Sophia Sakers
BME Ph.D Thesis Defense Presentation
Date: 2025-04-29
Time: 3:00 PM
Location / Meeting Link: Krone Building (EBB) CHOA Room/https://emory.zoom.us/j/99988963225

Committee Members:
Mark Prausnitz, PhD (Advisor); James Dahlman, PhD; Brandon Dixon, PhD; Marcus Cicerone, PhD; Baozhong Wang, PhD


Title: Development of a microneedle patch for delivery of mRNA in lipid nanoparticles

Abstract:
mRNA technology offers an efficient way to develop new vaccines and therapeutics to address unmet medical needs. However, it is limited by its instability and low transfection efficiency. Lipid nanoparticles (LNPs) improve transfection and protect mRNA from enzymes in vivo but introduce more complexity and instability. Additional methods of delivery could increase the accessibility of novel mRNA technologies. In this thesis, we developed a microneedle patch (MNP) for the delivery of mRNA in LNPs. Specifically, we addressed 1) the factors of the MNP manufacturing process that influence mRNA-LNP stability and 2) the effect of LNP composition on stability in a MNP. First, we investigated elements of the MNP manufacturing process, including concentrating the mRNA-LNPs, types of excipients, excipient concentrations, pH, drying conditions, and backing cast formulations. We found that the optimal MNP design contained PVA with an epoxy backing cast, and that fabricating mRNA-LNPs at a higher initial concentration was more effective for loading into an MNP than concentrating post-fabrication. We found that pH and drying conditions had less significant effects on mRNA-LNP stability. We developed a mRNA-LNP MNP that produced in vivo expression of reporter mRNA, which was necessary for translating in vitro results to in vivo. Second, we investigated the effects of LNP composition changes on mRNA-LNP stability in MNPs, including the ionizable lipid:mRNA ratio, the lipid molar ratios, the ionizable lipid, cholesterol analogues, the phospholipid, and the PEG-linked lipid. We found that increasing the ionizable lipid content increased the stability during MNP manufacturing and that ionizable lipids that led to high in vivo expression via intradermal injection also had high expression via MNP application. We found that the ionizable lipid:mRNA ratio, cholesterol analogues, and PEG-linked lipid identity did not significantly affect mRNA-LNP MNP expression. We also discovered that in vitro characterization of mRNA-LNPs did not correlate well with in vivo expression, indicating the importance of testing new formulations in vivo. This body of work contributes to continuing efforts to develop a translatable mRNA-LNP MNP and to further the understanding of the complex nature of mRNA-LNP stability.