Scalable mRNA and siRNA Lipid Nanoparticle Production Using a Parallelized Microfluidic Device

Ionizable lipid nanoparticles with functionalized PEG-lipids increase retention in the tumor microenvironment

This study explores the efficacy of ionizable lipid nanoparticles (LNPs) modified with various functionalized polyethylene glycol (PEG)-lipids for retention within the tumor microenvironment after intratumoral (IT) injection. LNPs were synthesized and characterized with four different functionalized PEG-lipids, and the top performing lipids were evaluated under formulation conditions that varied the ratio of non-modified to functionalized PEG within the LNP. These LNPs were evaluated for size, polydispersity index, zeta potential, pKa, and mRNA encapsulation efficiency, with subsequent in vitro analysis of transfection and association efficiency to HepG2 liver cancer cells. Results demonstrated that LNPs formulated with PEG-folate and PEG-maleimide showed increased association to and interaction with cancer cells, compared with the base LNP formulation, which contained only non-functionalized lipid-PEG. In vivo studies showed increased retention of surface functionalized LNPs after IT injection in a xenograft model of hepatoblastoma. By slightly modifying LNPs in this manner, it is possible to develop delivery platforms that are better suited for local intratumoral administration. Ultimately, this research underscores the potential of LNPs as a vehicle for localized cancer therapy and emphasizes the need for future investigation into the long-term retention and therapeutic efficacy of LNP formulations.

Optimizing Microfluidic Channel Design with Tilted Rectangular Baffles for Enhanced mRNA-Lipid Nanoparticle Preparation

RNA therapeutics represent a pivotal advancement in contemporary medicine, pioneering innovative treatments in oncology and vaccine production. The inherent instability of RNA and its delivery challenges necessitate the use of lipid-based nanoparticles as crucial transport vehicles. This research focuses on the design, simulation, and optimization of various microfluidic channel configurations for fabricating poly(dimethylsiloxane) (PDMS) microfluidic chips, aimed at producing lipid nanoparticles (LNPs) encapsulating green fluorescent protein mRNA (GFP mRNA). Aiming for high mixing efficiency and acceptable pressure drop suitable for scale-up, we designed and improved multiple microfluidic channels featuring flow focusing and diverse tilted rectangular baffle structures via computational fluid dynamics (CFD). Simulation results indicated that baffle angles ranging from 70 to 90° exhibited similar mixing efficiencies at different total flow rates, with pressure drops increasing alongside the baffle angle. Additionally, increasing the baffle length at a fixed angle of 70° not only improved mixing efficiency but also increased the pressure drop. To validate these findings, PDMS microfluidic chips were fabricated for all designs to prepare empty LNPs. The baffle structure with a 70° angle and 150 μm length was identified as the best configuration based on both simulation and experimental results. This optimal design was then used to prepare LNPs with varying GFP mRNA concentrations, demonstrating that an N/P ratio of 5.6 yielded the highest transfection efficiency from in vitro experiments. This work not only advances the production of lipid-based nanoparticles through microfluidics but also provides a scalable and reproducible method that can potentially enhance the clinical translation of RNA therapeutics.

Quality by design (QbD) liposomes engineering using 3D printed Tesla microfluidic arrays

Microfluidic arrays have been successfully implemented for the design and development of liposome nanoparticles. In this study we have applied a Quality by Design (QbD) approach to investigate the effect of 3D printed Tesla microfluidic designs (direct and serpentine shape) on the liposome nanoparticles in comparison with conventional ultrasonication methodology. Critical processing parameters (CPP) such as the shape, length and channel width of the Tesla arrays were also studied. Furthermore, the effect of critical material attributes (CMA), including the length of the phosphatidylcholine (PC) carbon chain and the lipid:cholesterol ratio on the produced nanoparticles was investigated. The obtained findings revealed that both CPP and CMA play a key role in the formation of liposome nanoparticles. The liposome size was decreasing with a descending order for plain array > Tesla (serpentine) > Tesla (direct) > ultrasonication. However, improved Tesla arrays with narrow channel width (200 μm) produced the smallest liposome particle size (74 nm). The PC carbon chain length was critical for the obtained particle size where Lipoid S75 produced smaller nanoparticles when compared to Lipoid E80. The increase of cholesterol content resulted in liposome size reduction and decreased zeta-potential.

Unraveling the Molecular Mechanism of Transient Multilamellar Formation in Ethanol-Modified Vesicle Solutions

A recent microfluidic-based small-angle X-ray scattering (SAXS) measurement intriguingly suggested the transient formation of multilamellar structures during the mixing of unilamellar vesicles with ethanol in an aqueous solution. This study explores a possible molecular mechanism underlying this phenomenon, primarily through coarse-grained molecular dynamics (CG-MD) simulations. We first examined lipid aggregate morphology as a function of ethanol concentration in an aqueous solution. Even though vesicles were observed in pure aqueous solution, increasing ethanol concentrations led to more frequent pore formation in vesicular membranes. At ethanol concentrations above 52%, vesicles destabilized and transformed into worm-like micelles. We hypothesized that the transient multilamellar structures might arise from vesicle stacking due to variations in the effective interactions between vesicles. However, a series of potential of mean force (PMF) calculations consistently showed repulsive interactions between vesicles, regardless of ethanol concentration, ruling out this possibility. In contrast, once lipid aggregates transformed into worm-like micelles, the PMF barrier between them dropped (∼5kBT), promoting fusion. Our CG-MD simulations further demonstrated that lipid aggregates (micelles) readily fused and grew in high ethanol concentrations. Upon subsequent exposure to lower ethanol levels, these enlarged aggregates reorganized into vesicles with internal lamellar structure─multilamellar vesicles. These findings suggest that the heterogeneous mixing of unilamellar vesicular solutions with ethanol in a microfluidic device plays a key role in the emergence of transient multilamellar structures.

A Metabolite Co-Delivery Strategy to Improve mRNA Lipid Nanoparticle Delivery

Lipid nanoparticles (LNPs) effectively protect mRNA and facilitate its entry into target cells for protein synthesis. Despite these successes, cellular entry alone may not be enough for optimal protein expression, as mRNA translation also depends on the availability of essential metabolites, including metabolic energy sources, coenzymes, and amino acids. Without adequate metabolites, mRNA translation may be less efficient, potentially leading to higher dosing requirements or poorer therapeutic outcomes for LNP therapies. To address this, we develop a metabolite co-delivery strategy by encapsulating essential metabolites within mRNA LNPs, hypothesizing that our approach can uniformly improve mRNA delivery. Instead of adding a fifth component to the organic phase, our strategy involves mixing the metabolite with the mRNA payload in the aqueous phase, while maintaining the molar ratio of the components in the organic phase during LNP formulation. We verify our approach in vitro and in vivo, highlighting the broad applicability of our strategy through mechanism and efficacy studies across multiple cell lines, and physiological conditions, such as normoxia (i.e., 21% oxygen), hypoxia (i.e., 1% oxygen), and in mice. Taken collectively, we anticipate that our metabolite co-delivery strategy may serve as a generalizable strategy to enhance in vitro and in vivo protein expression using mRNA LNPs, potentially offering broad applicability for the study and treatment of disease.

