Label-Free Electrochemical Aptasensor Based Upon Thionine-Modified Molybdenum(IV) Sulfide Nanosheets for the Sensitive Determination of Prostate-Specific Antigen (PSA)

Prostate-specific antigen (PSA) is an important biomarker for the early diagnosis and monitoring of prostate cancer. To address the limitations of conventional diagnostic approaches and facilitate PSA analysis, a label-free electrochemical aptasensor based on thionine-modified molybdenum disulfide (MoS2-Thi) nanocomposites was developed. In this sensor, MoS2 nanosheets serve as an efficient carrier and a signal amplification platform, whereas aptamers are anchored onto the glassy carbon electrode (GCE) surface to accomplish target identification. The recognition mechanism is based on a conformational change of the aptamer, which generates both spatial steric hindrance and electrostatic repulsion at the electrode interface, thereby inhibiting electron transfer and decreasing the redox peak current of Thi. The current change is monitored by differential pulse voltammetry (DPV), enabling accurate quantification of PSA. Meanwhile, the ferrocene (Fc) peak was monitored as a secondary electrochemical signal complementary to the Thi-based quantitative response. Under the optimal conditions, the sensor exhibited a linear detection range for PSA from 1.0 × 10−12 to 1.0 × 10−7 mol/L, with a detection limit of 4.8 × 10−13 mol/L. In simulated human serum samples, the recovery ranged from 94.5% to 102.6%. This label-free aptasensor demonstrates potential applicability for PSA determination in complex biological matrices.