Self-calibrated magnetic aptamer sensor with dual Lanthanide-assisted Time-resolved luminescence for high-sensitive detection of melanoma exosomal PD-L1

•Self-calibrated magnetic aptamer sensor.•Dual lanthanide-assisted time-resolved luminescence signal.•Calculated detection limit as low as 1.88 × 102 particles/mL.•Exosome detection linear range 1.05 × 105–1.05 × 1010 particles/mL.•Efficient differentiation of the healthy from melanoma samples, including early metastatic cases.