Phenolic-compounds sensor based on immobilization of tyrosinase in polyacrylamide gel on long-period fiber grating

A phenolic-compounds sensor based on a long-period fiber grating coated with an enzyme-entrapped polyacrylamide gel is prepared and characterized, where the enzyme is tyrosinase (polyphenol oxidase). Phenolic compounds in contact with the enzyme-coated fiber grating can change the refractive index of the tyrosinase-immobilized gel through enzyme reaction and hence shift the resonance wavelength of the grating, which thus provides a measure of their concentration. Our experimental sensor shows a blue shift in the resonance wavelength with an increase in the concentration of the phenolic compounds in an aqueous solution with a maximum sensitivity of 0.0088 nm/µM at a pH value of 7.0. This fiber sensor offers numerous advantages, such as high sensitivity, wide operating range, fast response, reusability, reproducibility, biocompatibility, probe miniaturization, low cost, in-situ monitoring capability, and potential for remote sensing and multiplexing, and could be further developed for many industrial applications.