As no Cy5-mRNA uptake was visible with mRNA@ZIF-8, we tested the particle's protection against RNase and stability in biological media. After exposure to RNase A for 2 hours or biological media over 24 hours, particles were isolated with centrifugation. ZIF-8 was exfoliated off mRNA, and the mRNA was run on a native RNA gel (Figure ). When exposed to RNase A for 2 hours suspended in PBS, mRNA@ZIF-8 demonstrates clear protection of the mRNA as the isolated mRNA matches the control band, and no degradation is visible when compared to mRNA treated with RNase A (Figure ). However, when mRNA@ZIF-8 is exposed to biological media, the isolated mRNA@ZIF-8 pellet yields no mRNA bands in the 10% FBS-supplemented media after 1 hour of incubation (Figure ). When mRNA@ZIF-8 was exposed to other biological media, such as Opti-MEM and PBS (pH 7 and pH 5), mRNA isolated from the mRNA@ZIF-8 pellet showed retention of mRNA for at least 1 hour. However, Opti-MEM and PBS pH 5 treatments showed significant mRNA leakage/degradation over 24 hours. The medium supernatants were also tested, as in Figure , and confirmed that mRNA@ZIF-8 incubation with 10% FBS DMEM resulted in mRNA leakage. These findings corroborate earlier studies indicating the instability of ZIF-8 in diverse biological media. In one of those studies, Luzuriaga and collaborators demonstrated ZIF-8's leakage in serum and serum cell culture media. Additionally, Spitsyna and colleagues further revealed that high salt concentrations and exposure to specific amino acids also contribute to therapeutic leakage from ZIF-8. Collectively, these ZIF-8 leakage studies have identified that strong inorganic, organic, and proteinaceous zinc binders cause ZIF-8 leakage and breakdown, this includes amino acids, bicarbonate, phosphates, and serum proteins. RNA gel of mRNA@ZIF-8 after exposure to RNase A, compared with controls of mRNA, mRNA treated with RNase, and mRNA@ZIF-8. mRNA@ZIF-8 samples were exfoliated using EDTA before loading onto the gel. (B) Native RNA gel of mRNA@ZIF-8 incubated for 1, 4, and 24 hours with various biological media including DMEM culture medium with 10% FBS, Opti-MEM culture medium, and PBS at pH 7 and 5. (C) Native RNA gel of mRNA-PEI@ZIF-8 after exposure RNase A, compared with controls of mRNA, mRNA treated with RNase and mRNA-PEI@ZIF-8. mRNA-PEI@ZIF-8 samples were exfoliated using EDTA and heparin before loading onto the gel. (D) Native RNA gel of mRNA-PEI@ZIF-8 incubated for 1, 4, and 24 hours with various biological media including DMEM culture medium with 10% FBS, Opti-MEM culture medium, and PBS at pH 7 and 5.