Isothermal nucleic acid amplification-based magnetic aptasensor for sensitive detection and in situ imaging of Trop-2 in triple-negative breast cancer

Background Triple-negative breast cancer (TNBC) is strongly linked to overexpression of Trop-2, a transmembrane glycoprotein biomarker implicated in its aggressive behavior. For in situ imaging and quantification of this membrane protein, we developed a highly sensitive fluorescence aptasensor. Results Upon recognition of Trop-2 by its specific aptamer, hybridization chain reaction (HCR) was triggered for in situ imaging of cell-surface Trop-2. Concurrently, catalytic hairpin assembly (CHA) amplified fluorescence signals for quantitative Trop-2 detection. Successful cellular imaging and quantitative Trop-2 detection were achieved a linear response was observed from 0.001 μM to 0.1 μM, the limit of detection (LOD) was determined to be 0.0009 μM. Trop-2 surface density measurements revealed average amount per cell of: 6.0 × 10 6 molecules per cell (MDA-MB-468), 2.0 × 10 6 molecules per cell (MCF-7), 6.6 × 10 5 molecules per cell (MDA-MB-231), and 4.1 × 10 5 molecules per cell (HL-7702). Significance To our current knowledge, the work represents the first aptasensor enabling both in situ Trop-2 protein imaging and quantitative comparison across diverse cell types. The proposed method shows promise for tumor diagnosis and therapeutic evaluation.