Figure 5: Controlled release of bioactive enzymes and proteins from ZIF-8 biocomposites.

(a) Fluorescent measurement of the PBS solution containing biomimetically mineralized zeolitic imidazolate framework-fluorogenic protein (ZIF-8/DQ-OVA) and biomimetically mineralized zeolitic imidazolate framework-trypsin (ZIF-8/trypsin) particles. At pH 7.4, the fluorescent emission (blue line) was analogous to that of free intact DQ-OVA protein (brown line). At pH 6.0, a drastic increase in the fluorescence intensity (red line) was observed, which was attributed to the proteolysis of the DQ-OVA into luminescent fragments suggesting that trypsin and DQ-OVA have been released and are free to interact in solution. (b–e) Schematics showing the release of DQ-OVA (red) and trypsin (yellow) from ZIF-8 biocomposites at pH 6.0, and degradation of DQ-OVA into fluorescent fragments as a result of proteolysis by trypsin.