Upconversion luminescence assay for the detection of the vascular endothelial growth factor, a biomarker for breast cancer

Upconversion nanoparticles (UCNPs) of the type α-NaYF 4 :Yb 3+ , Er 3+ and a typical diameter of 6–7 nm were synthesized by thermal decomposition of the respective rare-earth stearate. The oleic acid on the surface of the UCNPs was then replaced by aptamer DNA. The assay was performed in a microplate format with a capture probe immobilized in the wells. Following binding of the vascular endothelial growth factor (VEGF), an auxiliary probe DNA is added that is labeled with UCNPs and binds to the VEGF-loaded capture probe. The method enables highly sensitive and highly specific detection of the VEGF which is a marker for breast cancer. Under the optimum conditions, the intensity of the upconversion luminescence (at excitation/emission wavelengths of 980/541 nm) is linearly proportional to the VEGF concentration in the 50 pM to 2000 pM concentration range, with a 6 pM detection limit. The method was applied to the determination of VEGF in spiked serum, typically at a 500 pM level, and gave recoveries that ranged from 98 to 113 %, with RSDs between 2.9 and 3.6 %. This makes it a viable tool for early diagnosis of breast cancer. Graphical abstract An upconversion luminescence based assay is presented for trace analysis of vascular endothelial growth factor. It is based on a sequence fragment-linked technique of target-induced aptamer (AP) and upconversion nanoparticles (UCNPs) and has potential application in the early diagnosis of breast cancer.