Generation of continuous production of polymeric nanoparticles via microfluidics for aerosolised localised drug delivery

Transferring the production of nanoparticles from laboratory batches to large-scale production for preclinical and clinical applications represents a challenge due to difficulties in scaling up formulations and lack of suitable preclinical models for testing. Here, we transpose the production of hyaluronic acid and polyarginine-based nanoparticles encapsulating the platinum-derivative dichloro(1,2 diaminocyclohexane)platinum(II), from conventional bulk method to continuous production using microfluidics. The microfluidic-based drug delivery system is then tested in a customised preclinical setup to assess its suitability for pressurised intraperitoneal aerosol chemotherapy (PIPAC), a locoregional chemotherapy used to treat peritoneal carcinomatosis. PIPAC consists of the aerosolization of drugs under pressure using laparoscopy. In our preclinical setup, two clinical aerosol devices, CapnoPen® and TOPOL®, are used in conjunction with syringe pump to achieve the clinically optimal aerosol droplet size range (25-50 μm). Aerosol droplet sizes of 38 and 64 μm are obtained at upstream pressures of 14.7 and 7.4 bar and flow rates of 0.4 and 1.1 mL/s, for CapnoPen® and TOPOL®, respectively. To study the spatial distribution of the aerosol, our preclinical setup is then coupled to an ex-vivo model (inverted porcine urinary bladder) that mimics the physiological peritoneal cavity environment. The smaller droplet size obtained with CapnoPen® provided more homogeneous aerosol distribution in the bladder cavity, crucial for maximising treatment coverage within the peritoneal cavity. Furthermore, stability studies reveal that nanoparticles maintained their physicochemical properties and anticancer activity post-aerosolization. Overall, this study provides a scalable approach for the production of platinum-derivative-loaded polymeric nanoparticles and demonstrates the suitability of this DDS for PIPAC.

Fabrication of a Spiral Microfluidic Chip for the Mass Production of Lipid Nanoparticles Using Laser Engraving

A spiral microfluidic chip (SMC) and multi-spiral microfluidic chip (MSMC) for lipid nanoparticle (LNP) production were fabricated using a CO2 laser engraving method, using perfluoropolyether (PFPE) and poly(ethylene glycol) diacrylate as photopolymerizable base materials. The SMC includes a spiral microchannel that enables rapid fluid mixing, thereby facilitating the production of small and uniform LNPs with a size of 72.82 ± 24.14 nm and a PDI of 0.111 ± 0.011. The MSMC integrates multiple parallel SMC structures, which enables high-throughput LNP production without compromising quality and achieves a maximum production capacity of 960 mL per hour. The LNP fabrication technology using SMC and MSMC has potential applications in the pharmaceutical field due to the ease of chip fabrication, the simplicity and cost-effectiveness of the process, and the ability to produce high-quality LNPs.

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.

Synergy of Microfluidics and Nanomaterials: A Revolutionary Approach for Cancer Management

Cancer affects millions of individuals every year and is the second most common cause of death. Various therapeutic strategies are explored for the management of cancer including radiation therapy and chemotherapy with or without surgical procedures. However, the drawbacks like poor cancer cell targeting and higher toxicity for healthy cells need the advancement of the therapeutic strategy. The exploration of nanomedicine achieves targeted distribution, and the adoption of microfluidics technology for the preparation of the nanoparticulate system has enhanced the efficacy and uniformity of the nanocarriers. The overview of the existing designs of the microfluidics device assisted in the preparation of the nanoparticles, and various nanodelivery systems formulated using the microfluidic device including liposomes, lipidic nanocarriers, quantum dots, polymeric nanoparticles, and metallic nanocarriers are discussed in this review. Further, the challenges associated with the fabrication of the microfluidics device and the fabrication of microfluidics device-based nanoparticles are detailed here.

Enhancing vaccine stability in transdermal microneedle platforms

Micron-scale needles, so-called microneedles (MNs) offer a minimally invasive, nearly painless, and user-friendly method for effective intradermal immunization. Maintaining the stability of antigens and therapeutics is the primary challenge in producing vaccine or drug-loaded MNs. The manufacturing of MNs patches involves processes at ambient or higher temperatures and various physio-mechanical stresses that can impact the therapeutic efficacy of sensitive biologics or vaccines. Therefore, it is crucial to develop techniques that safeguard vaccines and other biological payloads within MNs. Despite growing research interest in deploying MNs as an efficient tool for delivering vaccines, there is no comprehensive review that integrates the strategies and efforts to preserve the thermostability of vaccine payloads to ensure compatibility with MNs fabrication. The discussion delves into various physical and chemical approaches for stabilizing antigens in vaccine formulations, which are subsequently integrated into the MNs matrix. The primary focus is to comprehensively examine the challenges associated with the translation of thermostable vaccine MNs for clinical applications while considering a safe, cost-effective approach with a regulatory roadmap. The recent cutting-edge advances facilitating flexible and scalable manufacturing of stabilized MNs patches have been emphasized. In conclusion, the ability to stabilize vaccines and therapeutics for MNs applications could bolster the effectiveness, safety and user-compliance for various drugs and vaccines, potentially offering a substantial impact on global public health.

Lipid Nanoparticles for In Vivo Lung Delivery of CRISPR-Cas9 Ribonucleoproteins Allow Gene Editing of Clinical Targets

In the past 10 years, CRISPR-Cas9 has revolutionized the gene-editing field due to its modularity, simplicity, and efficacy. It has been applied for the creation of in vivo models, to further understand human biology, and toward the curing of genetic diseases. However, there remain significant delivery barriers for CRISPR-Cas9 application in the clinic, especially for in vivo and extrahepatic applications. In this work, high-throughput molecular barcoding techniques were used alongside traditional screening methodologies to simultaneously evaluate LNP formulations encapsulating ribonucleoproteins (RNPs) for in vitro gene-editing efficiency and in vivo biodistribution. This resulted in the identification of a lung-tropic LNP formulation, which shows efficient gene editing in endothelial and epithelial cells within the lung, targeting both model reporter and clinically relevant genomic targets. Further, this LNP shows no off-target indel formation in the liver, making it a highly specific extrahepatic delivery system for lung-editing applications.

Dynamic Liquid Integrated Single-Cell SERS Platform Based on the Twisted Mixing Microfluidic Chip and Multi-Modified Nanoprobe for the Label-Free Detection of Cancer Cells

Surface-enhanced Raman scattering (SERS) has emerged as a potent spectroscopic technique for the detection of single cells. However, it is difficult to achieve label-free detection at the single-cell level in dynamic liquids because nanoprobe aggregation in biological fluids and the low combination of nanoprobes and cells reduce the sensitivity of SERS detection. Herein, a dynamic liquid integrated single-cell SERS (DLISC-SERS) platform is developed for the label-free detection of single cancer cells. DLISC-SERS consists of three components, including a twisted mixing microfluidic chip to achieve an efficient combination of nanoprobes and cells, a commercial coaxial needle to accomplish 3D dynamic liquid focusing by annular sheath flow, and a quartz capillary to offer a SERS detection area with low noise. The mixing intensity of the twisted mixing microfluidic chip is almost 3.67-fold higher than that of straight mixing. The multifunctionally modified nanoprobe, Ag NSs@PEG@3COOH, can be stably dispersed in biological fluids for at least 30 min. The segment weighting similarity-based KNN model can classify single-cell spectra with sensitivity, specificity, and accuracy up to 100, 99.4, and 99.5%, respectively. The accuracy of the model for three-way classification is 95.2%. The DLISC-SERS platform is a powerful tool for detecting cancer cells at the single-cell level.

