Hydrolase stabilization via entanglement in poly(propylene sulfide) nanoparticles: Stability towards reactive oxygen species

摘要

In the advancement of green syntheses and sustainable reactions, enzymatic biocatalysis offers extremely high reaction rates and selectivity that goes far beyond the reach of chemical catalysts; however, these enzymes suffer from typical environmental constraints, e.g.operational temperature, pH and tolerance to oxidative environments. A common hydrolase enzyme, diisopropylfluorophosphatase (DFPase, EC 3.1.8.2), has demonstrated a pronounced efficacy for the hydrolysis of a variety of substrates for potential toxin remediation, but suffers from the aforementioned limitations. As a means to enhance DFPases stability in oxidative environments, enzymatic covalent immobilization within the polymeric matrix of poly(propylene sulfide) (PPS) nanoparticles was performed. By modifying the enzymes exposed lysine residues via thiolation, DFPase is utilized as a comonomer/crosslinker in a mild emulsion polymerization. The resultant polymeric polysulfide shell acts as a sacrificial barrier by first oxidizing to polysulfoxides and polysulfones, rendering DFPase in an active state. DFPase-PPS nanoparticles thus retain activity upon exposure to as high as 50 parts per million (ppm) of hypochlorous acid (HOCl), while native DFPase is observed as inactive at 500 parts per billion (ppb). This trend is also confirmed by enzyme-generated (chloroperoxidase (CPO), EC 1.11.1.10) reactive oxygen species (ROS) including both HOCl (3 ppm) and ClO _2 (100 ppm).