@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{hatada_pavlidis_sode_2024, title={Development of a glycated albumin sensor employing dual aptamer-based extended gate field effect transistors}, volume={251}, ISSN={["1873-4235"]}, url={https://doi.org/10.1016/j.bios.2024.116118}, DOI={10.1016/j.bios.2024.116118}, abstractNote={Glycated albumin (GA), defined as the percentage of serum albumin glycation, is a mid-term glycemic control marker for diabetes. The concentrations of both glycated human serum albumin (GHSA) and total human serum albumin (HSA) are required to calculate GA. Here, we report the development of a GA sensor employing two albumin aptamers: anti-GHSA aptamer which is specific to GHSA and anti-HSA aptamer which recognizes both glycated and non-glycated HSA. We combine these aptamers with extended gate field effect transistors (EGFETs) to realize GA monitoring without the need to pretreat serum samples, and therefore suitable for point of care and home-testing applications. Using anti-GHSA aptamer-immobilized electrodes and EGFETs, we measured GHSA concentrations between 0.110 μM within 20 min. The sensor was able to measure GHSA concentration in the presence of BSA for a range of known GA levels (5–29%). With anti-HSA aptamer-immobilized electrodes and EGFETs, we measured total HSA concentrations from 117 μM. Furthermore, GHSA and total HSA concentrations of both healthy and diabetic-level samples were determined with GHSA and HSA sensors. The measured GHSA and total HSA concentrations in three samples were used to determine respective GA percentages, and our calculations agreed with GA levels determined by reference methods. Thus, we developed simple and rapid dual aptamer-based EGFET sensors to monitor GA through measuring GHSA and total HSA concentration, without the need for sample pretreatment, a mandatory step in the current standard of enzymatic GA monitoring.}, journal={BIOSENSORS & BIOELECTRONICS}, author={Hatada, Mika and Pavlidis, Spyridon and Sode, Koji}, year={2024}, month={May} }
 @article{khanwalker_hatada_labelle_sode_2024, title={Development of an electrochemical impedance spectroscopy immunosensor for insulin monitoring employing pyrroloquinoline quinone as an ingestible redox probe}, volume={250}, ISSN={["1873-4235"]}, url={https://doi.org/10.1016/j.bios.2024.116049}, DOI={10.1016/j.bios.2024.116049}, abstractNote={Contemporary electrochemical impedance spectroscopy (EIS)-based biosensors face limitations in their applicability for in vivo measurements, primarily due to the necessity of using a redox probe capable of undergoing oxidation and reduction reactions in solution. Although previous investigations have demonstrated the effectiveness of EIS-based biosensors in detecting various target analytes using potassium ferricyanide as a redox probe, its unsuitability for blood or serum measurements, attributed to its inherent toxicity, poses a significant challenge. In response to this challenge, our study adopted a unique approach, focusing on the use of ingestible materials, by exploring naturally occurring substances within the body, with a specific emphasis on pyrroloquinoline quinone (PQQ). Following an assessment of PQQ's electrochemical attributes, we conducted a comprehensive series of EIS measurements. This involved the thorough characterization of the sensor's evolution, starting from the bare electrode and progressing to the immobilization of antibodies. The sensor's performance was then evaluated through the quantification of insulin concentrations ranging from 1 pM to 100 nM. A single frequency was identified for insulin measurements, offering a pathway for potential in vivo applications by combining PQQ as a redox probe with EIS measurements. This innovative approach holds promise for advancing the field of in vivo biosensing based on the EIS method.}, journal={BIOSENSORS & BIOELECTRONICS}, author={Khanwalker, Mukund and Hatada, Mika and LaBelle, Jeffery T. and Sode, Koji}, year={2024}, month={Apr} }
 @article{ikegai_okuda-shimazaki_tran_hatada_asano_ikebukuro_tsugawa_sode_2024, title={The 2.5th generation enzymatic sensors based on the construction of quasi-direct electron transfer type NAD(P)-Dependent dehydrogenases}, volume={255}, ISSN={["1873-4235"]}, url={https://doi.org/10.1016/j.bios.2024.116219}, DOI={10.1016/j.bios.2024.116219}, abstractNote={We introduce a versatile method to convert NAD+ or NADP+ -dependent dehydrogenases into quasi-direct electron transfer (quasi-DET)-type dehydrogenases, by modifying with a mediator on the enzyme surface toward the development of 2.5th generation enzymatic sensors. In this study, we use β-hydroxybutyrate (BHB) dehydrogenase (BHBDh) from Alcaligenes faecalis (AfBHBDh) as a representative example NAD+ or NADP+ -dependent dehydrogenase. BHBDhs are important in ketone monitoring, especially for the diagnosis of diabetic ketoacidosis. We modified AfBHBDh with a thiol-reactive phenazine ethosulfate (trPES). We designed, constructed, and modified mutant BHBDhs harboring cysteine residues within 20 Å from the C4 nicotinamide in NAD+/NADH. Mutants Ser65Cys, Thr96Cys, and Lys106Cys showed indistinguishable catalytic activities from the wild-type enzyme, even after trPES modification. These trPES-modified mutants were immobilized on gold disk electrodes via amine coupling with succinimide-groups of dithiobis (succinimidyl hexanoate) self-assembled monolayers for electrochemical measurements. Considering there is a wide range of BHB concentrations, we exploited the linear regression in log scales. The linear range for the sensors with trPES-modified BHBDh mutants Ser65Cys, Thr96Cys, and Lys106Cys were 0.1–4.0 mM in both buffer solution and artificial interstitial fluid (ISF). They have limits of detection of 0.047 mM for Ser65Cys, 0.15 mM for Thr96Cys, and 0.060 mM for Lys106Cys in buffer solution, and 0.12 mM, 0.089 mM, and 0.044 mM in artificial ISF, respectively. These results indicate redox mediator modification of NAD(P)-dependent dehydrogenases converts them into quasi-DET-type dehydrogenases, thereby enabling their utilization in 2.5th generation enzymatic sensors, which will facilitate the construction of enzymatic sensors suitable for continuous monitoring systems.}, journal={BIOSENSORS & BIOELECTRONICS}, author={Ikegai, Kurea and Okuda-Shimazaki, Junko and Tran, Truc Thanh and Hatada, Mika and Asano, Ryutaro and Ikebukuro, Kazunori and Tsugawa, Wakako and Sode, Koji}, year={2024}, month={Jul} }