Quantum Dots Labeling Strategy for "Counting and Visualization" of HepG2 Cells.

We report a sensitive, selective, simple, and reliable magnetic immunoassay protocol for detection and imaging of HepG2 cells. After being captured by Cs-doped multicore magnetic nanoparticles (MMNPs), HepG2 cells were labeled by CdSe/ZnS quantum dots (QDs), which could be visualized by fluorescence imaging using the photoluminescence property of QDs, and subsequently, they can be counted by inductively coupled plasma mass spectrometry (ICP-MS) with Cd/Cs as elemental tag. Because of the superior photoluminescence properties and the large quantities of detectable Cd atoms contained in the QDs core, QDs play a dual function role in this assay, making the method easier and more comprehensive than other similar approaches. Under the optimal conditions, the limit of detection of 61 HepG2 cells and the relative standard deviation of 5.4% (800 HepG2 cells, n = 7) were obtained. The linear range was 200-30 000 cells, and the recoveries in human whole blood were in the range of 86-104%. The proposed method enables us not only to count but also to see the cancer cells with the same labeling process, opening a promising avenue for research and clinical application.