Construction of Flexible Electrochemical Sensing Interfaces Based on Paper/PEDOT:PSS for the Detection of Cystatin C.

Chronic kidney disease (CKD) is a global public health issue, with high prevalence and mortality. As cystatin C is a biomarker for the early diagnosis of CKD, there is an urgent need to develop a simple and inexpensive method for the detection of Cys C in human plasma. Herein, a sensitive method with flexible electrochemical aptamer-based (E-AB) sensing interfaces has been established using poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)-treated paper-based electrodes. Introduction of MoS₂ quantum dots increased the specific surface area and realized effective immobilization of the thiolated Cys C aptamer (Cys C Apt) modified with methylene blue through the formation of disulfide bonds. The E-AB sensing interfaces were successfully applied to the quantification of Cys C in human venous whole blood and plasma samples based on the binding-induced conformational change mechanism of Cys C Apt by employing square wave voltammetry. The flexible E-AB sensing interfaces show significant potential to be developed into wearable patches for in vivo detection of Cys C, which will pave the way for early diagnosis and long-term monitoring of CKD.