Reticulated Ferrocene−Polycarbazole Nanofibers Coupled with CuAl-LDH for Ultrasensitive Label-Free Electrochemical Detection of CA125

Abstract The development of highly sensitive and reliable sensing platforms for ovarian cancer biomarkers is of considerable importance for improving the early diagnostic performance and supporting clinical decision-making. Cancer antigen 125 (CA125) is among the most critical tumor markers for early detection and diagnosis. This study reports the synthesis and characterization of ferrocene-appended carbazole monomer and ferrocene-appended polycarbazole (PFC) using analytical techniques such as NMR, MALDI-MS, FTIR, single-crystal X-ray diffraction, UV−vis spectroscopy, TGA, and SEM. Carbazole was chosen for its superior conductivity, while ferrocene was integrated for its remarkable electroactivity. Subsequently, a blend of PFC and polycaprolactone (PCL) was electrospun onto a glassy carbon electrode (GCE), creating a reticulated PFC@PCL/GCE surface with enhanced electrochemical performance. CuAl-layered double hydroxide (CuAl-LDH) was synthesized and functionalized with amine (−NH2) groups (CuAl@A) via functional organosilane, creating a highly effective immobilization matrix for anti-CA125. The structural and morphological properties of CuAl-LDH and CuAl@A were characterized with SEM, TEM, FTIR, XRD, and TGA. CuAl@A was drop-cast onto the reticulated electrode surface to create a suitable platform for immobilizing anti-CA125, resulting in a modified immunosensor (Ab-CA125/CuAl@A/PFC/GCE). Under the optimized conditions, the immunosensor exhibited high selectivity and sensitivity, enabling the detection of CA125 at low concentrations. The sensor demonstrated a broad linear detection range from 1.0 pg/mL to 100 ng/mL with a detection limit of 0.62 pg/mL. The validation of the proposed electrochemical immunosensor system was performed with spike tests and a reference method (ELISA), both of which demonstrated high accuracy. This label-free electrochemical immunosensor represents a promising platform for the clinical detection of tumor markers, offering a simple, reliable, and highly sensitive approach for CA125 quantification.