Electropolymerized Aptasensor for Femtogram-Level Cytokine Detection

Detecting cytokines at ultralow concentrations is important for the early diagnosis and monitoring of inflammatory and immune disorders, yet remains constrained by the sensitivity and stability of bioelectronic interfaces. Here, we present an electropolymerization strategy for preparing poly(amino-ʟ-tyrosine) (pALT) nanofilms as functional biointerfaces for DNA aptamer-based cytokine recognition. Electropolymerization yields ultrathin, continuous, and ultrasmooth coatings that combine chemical stability with accessible carboxyl functionalities for the direct bioconjugation of amine-terminated aptamers. Integrated into fiber-optic surface plasmon resonance and organic electrochemical transistor platforms, the pALT interfaces support interleukin-6 detection with femtogram-level sensitivity (100 fg mL^-1) across five orders of magnitude in dynamic range, among the lower reported detection ranges. By coupling controllable electropolymerization with direct surface biofunctionalization, this approach provides a versatile route to optical and bioelectronics sensing interfaces on electrically conductive substrates.