Faradaic electrochemical impedance spectroscopy (f-EIS) in the presence of redox reagent, e.g., [Fe(CN)6]3-/4-, is widely used in biosensors owing to its high sensitivity. However, in sensors detecting amyloid beta (Aβ), the redox reagent can cause the aggregation of Aβ, which is a disturbance factor in accurate detection. Here, we propose an interdigitated microelectrode (IME) based f-EIS technique that can alleviate the aggregation of Aβ and achieve high sensitivity by buffer control. The proposed method was verified by analyzing three different EIS-based sensors: non-faradaic EIS (nf-EIS), f-EIS, and the proposed f-EIS with buffer control. We analyzed the equivalent circuits of nf-EIS and f-EIS sensors. The dominant factors of sensitivity were analyzed, and the impedance change rates via Aβ reaction was compared. We measured the sensitivity of the IME sensors based on nf-EIS, f-EIS, and the proposed f-EIS. The results demonstrate that the proposed EIS-based IME sensor can detect Aβ with a sensitivity of 7.40-fold and 10.93-fold higher than the nf-EIS and the f-EIS sensors, respectively.
Bibliographical noteFunding Information:
Acknowledgments: This work was supported by the Korea Institute of Science and Technology (KIST) institutional program (2E26840). The authors are grateful for the financial support from the Korea Health Industry Development Institute (KHIDI, HI14C3319). Fabrication of the IME sensors was performed at the KIST Micro-Nano Fabrication center (Seoul, Korea). Scanning electron microscopy (SEM) of the IME sensors was executed at the KIST Advanced Analysis center (Seoul, Korea).
© 2018 by the authors. Licensee MDPI, Basel, Switzerland.
- Amyloid beta
- Faradaic electrochemical impedance spectroscopy
- High sensitivity
- Redox reagent
ASJC Scopus subject areas
- Analytical Chemistry
- Information Systems
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering