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@TiO₂ 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.