Andrus, Liam P (2015-08). Characterization of Lactate Sensors Based on Lactate Oxidase and Palladium Benzoporphyrin Immobilized in Hydrogels. Master's Thesis.
Thesis
An optical biosensor for lactate detection is described. By encapsulating enzymes and phosphorescent oxygen sensing molecules within permeable hydrogel materials, a lactate-sensitive change in emission lifetimes was achieved. The relative amount of monomer was varied to compare the response of the enzyme-phosphor system in three homo- and co-polymer materials: poly(2-hydroxyethyl methacrylate) (pHEMA) and two copolymers of pHEMA and poly(acrylamide) (pAam). Diffusion analysis demonstrated the ability to control lactate transport by varying the hydrogel composition, while having a minimal effect on oxygen diffusion. Sensors displayed the desired dose-variable response to lactate challenges, highlighting the tunable, diffusion-controlled nature of the sensing platform. Short-term repeated exposure tests revealed enhanced stability for sensors comprising hydrogels with acrylamide additives; after an initial "break-in" period, signal retention was 100% for 15 repeated cycles. Evaluation of long-term sensor performance revealed significant reduction in lactate sensitivity for all materials investigated. Sensor response was quickly saturated in a low oxygen testing environment, indicating further work is needed to enhance viability of platform for implantation. Finally, because this study describes the modification of a previously developed glucose sensor for lactate analysis, it demonstrates the potential for mix-and-match enzyme-phosphor-hydrogel sensing for use in future multi-analyte sensors.
