Dual-mode fluorescence and UV-vis aptasensor for hepatocellular carcinoma detection using magnetic separation

A dual-mode aptasensor based on magnetic separation with a sequential signal conversion mechanism is developed for sensitive and specific detection of HepG2 cells. The system uses magnetic bead-labeled aptamers (MB-Apt, T1 strand), thiol-modified T2-functionalized silver nanoparticles (T2-AgNPs), and CdTe quantum dots (QDs). Without target cells, T2-AgNPs hybridize with MB-T1, leaving no AgNPs in the supernatant (no UV-vis absorption signal) while CdTe QDs produce strong fluorescence. Upon addition of HepG2 cells, aptamers bind to the cells, releasing AgNPs into the supernatant (UV-vis absorption signal). Subsequent acidolysis releases Ag⁺ ions, quenching QD fluorescence via cation exchange (FL signal). The dual signals offer self-validation and high anti-interference. Under optimal conditions, the fluorescence signal is linear from 0 to 2 × 10⁷ cells/mL (R²=0.985) and UV-vis absorption signal shows good linearity (R²=0.978). The sensor exhibits high specificity for HepG2 over other tumor cells. It successfully detects HepG2 cells spiked in human serum with satisfactory recoveries ranging from 96.2% to 102.5% for the fluorescence mode and 94.8% to 98.7% for the UV/colorimetric mode (RSDs < 5.3%), demonstrating its potential for practical clinical application.