Capsules as Miniature Factories: On‐Demand Synthesis in Prepackaged Capsules Enabled by Switching on a Catalytic Reaction

• Published in: Advanced functional materials Vol. 32; no. 18
• Main Authors: DeMella, Kerry C., Subraveti, Sai Nikhil, Perry, Karima J., Karna, Shashi P., Raghavan, Srinivasa R.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.05.2022
• Subjects: biomanufacturing; biomimetic containers; Catalytic converters; Chemical fuels; Chemical synthesis; Compartments; Factories; Fluorescence; Hydrogen peroxide; Materials science; Medical imaging; Nanoclusters; nanomanufacturing; protocells; reaction cascades
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202110191

Biological cells convert reactants into products using enzymatic catalysis—moreover, such synthesis is done as needed. This paper presents a platform of polymer capsules that emulate the ability to synthesize products on‐demand (i.e., these “miniature factories” remain dormant at the outset, but can be switched on when needed). The structures created are multicompartment capsules (MCCs) having one or more internal compartments. Hydrophilic solutes are “hermetically sealed” in the compartments by constructing a hydrophobic wax shell around the aqueous core. While such a shell is initially impermeable, solute transport can be activated by a thermal switch, i.e., by melting the shell. The MCC factory is used to synthesize fluorescent nanoclusters (NCs) of gold and cadmium, which are useful as sensors and in bioimaging. The reaction is triggered by releasing a base from its compartment, whereupon a protein in the MCC lumen catalyzes the NC synthesis. In another example, a chemical fuel (H2O2) is released into the MCC lumen, where catalytic silver particles decompose the fuel to generate oxygen gas. The gas induces the MCC to inflate and eventually rupture—the MCC thus exhibits an emergent autonomous response that is the property of the whole, but not of any component parts. Multicompartment capsules (MCCs) are shown to serve as miniature factories. The MCC has all reagents prepackaged in it, but remains dormant initially. When switched on by heat, reagents released from the compartments come in contact with catalysts in the MCC lumen. This results in the synthesis of useful products, including gold nanoclusters.