@article{probst_twiddy_hatada_pavlidis_daniele_sode_2024, title={Development of Direct Electron Transfer-Type Extended Gate Field Effect Transistor Enzymatic Sensors for Metabolite Detection}, volume={96}, ISSN={["1520-6882"]}, url={https://doi.org/10.1021/acs.analchem.3c04599}, DOI={10.1021/acs.analchem.3c04599}, abstractNote={In this work, direct electron transfer (DET)-type extended gate field effect transistor (EGFET) enzymatic sensors were developed by employing DET-type or quasi-DET-type enzymes to detect glucose or lactate in both 100 mM potassium phosphate buffer and artificial sweat. The system employed either a DET-type glucose dehydrogenase or a quasi-DET-type lactate oxidase, the latter of which was a mutant enzyme with suppressed oxidase activity and modified with amine-reactive phenazine ethosulfate. These enzymes were immobilized on the extended gate electrodes. Changes in the measured transistor drain current (ID) resulting from changes to the working electrode junction potential (φ) were observed as glucose and lactate concentrations were varied. Calibration curves were generated for both absolute measured ID and ΔID (normalized to a blank solution containing no substrate) to account for variations in enzyme immobilization and conjugation to the mediator and variations in reference electrode potential. This work resulted in a limit of detection of 53.9 μM (based on ID) for glucose and 2.12 mM (based on ID) for lactate, respectively. The DET-type and Quasi-DET-type EGFET enzymatic sensor was then modeled using the case of the lactate sensor as an equivalent circuit to validate the principle of sensor operation being driven through OCP changes caused by the substrate-enzyme interaction. The model showed slight deviation from collected empirical data with 7.3% error for the slope and 8.6% error for the y-intercept.}, number={10}, journal={ANALYTICAL CHEMISTRY}, author={Probst, David and Twiddy, Jack and Hatada, Mika and Pavlidis, Spyridon and Daniele, Michael and Sode, Koji}, year={2024}, month={Feb}, pages={4076–4085} }
 @article{lee_probst_klonoff_sode_2021, title={Continuous glucose monitoring systems-Current status and future perspectives of the flagship technologies in biosensor research}, volume={181}, ISSN={["1873-4235"]}, DOI={10.1016/j.bios.2021.113054}, abstractNote={Diabetes mellitus is a chronic illness in the United States affecting nearly 120 million adults, as well as increasing in children under the age of 18. Diabetes was also the 7th leading cause of death in the United States with 270 K deaths in 2017. Diabetes is best managed by tight glycemic control, as achieving near-normal glucose levels is key to reduce the risk of microvascular complications. Currently, continuous glucose monitoring (CGM) systems have been recognized as the ideal monitoring systems for glycemic control of diabetic patients. Briefly, a CGM system measures blood glucose levels in subcutaneous tissue by attaching a CGM sensor to the skin, allowing the users to make appropriate modifications to their medical interventions according to experience or empirically derived algorithms. The principles of the glucose sensing employed in the current commercially available CGM systems are mainly electrochemical, and employ the gold standard enzyme, glucose oxidase, as the glucose sensing molecule with the combination of hydrogen peroxide monitoring or with the combination of redox mediator harboring hydrogel. Recently, by employing an abiotic synthetic receptor harboring a fluorescent probe combined with a fluorescent detection system, a chronic CGM was commercialized. In addition, the development of less or non-invasive monitoring sensors targeting glucose in tears, sweat, saliva and urine have become of great interest although their clinical relevancy is still controversial. This review article introduces current and future technological aspects of CGM systems, the flagship technology in biosensor research, which was initiated, matured and is still growing in North America.}, journal={BIOSENSORS & BIOELECTRONICS}, author={Lee, Inyoung and Probst, David and Klonoff, David and Sode, Koji}, year={2021}, month={Jun} }