Reversible capture and release of circulating tumor cells on a three-dimensional conductive interface to improve cell purity for gene mutation analysis

Rare circulating tumor cells (CTCs) are always harvested with large numbers of white blood cells (WBCs) by current CTC isolation techniques, which influences the accuracy of CTC-related gene and protein analysis. Therefore, it is very urgent to develop a method for efficient isolation of CTCs with high purity. In this work, we fabricated a reversibly assembled interface by layer-by-layer assembly of biotinylated poly-(L-lysine-graft-ethylene glycol) (PLL-g-PEG-biotin), streptavidin, and CTC-specific antibody on a three-dimensional conductive scaffold, and further embedded it into a customized microchip for CTC capture. The assembled multilayers increased the roughness of the scaffold, which improved the capture efficiency. Importantly, the PLL-g-PEG-biotin covalently coupled with CTCs could be detached from the scaffold by electrostatic repulsion, and the released CTCs could be recaptured on the conductive scaffold via electrostatic attraction while the WBCs were continuously drifted away. This reversible capture and release strategy significantly improved the purity of CTCs, and pure CTCs were obtained from cancer patients' blood samples for gene mutation assay, which will be of great significance for assisting cancer diagnosis and treatment in a noninvasive way.