Preparation of mRNA@ZIF-8: Precursor solutions of zinc nitrate hexahydrate (11.9 mg mL -1 ) and 2-methylimidazole (13.15 mg mL -1 ) were prepared in methanol, ethanol, or nuclease-free water. mRNA (1 mg mL -1 ), 1 µg, was aliquoted into a centrifuge tube and mixed with 10 µL of 2-methyl imidazole solution. Another 10 µL of zinc nitrate was added and mixed for 30 seconds. The solution was incubated at room temperature for 2 hours. Particles were isolated by centrifugation at 16,000 x g for 5 min and washed with ethanol two times. Particles were stored at -80˚C until use.