nanocarriers (SMNs) for drug and gene delivery, offering unprecedented precision, efficiency, and personalization in therapeutic applications. AI-driven approaches enhance the development of these nanocarriers by accelerating their design, optimizing drug loading and release kinetics, improving biocompatibility, and predicting interactions with biological barriers. This review explores the transformative role of AI in the fabrication and functionalization of SMNs, emphasizing its impact on overcoming challenges in targeted drug delivery, controlled release, and theranostics. We discuss the integration of AI with advanced nanomaterials-such as polymeric, lipidic, and inorganic nanoparticles-highlighting their potential in oncology and hematology. Furthermore, we examine recent clinical and preclinical case studies demonstrating AI-assisted nanocarrier development for personalized medicine. The synergy between AI and nanotechnology paves the way for next-generation precision therapeutics, addressing critical limitations in traditional drug delivery systems. However, data standardization, regulatory compliance, and translational scalability challenges remain. This review underscores the need for interdisciplinary collaboration to unlock AI's potential in nanomedicine fully, ultimately advancing the clinical application of SMNs for more effective and safer patient care.

Exosome-Inspired Lipid Nanoparticles for Enhanced Tissue Penetration

The extracellular matrix (ECM) is a complex network of biomolecules with varying pore sizes, posing a challenge for the effective penetration of lipid nanoparticles. In contrast, cell-derived lipid nanoparticles, such as exosomes, have demonstrated the ability to travel to distant organs, indicating their capacity to penetrate the ECM. Here, we designed exosome-like vesicles (ELVs) inspired by exosomes' distinct transport phenomena. Specifically, we integrated three exosomal components (anionic lipid, cholesterol, and aquaporin-1) associated with transport into our ELVs to mimic the superior diffusion behavior of exosomes over synthetic lipid nanoparticles. Surprisingly, both bulk- and single-particle-diffusion studies revealed a more than 33 times increase in the effective diffusion coefficient within model ECM compared to conventional lipid nanoparticles. Furthermore, ELVs show an 80% increase in the effective diffusion coefficient within biological tissues. The excellent transport behavior of ELVs was further validated in vivo, where intratumoral injection showcased their superior transport. These findings provide insights into lipid nanoparticle design for improved tissue penetration.

Computational Methods for Modeling Lipid-Mediated Active Pharmaceutical Ingredient Delivery

Lipid-mediated delivery of active pharmaceutical ingredients (API) opened new possibilities in advanced therapies. By encapsulating an API into a lipid nanocarrier (LNC), one can safely deliver APIs not soluble in water, those with otherwise strong adverse effects, or very fragile ones such as nucleic acids. However, for the rational design of LNCs, a detailed understanding of the composition-structure-function relationships is missing. This review presents currently available computational methods for LNC investigation, screening, and design. The state-of-the-art physics-based approaches are described, with the focus on molecular dynamics simulations in all-atom and coarse-grained resolution. Their strengths and weaknesses are discussed, highlighting the aspects necessary for obtaining reliable results in the simulations. Furthermore, a machine learning, i.e., data-based learning, approach to the design of lipid-mediated API delivery is introduced. The data produced by the experimental and theoretical approaches provide valuable insights. Processing these data can help optimize the design of LNCs for better performance. In the final section of this Review, state-of-the-art of computer simulations of LNCs are reviewed, specifically addressing the compatibility of experimental and computational insights.

Intelligent Design of Lipid Nanoparticles for Enhanced Gene Therapeutics

Lipid nanoparticles (LNPs) are an effective delivery system for gene therapeutics. By optimizing their formulation, the physiochemical properties of LNPs can be tailored to improve tissue penetration, cellular uptake, and precise targeting. The application of these targeted delivery strategies within the LNP framework ensures efficient delivery of therapeutic agents to specific organs or cell types, thereby maximizing therapeutic efficacy. In the realm of genome editing, LNPs have emerged as a potent vehicle for delivering CRISPR/Cas components, offering significant advantages such as high in vivo efficacy. The incorporation of machine learning into the optimization of LNP platforms for gene therapeutics represents a significant advancement, harnessing its predictive capabilities to substantially accelerate the research and development process. This review highlights the dynamic evolution of LNP technology, which is expected to drive transformative progress in the field of gene therapy.

Engineering Lipid Nanoparticles for mRNA Immunotherapy

Over the last decades, messenger RNA (mRNA) has emerged as a promising therapeutic modality, enabling the delivery of genetic instructions to cells for producing therapeutic proteins or antigens. As such, mRNA-based therapies can be developed for a wide range of conditions, including infections, cancer, metabolic disorders, and genetic diseases. Nevertheless, using mRNA therapeutically requires chemical modifications to reduce immunostimulatory effects and nanotechnology to prevent degradation and ensure intracellular delivery. Lipid nanoparticles (LNPs) have become the most effective delivery platform for mRNA therapeutics, which are primarily employed for vaccine purposes following local administration and hepatic applications following systemic administration. Here, we review the state-of-the-art LNP-mRNA technology and discuss its potential for immunotherapy. We first outline the requirements for mRNA to be used therapeutically, including the role of LNP-mediated delivery. Next, we highlight LNP-mRNA immunotherapy approaches for vaccination, immuno-oncology, and autoimmune disorders. In addition, we discuss challenges that are limiting LNP-mRNA's widespread use, including tunable biodistribution and immunostimulatory effects. Finally, we provide an outlook on how implementing approaches such as library screening and machine learning will guide the development of next-generation mRNA therapeutics.

