Full-cycle study on developing a novel structured micromixer and evaluating the nanoparticle products as mRNA delivery carriers.

Achieving precise control of nanoparticle size while maintaining consistency and high uniformity is of paramount importance for improving the efficacy of nanoparticle-based therapies and minimizing potential side effects. Although microfluidic technologies are widely used for reliable nanoparticle synthesis, they face challenges in meeting critical homogeneity requirements, mainly due to imperfect mixing efficiency. Furthermore, channel clogging during continuous operation presents a significant obstacle in terms of quality control, as it progressively impedes the mixing behavior necessary for consistent nanoparticle production for therapeutic delivery and complicates the scaling-up process. This study entailed the development of a 3D-printed novel micromixer embedded with hemispherical baffle microstructures, a dual vortex mixer (DVM), which integrates Dean vortices to generate two symmetrical counter-rotating intensified secondary flows. The DVM with a relatively large mixer volume showed rapid mixing characteristics even at a flow rate of several mL min-1 and produced highly uniform lipids, liposomes, and polymer nanoparticles in a size range (50-130 nm) and polydispersity index (PDI) values below 0.15. For the evaluation of products, SARS-CoV-2 Spike mRNA-loaded lipid nanoparticles were examined to verify protein expression in vitro and in vivo using firefly luciferase (FLuc) mRNA. This showed that the performance of the system is comparable to that of a commercial toroidal mixer. Moreover, the vigorous in-situ dispersion of nanoparticles by harnessing the power of vortex physically minimizes the occurrence of aggregation, ensuring consistent production performance without internal clogging of a half-day operation and facilitating quality control of the nanoparticles at desired scales.

Facile scalable one-flow synthesis of ionizable cationic lipid library as precursors of nanoparticle carriers.

A variety of ionizable and cationic lipids have been synthesized as precursors for nanoparticle carriers. However, the laborious synthetic routes in batch reactors often involve the use of toxic and carcinogenic agents, as well as challenge of removing gaseous byproducts. In this study, we present facile one-flow micro-reaction process that enables the synthesis of 11 ionizable lipids as well as 7 cationic lipids, including the well-known DODAP and DOTAP. These lipids can be scaled up to produce approximately ∼10g/h by using a straightforward size-up approach. The development of the lipid library was involved generating highly moisture-sensitive acyl chloride at 25 °C for 1.5 min. The toxic byproducts such as HCl, CO2 and CO were subsequently removed using a liquid-gas separator. The esterification with dimethylamino-1,2-diol at 25 °C for 3 min, monitored in-line with FTIR, completed the process. Additionally, the synthesized ionizable lipids were converted to cationic lipids with methyl sulfate, chloride ions via dimethyl sulfate and Steglich esterification in a continuous flow system. Finally, the produced DODAP was transformed into a uniform-sized LNPs (64 nm, PDI 0.07) and liposomal nanoparticles (72 nm, PDI 0.05) while DOTAP was converted to liposomes (55 nm, PDI 0.08) using a custom micro-mixer. This efficient platform for lipid synthesis significantly contributes to the practical applications of lipid-based nanomedicines.

A Perfluoropolyether Microfluidic Device for Cell-Based Drug Screening with Accurate Quantitative Analysis.

Microfluidic drug screening technologies have been extensively explored to evaluate the pharmacology and therapeutic implications of promising chemical compounds in multiplexed physiological microenvironments in vivo. However, conventional poly(dimethylsiloxane) microchips are susceptible to adsorption by hydrophobic molecules on channel surfaces and permeation in the matrix. These can significantly compromise the drug availability and accuracy of dose-dependent quantitative analyses. Here, we prepared a perfluorinated polyether (PFPE) microchip via digital light processing 3D printing as a quantitative drug screening platform for precise concentration-dependent pharmaceutical assays. Cells cultured on PFPE microchips exhibited excellent viability with a spread morphology as well as superior proliferative capability. Importantly, PFPE constructions with a low surface energy significantly prevented the nonspecific molecular adsorption into their surfaces or permeation into the matrix. In particular, the PFPE multibranched channel preserved the concentration of the pharmaceutical drug during the perfusion process and generated a linear concentration gradient, resulting in a dose-dependent chemotherapeutic effect. We suggest that the biocompatible and nonadsorbing PFPE microchannel can provide a cell-based drug screening platform for concentration-dependent quantitative analyses.