Incorporation of optical enzymatic sensing chemistry into biocompatible hydrogels

Oxidative enzymes coupled with analyte-sensitive luminophores present a way to optically transduce levels of biochemical substrates. In combination with implantable biocompatible materials, such sensing chemistry could become a powerful tool in the continuous monitoring of analytes in a non-invasive manner. This work presents model optical sensing systems containing the enzyme glucose oxidase (GOx) and an oxygen-sensitive or pH-sensitive luminophore incorporated into biocompatible poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels. Gel discs were exposed to step intervals of glucose in the physiologic range (0-400 mg/dL) to determine sensor response. Gels containing pH-sensitive chemistry showed drops in pH from 7.2 to 5.9 over the full glucose range. Gels containing GOx and O₂-sensitive phosphor showed extremely high percent change in response (1270%) as glucose was increased. Addition of catalase (CAT) reduced the sensitivity of the O₂-sensitive gels (995%), but also increased the analytical range by 26%. These findings show the promise of the described optically-transduced hydrogel systems with adjustable response profiles in the development of fully-implantable biosensors.