Microfluidic Synthesis of Highly Potent Limit-size Lipid Nanoparticles for In Vivo Delivery of siRNA

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.

RNA nanomedicine in liver diseases

The remarkable impact of RNA nanomedicine during the COVID-19 pandemic has demonstrated the expansive therapeutic potential of this field in diverse disease contexts. In recent years, RNA nanomedicine targeting the liver has been paradigm-shifting in the management of metabolic diseases such as hyperoxaluria and amyloidosis. RNA nanomedicine has significant potential in the management of liver diseases, where optimal management would benefit from targeted delivery, doses titrated to liver metabolism, and personalized therapy based on the specific site of interest. In this review, we discuss in-depth the different types of RNA and nanocarriers used for liver targeting along with their specific applications in metabolic dysfunction-associated steatotic liver disease, liver fibrosis, and liver cancers. We further highlight the strategies for cell-specific delivery and future perspectives in this field of research with the emergence of small activating RNA, circular RNA, and RNA base editing approaches.

Multiparametric functional characterization of individual lipid nanoparticles using surface-sensitive light-scattering microscopy

The most efficient lipid nanoparticles (LNPs) for gene therapeutics rely on specific lipids that protect the oligonucleotide cargo and aid cellular uptake and subsequent endosomal escape. Yet, the efficacy of current state-of-the-art LNP formulations remains low, a few percent at best. A deeper understanding of how LNP cargo, lipid composition, stoichiometry, size, structure, and pH-induced conformational changes influence their efficiency is therefore necessary for improved design. Given the variability of these properties, preferred screening methods should offer single-particle-resolved multiparametric characterization. In this work, we employ combined surface-sensitive fluorescence and label-free scattering microscopy with single LNP resolution, which when integrated with microfluidics for liquid exchange between media of varying refractive index, enables quantification of LNP size, refractive index, and cargo content. We investigate two LNP formulations that, while similar in size and mRNA content, exhibit differences in functional mRNA delivery. Correlating size with the content of Cy5-labeled mRNA revealed that the cargo scaled with LNP volume for both types of LNPs, while the refractive index varied marginally across LNP size. While this multiparametric fingerprinting alone could not distinguish the two LNP formulations, we use the same experimental platform to show that their difference in fusogenicity to a supporting lipid bilayer under early endosomal conditions (drop in pH from 7.4 to 6.0) correlates with observed differences in in vitro cellular data. This highlights a limitation of the current state-of-the-art toolbox for in situ LNP characterization, which generally focuses on structural properties of suspended LNPs, which may not adequately capture functional performance.

Formation of RNA lipid nanoparticles: an equilibrium process with a liquid intermediate stage

This paper presents evidence that RNA-lipid nanoparticles (LNPs) can be assembled using a slow, thermodynamically controlled process. The lipid mixture used in the Spikevax vaccine was dissolved in 52% (v/v) ethanol and titrated into a solution containing tRNA. The titration was conducted using an isothermal titration calorimeter (ITC) and consisted of 40 injections with enough time between each injection so that equilibrium was reached before the next injection. Liquid phase separation occurred where the RNA-lipid complex had a lipid amine to RNA phosphate (N/P) ratio around 1 : 1. The liquid droplets had a mean hydrodynamic diameter of 1020 ± 150 nm measured using dynamic light scattering (DLS) and were clearly observable by light microscopy. At a N/P ratio of 6 : 1 the LNPs were 109 ± 0 nm and LNPs were observed using transmission electron microscopy. The mechanism for conversion of the liquid intermediate into LNPs is likely to be spontaneous emulsification driven by negative surface tension. This equilibrium process for making RNA-LNPs is very different from current manufacture strategies using rapid single step mixing in a microfluidic device. This approach provides a low shear alternative process that could be adapted to a stirred tank.

Prediction and control of the particle size of polyethylene glycol-free lipid nanoparticles using a design of experiment

Rigorous control of the properties of lipid nanoparticles (LNPs) such as the particle size, polydispersity index (PdI), ζ-potential, and encapsulation efficiency of small interfering RNA (siRNA) with good reproducibility is important for LNP-based siRNA delivery. In this study, polyethylene glycol (PEG)-free LNPs containing a dioleoylglycerophosphate-diethylenediamine conjugate (DOP-DEDA), which is a pH-responsive lipid derivative, were prepared by using a microfluidic technology to construct a predictive model for particle size control using the design of experiment (DoE). PEG-free DOP-DEDA-based LNPs (DEDA LNPs) encapsulating siRNA, which were prepared by using a microfluidic technology, formed uniform particles and triggered effective gene silencing. The effects of the preparation conditions such as the total flow rate, lipid concentration, and lipid solution ratio on the LNP properties were investigated, and results indicated that the lipid solution ratio is the most important parameter to control the particle size and PdI of DEDA LNPs. Conversely, the ζ-potential and siRNA encapsulation efficiency of DEDA LNPs were not affected by the preparation conditions. The predictive model constructed using the DoE data showed that the particle size of the prepared DEDA LNPs was consistent with that predicted. Therefore, our approach using the DoE will contribute to the rigorous prediction and control of the particle size of PEG-free LNPs for nucleic acid delivery.

A Post-Encapsulation Method for the Preparation of mRNA-LNPs via the Nucleic Acid-Bridged Fusion of mRNA-Free LNPs

Lipid nanoparticles with encapsulated mRNA (mRNA-LNPs) have become key modalities for personalized medicines and RNA vaccines. Once the platform technology is established, the mRNA-LNPs could be applicable to a variety of protein-based therapeutic strategies. A post-encapsulation method, in which the mRNA solution is incubated with preformed mRNA-free LNPs to prepare the mRNA-LNPs, would accelerate the development of RNA-based therapeutics since even nonexperts could manufacture the mRNA-LNPs. In this study, we describe that the post-encapsulation of mRNA into mRNA-free LNPs is accompanied by "nucleic acid-bridged fusion" of them. The adsorption of mRNA onto mRNA-free LNPs via electrostatic interactions and the internalization of mRNA into the LNPs via particle-to-particle fusion are two steps that occur at different levels of pH. To complete post-encapsulation using only one-step mixing, the pH must be controlled within a limited region where both processes occur simultaneously. The size of the mRNA-free LNPs determines the effectiveness of mRNA loading.

