(712g) Substrate Functionalized Carbon Nanotubes As a Modular Tool for Tracking Soil Enzyme Activity

Soil microbes form an ecosystem that is vital for sustenance of plant, animal, and ultimately human life through the regulation of biological carbon, nitrogen, and phosphorous. The cycling of biological elements is largely regulated through activities of hydrolytic enzymes, such as proteases, glucanases, ureases, phosphatases, and sulphatases, and oxidative enzymes, such as phenol oxidases and peroxidases. While development of fluorophore-labeled substrates and fluorogenic substrate analogs has improved the ability to detect and characterize these enzymes, the cost of each of these custom reagents can limit their use. Moreover, they have limitations in the time required to complete the assay, and there are concerns about their use in complex mixtures (like soils). Single-walled carbon nanotubes non-covalently functionalized with substrates to enzymes may be used to track enzymatic activity. Theses sensors feature the advantages of simple preparation techniques, fast and facile detection procedures, and high modularity. Substrate degradation is directly tracked by monitoring the nanotube fluorescence, which decreases due to proximity quenching and changes in the local dielectric environment caused by substrate removal. The ability to use native substrates with little to no synthetic modification allows for order of magnitude reduction of costs. Tests with soil samples have demonstrated these sensors’ ability to respond to activity of proteases, chitosanases, and cellulases. This method may be further developed to detect a wider range of enzymes and adapted to distinguish between free soil enzymes, soil-stabilized enzymes, intercellular enzymes, and intracellular enzymes.