Electrochemical Determination of the Ovarian Cancer Biomarker CA125 Using TiO₂–ZnO Nanocomposites

Early and accurate detection of ovarian cancer is essential for improving patient outcomes, as most cases are diagnosed at an advanced stage. Cancer antigen 125 (CA125) is a clinically established biomarker that plays a critical role in the diagnosis, prognosis, and recurrence monitoring of epithelial ovarian carcinoma. This study presents a dual-channel electrochemical platform employing ZnO@TiO 2 nanotube arrays for the immunoanalysis of CA125 in complex biological matrices. The nanostructured electrode, fabricated through a sequential hydrothermal and annealing process, exhibited vertically aligned tubular morphology with a mean length of ~2.5   µm and shell thickness of ~20   nm. Electrochemical measurements leveraged dopamine and cytosine as reduction and oxidation probes, respectively, enabling orthogonal signal acquisition. Differential pulse voltammetry revealed wide linear response ranges: 0.1–1000 mU∙mL -1 for cytosine (R² = 0.996; LOD = 0.0002 mU∙mL -1 ) and 0.1–100 mU∙mL -1 for dopamine (R² = 0.992; LOD = 0.0025 mU∙mL -1 ). Impedance spectroscopy confirmed systematic resistance increases during antibody immobilization and antigen binding. The sensor demonstrated excellent reproducibility (RSD ≤ 8.9%), signal stability over 30 days (≥89.1% retention), and selectivity against six common interferents with <5% deviation. Application in 0.2% diluted serum showed recoveries from 99.6% to 100.0% and RSDs <2.01%, validating its performance in real matrices. The combination of core–shell architecture, dual-probe mechanism, and surface regeneration capability positions this system as a promising diagnostic platform for clinical biosensing.