Role of PEGylated lipid in lipid nanoparticle formulation for in vitro and in vivo delivery of mRNA vaccines

mRNA-loaded lipid nanoparticles (mRNA-LNPs) hold great potential for disease treatment and prevention. LNPs are normally made from four lipids including ionizable lipid, helper lipid, cholesterol, and PEGylated lipid (PEG-lipid). Although PEG-lipid has the lowest content, it plays a crucial role in the effective delivery of mRNA-LNPs. However, previous studies have yet to elucidate the key factors of PEG-lipid that influence the properties of LNPs. This study reported how PEG-lipid content, lipid tail length, and chemical linkage between PEG and lipid affected in vitro and in vivo properties of mRNA-LNPs. Forty-eight LNP formulations were prepared and characterized. The results revealed that a PEG-lipid molar content exceeding 3.0 % significantly reduced the encapsulation efficiency of mRNA in LNPs via manual mixing. An increased PEG-lipid content also significantly decreased mRNA translation efficiency. Although the chemical linkage had minimal impact, the lipid tail length of PEG-lipid significantly affected the properties of mRNA-LNPs, irrespective of whether the LNPs were prepared using manual or microfluidic mixing. mRNA-LNPs made from ALC-0159 with C14 lipid tails, which is used in Pfizer/BioNTech COVID-19 mRNA vaccines, or C16-Ceramide-PEG preferably accumulated in the liver, while mRNA-LNPs prepared from C8-Ceramide-PEG were largely found in the lymph nodes. In a mouse SARS-CoV-2 Delta variant spike protein-encoded mRNA vaccine model, mRNA-LNPs made from either C8-Ceramide-PEG or C16-Ceramide-PEG yielded comparable vaccination efficacy to mRNA-LNPs made from ALC-0159, while mRNA-LNPs formulated with DSPE-PEG with C18 lipid tails mediated lower vaccination efficacy. C16-Ceramide-PEG LNPs and DSPE-PEG LNPs induced higher anti-PEG antibody response than C8-Ceramide-PEG and ALC-0159 LNPs. All the LNPs tested did not cause significant toxicity in mice. These results offer valuable insights into the use of PEG-lipid in LNP formulations and suggest that C8-Ceramide-PEG holds potential for use in the formulation of mRNA vaccine-loaded LNPs.

Using aptamers for targeted delivery of RNA therapies

RNA-based treatments that can silence, introduce, or restore gene expression to target human diseases are emerging as a new class of therapeutics. Despite their potential for use in broad applications, their clinical translation has been hampered by a need for delivery to specific cells and tissues. Cell targeting based on the use of aptamers provides an approach for improving their delivery to the desired sites of action. Aptamers are nucleic acid oligonucleotides with structural conformations that provide a robust capacity for the recognition of cell surface molecules and that can be used for directed targeting. Aptamers can be directly conjugated to therapeutic RNA molecules, in the form of aptamer-oligonucleotide chimeras, or incorporated into nanoparticles used as vehicles for the delivery of these therapeutics. Herein, we discuss the use of aptamers for cell-directed RNA therapies, provide an overview of different types of aptamer-targeting RNA therapeutics, and review examples of their therapeutic applications. Challenges associated with manufacturing and scaling up production, and key considerations for their clinical implementation, are also outlined.

Nanoodor Particles Deliver Drugs to Central Nervous System via Olfactory Pathway

Central nervous system (CNS) disorders confront significant challenges in drug delivery due to the blood-brain barrier (BBB). Inspired by the rapid and precise binding of odor molecules to olfactory receptors (ORs), this research uses thiolated HPMA to construct odor nanoparticles (nanoodors) capable of delivering drugs to the CNS via the olfacto-cerebral pathway to overcome the delivery obstruction. The nanoodor core is used to encapsulate agomelatine (AGO), a CNS-targeting antidepressant, and the encapsulation efficiency exceeded 80%. A series of thiol-presenting nanoscale structures with different surface densities of thiol groups are constructed, and the effectiveness positively correlated with the density of thiol groups on their surface. Notably, the nanoodors enable precise brain-targeted delivery, outperforming commercially available oral formulations in terms of drug accumulation in the brain and antidepressant effects. The study of the nanoodor transport and action mechanisms revealed that after binding to ORs, the nanoodors are rapidly delivered to the brain via the olfactory pathway. Nanoodors, the first design to deliver CNS drugs via the olfactory pathway by mimicking natural smells for the treatment of CNS disorders, are expected to achieve clinical transformation, benefiting human health.

Choice of organic solvent affects function of mRNA-LNP; pyridine produces highly functional mRNA-LNP

Lipid nanoparticles (LNPs) are well-known nanocarriers for mRNA delivery. mRNA-encapsulated LNPs (mRNA-LNPs) are prepared by alcohol dilution (broadly defined as solvent dilution) method, in which mRNA dissolved in acidic buffer is mixed with lipid dissolved in an organic solvent. Ethanol is the most commonly used organic solvent for dissolving lipids during the preparation of mRNA-LNPs. However, no studies have systematically investigated the effects of organic solvents that dissolve lipids during the preparation of mRNA-LNPs on the properties and functions of mRNA-LNPs. In this study, we prepared mRNA-LNPs by using a series of organic solvents and evaluated their characteristics. After screening, we discovered that pyridine, an organic solvent, improved the quality of mRNA-LNPs and their function in vitro and in vivo. Pyridine was applied versatilely to some lipid-composition combinations generally used in the preparation of mRNA-LNPs and can also be adapted to microfluidic-based preparation. Furthermore, with appropriate purification, the amount of pyridine remaining in the final preparation of the mRNA-LNPs was extremely low and did not affect safety. Although further mechanism-based studies are required, we conclude that pyridine is a solvent that can be applied to the production of mRNA-LNPs as a pharmaceutical product.

Physicochemical Characterization and Oral Bioavailability of Curcumin-Phospholipid Complex Nanosuspensions Prepared Based on Microfluidic System

Background: Curcumin has been proved to have promising prospects in the fields of anti-inflammation, antibacterial, anti-oxidation, and neuroprotection. However, its poor water solubility and stability in strong acid, as well as fast metabolism, lead to low bioavailability, making it difficult to develop further. This study aimed to improve the bioavailability of curcumin by using microfluidic preparation technology. Methods: Using a self-built microfluidic system, polyvinylpyrrolidone K30 and sodium dodecyl sulfate were used as stabilizers to further prepare curcumin-phospholipid complex nanoparticles (CPC-NPs) on the basis of curcumin-phospholipid complex (CPC). The CPC-NPs were characterized and evaluated by X-ray powder diffraction (XRD), differential scanning caborimetry (DSC), dynamic light scattering, and transmission electron microscopy (TEM). Blood samples were collected from rats after oral administration of curcumin, CPC, curcumin nanoparticles (CUR-NPs), and CPC-NPs, respectively. The pharmacokinetics were analyzed by enzymatic digestion and HPLC. Results: The optimized CPC-NPs had a particle size of 71.19 ± 1.37 nm, a PDI of 0.226 ± 0.047, and a zeta potential of -38.23 ± 0.89 mV, which showed a spherical structure under TEM and good stability within 5 days at 4 °C and 25 °C. It was successfully characterized by XRD combined with DSC, indicating the integrational state of curcumin-soy lecithin and conversion to an amorphous form. The results of the pharmacokinetic study showed that the Cmax of curcumin, CUR-NPs, CPC, and CPC-NPs were 133.60 ± 28.10, 270.23 ± 125.42, 1894.43 ± 672.65, and 2163.87 ± 777.36 ng/mL, respectively; the AUC0-t of curcumin, CUR-NPs, CPC, and CPC-NPs were 936.99 ± 201.83, 1155.46 ± 340.38, 5888.79 ± 1073.32, and 9494.28 ± 1863.64 ng/mL/h. Conclusions: CPC-NPs prepared by microfluidic technology had more controllable quality than that of traditional preparation and showed superior bioavailability compared with free drug, CPC, and CUR-NPs. Pharmacodynamic evaluation of anti-inflammatory, anti-oxidation, and neuroprotection needs to be confirmed in follow-up studies.

