A CD44-biosensor for evaluating metastatic potential of breast cancer cells based on quartz crystal microbalance

A sensitive CD44-biosensor based on quartz crystal microbalance (QCM) was proposed for evaluating metastatic potential of breast cancer cells by using hyaluronan (HA) functionalized substrate film, polydopamine and polyethyleneimine composite film, for the purpose of capturing CD44-positive cancer cells through specific binding of HA to CD44. Two differently CD44-expressed breast cancer cell lines (MDA-MB-231 cells and MCF-7 cells) were put to use as targets for quantitative analysis as well as evaluation of metastatic potential of the cells. The limit of detection for MDA-MB-231 (M231) cells and MCF-7 cells were 300 and 1,000cellsmL^-1, respectively. The expression level of CD44 on M231 cells exhibited two times higher than that of MCF-7 cells, indicating of a higher metastatic potential. Moreover, poly-L-lysine modified QCM sensor was applied to monitor the stiffness of breast cancer cells that can reflect metastatic potential of cells. The results revealed that the MCF-7 cells were stiffer than M231 cells, implying that the M231 cells possessed higher metastatic potential. The proposed protocol is simple and rapid to evaluate the metastatic potential of cancer cells, in addition to offering a promising diagnostic tool for metastatic cancer.