Redox-Responsive Polymer Nanoreactors Based on Methionine Sulfoxide for Monitoring Cell Adhesion

Expanding the category of redox-responsive monomers suitable for enzymolysis efficiency regulation and application to living biosystems is a prerequisite to complementing the fabrication of stimuli-responsive polymer nanoreactors. However, the development of redox-responsive monomers is severely limited by chemical oxidation and low biocompatibility. This work presents a protocol for overcoming this problem by the self-assembly of redox-responsive polymer nanoreactors containing segments of water-soluble methionine sulfoxide residues and poly(styrene-co-maleic anhydride-l-methionine), and by immobilizing α-l-fucosidase into the nanoreactors. These nanoreactors demonstrate highly selective responses to a mild redox triggered by H₂O₂ from the initial state (V^O) to an oxidation state (V^O1), and are reduced by methionine sulfoxide reductase A to mold the V^O' state. It resulted in significantly enhanced enzymolysis efficiency and maximal reaction rates 8.1-fold (V^O) and 23.3-fold (V^O1) higher than those of the free enzyme. Moreover, cell adhesion was evaluated by the highly selective determination of l-fucose on cell surfaces. Using a combination of chemical oxidation and enzymatic reduction, this work achieves reiterative enzymolysis efficiency regulation of polymer nanoreactors, which has great potential for the construction of redox-responsive nanoreactors and for monitoring cell adhesion.