Targeted delivery of RNA using synthetic bacterial spores

Background: RNA therapy holds increasing promise for the treatment of various diseases. Delivering RNA, however, typically requires encapsulation in lipid nanoparticles, and a limitation of this technology is achieving tissue specificity beyond the liver and kidneys. We previously reported synthetic bacterial spore-like particles, termed “SSHELs,” for targeted cargo delivery [1]. SSHELs, composed of defined, biocompatible materials, were shown to specifically bind to HER2-positive cancer cells and accumulate in tumors [2]. This study explores whether SSHELs can deliver RNA to tissue-specific locations, focusing on HER2-positive cells. Methods: The experimental approach involved protein purification, SSHEL assembly, mRNA and siRNA loading, and assessing RNA delivery specificity via confocal microscopy and flow cytometry. In vitro and in vivo assays were conducted to assess the production of EGFP and luciferase in target cells. Experimental models included cell cultures and mice. Results: By decorating SSHELs with anti-HER2 affibodies and modulating lipid composition, we achieved specific mRNA and siRNA delivery to HER2-positive cells, resulting in selective protein induction or silencing. Loading SSHELs with RNA was highly efficient (~95%), yielding thousands of transcripts per particle. In further investigations, we observed a distinctive feature of SSHELs made with DOTAP: they did not elicit or suppress inflammatory cytokine production (e.g., TNF-alpha, IL-6). This characteristic is noteworthy, as it suggests the biocompatibility and immunologically inert nature of SSHELs formulated with DOTAP. Ongoing in vivo experiments are assessing the efficacy of mRNA-loaded SSHELs in delivering cargo to HER2-positive tumors. Conclusions: SSHELs represent a novel approach in RNA therapeutics due to their unique characteristics. These particles, which mimic the structure of bacterial spores, provide a biocompatible and versatile platform for the targeted delivery of myriad therapeutics, such as small molecules, peptides, and RNAs. References: Wu, I.-L., et al. (2015). A versatile nano display platform from bacterial spore coat proteins. Nature Communications , 6, 6777. Kong, M., D'Atri, D., et al. (2023). Cell-specific cargo delivery using synthetic bacterial spores. Cell Reports , 42(1), 111955.