An aptamer biosensor for CA125 quantification in human serum based on upconversion luminescence resonance energy transfer

•A LRET-based fluorescent probe based on UCNPs and carbon dots was prepared.•Fluorescence assay of CA125 was successfully performed using UCNPs/CDs based probe.•High performances were obtained for fluorescence assay of CA125 even in serum samples. CA125 is the most widely used biomarker for the early detection of ovarian cancer. Luminescence resonance energy transfer (LRET)-based probes show pronounced specificity and simplicity for CA125 detection, but they suffer from strong interference from autofluorescence of biosamples. To resolve this problem, near-infrared (NIR)-excitable upconversion nanoparticles (UCNPs) was employed as energy donor to fabricate CA125 biosensor. Carbon dots (CDs) were utilized as energy acceptor for the overlap between the upconversion luminescence (UCL) spectrum of UCNPs and the absorption spectrum of CDs. Aptamer-modified UCNPs were combined with CDs through π-π stacking interaction, which triggered the LRET process and induce UCL quenching with a high quenching efficiency of up to 90%. In presence of CA125, the formation of CA125-aptamer complex blocked the π-π stacking and recovered UCL. The UCL intensity increased linearly with the logarithm of CA125 concentration in the range from 0.01 to 100 U·mL−1. A detection limit of 9.0 × 10−3 U·mL−1 was obtained. This probe is also available for CA125 detection in human serum and may be a useful tool for the early detection of ovarian cancer.