From Basic to Breakthroughs: The Journey of Microfluidic Devices in Hydrogel Droplet Generation

Hydrogel particles are essential in biological applications because of their distinctive capacity to retain water and encapsulate active molecules within their three-dimensional structure. Typical particle sizes range from nanometers (10-500 nm) to micrometers (1-500 µm), depending on the specific application and method of preparation. These characteristics render them optimal carriers for the administration of active compounds, facilitating the regulated and prolonged release of pharmaceuticals, including anticancer agents, antibiotics, and therapeutic proteins. Hydrogel particles can exhibit various morphologies, including spherical, rod-shaped, disk-shaped, and core-shell structures. Each shape offers distinct advantages, such as improved circulation time, targeted drug delivery, or enhanced cellular uptake. Additionally, hydrogel particles can be engineered to respond to various stimuli, such as temperature, pH, light, magnetic fields, and biochemical signals. Furthermore, their biocompatibility and capacity to acclimate to many biological conditions make them appropriate for sophisticated applications, including gene treatments, tissue regeneration, and cell therapies. Microfluidics has transformed the creation of hydrogel particles, providing precise control over their dimensions, morphology, and stability. This technique facilitates reproducible and highly efficient production, reducing reagent waste and optimizing drug encapsulation. The integration of microfluidics with hydrogels provides opportunities for the advancement of creative and effective solutions in contemporary medicine.

Nanoparticle delivery of a prodrug-activating bacterial enzyme leads to anti-tumor responses

Most cancer patients diagnosed with late-stage head and neck squamous cell carcinoma are treated with chemoradiotherapy, which can lead to toxicity. One potential alternative is tumor-limited conversion of a prodrug into its cytotoxic form. We reason this could be achieved by transient and tumor-specific expression of purine nucleoside phosphorylase (PNP), an Escherichia coli enzyme that converts fludarabine into 2-fluoroadenine, a potent cytotoxic drug. To efficiently express bacterial PNP in tumors, we evaluate 44 chemically distinct lipid nanoparticles (LNPs) using species-agnostic DNA barcoding in tumor-bearing mice. Our lead LNP, designated LNP intratumoral (LNPIT), delivers mRNA that leads to PNP expression in vivo. Additionally, in tumor cells transfected with LNPIT, we observe upregulated pathways related to RNA and protein metabolism, providing insight into the tumor cell response to LNPs in vivo. When mice are treated with LNPIT-PNP, then subsequently given fludarabine phosphate, we observe anti-tumor responses. These data are consistent with an approach in which LNP-mRNA expression of a bacterial enzyme activates a prodrug in solid tumors.

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.

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.

Recent advances in functional lipid-based nanomedicines as drug carriers for organ-specific delivery

Lipid-based nanoparticles have emerged as promising drug delivery systems for a wide range of therapeutic agents, including plasmids, mRNA, and proteins. However, these nanoparticles still encounter various challenges in drug delivery, including drug leakage, poor solubility, and inadequate target specificity. In this comprehensive review, we present an in-depth investigation of four distinct drug delivery methods: liposomes, lipid nanoparticle formulations, solid lipid nanoparticles, and nanoemulsions. Moreover, we explore recent advances in lipid-based nanomedicines (LBNs) for organ-specific delivery, employing ligand-functionalized particles that specifically target receptors in desired organs. Through this strategy, LBNs enable direct and efficient drug delivery to the intended organs, leading to superior DNA or mRNA expression outcomes compared to conventional approaches. Importantly, the development of novel ligands and their judicious combination holds promise for minimizing the side effects associated with nonspecific drug delivery. By leveraging the unique properties of lipid-based nanoparticles and optimizing their design, researchers can overcome the limitations associated with current drug delivery systems. In this review, we aim to provide valuable insights into the advancements, challenges, and future directions of lipid-based nanoparticles in the field of drug delivery, paving the way for enhanced therapeutic strategies with improved efficacy and reduced adverse effects.

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.

Glucocorticoid pre-administration improves LNP-mRNA mediated protein replacement and genome editing therapies

Lipid nanoparticles (LNPs) are among the most promising non-viral mRNA delivery systems for gene therapeutic applications. However, the in vivo delivery of LNP-mRNA remains challenging due to multiple intrinsic barriers that hinder LNPs from reaching their target cells. In this study, we sought to enhance LNP delivery by manipulating intrinsic regulatory mechanisms involved in their metabolism. We demonstrated that activation of the glucocorticoid pathway significantly increased the systemic delivery of LNP-mRNA in both mice and monkeys, achieving up to a fourfold improvement. This enhancement was primarily attributed to the glucocorticoid-mediated inhibition of macrophage phagocytosis in circulation and the liver, which resulted in higher LNP accumulation in hepatocytes. Consequently, glucocorticoid activation improved the therapeutic efficacy of LNP-based protein replacement and CRISPR/Cas9 genome editing therapies. Together, these findings establish a practical strategy to enhance the systemic delivery of RNA-based protein replacement and genome editing therapeutics, highlighting the potential of manipulating endogenous mechanisms to optimize exogenous gene delivery.

