ZIF-8 Encapsulation of Protein Biomarkers

Example 2

To quantify the encapsulation efficiency, the supernatant after crystals centrifugation was collected and remaining NGAL concentration was determined using sandwich enzyme-linked immunosorbent assay (ELISA). The encapsulation efficiency was found to be dependent on the concentration of ZIF-8 precursors. Specifically, when the concentrations of zinc acetate and 2-methylimidazole in the mixture increased to 40 mM and 160 mM, respectively, ˜95% NGAL was encapsulated within ZIF-8 crystals (FIG. 7). The encapsulation efficiency was calculated by subtracting the remaining NGAL amount in the supernatant after encapsulation and centrifugation (concentration measured by ELISA) from the total NGAL amount. Results are the mean and standard deviation from three independent experiments. As a control experiment, mixing of NGAL-spiked artificial urine with pure ZIF-8 crystals resulted in extremely low (˜10%, owing to the physical adsorption) encapsulation efficiency. This physical mixing of pre-formed ZIF-8 crystals with the protein biomarkers is in stark contrast with the protein-embedding approach (i.e. formation of ZIF-8 crystals in the presence of protein biomarkers), which exhibited high encapsulation efficiency (95%).