Intracellular Microreactors as Artificial Organelles to Conduct Multiple Enzymatic Reactions Simultaneously

The creation of artificial organelles is a new paradigm in medical therapy that aims to substitute for missing cellular function by replenishing a specific cellular task. Artificial organelles tackle the challenge of mimicking metabolism, which is the set of chemical reactions that occur within a cell, mainly catalyzed by enzymes. So far, the few reported carriers able to conduct enzymatic reactions intracellularly are based on single-compartment carriers. However, cell organelles outperform by conducting multiple reactions simultaneously within confined sub-compartments. Here, the field of artificial organelles is advanced by reporting the assembly of a microreactor consisting of polymer capsules entrapping gold nanoclusters (AuNCs) and liposomes as sub-compartments. The fluorescence properties of AuNCs are employed to monitor the microreactors uptake by macrophages. Encapsulation is demonstrated and functionality of microreactors with trypsin (TRP) and horseradish peroxidase (HRP)-loaded liposomes is preserved. Multiple enzymatic reactions taking place simultaneously is demonstrated by exposing macrophages with the internalized microreactors to bis-(benzyloxycarbonyl-Ile-Pro-Arg)-Rho-110 and Amplex Red substrates, which are specific for TRP and HRP, respectively. Conversion of the substrates into the respective fluorescent products is observed. This report on the first microreactor conducting multiple enzymatic reactions simultaneously inside a cell is a considerable step in the field of artificial organelles.