Fig.2 Chemical and mechanical stability of pALT nanofilms. (A) SEM images showing that the films remain continuous and crack-free after incubation in different media. Milli-Q water at pH 2 and pH 10 were selected to test stability under acidic and basic conditions, respectively; hexane was used as a nonpolar organic solvent, and DMSO as a strongly polar aprotic solvent. (B) Survey XPS-derived elemental composition of the incubated pALT films. C1s, N1s, and O1s signals were retained under all tested conditions, confirming persistence of the organic pALT layer. The increased Au4f signal observed after DMSO, hexane, and pH 2 incubation indicates increased visibility of the underlying Au substrate, consistent with limited interfacial reorganization and/or partial removal of weakly bound oligomeric species. (C) Relative C1s component distribution obtained from high-resolution C1s fitting. The largely preserved component distribution supports retention of the main pALT chemical structure, while the pH 10-treated sample showed increased C–C/C–Hx and decreased C–O/C–N contributions, suggesting alkaline-induced reorganization or further coupling/crosslinking. (D) AFM image and the 3D image of pALT5c nanofilms transferred to polydimethylsiloxane (PDMS) substrates. The corresponding Young’s modulus of pALT5c is 1.3 ± 0.2 GPa, as determined from three independent measurements. (E) Photograph of the flexible pALT5c nanofilms supported by a polycarbonate membrane.#

Fig.3 Aptamer functionalization and characterization. (A) Schematic of aptamer immobilization on pALT-coated gold substrates via EDC/NHS coupling. Confocal fluorescence micrographs of aptamer-functionalized pALT nanofilms following incubation with: (B) Cy3-labeled complementary strand (Apt′) and (C) Cy3-labeled scrambled control sequence (Scr). Bright fluorescence appears exclusively for Apt′ hybridization, confirming specific aptamer immobilization.#

Fig.4 Concept and operation of the pALT-based cytokine aptasensor. (A) Cytokines such as IL-6 are present in diverse biofluids, including blood, saliva, and sweat. (B) Schematic of IL-6 binding to surface-immobilized aptamers on pALT nanofilms. The recognition event modulates the interfacial environment, giving rise to (C) a wavelength shift in FO-SPR or the current modulation of OECTs (D) with functionalized pALT-gate electrodes (E).#

研究将这套界面分别搭载 FO‑SPR 光学传感与 OECT 有机电化学晶体管平台，实现两种信号读出。FO‑SPR 可以捕捉 IL‑6 结合带来的共振偏移，但在超低浓度场景会受仪器分辨率限制。而OECT 电化学传感展现出核心性能突破，如图 5 所示，器件检测限低至 10 fg mL⁻¹（0.48 fM），线性检测范围横跨 100 fg mL⁻¹～10 ng mL⁻¹ 共 5 个数量级，同时对 TNF‑α 等对照细胞因子几乎无响应，证实优异的检测特异性，器件也具备基础存储稳定性，电聚合工艺可适配多种导电基底。

Fig.5 Biosensing performance of the pALT-based cytokine aptasensor. (A) Schematic of the FO-SPR setup. (B) Real-time resonance shifts during electropolymerization and aptamer functionalization. (C) FO-SPR response to IL-6 at different concentrations. Data were extracted from one continuous measurement on a single sensor and baseline-normalized for comparison. The full trace and independent repeats are shown in Figure S14A, B. (D) Planar OECT configuration with pALT-coated Au gate. (E) Stability of OECTs over six consecutive incubation cycles in PBS. Inset: gate-voltage shift over six consecutive cycles, calculated from the current value at VGS = 0.2 V with VDS fixed at –0.4 V. (F, G) Transfer-curve shifts upon exposure to IL-6 and TNF-α. (H) Analytical calibration of ΔVGS versus cytokine concentration. The error bars were obtained from the standard deviation of five devices for IL-6 and four devices for TNF-α. The black dashed line represents the linear detection range for IL-6, and the red dashed line represents the average of the variation of the gate voltage for TNF-α. (I) Comparison of tested lower concentration limits and the reported linear range with state-of-the-art IL-6 biosensors.#