Multivalent DNA nanospheres for enhanced capture of cancer cells in microfluidic devices

Isolation of circulating tumor cells (CTCs) from peripheral blood or cancer cells from bone marrow has significant applications in cancer diagnosis, therapy monitoring, and drug development. CTCs are cancer cells shed from primary tumors; they circulate in the bloodstream, leading to metastasis. The extraordinary rarity of CTCs in the bloodstream makes their isolation a significant technological challenge. Herein, we report the development of a platform combining multivalent DNA aptamer nanospheres with microfluidic devices for efficient isolation of cancer cells from blood. Gold nanoparticles (AuNPs) were used as an efficient platform for assembling a number of aptamers for high-efficiency cell capture. Up to 95 aptamers were attached onto each AuNP, resulting in enhanced molecular recognition capability. An increase of 39-fold in binding affinity was confirmed by flow cytometry for AuNP-aptamer conjugates (AuNP-aptamer) when compared with aptamer alone. With a laminar flow flat channel microfluidic device, the capture efficiency of human acute leukemia cells from a cell mixture in buffer increased from 49% using aptamer alone to 92% using AuNP-aptamer. We also employed AuNP-aptamer in a microfluidic device with herringbone mixing microstructures for isolation of leukemia cells in whole blood. The cell capture efficiency was also significantly increased with the AuNP-aptamer over aptamer alone, especially at high flow rates. Our results show that the platform combining DNA nanostructures with microfluidics has a great potential for sensitive isolation of CTCs and is promising for cancer diagnosis and prognosis.