Based on our synthesis development process we have revealed several facets about working with mRNA and ZIF-8. Firstly, ethanol is the superior solvent for mRNA encapsulation in ZIF-8 as it maintains mRNA length and expressibility. Secondly, mRNA@ZIF-8 is not stable in some biological media, explaining why transfection with mRNA@ZIF-8 does not work in vitro. With the addition of PEI, complexed mRNA is retained inside the ZIF-8 particle with the ZIF-8 shell stability possibly being improved by PEI's strong binding of Zn. Clear improvements in particle stability are demonstrated when comparing biological media exposure of mRNA@ZIF-8 to mRPZ. This stability improvement may be explained by PEI outcompeting the strong Zn binders described by Luzuriaga et al. Synthesized mRPZ was then characterized and successfully tested in vitro and in vivo.