Chemistry, manufacturing and controls strategies for using novel excipients in lipid nanoparticles

Lipid nanoparticles (LNPs) for nucleic acid delivery often use novel lipids as functional excipients to modulate the biodistribution, pharmacokinetics, pharmacodynamics and efficacy of the nucleic acid. Novel excipients used in pharmaceutical products are subject to heightened regulatory scrutiny and often require data packages comparable to an active pharmaceutical ingredient. Although these regulatory requirements may help to ensure patient safety they also create economic and procedural barriers that can disincentivize innovation and delay clinical investigation. Despite the unique structural and functional role of lipid excipients in LNPs, there is limited specific global regulatory guidance, which adds uncertainty and risk to the development of LNPs. In this Perspective we provide an industry view on the chemistry, manufacturing and controls challenges that pharmaceutical companies face in the use of novel lipid excipients at each stage of development, and propose consensus recommendations on how to streamline and clarify development and regulatory expectations.

A Fentanyl Hapten-Displaying Lipid Nanoparticle Vaccine that Non-Covalently Encapsulates a TLR7/8 Agonist and T-Helper Epitope Induces Protective Anti-Fentanyl Immunity

Opioid use disorder - particularly involving fentanyl - has precipitated a public health crisis characterized by a significant increase in addiction and overdose-related deaths. Fentanyl-specific immunotherapy, which aims at inducing fentanyl-specific antibodies capable of binding fentanyl molecules in the bloodstream, preventing their entry in the central nervous system, is therefore gaining momentum. Conventional opioid designs rely on the covalent conjugation of fentanyl analogues to immunogenic carrier proteins that hold the inherent capacity of mounting immunodominant responses. Here, we present an alternative fentanyl vaccine design that utilizes a non-covalent assembly of lipid nanoparticles (LNPs) to deliver fentanyl haptens in conjunction with a CD4+ T-helper peptide epitope and an imidazoquinoline TLR7/8 agonist. Our results demonstrate that a single intramuscular administration of the LNP-based nanovaccine elicits fentanyl-specific antibodies, significantly mitigating the effects of opioid overdose in preclinical mouse models. Furthermore, we analyzed the immunobiological behavior of the vaccine in vivo in mouse models, providing evidence that covalent attachment of a fentanyl hapten to a carrier proteins or peptide epitope is not necessary for inducing an effective immune response. However, co-delivery - specifically, the physical assembly of all immune cues into an LNP - remains essential for inducing hapten-specific immunity.

Loading of Extracellular Vesicles with Nucleic Acids via Hybridization with Non-Lamellar Liquid Crystalline Lipid Nanoparticles

The translation of cell-derived extracellular vesicles (EVs) into biogenic gene delivery systems is limited by relatively inefficient loading strategies. In this work, the loading of various nucleic acids into small EVs via their spontaneous hybridization with preloaded non-lamellar liquid crystalline lipid nanoparticles (LCNPs), forming hybrid EVs (HEVs) is described. It is demonstrated that LCNPs undergo pH-dependent structural transitions from inverse hexagonal (HII) phases at pH 5 to more disordered non-lamellar phases, possibly inverse micellar (L2) or sponge (L3) phases, at pH 7.4, which are particularly suitable for inducing a controlled hybridization process with EVs. State-of-the-art single-particle analysis techniques reveal that LCNPs interact with various EV subpopulations at physiological conditions and that ≈40% of HEVs are loaded with the genetic cargo. Importantly, this study demonstrates that EV membrane proteins remain accessible on HEV surfaces, with their intrinsic enzymatic activity unaffected after the hybridization process. Finally, HEVs show in vitro improved transfection efficiencies compared to unhybridized LCNPs. In summary, this versatile platform holds potential for loading various nucleic acid molecules into native EVs and may help developing EV-based therapeutics.

Nanocarrier-Mediated RNA Delivery Platform as a Frontier Strategy for Hepatic Disease Treatment: Challenges and Opportunities

Hepatic diseases cause serious public health problems worldwide, and there is an urgent need to develop effective therapeutic agents. In recent years, significant progress is made in RNA therapy, and RNA molecules, such as mRNAs, siRNAs, miRNAs, and RNA aptamers, are shown to provide significant advantages in the treatment of hepatic diseases. However, the drawbacks of RNAs, such as their poor biological stability, easy degradation by nucleases in vivo, low bioavailability, and low concentrations in target tissues, significantly limit the clinical application of RNA-based drugs. Therefore, exploring and developing effective nanoscale delivery platforms for RNA therapeutics are of immense value. This review focuses on the different types of hepatic diseases and RNA therapeutics, summarizing various nanoscale delivery platforms and their strengths and weaknesses. Finally, the current status and future prospects of nanoscale delivery systems for RNA therapy are discussed.

Exploring precision treatments in immune-mediated inflammatory diseases: Harnessing the infinite potential of nucleic acid delivery

Immune-mediated inflammatory diseases (IMIDs) impose an immeasurable burden on individuals and society. While the conventional use of immunosuppressants and disease-modifying drugs has provided partial relief and control, their inevitable side effects and limited efficacy cast a shadow over finding a cure. Promising nucleic acid drugs have shown the potential to exert precise effects at the molecular level, with different classes of nucleic acids having regulatory functions through varying mechanisms. For the better delivery of nucleic acids, safe and effective viral vectors and non-viral delivery systems (including liposomes, polymers, etc.) have been intensively explored. Herein, after describing a range of nucleic acid categories and vectors, we focus on the application of therapeutic nucleic acid delivery in various IMIDs, including rheumatoid arthritis, inflammatory bowel disease, psoriasis, multiple sclerosis, asthma, ankylosing spondylitis, systemic lupus erythematosus, and uveitis. Molecules implicated in inflammation and immune dysregulation are abnormally expressed in a series of IMIDs, and their meticulous modulation through nucleic acid therapy results in varying degrees of remission and improvement of these diseases. By synthesizing findings centered on specific molecular targets, this review delivers a systematic elucidation and perspective towards advancing and utilization of nucleic acid therapeutics for managing IMIDs.