Overview on LNP-mRNA encapsulation unit operation: Mixing technologies, scalability, and influence of formulation & process parameters on physico-chemical characteristics

Nanoparticles carrying active drug substances have been used since the 70's and have undergone numerous improvements since then. Nowadays, the latest generation of nanoparticles, called lipid nanoparticles (LNPs), is used for different applications such as vaccines and cancer treatments and offer a versatile approach to delivering genetic materials like RNA. LNPs are non-viral delivery vehicles obtained by the self-assembly of lipids during the rapid mixing of an aqueous phase containing mRNA with an organic phase containing lipids. During this process, mRNA is encapsulated within the LNP due to electrostatic interaction with an ionizable lipid. Different methods to produce LNPs are described in the literature and, as of now, continuous methods are mostly used to produce LNP-encapsulated mRNA (LNP-mRNA). T-shaped mixers are commonly used to produce mRNA-LNPs. This technology can operate at two different scales: microfluidic chips which can range from tens to hundreds of microns in size, and millimetric tubing for production scale up. This review intends to describe LNP-mRNA characteristics and their production modes with a special focus on the challenges related to the mixing quality, especially during scale-up.

A synthetic model of bioinspired liposomes to study cancer-cell derived extracellular vesicles and their uptake by recipient cells

Extracellular vesicles (EVs) are secreted by most cell types and play a central role in cell-cell communication. These naturally occurring nanoparticles have been particularly implicated in cancer, but EV heterogeneity and lengthy isolation methods with low yield make them difficult to study. To circumvent the challenges in EV research, we aimed to develop a unique synthetic model by engineering bioinspired liposomes to study EV properties and their impact on cellular uptake. We produced EV-like liposomes mimicking the physicochemical properties as cancer EVs. First, using a panel of cancer and non-cancer cell lines, small EVs were isolated by ultracentrifugation and characterized by dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). Cancer EVs ranged in mean size from 107.9 to 161 nm by NTA, hydrodynamic diameter from 152 to 355 nm by DLS, with a zeta potential ranging from - 25 to -6 mV. EV markers TSG101 and CD81 were positive on all EVs. Using a microfluidics bottom-up approach, liposomes were produced using the nanoprecipitation method adapted to micromixers developed by our group. A library of liposome formulations was created that mimicked the ranges of size (90-222 nm) and zeta potential (anionic [-47 mV] to neutral [-1 mV]) at a production throughput of up to 41 mL/h and yielding a concentration of 1 × 1012 particles per mL. EV size and zeta potential were reproduced by controlling the flow conditions and lipid composition set by a statistical model based on the response surface methodology. The model was fairly accurate with an R-squared > 70% for both parameters between the targeted EV and the obtained liposomes. Finally, the internalization of fluorescently labeled EV-like liposomes was assessed by confocal microscopy and flow cytometry, and correlated with decreasing liposome size and less negative zeta potential, providing insights into the effects of key EV physicochemical properties. Our data demonstrated that liposomes can be used as a powerful synthetic model of EVs. By mimicking cancer cell-derived EV properties, the effects on cellular internalization can be assessed individually and in combination. Taken together, we present a novel system that can accelerate research on the effects of EVs in cancer models.

Landscape of small nucleic acid therapeutics: moving from the bench to the clinic as next-generation medicines

The ability of small nucleic acids to modulate gene expression via a range of processes has been widely explored. Compared with conventional treatments, small nucleic acid therapeutics have the potential to achieve long-lasting or even curative effects via gene editing. As a result of recent technological advances, efficient small nucleic acid delivery for therapeutic and biomedical applications has been achieved, accelerating their clinical translation. Here, we review the increasing number of small nucleic acid therapeutic classes and the most common chemical modifications and delivery platforms. We also discuss the key advances in the design, development and therapeutic application of each delivery platform. Furthermore, this review presents comprehensive profiles of currently approved small nucleic acid drugs, including 11 antisense oligonucleotides (ASOs), 2 aptamers and 6 siRNA drugs, summarizing their modifications, disease-specific mechanisms of action and delivery strategies. Other candidates whose clinical trial status has been recorded and updated are also discussed. We also consider strategic issues such as important safety considerations, novel vectors and hurdles for translating academic breakthroughs to the clinic. Small nucleic acid therapeutics have produced favorable results in clinical trials and have the potential to address previously "undruggable" targets, suggesting that they could be useful for guiding the development of additional clinical candidates.

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.

A review of RNA nanoparticles for drug/gene/protein delivery in advanced therapies: Current state and future prospects

Nanotechnology involves the utilization of materials with exceptional properties at the nanoscale. Over the past few years, nanotechnologies have demonstrated significant potential in improving human health, particularly in medical treatments. The self-assembly characteristic of RNA is a highly effective method for designing and constructing nanostructures using a combination of biological, chemical, and physical techniques from different fields. There is great potential for the application of RNA nanotechnology in therapeutics. This review explores various nano-based drug delivery systems and their unique features through the impressive progress of the RNA field and their significant therapeutic promises due to their unique performance in the COVID-19 pandemic. However, a significant hurdle in fully harnessing the power of RNA drugs lies in effectively delivering RNA to precise organs and tissues, a critical factor for achieving therapeutic effectiveness, minimizing side effects, and optimizing treatment outcomes. There have been many efforts to pursue targeting, but the clinical translation of RNA drugs has been hindered by the lack of clear guidelines and shared understanding. A comprehensive understanding of various principles is essential to develop vaccines using nucleic acids and nanomedicine successfully. These include mechanisms of immune responses, functions of nucleic acids, nanotechnology, and vaccinations. Regarding this matter, the aim of this review is to revisit the fundamental principles of the immune system's function, vaccination, nanotechnology, and drug delivery in relation to the creation and manufacturing of vaccines utilizing nanotechnology and nucleic acids. RNA drugs have demonstrated significant potential in treating a wide range of diseases in both clinical and preclinical research. One of the reasons is their capacity to regulate gene expression and manage protein production efficiently. Different methods, like modifying chemicals, connecting ligands, and utilizing nanotechnology, have been essential in enabling the effective use of RNA-based treatments in medical environments. The article reviews stimuli-responsive nanotechnologies for RNA delivery and their potential in RNA medicines. It emphasizes the notable benefits of these technologies in improving the effectiveness of RNA and targeting specific cells and organs. This review offers a comprehensive analysis of different RNA drugs and how they work to produce therapeutic benefits. Recent progress in using RNA-based drugs, especially mRNA treatments, has shown that targeted delivery methods work well in medical treatments.

