Synthesized mRPZ was imaged with SEM and TEM along with literaturesynthesized ZIF-8 and mRNA@ZIF-8 (Figure and). mRPZ features the distinct dodecahedron morphology that is present in the ZIF-8 literature. Using imaging analysis on acquired SEM images, mRPZ was about 107 nm, larger than literature-synthesized ZIF-8 and mRNA@ZIF-8, 74 nm and 80 nm, respectively (Figure ). Some variation in size occurred from batch to batch. The mean hydrodynamic diameter, as determined by dynamic light scattering (DLS), of mRPZ was 146 nm (Figure ) which may be explained by uncomplexed PEI. Interestingly, the hydrodynamic diameter of mRNA@ZIF-8 was larger than mRPZ and literature-synthesized ZIF-8, contrary to the size obtained with SEM (∆d = 80 nm larger). The difference in diameter may indicate that mRNA is loosely associated with the surface of the mRNA@ZIF-8 particle, which increases its hydrodynamic diameter and is later confirmed with a molecular probing technique. PXRD confirmed the synthesis of the ZIF-8 particles. The diffraction patterns of mRPZ and mRNA@ZIF-8 match well with simulated ZIF-8 and literature-synthetized ZIF-8 peaks (Figure ). Further characterization of this novel particle was undertaken to ascertain mRNA loading within mRPZ and to assess the particle's composition. Loading efficiency and loading capacity are crucial parameters in nucleic acid delivery, representing the efficiency of mRNA encapsulation and the quantity of mRNA the material can accommodate, respectively. Elevated loading efficiencies and capacities minimize the waste of unloaded therapeutic material, reduce the required exogenous materials for mRNA delivery, and lower the risk of systemic toxicity. The loading efficiency of mRPZ was measured as the amount of RNA released from nanoparticles after exfoliation of ZIF-8 with EDTA and dissociation from PEI with heparin sulfate (Figure ) divided by the mRNA used in synthesis. Gel electrophoresis and ImageJ analysis were utilized to compare band intensities of released RNA to standards. The loading efficiency of mRPZ and mRNA@ZIF-8 was found to be 91.1% +/-7.7% and 91.5% +/-9.5%, respectively (Figure and S11-S12). of mRPZ was further validated using a fluorescent probe assay, confirming a similar loading capacity of 92.3% +/-2.5% (Figure ). The loading capacity of mRPZ was determined through thermogravimetric analysis, where the organic components of mRPZ exhibit lower burning temperatures than ZIF-8. Differential mass loss over a temperature range helped identify the weight composition of each particle component. Weight compositions of mRNA@ZIF-8, PEI-ZIF-8, and ZIF-8 were employed to confirm the decomposition of each component (Figure and). From the literature RNA, PEI, and ZIF-8, decompose between 100-300˚C, 60 300-400˚C, and 400˚C-600˚C under nitrogen, respectively. The mRNA loading capacity of mRPZ was calculated to be 5.3%, which is considered high compared to previous work loading high molecular weight nucleic acids in MOFs. The loading capacity for mRNA@ZIF-8 was slightly higher at 6.0%, possibly due to the absence of PEI contributing to the overall weight. Intriguingly, the incorporation of mRNA and PEI within ZIF-8 reduced its decomposition temperature, evidenced by shifts in the composite ZIF-8 materials. This phenomenon aligns with observations made by Kang et al. in their study involving coprecipitation of PVP and Urease with ZIF-8. FTIR was also performed to ensure chemical consistency between tested samples and ZIF-8 (Figure ).