Exploring the impact of commonly used ionizable and pegylated lipids on mRNA-LNPs: A combined in vitro and preclinical perspective

Ionizable lipids are widely recognized as the crucial component of lipid nanoparticles (LNPs). They enable mRNA encapsulation, shield it from enzymatic degradation, facilitate cellular uptake, and foster its cytosolic release for subsequent translation into proteins. In addition, PEGylated lipids are added to stabilize the particles in storage and in vivo. In this study, we investigate the potency of LNPs prepared using commonly adopted ionizable and pegylated lipids in vitro (using HEK293 cells) and in vivo (mouse studies) to consider the impact of structure on potency. LNPs were prepared using a fixed molar ratio of DSPC: Cholesterol: ionizable/cationic lipid: PEG lipid (10:38.5:50:1.5 mol%). All LNP formulations exhibited similar critical quality attributes (CQAs), including particle size <100 nm, low PDI (<0.2), near-neutral zeta potential, and high encapsulation efficiency (>90%). However, the potency of these LNPs, as measured by in vitro mRNA expression and in vivo expression following intramuscular injection in mice varied significantly. LNPs formulated with SM-102 exhibited the highest expression in vitro, whilst in vivo SM-102 and ALC-0315 LNPs showed significantly higher mRNA expression than DLin-MC3-DMA (MC3), DODAP and DOTAP LNPs. We also investigated the effect of PEG lipid choice (ALC-0159, DMG-PEG2k, and DSPE-PEG2k), which did not impact LNP CQAs, nor their clearance from the injection site. However, PEG lipid choice significantly influenced mRNA expression with the incorporation of DSPE-PEG2k reducing expression. This work contributes valuable insights to the evolving landscape of mRNA research, emphasizing that CQAs are a marker of the quality of the LNP production process, but not discriminatory regarding LNP potency. Similarly, standard in vitro studies do not provide insights into in vivo potency. These results further emphasize the intricacies of formulation design and the importance of bridging gaps between experimental outcomes in different settings.

Therapeutic applications of cell engineering using mRNA technology

Engineering and reprogramming cells has significant therapeutic potential to treat a wide range of diseases, by replacing missing or defective proteins, to provide transcription factors (TFs) to reprogram cell phenotypes, or to provide enzymes such as RNA-guided Cas9 derivatives for CRISPR-based cell engineering. While viral vector-mediated gene transfer has played an important role in this field, the use of mRNA avoids safety concerns associated with the integration of DNA into the host cell genome, making mRNA particularly attractive for in vivo applications. Widespread application of mRNA for cell engineering is limited by its instability in the biological environment and challenges involved in the delivery of mRNA to its target site. In this review, we examine challenges that must be overcome to develop effective therapeutics.

Nano Plasma Membrane Vesicle-Lipid Nanoparticle Hybrids for Enhanced Gene Delivery and Expression

Lipid nanoparticles (LNPs) have emerged as the leading nonviral nucleic acid (NA) delivery system, gaining widespread attention for their use in COVID-19 vaccines. They are recognized for their efficient NA encapsulation, modifiability, and scalable production. However, LNPs face efficacy and potency limitations due to suboptimal intracellular processing, with endosomal escape efficiencies (ESE) below 2.5%. Additionally, up to 70% of NPs undergo recycling and exocytosis after cellular uptake. In contrast, cell-derived vesicles offer biocompatibility and high-delivery efficacy but are challenging to load with exogenous NAs and to manufacture at large-scale. To leverage the strengths of both systems, a hybrid system is designed by combining cell-derived vesicles, such as nano plasma membrane vesicles (nPMVs), with LNPs through microfluidic mixing and subsequent dialysis. These hybrids demonstrate up to tenfold increase in ESE and an 18-fold rise in reporter gene expression in vitro and in vivo in zebrafish larvae (ZFL) and mice, compared to traditional LNPs. These improvements are linked to their unique physico-chemical properties, composition, and morphology. By incorporating cell-derived vesicles, this strategy streamlines the development process, significantly enhancing the efficacy and potency of gene delivery systems without the need for extensive screening.

Bioengineered Nanomaterials for siRNA Therapy of Chemoresistant Cancers

Chemoresistance remains a long-standing challenge after cancer treatment. Over the last two decades, RNA interference (RNAi) has emerged as a gene therapy modality to sensitize cancer cells to chemotherapy. However, the use of RNAi, specifically small-interfering RNA (siRNA), is hindered by biological barriers that limit its intracellular delivery. Nanoparticles can overcome these barriers by protecting siRNA in physiological environments and facilitating its delivery to cancer cells. In this review, we discuss the development of nanomaterials for siRNA delivery in cancer therapy, current challenges, and future perspectives for their implementation to overcome cancer chemoresistance.

Development of Thermally Stable mRNA-LNP Delivery Systems: Current Progress and Future Prospects

The success of mRNA-LNP-based COVID-19 vaccines opens a new era for mRNA-LNP-based therapy. This breakthrough is expected to catalyze the development of more mRNA-LNP-based medicines, not only for preventive vaccines but also for therapeutic purposes. Despite the promising outlook, there are fundamental challenges impeding the progress and widespread application of mRNA-LNP formulations. One of the significant challenges is their thermal instability, requiring these products to be stored at ultralow temperatures for long-term stability. The specific requirements present significant challenges for the storage, transportation, and distribution of mRNA-LNP formulations. To effectively prepare for future infectious disease outbreaks and broaden the application of mRNA-LNP-based therapies for other illnesses, improving the thermostability of mRNA-LNP formulations is critical. In this review, we discuss the potential factors contributing to the thermal instability of mRNA-LNP formulations and examine the roles of key components such as ionizable lipids, cholesterol, pH, buffers, and stabilizing agents like sugars in maintaining their thermal stability, with the goal of providing insights that can guide the future development of thermally stable mRNA-LNP formulations.