Navigating Tumor Microenvironment Barriers with Nanotherapeutic Strategies for Targeting Metastasis

Therapeutic strategy for efficiently targeting cancer cells needs an in-depth understanding of the cellular and molecular interplay in the tumor microenvironment (TME). TME comprises heterogeneous cells clustered together to translate tumor initiation, migration, and proliferation. The TME mainly comprises proliferating tumor cells, stromal cells, blood vessels, lymphatic vessels, cancer-associated fibroblasts (CAFs), extracellular matrix (ECM), and cancer stem cells (CSC). The heterogeneity and genetic evolution of metastatic tumors can substantially impact the clinical effectiveness of therapeutic agents. Therefore, the therapeutic strategy shall target TME of all metastatic stages. Since the advent of nanotechnology, smart drug delivery strategies are employed to deliver effective drug formulations directly into tumors, ensuring controlled and sustained therapeutic efficacy. The state-of-the-art nano-drug delivery systems are shown to have innocuous modes of action in targeting the metastatic players of TME. Therefore, this review provides insight into the mechanism of cancer metastasis involving invasion, intravasation, systemic transport of circulating tumor cells (CTCs), extravasation, metastatic colonization, and angiogenesis. Further, the novel perspectives associated with current nanotherapeutic strategies are highlighted on different stages of metastasis.

Preclinical testing of antiviral siRNA therapeutics delivered in lipid nanoparticles in animal models - a comprehensive review

The advent of RNA interference (RNAi) technology through the use of short-interfering RNAs (siRNAs) represents a paradigm shift in the fight against viral infections. siRNAs, with their ability to directly target and silence specific posttranscriptional genes, offer a novel mechanism of action distinct from that of traditional pharmacotherapeutics. This review delves into the growing field of siRNA therapeutics against viral infections, highlighting their critical role in contemporary antiviral strategies. Importantly, this review will solely focus on the use of lipid nanoparticles (LNPs) as the ideal antiviral siRNA delivery agent for use in vivo. We discuss the challenges of siRNA delivery and how LNPs have emerged as a pivotal solution to enhance antiviral efficacy. Specifically, this review focuses on work that have preclinically tested LNP formulated siRNA on virus infection animal models. Since the COVID-19 pandemic, we have witnessed a resurgence in the field of RNA-based therapies, including siRNAs against viruses including, SARS-CoV-2. Notably, the critical importance of LNPs as the ideal carrier for precious 'RNA cargo' can no longer be ignored with the advent of mRNA-LNP based COVID-19 vaccines. siRNA-based therapeutics represents an emerging class of anti-infective drugs with a foreseeable future as suitable antiviral agents.

Manufacturing of Liposomes Using a Stainless-Steel Microfluidic Device: An Investigation into Design of Experiments

Liposomes are highly beneficial nanocarrier systems due to their biocompatibility, low toxicity, and exceptional inclusiveness, which lead to improved drug bioavailability. For biological applications, accurate control over these nanoparticles' mean size and size distribution is essential. Micromixers facilitate the continuous production of liposomes, enhancing the precision of size regulation and reproducibility. In this research, the performance of a stainless steel 316L micromixer was evaluated by using COMSOL Multiphysics simulations. The liposomes were precisely optimized using design of experiments techniques in a microfluidic setup, and then dexamethasone sodium phosphate (DSP) was successfully encapsulated in liposome nanoparticles. The physicochemical characteristics of liposomes, such as their ζ-potential, size, DSP loading capacity, encapsulation efficiency, and drug release, were assessed. Transmission electron microscopy and dynamic light scattering analysis were used to examine the structures of the liposomes. The drug release kinetics study was conducted to analyze the drug delivery system, and the Higuchi equation was determined to be the most suitable equation. The microfluidic chip was shown to be capable of creating small-sized liposomes with a size as small as 130 nm, exhibiting monodispersed characteristics and low polydispersity liposome populations.

The use of nanocarriers in treating Batten disease: A systematic review

The neuronal ceroid lipofuscinoses, commonly known as Batten disease, are a group of lysosomal storage disorders affecting children. There is extensive central nervous system and retinal degeneration, resulting in seizures, vision loss and a progressive cognitive and motor decline. Enzyme replacement and gene therapies are being developed, and mRNA and oligonucleotide therapies are more recently being considered. Overcoming the challenges of the blood-brain barrier and blood-ocular barrier is crucial for effectively targeting the brain and eye, whatever the therapeutic approach. Nanoparticles and extracellular vesicles are small carriers that can encapsulate a cargo and pass through these cell barriers. They have been investigated as drug carriers for other pathologies and could be a promising treatment strategy for Batten disease. Their use in gene, enzyme, or mRNA replacement therapy of all lysosomal storage disorders, including Mucopolysaccharidoses, Niemann-Pick diseases, and Fabry disease, is investigated in this systematic review. Different nanocarriers can efficiently target the lysosome and cross the barriers into the brain and eyes. This supports continued exploration of nanocarriers as potential future treatment options for Batten disease.

