@article{tang_saquing_morton_glatz_kelly_khan_2014, title={Cross-linked Polymer Nanofibers for Hyperthermophilic Enzyme Immobilization: Approaches to Improve Enzyme Performance}, volume={6}, ISSN={["1944-8244"]}, DOI={10.1021/am5033633}, abstractNote={We report an enzyme immobilization method effective at elevated temperatures (up to 105 °C) and sufficiently robust for hyperthermophilic enzymes. Using a model hyperthermophilic enzyme, α-galactosidase from Thermotoga maritima, immobilization within chemically cross-linked poly(vinyl alcohol) (PVA) nanofibers to provide high specific surface area is achieved by (1) electrospinning a blend of a PVA and enzyme and (2) chemically cross-linking the polymer to entrap the enzyme within a water insoluble PVA fiber. The resulting enzyme-loaded nanofibers are water-insoluble at elevated temperatures, and enzyme leaching is not observed, indicating that the cross-linking effectively immobilizes the enzyme within the fibers. Upon immobilization, the enzyme retains its hyperthermophilic nature and shows improved thermal stability indicated by a 5.5-fold increase in apparent half-life at 90 °C, but with a significant decrease in apparent activity. The loss in apparent activity is attributed to enzyme deactivation and mass transfer limitations. Improvements in the apparent activity can be achieved by incorporating a cryoprotectant during immobilization to prevent enzyme deactivation. For example, immobilization in the presence of trehalose improved the apparent activity by 10-fold. Minimizing the mat thickness to reduce interfiber diffusion was a simple and effective method to further improve the performance of the immobilized enzyme.}, number={15}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Tang, Christina and Saquing, Carl D. and Morton, Stephen W. and Glatz, Brittany N. and Kelly, Robert M. and Khan, Saad A.}, year={2014}, month={Aug}, pages={11899–11906} }
 @article{sanford_morton_whitehouse_oara_lugo-morales_roberts_sombers_2010, title={Voltammetric Detection of Hydrogen Peroxide at Carbon Fiber Microelectrodes}, volume={82}, ISSN={["1520-6882"]}, DOI={10.1021/ac100536s}, abstractNote={Hydrogen peroxide is a reactive oxygen species that is implicated in a number of neurological disease states and that serves a critical role in normal cell function. It is commonly exploited as a reporter molecule enabling the electrochemical detection of nonelectroactive molecules at electrodes modified with substrate-specific oxidative enzymes. We present the first voltammetric characterization of rapid hydrogen peroxide fluctuations at an uncoated carbon fiber microelectrode, demonstrating unprecedented chemical and spatial resolution. The carbon surface was electrochemically conditioned on the anodic scan and the irreversible oxidation of peroxide was detected on the cathodic scan. The oxidation potential was dependent on scan rate, occurring at +1.2 V versus Ag/AgCl at a scan rate of 400 V.s(-1). The relationship between peak oxidation current and concentration was linear across the physiological range tested, with deviation from linearity above 2 mM and a detection limit of 2 muM. Peroxide was distinguished from multiple interferents, both in vitro and in brain slices. The enzymatic degradation of peroxide was monitored, as was peroxide evolution in response to glucose at a glucose oxidase modified carbon fiber electrode. This novel approach provides the requisite sensitivity, selectivity, spatial and temporal resolution to study dynamic peroxide fluctuations in discrete biological locations.}, number={12}, journal={ANALYTICAL CHEMISTRY}, author={Sanford, Audrey L. and Morton, Stephen W. and Whitehouse, Kelsey L. and Oara, Hannah M. and Lugo-Morales, Leyda Z. and Roberts, James G. and Sombers, Leslie A.}, year={2010}, month={Jun}, pages={5205–5210} }