Advances in the study of LNPs for mRNA delivery and clinical applications

Messenger ribonucleic acid (mRNA) was discovered in 1961 as an intermediary for transferring genetic information from DNA to ribosomes for protein synthesis. The COVID-19 pandemic brought worldwide attention to mRNA vaccines. The emergency use authorization of two COVID-19 mRNA vaccines, BNT162b2 and mRNA-1273, were major achievements in the history of vaccine development. Lipid nanoparticles (LNPs), one of the most superior non-viral delivery vectors available, have made many exciting advances in clinical translation as part of the COVID-19 vaccine and therefore has the potential to accelerate the clinical translation of many gene drugs. In addition, due to these small size, biocompatibility and excellent biodegradability, LNPs can efficiently deliver nucleic acids into cells, which is particularly important for current mRNA therapeutic regimens. LNPs are composed cationic or pH-dependent ionizable lipid bilayer, polyethylene glycol (PEG), phospholipids, and cholesterol, represents an advanced system for the delivery of mRNA vaccines. Furthermore, optimization of these four components constituting the LNPs have demonstrated enhanced vaccine efficacy and diminished adverse effects. The incorporation of biodegradable lipids enhance the biocompatibility of LNPs, thereby improving its potential as an efficacious therapeutic approach for a wide range of challenging and intricate diseases, encompassing infectious diseases, liver disorders, cancer, cardiovascular diseases, cerebrovascular conditions, among others. Consequently, this review aims to furnish the scientific community with the most up-to-date information regarding mRNA vaccines and LNP delivery systems.

CO-DELIVERY of glutamic acid-extended peptide antigen and imidazoquinoline TLR7/8 agonist via ionizable lipid nanoparticles induces protective anti-tumor immunity

Cancer vaccines aim at generating cytotoxic CD8+ T cells that kill cancer cells and confer durable tumor regression. Hereto, CD8+ peptide epitopes should be presented by antigen presenting cells to CD8+ T cells in lymphoid tissue. Unfortunately, in unformulated soluble form, peptide antigens are poorly taken up by antigen presenting cells and do not efficiently reach lymph nodes. Hence, the lack of efficient delivery remains a major limitation for successful clinical translation of cancer vaccination using peptide antigens. Here we propose a generic peptide nanoformulation strategy by extending the amino acid sequence of the peptide antigen epitope with 10 glutamic acid residues. The resulting overall anionic charge of the peptide allows encapsulation into lipid nanoparticles (peptide-LNP) by electrostatic interaction with an ionizable cationic lipid. We demonstrate that intravenous injection of peptide-LNP efficiently delivers the peptide to immune cells in the spleen. Peptide-LNP that co-encapsulate an imidazoquinoline TLR7/8 agonist (IMDQ) induce robust innate immune activation in a broad range of immune cell subsets in the spleen. Peptide-LNP containing the minimal CD8+ T cell epitope of the HPV type 16 E7 oncoprotein and IMDQ induces high levels of antigen-specific CD8+ T cells in the blood, and can confer protective immunity against E7-expressing tumors in both prophylactic and therapeutic settings.

Comprehensive analysis of lipid nanoparticle formulation and preparation for RNA delivery

Nucleic acid-based therapeutics are a common approach that is increasingly popular for a wide spectrum of diseases. Lipid nanoparticles (LNPs) are promising delivery carriers that provide RNA stability, with strong transfection efficiency, favorable and tailorable pharmacokinetics, limited toxicity, and established translatability. In this review article, we describe the lipid-based delivery systems, focusing on lipid nanoparticles, the need of their use, provide a comprehensive analysis of each component, and highlight the advantages and disadvantages of the existing manufacturing processes. We further summarize the ongoing and completed clinical trials utilizing LNPs, indicating important aspects/questions worth of investigation, and analyze the future perspectives of this significant and promising therapeutic approach.

Review of machine learning for lipid nanoparticle formulation and process development

Lipid nanoparticles (LNPs) are a subset of pharmaceutical nanoparticulate formulations designed to encapsulate, stabilize, and deliver nucleic acid cargoes in vivo. Applications for LNPs include new interventions for genetic disorders, novel classes of vaccines, and alternate modes of intracellular delivery for therapeutic proteins. In the pharmaceutical industry, establishing a robust formulation and process to achieve target product performance is a critical component of drug development. Fundamental understanding of the processes for making LNPs and their interactions with biological systems have advanced considerably in the wake of the COVID-19 pandemic. Nevertheless, LNP formulation research remains largely empirical and resource intensive due to the multitude of input parameters and the complex physical phenomena that govern the processes of nanoparticle precipitation, self-assembly, structure evolution, and stability. Increasingly, artificial intelligence and machine learning (AI/ML) are being applied to improve the efficiency of research activities through in silico models and predictions, and to drive deeper fundamental understanding of experimental inputs to functional outputs. This review will identify current challenges and opportunities in the development of robust LNP formulations of nucleic acids, review studies that apply machine learning methods to experimental datasets, and provide discussion on associated data science challenges to facilitate collaboration between formulation and data scientists, aiming to accelerate the advancement of AI/ML applied to LNP formulation and process optimization.