A study on the treatment of rheumatoid arthritis with lipid nanoparticles containing mRNA encoding heat shock protein 10

In order to delay the progression of Rheumatoid Arthritis (RA) in patients, and to prevent further teratogenesis and irreversible bone erosion through drug intervention in the early stages of inflammation, this experiment used the mRNA encoding heat shock protein 10 (HSP10) (H-mRNA) as the main therapeutic drug and used Microfluidics technology to prepare lipid nanoparticles (LNP) (H-mRNA LNPs) containing H-mRNA, and the surface of H-mRNA-LNPs was modified using heparin particals to obtain the final formulation H-mRNA-LNPs @ heparin/ Protamine. Through the sequence modification and effect evaluation of H-mRNA, we explored the formulation screening, physical characterization, cytotoxicity in vitro, distribution in vivo, pharmacodynamics in vivo, and safety in vivo of the prepared lipid nanoparticles, which proved that this nano-preparation had good anti Rheumatoid Arthritis effects, and conducted a preliminary exploration for the application of nucleic acid drugs in the treatment of diseases outside of tumors. This research would provide new ideas for the treatment of RA.

Microfluidics Based Particle and Droplet Generation for Gene and Drug Delivery Approaches

Microfluidics-based droplets have emerged as a powerful technology for biomedical research, offering precise control over droplet size and structure, optimal mixing of solutions, and prevention of cross-contamination. It is a major branch of microfluidic technology with applications in diagnostic testing, imaging, separation, and gene amplification. This review discusses the different aspects of microfluidic devices, droplet generation techniques, droplet types, and the production of micro/nano particles, along with their advantages and limitations. Passive and active methods for droplet formation are discussed, as well as the manipulation of droplet shape and content. This review also highlights the potential applications of droplet microfluidics in tissue engineering, cancer therapy, and drug delivery systems. The use of microfluidics in the production of lipid nanoparticles and polymeric microparticles is also presented, with emphasis on their potential in drug delivery and biomedical research. Finally, the contributions of microfluidics to vaccines, gene therapy, personalized medicine, and future perspectives are discussed, emphasizing the need for continuous innovation and integration with other technologies, such as AI and wearable devices, to further enhance its potential in personalized medicine and drug delivery. However, it is also noted that challenges in commercialization and widespread adoption still need to be addressed.

A journey into siRNA therapeutics development: A focus on Pharmacokinetics and Pharmacodynamics

siRNA therapeutics are emerging novel modalities targeting highly specific mRNA via RNA interference mechanism. Its unique pharmacokinetics (PKs) and pharmacodynamics (PDs) are significant challenges for clinical use. Furthermore, naked siRNA is a highly soluble macromolecule with a negative charge, making plasma membrane penetration a significant hurdle. It is also vulnerable to nuclease degradation. Therefore, advanced formulation technologies, such as lipid nanoparticles and N-acetylgalactosamine conjugation, have been developed and are now used in clinical practice to enhance target organ delivery and stability. The innate complex biological mechanisms of siRNA, along with its formulation, are major determinants of the PK/PD characteristics of siRNA products. To systematically and quantitatively understand these characteristics, it is essential to develop and utilize quantitative PK/PD models for siRNA therapeutics. In this review, the effects of formulation on the PKs and PK/PD models of approved siRNA products were presented, highlighting the importance of selecting appropriate biomarkers and understanding formulation, PKs, and PDs for quantitative interpreting the relationship between plasma concentration, organ concentration, biomarkers, and efficacy.

Robust genome and cell engineering via in vitro and in situ circularized RNAs

Circularization can improve RNA persistence, yet simple and scalable approaches to achieve this are lacking. Here we report two methods that facilitate the pursuit of circular RNAs (cRNAs): cRNAs developed via in vitro circularization using group II introns, and cRNAs developed via in-cell circularization by the ubiquitously expressed RtcB protein. We also report simple purification protocols that enable high cRNA yields (40-75%) while maintaining low immune responses. These methods and protocols facilitate a broad range of applications in stem cell engineering as well as robust genome and epigenome targeting via zinc finger proteins and CRISPR-Cas9. Notably, cRNAs bearing the encephalomyocarditis internal ribosome entry enabled robust expression and persistence compared with linear capped RNAs in cardiomyocytes and neurons, which highlights the utility of cRNAs in these non-dividing cells. We also describe genome targeting via deimmunized Cas9 delivered as cRNA and a long-range multiplexed protein engineering methodology for the combinatorial screening of deimmunized protein variants that enables compatibility between persistence of expression and immunogenicity in cRNA-delivered proteins. The cRNA toolset will aid research and the development of therapeutics.

Process Optimization of Charge-Reversible Lipid Nanoparticles for Cytosolic Protein Delivery Using the Design-of-Experiment Approach

This study aimed to elucidate the manufacturing process parameters with optimal quality characteristics of protein-encapsulated dioleoylglycerophosphate-diethylenediamine (DOP-DEDA)-based lipid nanoparticles (LNPs) for intracellular protein drug delivery. DOP-DEDA is a pH-responsive and charge-reversible lipid for intracellular cargo delivery. In this study, bovine serum albumin (BSA) was used as a weakly acidic protein model, and LNPs were prepared using microfluidic technology, which has many advantages for practical applications. BSA-encapsulated DOP-DEDA-based LNPs showed pH-responsive charge reversibility and excellent quality characteristics for the intracellular delivery of proteins. A process optimization study was conducted by applying the Box-Behnken design in a design-of-experiment approach. The particle size, ζ-potential, and encapsulation efficiency were evaluated in response to the total flow rate, lipid concentration, and lipid solution ratio. The lipid solution ratio and total flow rate significantly affected the particle size and encapsulation efficiency, respectively. On the contrary, none of the process parameters affected the ζ-potential. Moreover, a map of the predicted values was constructed for the particle size and encapsulation efficiency using a multiple regression equation. In the predicted particle size range of 77-215 nm and encapsulation efficiency of 14-35%, the observed values were close to the predicted values, and 100-nm LNPs were reproduced with an encapsulation efficiency of 27%. Therefore, manufacturing process parameters were established to obtain protein-encapsulated DOP-DEDA-based LNPs with optimal quality characteristics.

