Resolving the\nKinetics of Single-Walled Carbon Nanotube–Polyester\nPolyurethane Nanoparticle Conjugate Fluorescence Sensors toward Polymer\nDegrading Enzymes

Single-walled carbon nanotubes (SWCNTs) are fluorescent\nmaterials\nthat have been developed as sensors for measuring the activities of\nenzymes. However, most sensors to date rely on end-point measurement\nand empirical functions to correlate enzyme concentrations with fluorescence\nresponses. Less emphasis is put on analyzing time-dependent fluorescence\nresponses and their connections with enzymatic kinetics. Here, improved\nfrom our previous sensor design, we use trimethylchitosan-wrapped\nSWCNTs to measure the enzymatic degradation rate of Impranil nanoparticles,\na polyester polyurethane model substrate. Through careful analysis\nof the characteristic time constant and saturation fluorescence, which\nare resolved from time-dependent brightening responses of the sensors,\nlinear relations are found between fluorescence change rates and both\nenzyme concentrations and Impranil-to-SWCNT ratios, thus showing that\nthe reaction is first-ordered toward both enzyme and substrate concentrations.\nThe proposed sensor design and data analysis strategy can quantitively\ndetermine the relative enzymatic activity and provide insights into\nthe kinetics of sensors and enzymatic reactions.