Design, synthesis, and in vitro gene transfer efficacy of novel ionizable cholesterol derivatives

ABSTACTThe medicinal properties of genetic drugs are highly dependent on the design of delivery systems. Ionizable cationic lipids are considered core materials in delivery systems. However, there has not yet been a widespread consensus on the relationship between the wide diversity of lipid structure design and gene delivery efficiency. The aims of the research work were to synthesize ionizable cholesterol derivatives (iChol-lipids) and to evaluate their potential applications as gene delivery vector. A series of iChol-lipids with different head groups were synthesized with carbamate bond spacer. The chemical structures were characterized by 1H NMR, MS, melting range, and pKa. The interactions between iChol-lipids and MALAT1-siRNA were studied by molecular dynamics simulations and compared with market available DC-Chol, which revealed that hydrogen bonds, salt-bridge, and electrostatic interaction were probably involved. The self-assemble behaviors of these lipids were intensively investigated and evaluated by dynamic laser scattering in the presence of different helper lipids and PEGylated lipids. Their plasmid binding ability, transfection efficiency, hemolytic toxicity, and cytotoxicity were fully studied. IZ-Chol-LNPs was proved to be highly potential to effectively complex with DNA, and endosome escape mechanisms mediated by proton sponge effect was verified by pH-sensitive fluorescence probe BCFL.

Extracellular vesicles versus lipid nanoparticles for the delivery of nucleic acids

Extracellular vesicles (EVs) are increasingly investigated for delivering nucleic acid (NA) therapeutics, leveraging their natural role in transporting NA and protein-based cargo in cell-to-cell signaling. Their synthetic counterparts, lipid nanoparticles (LNPs), have been developed over the past decades as NA carriers, culminating in the approval of several marketed formulations such as patisiran/Onpattro® and the mRNA-1273/BNT162 COVID-19 vaccines. The success of LNPs has sparked efforts to develop innovative technologies to target extrahepatic organs, and to deliver novel therapeutic modalities, such as tools for in vivo gene editing. Fueled by the recent advancements in both fields, this review aims to provide a comprehensive overview of the basic characteristics of EV and LNP-based NA delivery systems, from EV biogenesis to structural properties of LNPs. It addresses the primary challenges encountered in utilizing these nanocarriers from a drug formulation and delivery perspective. Additionally, biodistribution profiles, in vitro and in vivo transfection outcomes, as well as their status in clinical trials are compared. Overall, this review provides insights into promising research avenues and potential dead ends for EV and LNP-based NA delivery systems.

Effect of Lipid Nanoparticle Physico-Chemical Properties and Composition on Their Interaction with the Immune System

Lipid nanoparticles (LNPs) have shown promise as a delivery system for nucleic acid-based therapeutics, including DNA, siRNA, and mRNA vaccines. The immune system plays a critical role in the response to these nanocarriers, with innate immune cells initiating an early response and adaptive immune cells mediating a more specific reaction, sometimes leading to potential adverse effects. Recent studies have shown that the innate immune response to LNPs is mediated by Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs), which recognize the lipid components of the nanoparticles. This recognition can trigger the activation of inflammatory pathways and the production of cytokines and chemokines, leading to potential adverse effects such as fever, inflammation, and pain at the injection site. On the other hand, the adaptive immune response to LNPs appears to be primarily directed against the protein encoded by the mRNA cargo, with little evidence of an ongoing adaptive immune response to the components of the LNP itself. Understanding the relationship between LNPs and the immune system is critical for the development of safe and effective nucleic acid-based delivery systems. In fact, targeting the immune system is essential to develop effective vaccines, as well as therapies against cancer or infections. There is a lack of research in the literature that has systematically studied the factors that influence the interaction between LNPs and the immune system and further research is needed to better elucidate the mechanisms underlying the immune response to LNPs. In this review, we discuss LNPs' composition, physico-chemical properties, such as size, shape, and surface charge, and the protein corona formation which can affect the reactivity of the immune system, thus providing a guide for the research on new formulations that could gain a favorable efficacy/safety profile.

Lipid nanoparticle-mediated mRNA delivery to CD34+ cells in rhesus monkeys

Transplantation of ex vivo engineered hematopoietic stem cells (HSCs) can lead to robust clinical responses but carries risks of adverse events from bone marrow mobilization, chemotherapy conditioning and other factors. HSCs have been modified in vivo using lipid nanoparticles (LNPs) decorated with targeting moieties, which increases manufacturing complexity. Here we screen 105 LNPs without targeting ligands for effective homing to the bone marrow in mouse. We report an LNP named LNP67 that delivers mRNA to murine HSCs in vivo, primary human HSCs ex vivo and CD34+ cells in rhesus monkeys (Macaca mulatta) in vivo at doses of 0.25 and 0.4 mg kg-1. Without mobilization and conditioning, LNP67 can mediate delivery of mRNA to HSCs and their progenitor cells (HSPCs), as well as to the liver in rhesus monkeys, without serum cytokine activation. These data support the hypothesis that in vivo delivery to HSCs and HSPCs in nonhuman primates is feasible without targeting ligands.

Progress and prospects of mRNA-based drugs in pre-clinical and clinical applications

In the last decade, messenger ribonucleic acid (mRNA)-based drugs have gained great interest in both immunotherapy and non-immunogenic applications. This surge in interest can be largely attributed to the demonstration of distinct advantages offered by various mRNA molecules, alongside the rapid advancements in nucleic acid delivery systems. It is noteworthy that the immunogenicity of mRNA drugs presents a double-edged sword. In the context of immunotherapy, extra supplementation of adjuvant is generally required for induction of robust immune responses. Conversely, in non-immunotherapeutic scenarios, immune activation is unwanted considering the host tolerability and high expression demand for mRNA-encoded functional proteins. Herein, mainly focused on the linear non-replicating mRNA, we overview the preclinical and clinical progress and prospects of mRNA medicines encompassing vaccines and other therapeutics. We also highlight the importance of focusing on the host-specific variations, including age, gender, pathological condition, and concurrent medication of individual patient, for maximized efficacy and safety upon mRNA administration. Furthermore, we deliberate on the potential challenges that mRNA drugs may encounter in the realm of disease treatment, the current endeavors of improvement, as well as the application prospects for future advancements. Overall, this review aims to present a comprehensive understanding of mRNA-based therapies while illuminating the prospective development and clinical application of mRNA drugs.