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.

Deciphering the Role of PEGylation on the Lipid Nanoparticle-Mediated mRNA Delivery to the Liver

Organ- and cell-specific delivery of mRNA via modular lipid nanoparticles (LNPs) is promising in treating various diseases, but targeted cargo delivery is still very challenging. Most previous work focuses on screening ionizable and helper lipids to address the above issues. Here, we report the multifacial role of PEGylated lipids in manipulating LNP-mediated delivery of mRNA to the liver. We employed the typical excipients in LNP products, including DLin-MC3-DMA, DPSC, and cholesterol. Five types of PEGylated lipids were selected, and their molar ratio was fixed at 1.5% with a constant PEG molecular weight of 2000 Da. The architecture of steric lipids dramatically affected the in vitro gene transfection, in vivo blood clearance, liver deposition, and targeting of specific cells, all of which were closely linked to the de-PEGylation rate. The fast de-PEGylation resulted in short blood circulation and high accumulation in the liver. However, the ultrafast de-PEGylation enabled the deposition of more LNPs in Kupffer cells other than hepatocytes. Surprisingly, simply changing the terminal groups of PEGylated lipids from methoxyl to carboxyl or amine could dramatically increase the liver delivery of LNPs, which might be associated with the accelerated de-PEGylation rate and enhanced LNP-cell interaction. The current work highlights the importance of manipulating steric lipids in promoting mRNA delivery, offering an alternative approach for formulating and optimizing mRNA LNPs.

Microfluidics-Assembled Nanovesicles for Nucleic Acid Delivery

Microfluidic technologies have become a highly effective platform for the precise and reproducible production of nanovesicles used in drug and nucleic acid delivery. One of their key advantages lies in the one-step assembly of multidrug delivery nanovesicles, which improves batch-to-batch reproducibility by minimizing the intermediate steps typically required in conventional methods. These steps often involve complex hydrophobic and electrostatic interactions, leading to variability in the nanovesicle composition and performance. Microfluidic systems streamline the encapsulation of diverse therapeutic agents, including hydrophilic nucleic acids, proteins, and both hydrophobic and hydrophilic small molecules, within a single chip, ensuring a more consistent production process. This capability enables the codelivery of multiple drugs targeting different disease pathways, which is particularly valuable in reducing the risk of drug resistance. Despite the promise of nanovesicles for nucleic acid delivery, their clinical translation has been hindered by safety concerns, particularly cytotoxicity, which has overshadowed efforts to improve in vivo stability and delivery efficiency. Positively charged nanovesicles, commonly used to encapsulate negatively charged nucleic acids, tend to exhibit significant cytotoxicity. To address this, charge-shifting materials that respond to pH changes or surface modifications have been proposed as promising strategies. Shifting the surface charge from positive to neutral or negative at physiological pH can reduce the cytotoxicity, enhancing the clinical feasibility of these nanovesicle-based therapies. Microfluidic platforms offer precise control over key nanovesicle properties, including particle size, rigidity, morphology, and encapsulation efficiency. Particle size is relatively easy to adjust by controlling flow rates within microfluidic channels, with higher flow rates generally producing smaller particles. However, continuous tuning of the particle rigidity remains challenging. By manipulation of the interfacial water layer between hydrophobic and amphiphilic components during nanoparticle formation, future designs may achieve greater control over rigidity, which is critical for improving cellular uptake and biodistribution. While shape tuning using microfluidic chips has not yet been fully explored in biomedical applications, advances in materials science may enable this aspect in the future, offering further customization of the nanovesicle properties. The integration of nanovesicle assembly and surface modification within a single microfluidic platform presents challenges due to the differing speeds of these processes. Nanovesicle assembly is typically rapid, whereas surface modifications, such as those involving functional biomolecules, occur more slowly and often require purification steps. Recent advances, such as rotary valve designs and single-axis camshaft mechanisms, offer precise control over flow mixing at different stages of the process, allowing for the automation of nanovesicle assembly and surface modification, thereby improving batch-to-batch reproducibility. In conclusion, microfluidic technologies represent a promising approach for the development of multifunctional nanovesicles with the potential to address key challenges in drug delivery and precision medicine. While obstacles related to cytotoxicity, scalability, and reproducibility remain, innovations in chip design, materials, and automation are paving the way for broader application in clinical settings. Future research, potentially incorporating machine learning, could further optimize the relationship between nanovesicle properties and biological outcomes, advancing the use of microfluidic technologies for therapeutic delivery.

Multi-stage-mixing to control the supramolecular structure of lipid nanoparticles, thereby creating a core-then-shell arrangement that improves performance by orders of magnitude

As they became the dominant gene therapy platform, lipid nanoparticles (LNPs) experienced nearly all their innovation in varying the structure of individual molecules in LNPs. This ignored control of the spatial arrangement of molecules, which is suboptimal because supramolecular structure determines function in biology. To control LNPs' supramolecular structure, we introduce multi-stage-mixing (MSM) to successively add different molecules to LNPs. We first utilize MSM to create a core-then-shell (CTS) synthesis. CTS-LNPs display a clear core-shell structure, vastly lower frequency of LNPs containing no detectable mRNA, and improved mRNA-LNP expression. With DNA-loaded LNPs, which for decades lagged behind mRNA-LNPs due to low expression, CTS improved DNA-LNPs' protein expression by 2-3 orders of magnitude, bringing it within range of mRNA-LNPs. These results show that supramolecular arrangement is critical to LNP performance and can be controlled by mixing methodology. Further, MSM/CTS have finally made DNA-LNPs into a practical platform for long-term gene expression.

Microfluidics for Nanomedicine Delivery

Nanomedicine is revolutionizing precision medicine, providing targeted, personalized treatment options. Lipid-based nanomedicines offer distinct benefits including high potency, targeted delivery, extended retention in the body, reduced toxicity, and lower required doses. These characteristics make lipid-based nanoparticles ideal for drug delivery in areas such as gene therapy, cancer treatment, and mRNA vaccines. However, traditional bulk synthesis methods for LNPs often produce larger particle sizes, significant polydispersity, and low encapsulation efficiency, which can reduce the therapeutic effectiveness. These issues primarily result from uneven mixing and limited control over particle formation during the synthesis. Microfluidic technology has emerged as a solution, providing precise control over particle size, uniformity, and encapsulation efficiency. In this mini review, we introduce the state-of-the-art microfluidic systems for lipid-based nanoparticle synthesis and functionalization. We include the working principles of different types of microfluidic systems, the use of microfluidic systems for LNP synthesis, cargo encapsulation, and nanomedicine delivery. In the end, we briefly discuss the clinical use of LNPs enabled by microfluidic devices.