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.

Targeted lipid nanoparticles distributed in hydrogel treat osteoarthritis by modulating cholesterol metabolism and promoting endogenous cartilage regeneration

Osteoarthritis (OA) is the most common disease in aging joints and has characteristics of cartilage destruction and inflammation. It is currently considered a metabolic disease, and the CH25H-CYP7B1-RORα axis of cholesterol metabolism in chondrocytes plays a crucial catabolic regulatory role in its pathogenesis. Targeting of this axis in chondrocytes may provide a therapeutic approach for OA treatment. Here, in this study, we propose to use a combination of stem cell-recruiting hydrogels and lipid nanoparticles (LNPs) that modulate cholesterol metabolism to jointly promote a regenerative microenvironment. Specifically, we first developed an injectable, bioactive hydrogel composed of self-assembling peptide nanofibers that recruits endogenous synovial stem cells (SMSCs) and promotes their chondrogenic differentiation. At the same time, LNPs that regulate cholesterol metabolism are incorporated into the hydrogel and slowly released, thereby improving the inflammatory environment of OA. Enhancements were noted in the inflammatory conditions associated with OA, alongside the successful attraction of mesenchymal stem cells (MSCs) from the synovial membrane. These cells were then observed to differentiate into chondrocytes, contributing to effective cartilage restoration and chondrocyte regeneration, thereby offering a promising approach for OA treatment. In summary, this approach provides a feasible siRNA-based therapeutic option, offering a potential nonsurgical solution for treatment of OA.

Fabrication of Biomimetic Hybrid Liposomes via Microfluidic Technology: Homotypic Targeting and Antitumor Efficacy Studies in Glioma Cells

Introduction

The treatment of glioblastoma is hindered by the blood-brain barrier (BBB) and rapid drug clearance by the immune system. To address these challenges, we propose a novel drug delivery system using liposomes modified with cell membrane fragments. These modified liposomes can evade the immune system, cross the BBB, and accumulate in tumor tissue through homotypic targeting, thereby delivering drugs like paclitaxel and carboplatin more effectively.

Methods

In this work, the hybrid liposomes were synthesized using microfluidics and integrating 3D printing to produce the microfluidic devices. In vitro, we explored the homotypic targeting capability, BBB passing ability, and therapeutic efficacy of paclitaxel and carboplatin.

Results

The production of hybrid liposomes by microfluidics has been key to creating high-quality biomimetic nanoparticles, and the integration of 3D printing has simplified the production of microfluidic devices, making the process more efficient and economical. In vitro experiments have shown that these drug-loaded biomimetic hybrid liposomes are able to reach the homotypic target, cross the BBB, and maintain the efficacy of paclitaxel and carboplatin.

Conclusions

The development of biomimetic hybrid liposomes represents a promising approach for the treatment of glioblastoma. By combining the advantages of liposomal drug delivery with the stealth properties and targeting capabilities of cell membrane fragments, these nanoparticles can potentially overcome the challenges associated with traditional therapies.

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.

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.

Nano-encapsulation of drugs to target hepatic stellate cells: Toward precision treatments of liver fibrosis

Liver fibrosis is characterized by excessive extracellular matrix (ECM) deposition triggered by hepatic stellate cells (HSCs). As central players in fibrosis progression, HSCs are the most important therapeutic targets for antifibrotic therapy. However, owing to the limitations of systemic drug administration, there is still no suitable and effective clinical treatment. In recent years, nanosystems have demonstrated expansive therapeutic potential and evolved into a clinical modality. In liver fibrosis, nanosystems have undergone a paradigm shift from targeting the whole liver to locally targeted modifying processes. Nanomedicine delivered to HSCs has significant potential in managing liver fibrosis, where optimal management would benefit from targeted delivery, personalized therapy based on the specific site of interest, and minor side effects. In this review, we present a brief overview of the role of HSCs in the pathogenesis of liver fibrosis, summarize the different types of nanocarriers and their specific delivery applications in liver fibrosis, and highlight the biological barriers associated with the use of nanosystems to target HSCs and approaches available to solve this issue. We further discuss in-depth all the molecular target receptors overexpressed during HSC activation in liver fibrosis and their corresponding ligands that have been used for drug or gene delivery targeting HSCs.

Albumin nanoparticles are a promising drug delivery system in dentistry

Periodontal infection is a long-lasting inflammatory condition caused by the growth and development of an abnormal and harmful community of microorganisms. This destructive illness leads to the loss of the tissues that support the teeth, degradation of the bone surrounding the teeth, and eventually tooth loss. To treat oral infections, it is necessary to use nonsurgical methods such as antibiotics. However, the indiscriminate and incorrect use of antibiotics results in drug resistance. Among these alternate therapeutic options, using nanoparticles to treat infectious dental disease was particularly significant. Consequently, researchers have worked to develop an effective and satisfactory drug delivery method for treating periodontal and dental illnesses. Albumin nanoparticles serve a considerable function as carriers in the drug delivery of chemical and biomolecular medications, such as anticancer treatments; they have several advantages, including biocompatibility and biodegradability, and they are well-tolerated with no adverse effects. Albumin nanoparticles have several benefits over other nanomaterials. Protein nanocarriers provide advantages such as biocompatibility, biodegradability, reduced immunogenicity, and lower cytotoxicity. Furthermore, this nanoparticle demonstrated significant intrinsic antibacterial properties without being loaded with antibiotic medicines. As a medication and antibacterial nanoparticle delivery method, albumin nanoparticles have substantial applications in periodontal and dental infectious disorders such as periodontal infection, apical periodontitis, and peri-implantitis. As a result, in this article, we studied the usage of albumin nanoparticles in dental disorders.