Navigating the intricate in-vivo journey of lipid nanoparticles tailored for the targeted delivery of RNA therapeutics: a quality-by-design approach

RNA therapeutics, such as mRNA, siRNA, and CRISPR-Cas9, present exciting avenues for treating diverse diseases. However, their potential is commonly hindered by vulnerability to degradation and poor cellular uptake, requiring effective delivery systems. Lipid nanoparticles (LNPs) have emerged as a leading choice for in vivo RNA delivery, offering protection against degradation, enhanced cellular uptake, and facilitation of endosomal escape. However, LNPs encounter numerous challenges for targeted RNA delivery in vivo, demanding advanced particle engineering, surface functionalization with targeting ligands, and a profound comprehension of the biological milieu in which they function. This review explores the structural and physicochemical characteristics of LNPs, in-vivo fate, and customization for RNA therapeutics. We highlight the quality-by-design (QbD) approach for targeted delivery beyond the liver, focusing on biodistribution, immunogenicity, and toxicity. In addition, we explored the current challenges and strategies associated with LNPs for in-vivo RNA delivery, such as ensuring repeated-dose efficacy, safety, and tissue-specific gene delivery. Furthermore, we provide insights into the current clinical applications in various classes of diseases and finally prospects of LNPs in RNA therapeutics.

Characterization of mRNA-LNP structural features and mechanisms for enhanced mRNA vaccine immunogenicity

Lipid nanoparticles (LNPs) used for nonviral gene delivery have achieved significant success, particularly in COVID-19 mRNA vaccines. LNPs are routinely characterized by their particle size, polydispersity, and mRNA loading efficiency. However, the internal structure of these particles has not been specified, despite evidence showing that LNPs can be highly heterogeneous, with variations in lipid composition and preparation methods. How these structural features contributed to mRNA LNP vaccine activities is also unclear. In this study, we prepared LNPs with distinctly different internal structures. They were named the emulsion-like LNPs (eLNPs) and membrane-rich LNPs (mLNPs) respectively and compared with the classic "bleb" structure LNPs (cLNPs). The eLNPs contained higher molar percent of the ionizable lipid and lower molar percent of DSPC and cholesterol. The different lipid organization structures lead to varying mRNA delivery activities in vitro and in vivo. After intramuscular injection, eLNPs remained at the injection site and expressed antigens locally. The resulted immune responses had a very fast onset (higher titer at week 2) and lasted longer and stronger (higher titers at week 8) than other LNPs (cLNPs and mLNPs). We hypothesize that the rapid onset and local expression of antigens by muscle cells in the eLNP groups may be favored by the antigen recognition and presentation process, despite the overall mRNA expression activities was not as high especially in liver and other organ. Our data support that eLNPs are potentially the more suitable delivery system for mRNA vaccine due to their high immunogenicity and low systemic toxicity.

Prevention of prostate cancer metastasis by a CRISPR-delivering nanoplatform for interleukin-30 genome editing

Prostate cancer (PC) is a leading cause of cancer-related deaths in men worldwide. Interleukin-30 (IL-30) is a PC progression driver, and its suppression would be strategic for fighting metastatic disease. Biocompatible lipid nanoparticles (NPs) were loaded with CRISPR-Cas9gRNA to delete the human IL30 (hIL30) gene and functionalized with anti-PSCA-Abs (Cas9hIL30-PSCA NPs). Efficiency of the NPs in targeting IL-30 and the metastatic potential of PC cells was examined in vivo in xenograft models of lung metastasis, and in vitro by using two organ-on-chip (2-OC)-containing 3D spheroids of IL30+ PC-endothelial cell co-cultures in circuit with either lung-mimicking spheroids or bone marrow (BM)-niche-mimicking scaffolds. Cas9hIL30-PSCA NPs demonstrated circulation stability, genome editing efficiency, without off-target effects and organ toxicity. Intravenous injection of three doses/13 days, or five doses/20 days, of NPs in mice bearing circulating PC cells and tumor microemboli substantially hindered lung metastasization. Cas9hIL30-PSCA NPs inhibited PC cell proliferation and expression of IL-30 and metastasis drivers, such as CXCR2, CXCR4, IGF1, L1CAM, METAP2, MMP2, and TNFSF10, whereas CDH1 was upregulated. PC-Lung and PC-BM 2-OCs revealed that Cas9hIL30-PSCA NPs suppressed PC cell release of CXCL2/GROβ, which was associated with intra-metastatic myeloid cell infiltrates, and of DKK1, OPG, and IL-6, which boosted endothelial network formation and cancer cell migration. Development of a patient-tailored nanoplatform for selective CRISPR-mediated IL-30 gene deletion is a clinically valuable tool against PC progression.

