Facile synthesis of 3D hierarchical micro-/nanostructures in capillaries for efficient capture of circulating tumor cells

The efficient capture of rare circulating tumor cells (CTCs) with high viability is of great importance in cancer diagnosis. The integration of three-dimensional (3D) nanobiointerfaces with capillary flow channel platforms can efficiently improve CTC capture performance by providing abundant binding sites and increasing the likelihood of contact as samples flow through the microchannels. However, due to the complex preparation processes, facile synthesis of nanostructures for use as substrates in flow channels for biomedical applications is still challenging. To reduce the encapsulation steps in the fabricating of nanostructured flow channel devices, we chose the enclosed glass capillaries as flow channels and accomplished all the experiments in the microchannels, including 3D nanostructure synthesis, surface modification and capture/release of CTCs. In this work, we constructed a novel 3D Zn(OH)F/ZnO nanoforest array in capillaries for CTC isolation via a facile microfluidic wet chemistry method. Because of the abundant binding sites of the 3D Zn(OH)F/ZnO nanoforest array, the capture efficiency was remarkably enhanced compared with that of vertical nanowires (90.3% vs 69.1%). In addition, a high release efficiency and cell viability of released cells were achieved by grafting poly(N-isopropylacrylamide) (PNIPPAm). These results may provide evidence for a novel method to fabricate hierarchical 3D substrates with a combination of biomolecule recognition and topographical interaction for biomedical applications.