Towards the clinical translation of a silver sulfide nanoparticle contrast agent: large scale production with a highly parallelized microfluidic chip

PURPOSE

Ultrasmall silver sulfide nanoparticles (Ag2S-NP) have been identified as promising contrast agents for a number of modalities and in particular for dual-energy mammography. These Ag2S-NP have demonstrated marked advantages over clinically available agents with the ability to generate higher contrast with high biocompatibility. However, current synthesis methods for inorganic nanoparticles are low-throughput and highly time-intensive, limiting the possibility of large animal studies or eventual clinical use of this potential imaging agent.

METHODS

We herein report the use of a scalable silicon microfluidic system (SSMS) for the large-scale synthesis of Ag2S-NP. Ag2S-NP produced using this system were compared to bulk synthesis and a commercially available microfluidic device through characterization, contrast generation, in vivo imaging, and clearance profiles.

RESULTS

Using SSMS chips with 1 channel, 10 parallelized channels, and 256 parallelized channels, we determined that the Ag2S-NP produced were of similar quality as measured by core size, concentration, UV-visible spectrometry, and in vitro contrast generation. Moreover, by combining parallelized chips with increasing reagent concentration, we were able to increase output by an overall factor of 5,100. We also found that in vivo imaging contrast generation was consistent across synthesis methods and confirmed renal clearance of the ultrasmall nanoparticles. Finally, we found best-in-class clearance of the Ag2S-NP occurred within 24 h.

CONCLUSIONS

These studies have identified a promising method for the large-scale production of Ag2S-NP, paving the way for eventual clinical translation.

Solution biophysics identifies lipid nanoparticle non-sphericity, polydispersity, and dependence on internal ordering for efficacious mRNA delivery

Lipid nanoparticles (LNPs) are the most advanced delivery system currently available for RNA therapeutics. Their development has accelerated since the success of Patisiran, the first siRNA-LNP therapeutic, and the mRNA vaccines that emerged during the COVID-19 pandemic. Designing LNPs with specific targeting, high potency, and minimal side effects is crucial for their successful clinical use. However, our understanding of how the composition and mixing method influences the structural, biophysical, and biological properties of the resulting LNPs remains limited, hindering the development of LNPs. Our lack of structural understanding extends from the physical and compositional polydispersity of LNPs, which render traditional characterization methods, such as dynamic light scattering (DLS), unable to accurately quantitate the physicochemical characteristics of LNPs. In this study, we address the challenge of structurally characterizing polydisperse LNP formulations using emerging solution-based biophysical methods that have higher resolution and provide biophysical data beyond size and polydispersity. These techniques include sedimentation velocity analytical ultracentrifugation (SV-AUC), field-flow fractionation followed by multi-angle light scattering (FFF-MALS), and size-exclusion chromatography in-line with synchrotron small-angle X-ray scattering (SEC-SAXS). Here, we show that the LNPs have intrinsic polydispersity in size, RNA loading, and shape, and that these parameters are dependent on both the formulation technique and lipid composition. Lastly, we demonstrate that these biophysical methods can be employed to predict transfection in human primary T cells, intravenous administration, and intramuscular administration by examining the relationship between mRNA translation and physicochemical characteristics. We envision that employing solution-based biophysical methods will be essential for determining LNP structure-function relationships, facilitating the creation of new design rules for LNPs.

Branched endosomal disruptor (BEND) lipids mediate delivery of mRNA and CRISPR-Cas9 ribonucleoprotein complex for hepatic gene editing and T cell engineering

Lipid nanoparticles (LNPs) are the preeminent non-viral drug delivery vehicle for mRNA-based therapies. Immense effort has been placed on optimizing the ionizable lipid (IL) structure, which contains an amine core conjugated to lipid tails, as small molecular adjustments can result in substantial changes in the overall efficacy of the resulting LNPs. However, despite some advancements, a major barrier for LNP delivery is endosomal escape. Here, we develop a platform for synthesizing a class of branched ILs that improve endosomal escape. These compounds incorporate terminally branched groups that increase hepatic mRNA and ribonucleoprotein complex delivery and gene editing efficiency as well as T cell transfection compared to non-branched lipids. Through an array of complementary experiments, we determine that our lipid architecture induces greater endosomal penetration and disruption. This work provides a scheme to generate a class of ILs for both mRNA and protein delivery.

Multiarm-Assisted Design of Dendron-like Degradable Ionizable Lipids Facilitates Systemic mRNA Delivery to the Spleen

Lipid nanoparticles (LNPs) have emerged as pivotal vehicles for messenger RNA (mRNA) delivery to hepatocytes upon systemic administration and to antigen-presenting cells following intramuscular injection. However, achieving systemic mRNA delivery to non-hepatocytes remains challenging without the incorporation of targeting ligands such as antibodies, peptides, or small molecules. Inspired by comb-like polymeric architecture, here we utilized a multiarm-assisted design to construct a library of 270 dendron-like degradable ionizable lipids by altering the structures of amine heads and multiarmed tails for optimal mRNA delivery. Following in vitro high-throughput screening, a series of top-dendron-like LNPs with high transfection efficacy were identified. These dendron-like ionizable lipids facilitated greater mRNA delivery to the spleen in vivo compared to ionizable lipid analogs lacking dendron-like structure. Proteomic analysis of corona-LNP pellets showed enhancement of key protein clusters, suggesting potential endogenous targeting to the spleen. A lead dendron-like LNP formulation, 18-2-9b2, was further used to encapsulate Cre mRNA and demonstrated excellent genome modification in splenic macrophages, outperforming a spleen-tropic MC3/18PA LNP in the Ai14 mice model. Moreover, 18-2-9b2 LNP encapsulating therapeutic BTB domain and CNC homologue 1 (BACH1) mRNA exhibited proficient BACH1 expression and subsequent Spic downregulation in splenic red pulp macrophages (RPM) in a Spic-GFP transgene model upon intravenous administration. These results underscore the potential of dendron-like LNPs to facilitate mRNA delivery to splenic macrophages, potentially opening avenues for a range of mRNA-LNP therapeutic applications, including regenerative medicine, protein replacement, and gene editing therapies.

