The toxicity of mRPZ, components, and commercial transfection reagents were assessed using a Resazurin assay which measures cell metabolic activity. The viability of the cells after transfection with Lipo 2K, Lipo MM, mRNA-PEI (N/P=28), and mRPZ were not statically different from the untreated cells (Figure ). Cells treated with Linear 20 kDa PEI (Figure ) showed no signs of toxicity up to a concentration of 3.6 µg mL -1 , which corresponds to transfecting with PEI at an N/P ratio of about 28. At higher concentrations, concentrations exceeding 12 µg mL -1 , PEI significantly reduces the metabolic activity of the cells. Interestingly, cells treated with 3.6 µg mL -1 of PEI and transfected with mRNA-PEI at N/P ratios of about 28 showed visible signs of reduced growth, as final cell confluency was lower compared to other treatments. Cells treated with ZIF-8 (Figure ) showed no significant metabolic change up to 50 µg mL -1 . For reference, mRPZ used to transfect one 96-well plate well would correspond to 16.62 µg mL -1 of ZIF-8. Higher concentrations of ZIF-8 cause a significant drop in metabolic activity and cause cell morphology to become round. The combination of PEI and ZIF-8 interestingly shows better transfection over PEI alone and reduces the amount of PEI needed. We further studied the kinetics of eGFP expression after transfection by treating HEK293t cells with mRPZ and monitoring the eGFP fluorescence in phenol red-free media for 96 hours with a plate reader (Figure ). mRPZ reaches a maximum eGFP signal at 72 hours and reaches 80% of its maximum expression at 44 hours. Lipo 2k and Lipo MM reach maximum expression around 48 hours and reach 80% of their maximum expression around 24 hours. mRNA-PEI (PEI N/P=9.3) reaches its maximum expression at 96 hours and 80% of its maximum expression at around 21 hours. This delayed expression may be explained by the slow dissociation of the ZIF-8 coating from mRPZ. Similar delayed expression has been observed in studies with pDNA and ZIF-8 biocomposites. Interestingly, our synthetic methodology for mRNA encapsulation also works for pDNA. After encapsulation in ZIF-8 using our coprecipitation method, pDNA-PEI@ZIF-8 (pDPZ) was imaged using SEM (Figure ) and applied for the transfection of HEK293t cells (Figure ). The eGFP expression in the cells was observed at 48 and 96 hours (Figure ). Interestingly, similar to mRPZ and previous reports, the expression of the eGFP-pDNA was also delayed, this time by 48 hours. The success of our synthetic methodology with pDNA (6.1 kbp) delivery may translate for larger mRNA.