Fig. 5.

Characterization of catalase incorporated into cell backpacks. A) Protease challenge test: free-standing catalase in solution, payload region films (PAH9.0/CAT9.0)30.5, and catalase containing backpacks had their activity measured before and after incubated in PBS (control) or in protease solution for 2 h, 37 °C. Remaining of activity (%) was calculated relative to time zero incubation time (initial activity). B) Activity of catalase released from backpacks was measured using hydrogen peroxide decomposition by monitoring the change in absorbance at 240 nm (the extinction coefficient of H₂O₂ is 44 M⁻¹cm⁻¹) [36]. C) Loading of catalase into backpacks increased stability of the enzyme against a mixture of proteinases (trypsin and pronase). Contrary to the free catalase (white bars) that was completely inactivated by proteinases after 2 h, backpack-incorporated catalase remained active for more than 72 h.