Toward understanding lipid reorganization in RNA lipid nanoparticles in acidic environments

The use of lipid nanoparticles (LNPs) for therapeutic RNA delivery has gained significant interest, particularly highlighted by recent milestones such as the approval of Onpattro and two mRNA-based SARS-CoV-2 vaccines. However, despite substantial advancements in this field, our understanding of the structure and internal organization of RNA-LNPs -and their relationship to efficacy, both in vitro and in vivo- remains limited. In this study, we present a coarse-grained molecular dynamics (MD) approach that allows for the simulations of full-size LNPs. By analyzing MD-derived structural characteristics in conjunction with cellular experiments, we investigate the effect of critical parameters, such as pH and composition, on LNP structure and potency. Additionally, we examine the mobility and chemical environment within LNPs at a molecular level. Our findings highlight the significant impact that LNP composition and internal molecular mobility can have on key stages of LNP-based intracellular RNA delivery.

Advances in mRNA LNP-Based Cancer Vaccines: Mechanisms, Formulation Aspects, Challenges, and Future Directions

After the COVID-19 pandemic, mRNA-based vaccines have emerged as a revolutionary technology in immunization and vaccination. These vaccines have shown remarkable efficacy against the virus and opened up avenues for their possible application in other diseases. This has renewed interest and investment in mRNA vaccine research and development, attracting the scientific community to explore all its other applications beyond infectious diseases. Recently, researchers have focused on the possibility of adapting this vaccination approach to cancer immunotherapy. While there is a huge potential, challenges still remain in the design and optimization of the synthetic mRNA molecules and the lipid nanoparticle delivery system required to ensure the adequate elicitation of the immune response and the successful eradication of tumors. This review points out the basic mechanisms of mRNA-LNP vaccines in cancer immunotherapy and recent approaches in mRNA vaccine design. This review displays the current mRNA modifications and lipid nanoparticle components and how these factors affect vaccine efficacy. Furthermore, this review discusses the future directions and clinical applications of mRNA-LNP vaccines in cancer treatment.

Advanced Applications of Nanomaterials in Atherosclerosis Diagnosis and Treatment: Challenges and Future Prospects

Atherosclerosis-induced coronary artery disease is a major cause of cardiovascular mortality. Clinically, conservative treatment strategies for atherosclerosis still focus on lifestyle interventions and the use of lipid-lowering and anticoagulant medications. Despite achieving some therapeutic effects, these approaches are limited by low bioavailability, long intervention periods, and significant side effects. With the advancement of nanotechnology, nanomaterials have demonstrated extraordinary potential in the biomedical field. Their excellent biocompatibility, surface modifiability, and high targeting capability not only enable efficient diagnosis of plaque progression but also allow precise drug delivery within atherosclerotic plaques, significantly enhancing drug bioavailability and reducing systemic side effects. Here, we systematically review the current research progress of nanomaterials in the field of atherosclerosis to summarize not only the types of nanomaterials but also their applications in both the diagnosis and treatment of atherosclerosis. Notably, in the context of plaque therapy, we provide a comprehensive overview of current nanomaterial applications based on their targeted therapeutic systems for different cell types within plaques. Additionally, we address the persistent challenge of clinical translation of nanomaterials by summarizing current issues and providing directions for innovation and improvement in nanomaterial design. Overall, we believe that this review systematically summarizes the applications and challenges of biomedical nanomaterials in atherosclerosis diagnosis and therapy, thereby offering insights and references for the development of therapeutic materials for atherosclerosis.

Optimizing lipid nanoparticles for fetal gene delivery in vitro, ex vivo, and aided with machine learning

There is a clinical need to develop lipid nanoparticles (LNPs) to deliver congenital therapies to the fetus during pregnancy. The aim of these therapies is to restore normal fetal development and prevent irreversible conditions after birth. As a first step, LNPs need to be optimized for transplacental transport, safety on the placental barrier and fetal organs and transfection efficiency. We developed and characterized a library of LNPs of varying compositions and used machine learning (ML) models to delineate the determinants of LNP size and zeta potential. Utilizing different in vitro placental models with the help of a Random Forest algorithm, we could identify the top features driving percentage LNP transport and kinetics at 24 h, out of a total of 18 input features represented by 41 LNP formulations and 48 different transport experiments. We further evaluated the LNPs for safety, placental cell uptake, transfection efficiency in placental trophoblasts and fetal lung fibroblasts. To ensure the integrity of the LNPs following transplacental transport, we screened LNPs for transport and transfection using a high-throughput integrated transport-transfection in vitro model. Finally, we assessed toxicity of the LNPs in a tracheal occlusion fetal lung explant model. LNPs showed little to no toxicity to fetal and placental cells. Immunoglobin G (IgG) orientation on the surface of LNPs, PEGylated lipids, and ionizable lipids had significant effects on placental transport. The Random Forest algorithm identified the top features driving LNPs placental transport percentage and kinetics. Zeta potential emerged in the top driving features. Building on the ML model results, we developed new LNP formulations to further optimize the transport leading to 622 % increase in transport at 24 h versus control LNP formulation. To induce preferential siRNA transfection of fetal lung, we further optimized cationic lipid percentage and the lipid-to-siRNA ratio. Studying LNPs in an integrated placental and fetal lung fibroblasts model showed a strong correlation between zeta potential and fetal lung transfection. Finally, we assessed the toxicity of LNPs in a tracheal occlusion lung explant model. The optimized formulations appeared to be safe on ex vivo fetal lungs as indicated by insignificant changes in apoptosis (Caspase-3) and proliferation (Ki67) markers. In conclusion, we have optimized an LNP formulation that is safe, with high transplacental transport and preferential transfection in fetal lung cells. Our research findings represent an important step toward establishing the safety and effectiveness of LNPs for gene delivery to the fetal organs.

