Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, Ohio 45433, United States.
UES Inc., Dayton, Ohio 45432, United States.
ACS Nano. 2023 Nov 14;17(21):20968-20978. doi: 10.1021/acsnano.3c02537. Epub 2023 Oct 18.
Biosensors with high selectivity, high sensitivity, and real-time detection capabilities are of significant interest for diagnostic applications as well as human health and performance monitoring. Graphene field-effect transistor (GFET) based biosensors are suitable for integration into wearable sensor technology and can potentially demonstrate the sensitivity and selectivity necessary for real-time detection and monitoring of biomarkers. Previously reported DC-mode GFET biosensors showed a high sensitivity for sensing biomarkers in solutions with a low salt concentration. However, due to Debye length screening, the sensitivity of the DC-mode GFET biosensors decreases significantly during operation in a physiological fluid such as sweat or interstitial fluid. To overcome the Debye screening length limitation, we report here alternating current (AC) mode heterodyne-based GFET biosensors for sensing neuropeptide-Y (NPY), a key stress biomarker, in artificial sweat at physiologically relevant ionic concentrations. Our AC-mode GFET biosensors show a record ultralow detection limit of 2 × 10 M with an extensive dynamic range of 10 orders of magnitude in sensor response to target NPY concentration. The sensors were characterized for various carrier frequencies (ranging from 30 kHz to 2 MHz) of the applied AC voltages and various salt concentrations (10, 50, and 100 mM). Contrary to DC-mode sensing, the AC-mode sensor response increases with an increase in salt concentration in the electrolyte. The sensor response can be further enhanced by tuning the carrier frequency of the applied AC voltage. The optimum response frequency of our sensor is approximately 400-600 kHz for salt concentrations of 50 and 100 mM, respectively. The salt-concentration- and frequency-dependent sensor response can be explained by an electrolyte-gated capacitance model.
生物传感器具有高选择性、高灵敏度和实时检测能力，对于诊断应用以及人体健康和性能监测具有重要意义。基于石墨烯场效应晶体管 (GFET) 的生物传感器适合集成到可穿戴传感器技术中，并有可能展示出实时检测和监测生物标志物所需的灵敏度和选择性。以前报道的直流模式 GFET 生物传感器在低盐浓度溶液中检测生物标志物时表现出很高的灵敏度。然而，由于德拜长度屏蔽，直流模式 GFET 生物传感器在生理流体（如汗液或间质液）中运行时灵敏度会显著降低。为了克服德拜屏蔽长度限制，我们在这里报告了用于在生理相关离子浓度的人工汗液中检测神经肽 -Y (NPY) 等关键应激生物标志物的交流 (AC) 模式外差基 GFET 生物传感器。我们的 AC 模式 GFET 生物传感器在对目标 NPY 浓度的传感器响应中表现出创纪录的超低检测限 2×10 M，具有 10 个数量级的广泛动态范围。我们对各种应用交流电压的载波频率（从 30 kHz 到 2 MHz）和各种盐浓度（10、50 和 100 mM）对传感器进行了表征。与直流模式传感相反，随着电解质中盐浓度的增加，AC 模式传感器响应增加。通过调整施加的交流电压的载波频率，可以进一步增强传感器响应。对于盐浓度分别为 50 和 100 mM 的情况，我们传感器的最佳响应频率约为 400-600 kHz。基于电解质门控电容模型，可以解释盐浓度和频率依赖性的传感器响应。
