In the past few years, there has been increasing focus on the use of messenger RNA (mRNA) as a new therapeutic modality. Current clinical efforts encompassing mRNA-based drugs are directed toward infectious disease vaccines, cancer immunotherapies, therapeutic protein replacement therapies, and treatment of genetic diseases. However, challenges that impede the successful translation of these molecules into drugs are that (i) mRNA is a very large molecule, (ii) it is intrinsically unstable and prone to degradation by nucleases, and (iii) it activates the immune system. Although some of these challenges have been partially solved by means of chemical modification of the mRNA, intracellular delivery of mRNA still represents a major hurdle. The clinical translation of mRNA-based therapeutics requires delivery technologies that can ensure stabilization of mRNA under physiological conditions. Here, we (i) review opportunities and challenges in the delivery of mRNA-based therapeutics with a focus on non-viral delivery systems, (ii) present the clinical status of mRNA vaccines, and (iii) highlight perspectives on the future of this promising new type of medicine.

Lipid nanoparticle (LNP) formulation requires a mixing step. Many studies, especially from academic groups, utilize microfluidic mixers or hand mixing to prepare LNPs, while commercial-scale processes use turbulent-flow mixers. This discrepancy in mixing techniques has been underexplored, as LNPs made by different techniques may exhibit different performance, meaning bench-scale results cannot be replicated using materials manufactured at scale. Here, we isolate and interrogate the effect of primary mixing on LNP formulation. LNPs are produced from ten mixers while holding all other formulation parameters constant, to directly compare across techniques. We show that LNPs produced from the different mixers exhibit widely different physical properties and biological performance. Notably, manual pipetting common in academic practice yields particles that do not resemble those produced by turbulent-flow mixers. Findings are connected mechanistically to physicochemical characteristics arising from different flow regimes. Further establishing the relationship between mixing and LNP properties is critical.

The formation of a biomolecular corona on nanoparticles in blood is a well-known phenomenon influencing in vivo performance. Analogous phenomena in other biological fluids, such as the formation of a gastrointestinal (GI) corona, remain under-investigated. The ingestion of medicines leads to the generation of drug particles in the GI fluids. Consequently, an understanding of the behavior of drug particles in the gut requires determination of the adsorption of bile components onto these drug particles. This work aims to elucidate the factors affecting adsorption of bile salts onto ritonavir (RTV) particles. Crystalline RTV particles were incubated with non-micellar or micellar bile salts and bile salt depletion from solution was measured using HPLC and small angle X-ray scattering (SAXS). HPLC results show that bile salts adsorb onto RTV particles, with greater adsorption observed for more hydrophobic bile salts, following the order sodium glycodeoxycholate (SGDC)>sodium taurodeoxycholate (STDC)>sodium glycochenodeoxycholate SGCDC>sodium glycocholate (SGC)>sodium taurocholate (STC). Increasing the ionic strength of the solution led to increased adsorption of STDC, where buffer containing 300 mM NaCl resulted in greater adsorption than 150 mM NaCl. Additionally, micellar bile salts showed greater affinity for RTV particles than unimeric bile salts. In contrast, the extent of bile salt depletion was unaltered by addition of phospholipid to form mixed micelles. SAXS analysis of mixed micelles after incubation with RTV particles confirms depletion of bile salt from the supernatant, evidenced by reduced intensity of the micellar scattering feature. In conclusion, this study investigated factors influencing bile salt adsorption onto drug particles, highlighting the need to consider adsorption of bile components in forming the GI-corona.