Robust, Scalable Microfluidic Manufacturing of RNA-Lipid Nanoparticles Using Immobilized Antifouling Lubricant Coating

Despite the numerous advantages demonstrated by microfluidic mixing for RNA-loaded lipid nanoparticle (RNA-LNP) production over bulk methods, such as precise size control, homogeneous distributions, higher encapsulation efficiencies, and improved reproducibility, their translation from research to commercial manufacturing remains elusive. A persistent challenge hindering the adoption of microfluidics for LNP production is the fouling of device surfaces during prolonged operation, which significantly diminishes performance and reliability. The complexity of LNP constituents, including lipids, cholesterol, RNA, and solvent mixtures, makes it difficult to find a single coating that can prevent fouling. To address this challenge, we propose using an immobilized liquid lubricant layer of perfluorodecalin (PFD) to create an antifouling surface that can repel the multiple LNP constituents. We apply this technology to a staggered herringbone microfluidic (SHM) mixing chip and achieve >3 h of stable operation, a >15× increase relative to gold standard approaches. We also demonstrate the compatibility of this approach with a parallelized microfluidic platform that incorporates 256 SHM mixers, with which we demonstrate scale up, stable production at L/h production rates suitable for commercial scale applications. We verify that the LNPs produced on our chip match both the physiochemical properties and performance for both in vitro and in vivo mRNA delivery as those made on chips without the coating. By suppressing surface fouling with an immobilized liquid lubricant layer, this technology not only enhances RNA-LNP production but also promises to transform the microfluidic manufacturing of diverse materials, ensuring more reliable and robust processes.

Syringable Microcapsules for Sustained, Localized, and Controllable siRNA Delivery

The clinical use of small interfering RNA (siRNA) and antisense oligonucleotides often requires invasive routes of administration, including intrathecal or intraocular injection. Additionally, these treatments often necessitate repeated injections. While nanoparticle formulation and chemical modifications have extended siRNA therapeutic durability, challenges persist, such as the side effects of bolus injections with high toxicity and maximum exposure in the acute phase. We present a microcapsule-based method to extend the activity of cholesterol-conjugated siRNA locally. Using microfluidics, microcapsules with well-defined size distribution and shell thickness are fabricated with poly(lactic-co-glycolic acid) (PLGA) with varying molecular weights and compositions. The microcapsules show a remarkably high drug encapsulation efficiency of nearly 100% and a high loading capacity (8900 μg siRNA/1 mg polymer). Additionally, microcapsules with an average diameter of 40 μm show superior syringeability when tested with needles ranging from gauge sizes of 27 to 32 G. This makes them suitable for various injection routes. Two sustained-release formulations were selected based on a 3-month in vitro release test. Subsequently, these formulations were injected subcutaneously into mice to verify their in vivo release profiles. The findings demonstrate that the microcapsules effectively shield the siRNAs from being cleared and enable them to be released constantly over 3 months. In contrast, unencapsulated siRNAs are rapidly cleared.

Microfluidic Nanoparticle Separation for Precision Medicine

A deeper understanding of disease heterogeneity highlights the urgent need for precision medicine. Microfluidics, with its unique advantages, such as high adjustability, diverse material selection, low cost, high processing efficiency, and minimal sample requirements, presents an ideal platform for precision medicine applications. As nanoparticles, both of biological origin and for therapeutic purposes, become increasingly important in precision medicine, microfluidic nanoparticle separation proves particularly advantageous for handling valuable samples in personalized medicine. This technology not only enhances detection, diagnosis, monitoring, and treatment accuracy, but also reduces invasiveness in medical procedures. This review summarizes the fundamentals of microfluidic nanoparticle separation techniques for precision medicine, starting with an examination of nanoparticle properties essential for separation and the core principles that guide various microfluidic methods. It then explores passive, active, and hybrid separation techniques, detailing their principles, structures, and applications. Furthermore, the review highlights their contributions to advancements in liquid biopsy and nanomedicine. Finally, it addresses existing challenges and envisions future development spurred by emerging technologies such as advanced materials science, 3D printing, and artificial intelligence. These interdisciplinary collaborations are anticipated to propel the platformization of microfluidic separation techniques, significantly expanding their potential in precision medicine.

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.

Applications of microfluidics in mRNA vaccine development: A review

The transformative potential of microfluidics in the development of mRNA vaccines is explored in this review, highlighting its pivotal role in enhancing easy-to-use functionality, efficacy, and production efficiency. Moreover, we examine the innovative applications of microfluidics in biomedical research, including its contribution to the rapid and cost-effective synthesis of lipid nanoparticles for mRNA delivery and delve into the advantages of mRNA vaccines, such as targeted delivery and controlled expression. Furthermore, it outlines the future prospects of microfluidic devices, their cutting-edge examples in both research and industry, and the potential to revolutionize vaccine formulation and production. The integration of microfluidics with mRNA vaccine development represents a significant advancement in public health and disease prevention strategies.

Patient-Derived Organoids on a Microarray for Drug Resistance Study in Breast Cancer

Drug resistance is always a challenge in cancer treatment, whether for chemotherapy, targeting, or immunotherapy. Although tumor cell lines are derived from cancer patients, they gradually lost the original characteristics, including heterogeneity and tumor microenvironment (TME), during the long period of in vitro culturing. Therefore, it is urgent to use patient-derived tumor models instead of cancer cell lines to study tumor drug resistance. Herein, we developed a microarray device that serves as a platform for high-throughput and three-dimensional culture of breast cancer patient-derived organoids (BCOs) and investigated their resistance to adriamycin (ADM). Coupled with fluorescence microscopy, this system enabled on-chip drug response monitoring and cell viability assessment without the consumption of a large number of tumor cells. The organoids were divided into a resistant BCO group (RBCO) and a sensitive BCO group (SBCO) according to their half-inhibitory concentration (IC50). Different from cancer cell lines, BCOs demonstrated obvious heterogeneity in drug treatment. Ivermectin (IVM), a broad-spectrum antiparasitic agent approved by the Food and Drug Administration (FDA), was observed to synergistically augment ADM-induced cytotoxicity in organoids. The BCO chip provides a promising platform for investigation of drug resistance and preclinical drug screening based on clinical samples.

Microfluidic Fabrication of Oleosin-Coated Liposomes as Anticancer Drug Carriers with Enhanced Sustained Drug Release

Microfluid-derived liposomes (M-Lipo) exhibit great potential as drug and functional substance carriers in pharmaceutical and food science. However, the low liposome membrane stability, attributed to the liquid core, limits their application range. Oleosin, a natural surfactant protein, can improve the stability of the lipid nanoparticle membrane against various environmental stresses, such as heat, drying, and pH change; in addition, it can enable sustained drug release. Here, we proposed the fabrication of oleosin-coated M-Lipo (OM-Lipo) through self-assembly on a microfluidic chip and the evaluation of its anticancer drug (carmustine) delivery efficiency. Nanoparticle characterization revealed that the oleosin coating slightly lowered the membrane potential of M-Lipo and greatly improved their dispersibility. Additionally, the in vitro drug release profile showed that the oleosin coating improved the sustained release of the hydrophobic drug from the phospholipid bilayer in body temperature. Our results suggest that OM-Lipo has sufficient potential in various fields, based on its easy production, excellent stability, and biocompatibility.

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.

Breaking the final barrier: Evolution of cationic and ionizable lipid structure in lipid nanoparticles to escape the endosome

In the past decade, nucleic acid therapies have seen a boon in development and clinical translation largely due to advances in nanotechnology that have enabled their safe and targeted delivery. Nanoparticles can protect nucleic acids from degradation by serum enzymes and can facilitate entry into cells. Still, achieving endosomal escape to allow nucleic acids to enter the cytoplasm has remained a significant barrier, where less than 5% of nanoparticles within the endo-lysosomal pathway are able to transfer their cargo to the cytosol. Lipid-based drug delivery vehicles, particularly lipid nanoparticles (LNPs), have been optimized to achieve potent endosomal escape, and thus have been the vector of choice in the clinic as demonstrated by their utilization in the COVID-19 mRNA vaccines. The success of LNPs is in large part due to the rational design of lipids that can specifically overcome endosomal barriers. In this review, we chart the evolution of lipid structure from cationic lipids to ionizable lipids, focusing on structure-function relationships, with a focus on how they relate to endosomal escape. Additionally, we examine recent advancements in ionizable lipid structure as well as discuss the future of lipid design.