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.

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.

Design of charge converting lipid nanoparticles via a microfluidic coating technique

It was the aim of this study to design charge converting lipid nanoparticles (LNP) via a microfluidic mixing technique used for the preparation and coating of LNP. LNP consisting of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), cholesterol, N-(carbonyl-methoxypolyethyleneglycol-2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (MPEG-2000-DSPE), and various cationic surfactants were prepared at diverging flow rate ratios (FRR) via microfluidic mixing. Utilizing a second chip in the microfluidic set-up, LNP were coated with polyoxyethylene (9) nonylphenol monophosphate ester (PNPP). LNP were examined for their stability in different physiologically relevant media as well as for hemolytic and cytotoxic effects. Finally, phosphate release and charge conversion of PNPP-coated LNP were evaluated after incubation with alkaline phosphatase and on Caco2-cells. LNP produced at an FRR of 5:1 exhibited a size between 80 and 150 nm and a positive zeta potential. Coating with PNPP within the second chip led to LNP exhibiting a negative zeta potential. After incubation with 1 U/ml alkaline phosphatase for 4 h, zeta potential of the LNP containing 1,2-dioleoyloxy-3-trimethylammonium-propane chloride (DOTAP) as cationic component shifted from - 35 mV to approximately + 5 mV. LNP prepared with other cationic surfactants remained slightly negative after enzymatic phosphate cleavage. Manufacturing of LNP containing PNPP and DOTAP via connection of two chips in a microfluidic instrument proves to show efficient change in zeta potential from negative to positive after incubation with alkaline phosphatase.

A Novel Acoustic Modulation of Oscillating Thin Elastic Membrane for Enhanced Streaming in Microfluidics and Nanoscale Liposome Production

Liposomes are widely utilized in therapeutic nanosystems as promising drug carriers for cancer treatment, which requires a meticulous synthesis approach to control the nanoprecipitation process. Acoustofluidic platforms offer a favorable synthesis environment by providing robust agitation and rapid mixing. Here, a novel high-throughput acoustofluidic micromixer is presented for a solvent and solvent-free synthesis of ultra-small and size-tunable liposomes. The size-tunability is achieved by incorporating glycerol as a new technique into the synthesis reagents, serving as a size regulator. The proposed device utilizes the synergistic effects of vibrating trapped microbubbles and an oscillating thin elastic membrane to generate vigorous acoustic microstreaming. The working principle and mixing mechanism of the device are explored numerically and experimentally. The platform exhibits remarkable mixing efficacy for aqueous and viscous solutions at flow rates up to 8000 µL/h, which makes it unique for high-throughput liposome formation and preventing aggregation. As a proof of concept, this study investigates the impact of phospholipid type and concentration, flow rate, and glycerol on the size and size distribution of liposomes. The results reveal a significant size reduction, from ≈900 nm to 40 nm, achieved by merely introducing 75% glycerol into the synthesis reagents, highlighting an innovative approach toward size-tunable liposomes.

Diffusive micromixing combined with dynamic in situ laser scattering allows shedding light on lipid nanoparticle precipitation

Pharmaceutical formulations are increasingly based on drug nanoparticles or carrier nanoparticles encapsulating drugs or mRNA molecules. Sizes and monodispersity of the nanoparticles regulate bioavailability, pharmacokinetics and pharmacology. Microfluidic mixers promise unique conditions for their continuous preparation. A novel microfluidic antisolvent precipitation device was realized by two-photon-polymerization with a mixing channel in which the organic phase formed a sheet with a homogeneous thickness of down to 7 μm completely wrapped in the aqueous phase. Homogeneous diffusion through the sheet accelerates mixing. Optical access was implemented to allow in-situ dynamic light scattering. By centering the thin sheet in the microchannel cross-section, two important requirements are met. On the one hand, the organic phase never reaches the channel walls, avoiding fouling and unstable flow conditions. On the other hand, in the sheet positioned at the maximum of the parabolic flow profile the nanoparticle velocities are homogenized which enables flow-compensated Dynamic Light Scattering (flowDLS). These unique features allowed in-situ particle size determination for the first time. Monitoring of lipid nanoparticle precipitation was demonstrated for different rates of solvent and antisolvent flows. This breakthrough innovation will not only enable feedback control of nanoparticle production but also will provide new insights into the dynamics of nanoparticle precipitation.

SARS-CoV2 mRNA vaccine intravenous administration induces myocarditis in chronic inflammation

The current COVID-19 mRNA vaccines were developed and applied for pandemic-emergent conditions. These vaccines use a small piece of the virus's genetic material (mRNA) to stimulate an immune response against COVID-19. However, their potential effects on individuals with chronic inflammatory conditions and vaccination routes remain questionable. Therefore, we investigated the effects of mRNA vaccines in a mouse model of chronic inflammation, focusing on their cardiac toxicity and immunogenicity dependent on the injection route. mRNA vaccine intravenous administration with or without chronic inflammation exacerbated cardiac pericarditis and myocarditis; immunization induced mild inflammation and inflammatory cytokine IL-1beta and IL-6 production in the heart. Further, IV mRNA vaccination induced cardiac damage in LPS chronic inflammation, particularly serum troponin I (TnI), which dramatically increased. IV vaccine administration may induce more cardiotoxicity in chronic inflammation. These findings highlight the need for further research to understand the underlying mechanisms of mRNA vaccines with chronic inflammatory conditions dependent on injection routes.