Tetrahydropyrimidine Ionizable Lipids for Efficient mRNA Delivery

Lipid nanoparticles (LNPs) have emerged as an effective and promising technology for messenger RNA (mRNA) delivery, offering a potential solution to physiological barriers and providing an alternative approach to gene therapy without the drawbacks associated with viral delivery. However, efficiently delivering mRNA remains a significant challenge in nucleic acid-based therapies due to the limitations of current LNP platforms in achieving optimal endosomal escape and mRNA release, which largely relies on finding a suitable ionizable lipid. Additionally, the synthesis of these ionizable lipids involves multiple chemical reactions, often making the process time-consuming and difficult to translate. In this study, we employed a facile, catalyst-free, and versatile one-pot multicomponent reaction (MCR) to develop a library of ionizable lipids featuring a pharmacologically significant tetrahydropyrimidine (THP) backbone, tailored for enhanced mRNA delivery. A library of 26 THP ionizable lipids was systematically synthesized in just 3 h and formulated with luciferase mRNA for initial in vitro screening. The THP LNPs exhibited tunable particle sizes, favorable ζ-potentials, and high encapsulation efficiencies. Among them, THP1 demonstrated the highest transfection efficiency both in vitro and in vivo after intramuscular administration, comparable to DLin-MC3-DMA (MC3), a conventional benchmark. Further optimization of THP1 with phospholipids significantly enhanced intramuscular mRNA delivery and showed sustained protein expression in vivo for up to 5 days. More importantly, it demonstrated successful intravenous delivery in a dose-dependent manner with minimal toxicity, as indicated by hematological, histopathological, and proinflammatory cytokine assessments. Furthermore, THP1 LNPs also demonstrated the ability to edit genes in specific liver tissues in a tdTomato transgenic mouse model, highlighting their precision and utility in targeted therapeutic applications. These findings position THP1 LNPs as promising candidates for advancing mRNA-based therapies, with significant implications for clinical translation in vaccine delivery and CRISPR/Cas9-mediated gene editing in the liver.

Machine Learning Elucidates Design Features of Plasmid Deoxyribonucleic Acid Lipid Nanoparticles for Cell Type-Preferential Transfection

To broaden the accessibility of cell and gene therapies, it is essential to develop and optimize nonviral, cell type-preferential gene carriers such as lipid nanoparticles (LNPs). While high-throughput screening (HTS) approaches have proven effective in accelerating LNP discovery, they are often costly, labor-intensive, and do not consistently yield actionable design rules that direct screening efforts toward the most relevant chemical and formulation parameters. In this study, we employed a machine learning (ML) workflow, utilizing well-curated plasmid DNA LNP transfection data sets across six cell types, to extract compositional and chemical insights from HTS studies. Our approach achieved prediction errors averaging between 5 and 10%, depending on the cell type. By applying SHapley Additive exPlanations to our ML models, we uncovered key composition-function relationships that govern cell type-preferential LNP transfection efficiency. Notably, we identified consistent LNP composition parameters that enhance in vitro transfection efficiency across diverse cell types, including a helper lipid molar percentage of charged lipids between 9 and 50% and the inclusion of cationic/zwitterionic helper lipids. Additionally, several parameters were found to modulate cell type-preferentiality, such as the total molar percentage of ionizable and helper lipids, N/P ratio, PEGylated lipid molar percentage of uncharged lipids, and hydrophobicity of the helper lipid. This study leverages HTS of compositionally diverse LNP libraries combined with ML analysis to elucidate the interactions between lipid components in LNP formulations, providing insights that contribute to the design of LNP compositions tailored for cell type-preferential transfection.

Ionizable Cationic Lipids and Helper Lipids Synergistically Contribute to RNA Packing and Protection in Lipid-Based Nanomaterials

Lipid-based nanomaterials are used as a common delivery vehicle for RNA therapeutics. They typically include a formulation containing ionizable cationic lipids, cholesterol, phospholipids, and a small molar fraction of PEGylated lipids. The ionizable cationic lipids are considered a crucial element of the formulation for the way they mediate interactions with the anionic RNA as a function of pH. Here, we show, by means of molecular dynamics simulation of lipid formulations containing two different ionizable cationic lipids (DLinDMA and DLinDAP), that the direct interactions of those lipids with RNA, taken alone, may not be sufficient to determine the level of protection and packaging of mRNA. Our simulations help and highlight how the collective behavior of the lipids in the formulation, which determines the ability to envelop the RNA, and the level of hydration of the lipid-RNA interface may also play a significant role. This allows the drawing of a hypothesis about the experimentally observed differences in the transfection efficiency of the two ionizable cationic lipids.

Comprehensive insights into mechanism of nanotoxicity, assessment methods and regulatory challenges of nanomedicines

Nanomedicine has the potential to transform healthcare by offering targeted therapies, precise diagnostics, and enhanced drug delivery systems. The National Institutes of Health has coined the term "nanomedicine" to describe the use of nanotechnology in biological system monitoring, control, diagnosis, and treatment. Nanomedicine continues to receive increasing interest for the rationalized delivery of therapeutics and pharmaceutical agents to achieve the required response while reducing its side effects. However, as nanotechnology continues to advance, concerns about its potential toxicological effects have also grown. This review explores the current state of nanomedicine, focusing on the types of nanoparticles used and their associated properties that contribute to nanotoxicity. It examines the mechanisms through which nanoparticles exert toxicity, encompassing various cellular and molecular interactions. Furthermore, it discusses the assessment methods employed to evaluate nanotoxicity, encompassing in-vitro and in-vivo models, as well as emerging techniques. The review also addresses the regulatory issues surrounding nanotoxicology, highlighting the challenges in developing standardized guidelines and ensuring the secure translation of nanomedicine into clinical settings. It also explores into the challenges and ethical issues associated with nanotoxicology, as understanding the safety profile of nanoparticles is essential for their effective translation into therapeutic applications.