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.

Lipid nanoparticles-based RNA therapies for breast cancer treatment

Breast cancer (BC) prevails as a major burden on global healthcare, being the most prevalent form of cancer among women. BC is a complex and heterogeneous disease, and current therapies, such as chemotherapy and radiotherapy, frequently fall short in providing effective solutions. These treatments fail to mitigate the risk of cancer recurrence and cause severe side effects that, in turn, compromise therapeutic responses in patients. Over the last decade, several strategies have been proposed to overcome these limitations. Among them, RNA-based technologies have demonstrated their potential across various clinical applications, notably in cancer therapy. However, RNA therapies are still limited by a series of critical issues like off-target effect and poor stability in circulation. Thus, novel approaches have been investigated to improve the targeting and bioavailability of RNA-based formulations to achieve an appropriate therapeutic outcome. Lipid nanoparticles (LNPs) have been largely proven to be an advantageous carrier for nucleic acids and RNA. This perspective explores the most recent advances on RNA-based technology with an emphasis on LNPs' utilization as effective nanocarriers in BC therapy and most recent progresses in their clinical applications.

Enhancing siRNA cancer therapy: Multifaceted strategies with lipid and polymer-based carrier systems

Cancers are increasing in prevalence and many challenges remain for their treatment, such as chemoresistance and toxicity. In this context, siRNA-based therapeutics have many potential advantages for cancer therapies as a result of their ability to reduce or prevent expression of specific cancer-related genes. However, the direct delivery of naked siRNA is hindered by issues like enzymatic degradation, insufficient cellular uptake, and poor pharmacokinetics. Hence, the discovery of a safe and efficient delivery vehicle is essential. This review explores various lipid and polymer-based delivery systems for siRNA in cancer treatment. Both polymers and lipids have garnered considerable attention as carriers for siRNA delivery. While all of these systems protect siRNA and enhance transfection efficacy, each exhibits its unique strengths. Lipid-based delivery systems, for instance, demonstrate high entrapment efficacy and utilize cost-effective materials. Conversely, polymeric-based delivery systems offer advantages through chemical modifications. Nonetheless, certain drawbacks still limit their usage. To address these limitations, combining different materials in formulations (lipid, polymer, or targeting agent) could enhance pharmaceutical properties, boost transfection efficacy, and reduce side effects. Furthermore, co-delivery of siRNA with other therapeutic agents presents a promising strategy to overcome cancer resistance. Lipid-based delivery systems have been demonstrated to encapsulate many therapeutic agents and with high efficiency, but most are limited in terms of the functionalities they display. In contrast, polymeric-based delivery systems can be chemically modified by a wide variety of routes to include multiple components, such as release or targeting elements, from the same materials backbone. Accordingly, by incorporating multiple materials such as lipids, polymers, and/or targeting agents in RNA formulations it is possible to improve the pharmaceutical properties and therapeutic efficacy while reducing side effects. This review focuses on strategies to improve siRNA cancer treatments and discusses future prospects in this important field.

Influence of ionizable lipid tail length on lipid nanoparticle delivery of mRNA of varying length

RNA-based therapeutics have gained traction for the prevention and treatment of a variety of diseases. However, their fragility and immunogenicity necessitate a drug carrier. Lipid nanoparticles (LNPs) have emerged as the predominant delivery vehicle for RNA therapeutics. An important component of LNPs is the ionizable lipid (IL), which is protonated in the acidic environment of the endosome, prompting cargo release into the cytosol. Currently, there is growing evidence that the structure of IL lipid tails significantly impacts the efficacy of LNP-mediated mRNA translation. Here, we optimized IL tail length for LNP-mediated delivery of three different mRNA cargos. Using C12-200, a gold standard IL, as a model, we designed a library of ILs with varying tail lengths and evaluated their potency in vivo. We demonstrated that small changes in lipophilicity can drastically increase or decrease mRNA translation. We identified that LNPs formulated with firefly luciferase mRNA (1929 base pairs) and C10-200, an IL with shorter tail lengths than C12-200, enhance liver transfection by over 10-fold. Furthermore, different IL tail lengths were found to be ideal for transfection of LNPs encapsulating mRNA cargos of varying sizes. LNPs formulated with erythropoietin (EPO), responsible for stimulating red blood cell production, mRNA (858 base pairs), and the C13-200 IL led to EPO translation at levels similar to the C12-200 LNP. The LNPs formulated with Cas9 mRNA (4521 base pairs) and the C9-200 IL induced over three times the quantity of indels compared with the C12-200 LNP. Our findings suggest that shorter IL tails may lead to higher transfection of LNPs encapsulating larger mRNAs, and that longer IL tails may be more efficacious for delivering smaller mRNA cargos. We envision that the results of this project can be utilized as future design criteria for the next generation of LNP delivery systems for RNA therapeutics.

Advances in Microfluidic-Based Core@Shell Nanoparticles Fabrication for Cancer Applications

Current research in cancer therapy focuses on personalized therapies, through nanotechnology-based targeted drug delivery systems. Particularly, controlled drug release with nanoparticles (NPs) can be designed to safely transport various active agents, optimizing delivery to specific organs and tumors, minimizing side effects. The use of microfluidics (MFs) in this field has stood out against conventional methods by allowing precise control over parameters like size, structure, composition, and mechanical/biological properties of nanoscale carriers. This review compiles applications of microfluidics in the production of core-shell NPs (CSNPs) for cancer therapy, discussing the versatility inherent in various microchannel and/or micromixer setups and showcasing how these setups can be utilized individually or in combination, as well as how this technology allows the development of new advances in more efficient and controlled fabrication of core-shell nanoformulations. Recent biological studies have achieved an effective, safe, and controlled delivery of otherwise unreliable encapsulants such as small interfering RNA (siRNA), plasmid DNA (pDNA), and cisplatin as a result of precisely tuned fabrication of nanocarriers, showing that this technology is paving the way for innovative strategies in cancer therapy nanofabrication, characterized by continuous production and high reproducibility. Finally, this review analyzes the technical, biological, and technological limitations that currently prevent this technology from becoming the standard.

A bibliometric insight into nanomaterials in vaccine: trends, collaborations, and future avenues

Background

The emergence of nanotechnology has injected new vigor into vaccine research. Nanovaccine research has witnessed exponential growth in recent years; yet, a comprehensive analysis of related publications has been notably absent.

Objective

This study utilizes bibliometric methodologies to reveal the evolution of themes and the distribution of nanovaccine research.

Methods

Using tools such as VOSviewer, CiteSpace, Scimago Graphica, Pajek, R-bibliometrix, and R packages for the bibliometric analysis and visualization of literature retrieved from the Web of Science database.