Microfluidic technologies for lipid vesicle generation

Encapsulating biological and non-biological materials in lipid vesicles presents significant potential in both industrial and academic settings. When smaller than 100 nm, lipid vesicles and lipid nanoparticles are ideal vehicles for drug delivery, facilitating the delivery of payloads, improving pharmacokinetics, and reducing the off-target effects of therapeutics. When larger than 1 μm, vesicles are useful as model membranes for biophysical studies, as synthetic cell chassis, as bio-inspired supramolecular devices, and as the basis of protocells to explore the origin of life. As applications of lipid vesicles gain prominence in the fields of nanomedicine, biotechnology, and synthetic biology, there is a demand for advanced technologies for their controlled construction, with microfluidic methods at the forefront of these developments. Compared to conventional bulk methods, emerging microfluidic methods offer advantages such as precise size control, increased production throughput, high encapsulation efficiency, user-defined membrane properties (i.e., lipid composition, vesicular architecture, compartmentalisation, membrane asymmetry, etc.), and potential integration with lab-on-chip manipulation and analysis modules. We provide a review of microfluidic lipid vesicle generation technologies, focusing on recent advances and state-of-the-art techniques. Principal technologies are described, and key research milestones are highlighted. The advantages and limitations of each approach are evaluated, and challenges and opportunities for microfluidic engineering of lipid vesicles to underpin a new generation of therapeutics, vaccines, sensors, and bio-inspired technologies are presented.

Advances in the design and delivery of RNA vaccines for infectious diseases

RNA medicines represent a paradigm shift in treatment and prevention of critical diseases of global significance, e.g., infectious diseases. The highly successful messenger RNA (mRNA) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were developed at record speed during the coronavirus disease 2019 pandemic. A consequence of this is exceptionally shortened vaccine development times, which in combination with adaptability makes the RNA vaccine technology highly attractive against infectious diseases and for pandemic preparedness. Here, we review state of the art in the design and delivery of RNA vaccines for infectious diseases based on different RNA modalities, including linear mRNA, self-amplifying RNA, trans-amplifying RNA, and circular RNA. We provide an overview of the clinical pipeline of RNA vaccines for infectious diseases, and present analytical procedures, which are paramount for characterizing quality attributes and guaranteeing their quality, and we discuss future perspectives for using RNA vaccines to combat pathogens beyond SARS-CoV-2.

Exploring dose and downregulation dynamics in lipid nanoparticles based siRNA therapy: Systematic review and meta-analysis

Small interfering RNA (siRNA) holds promise as a therapeutic approach for various diseases, yet challenges persist in achieving efficient delivery, biodistribution, and minimizing off-target effects. Lipidic nanoformulations are being developed to address these hurdles, but the optimal dose for preclinical investigations remains unclear. This systematic review and meta-analysis aims to determine the optimal dose of nanoformulated siRNA and explore factors influencing dose and biodistribution, informing future research in this field. A comprehensive search across four electronic databases identified 25 potential studies, with 15 selected for meta-analysis after screening. Quality assessment was conducted using SYRCLE's risk of bias tool modified for animal studies based on research question. Study found an average siRNA dose of 1.513 ± 0.377 mg/kg with mean downregulation of 65.79 % achieved, with siRNA-LNPs mainly accumulating in the liver. While individual factors showed no significant correlation, a positive association between dose and downregulation was observed, alongside other influencing factors. Extrapolating intravenous doses to potential oral doses, we suggest an initial oral dose range of 1.5 to 8 mg/kg, considering siRNA-LNPs bioavailability. These findings contribute to advancing RNA interference research and encourage further exploration of siRNA-based treatments in personalized medicine.

Safe and effective in vivo delivery of DNA and RNA using proteolipid vehicles

Genetic medicines show promise for treating various diseases, yet clinical success has been limited by tolerability, scalability, and immunogenicity issues of current delivery platforms. To overcome these, we developed a proteolipid vehicle (PLV) by combining features from viral and non-viral approaches. PLVs incorporate fusion-associated small transmembrane (FAST) proteins isolated from fusogenic orthoreoviruses into a well-tolerated lipid formulation, using scalable microfluidic mixing. Screening a FAST protein library, we identified a chimeric FAST protein with enhanced membrane fusion activity that improved gene expression from an optimized lipid formulation. Systemically administered FAST-PLVs showed broad biodistribution and effective mRNA and DNA delivery in mouse and non-human primate models. FAST-PLVs show low immunogenicity and maintain activity upon repeat dosing. Systemic administration of follistatin DNA gene therapy with FAST-PLVs raised circulating follistatin levels and significantly increased muscle mass and grip strength. These results demonstrate the promising potential of FAST-PLVs for redosable gene therapies and genetic medicines.

RP-CAD for Lipid Quantification: Systematic Method Development and Intensified LNP Process Characterization

Lipid nanoparticles (LNPs) and their versatile nucleic acid payloads bear great potential as delivery systems. Despite their complex lipid composition, their quality is primarily judged by particle characteristics and nucleic acid encapsulation. In this study, we present a holistic reversed-phase (RP)-charged aerosol detection (CAD)-based method developed for commonly used LNP formulations, allowing for intensified LNP and process characterization. We used an experimental approach for power function value (PFV) optimization termed exploratory calibration, providing a single PFV (1.3) in an appropriate linearity range for all six lipids. Followed by the procedure of method calibration and validation, linearity (10-400 ng, R2 > 0.996), precision, accuracy, and robustness were effectively proven. To complement the commonly determined LNP attributes and to evaluate the process performance across LNP processing, the developed RP-CAD method was applied in a process parameter study varying the total flow rate (TFR) during microfluidic mixing. The RP-CAD method revealed a constant lipid molar ratio across processing but identified deviations in the theoretical lipid content and general lipid loss, which were both, however, entirely TFR-independent. The deviations in lipid content could be successfully traced back to the lipid stock solution preparation. In contrast, the observed lipid loss was attributable to the small-scale dialysis following microfluidic mixing. Overall, this study establishes a foundation for employing RP-CAD for lipid quantification throughout LNP processing, and it highlights the potential to extend its applicability to other LNPs, process parameter studies, or processes such as cross-flow filtration.