Results

Nanovaccine research commenced in 1981. The publication volume exponentially increased, notably in 2021. Leading contributors include the United States, the Chinese Academy of Sciences, the "Vaccine", and researcher Zhao Kai. Other significant contributors comprise China, the University of California, San Diego, Veronique Preat, the Journal of Controlled Release, and the National Natural Science Foundation of China. The USA functions as a central hub for international cooperation. Financial support plays a pivotal role in driving research advancements. Key themes in highly cited articles include vaccine carrier design, cancer vaccines, nanomaterial properties, and COVID-19 vaccines. Among 7402 keywords, the principal nanocarriers include Chitosan, virus-like particles, gold nanoparticles, PLGA, and lipid nanoparticles. Nanovaccine is primarily intended to address diseases including SARS-CoV-2, cancer, influenza, and HIV. Clustering analysis of co-citation networks identifies 9 primary clusters, vividly illustrating the evolution of research themes over different periods. Co-citation bursts indicate that cancer vaccines, COVID-19 vaccines, and mRNA vaccines are pivotal areas of focus for current and future research in nanovaccines. "candidate vaccines," "protein nanoparticle," "cationic lipids," "ionizable lipids," "machine learning," "long-term storage," "personalized cancer vaccines," "neoantigens," "outer membrane vesicles," "in situ nanovaccine," and "biomimetic nanotechnologies" stand out as research interest.

Conclusions

This analysis emphasizes the increasing scholarly interest in nanovaccine research and highlights pivotal recent research themes such as cancer and COVID-19 vaccines, with lipid nanoparticle-mRNA vaccines leading novel research directions.

Optimized microfluidic formulation and organic excipients for improved lipid nanoparticle mediated genome editing

mRNA-based gene editing platforms have tremendous promise in the treatment of genetic diseases. However, for this potential to be realized in vivo, these nucleic acid cargos must be delivered safely and effectively to cells of interest. Ionizable lipid nanoparticles (LNPs), the most clinically advanced non-viral RNA delivery system, have been well-studied for the delivery of mRNA but have not been systematically optimized for the delivery of mRNA-based CRISPR-Cas9 platforms. In this study, we investigated the effect of microfluidic and lipid excipient parameters on LNP gene editing efficacy. Through in vitro screening in liver cells, we discovered distinct trends in delivery based on phospholipid, cholesterol, and lipid-PEG structure in LNP formulations. Combination of top-performing lipid excipients produced an LNP formulation that resulted in 3-fold greater gene editing in vitro and facilitated 3-fold greater reduction of a therapeutically-relevant protein in vivo relative to the unoptimized LNP formulation. Thus, systematic optimization of LNP formulation parameters revealed a novel LNP formulation that has strong potential for delivery of gene editors to the liver to treat metabolic disease.

Research Advances of Lipid Nanoparticles in the Treatment of Colorectal Cancer

Colorectal cancer (CRC) is a common type of gastrointestinal tract (GIT) cancer and poses an enormous threat to human health. Current strategies for metastatic colorectal cancer (mCRC) therapy primarily focus on chemotherapy, targeted therapy, immunotherapy, and radiotherapy; however, their adverse reactions and drug resistance limit their clinical application. Advances in nanotechnology have rendered lipid nanoparticles (LNPs) a promising nanomaterial-based drug delivery system for CRC therapy. LNPs can adapt to the biological characteristics of CRC by modifying their formulation, enabling the selective delivery of drugs to cancer tissues. They overcome the limitations of traditional therapies, such as poor water solubility, nonspecific biodistribution, and limited bioavailability. Herein, we review the composition and targeting strategies of LNPs for CRC therapy. Subsequently, the applications of these nanoparticles in CRC treatment including drug delivery, thermal therapy, and nucleic acid-based gene therapy are summarized with examples provided. The last section provides a glimpse into the advantages, current limitations, and prospects of LNPs in the treatment of CRC.

Molecular Engineering of Functional SiRNA Agents

Synthetic biology constitutes a scientific domain focused on intentional redesign of organisms to confer novel functionalities or create new products through strategic engineering of their genetic makeup. Leveraging the inherent capabilities of nature, one may address challenges across diverse sectors including medicine. Inspired by this concept, we have developed an innovative bioengineering platform, enabling high-yield and large-scale production of biological small interfering RNA (BioRNA/siRNA) agents via bacterial fermentation. Herein, we show that with the use of a new tRNA fused pre-miRNA carrier, we can produce various forms of BioRNA/siRNA agents within living host cells. We report a high-level overexpression of nine target BioRNA/siRNA molecules at 100% success rate, yielding 3-10 mg of BioRNA/siRNA per 0.25 L of bacterial culture with high purity (>98%) and low endotoxin (<5 EU/μg RNA). Furthermore, we demonstrate that three representative BioRNA/siRNAs against GFP, BCL2, and PD-L1 are biologically active and can specifically and efficiently silence their respective targets with the potential to effectively produce downstream antiproliferation effects by PD-L1-siRNA. With these promising results, we aim to advance the field of synthetic biology by offering a novel platform to bioengineer functional siRNA agents for research and drug development.

Single-Particle Spectroscopic Chromatography Reveals Heterogeneous RNA Loading and Size Correlations in Lipid Nanoparticles

Lipid nanoparticles (LNP) have emerged as pivotal delivery vehicles for RNA therapeutics. Previous research and development usually assumed that LNPs are homogeneous in population, loading density, and composition. Such perspectives are difficult to examine due to the lack of suitable tools to characterize these physicochemical properties at the single-nanoparticle level. Here, we report an integrated spectroscopy-chromatography approach as a generalizable strategy to dissect the complexities of multicomponent LNP assembly. Our platform couples cylindrical illumination confocal spectroscopy (CICS) with single-nanoparticle free solution hydrodynamic separation (SN-FSHS) to simultaneously profile population identity, hydrodynamic size, RNA loading levels, and distributions of helper lipid and PEGylated lipid of LNPs at the single-particle level and in a high-throughput manner. Using a benchmark siRNA LNP formulation, we demonstrate the capability of this platform by distinguishing seven distinct LNP populations, quantitatively characterizing size distribution and RNA loading level in wide ranges, and more importantly, resolving composition-size correlations. This SN-FSHS-CICS analysis provides critical insights into a substantial degree of heterogeneity in the packing density of RNA in LNPs and size-dependent loading-size correlations, explained by kinetics-driven assembly mechanisms of RNA LNPs.

Quantitative analysis of mRNA-lipid nanoparticle stability in human plasma and serum by size-exclusion chromatography coupled with dual-angle light scattering

Understanding the stability of mRNA loaded lipid nanoparticles (mRNA-LNPs) is imperative for their clinical development. Herein, we propose the use of size-exclusion chromatography coupled with dual-angle light scattering (SEC-MALS) as a new approach to assessing mRNA-LNP stability in pure human serum and plasma. By applying a dual-column configuration to attenuate interference from plasma components, SEC-MALS was able to elucidate the degradation kinetics and physical property changes of mRNA-LNPs, which have not been observed accurately by conventional dynamic light scattering techniques. Interestingly, both serum and plasma had significantly different impacts on the molecular weight and radius of gyration of mRNA-LNPs, suggesting the involvement of clotting factors in desorption of lipids from mRNA-LNPs. We also discovered that a trace impurity (~1 %) in ALC-0315, identified as its O-tert-butyloxycarbonyl-protected form, greatly diminished mRNA-LNP stability in serum. These results demonstrated the potential utility of SEC-MALS for optimization and quality control of LNP formulations.