The isolation and analysis of circulating tumor cells (CTCs) in peripheral blood can offer real-time tumor progression information, thus has important clinical application value. Obtaining high-purity, non-destructive, and viable CTCs from peripheral blood through efficient and accurate separation and enrichment approaches is a prerequisite for downstream analysis. Herein, we propose a highly ordered and reversible circulating tumor cell capture interface based on magnetic boronic acid-functionalized g-C3N4 nanosheets (M-BCN). We used the interaction between boronic acid and glycoproteins to link avidin and biotin-modified aptamers on nanosheets, and realized the highly ordered connection of aptamers. With the combination of oriented decoration of avidin on BCN surface and the well-arranged biotinylated aptamer in the biotin-binding sites in avidin structure, the inter-strand entanglement and the local overcrowding issues were relieved, thus promoting better cell capture performance. The one molar avidin vs four molar biotin stoichiometric relationship enhanced the local multivalency effect of capture ligands. Meanwhile, avidin acted as a "cushion" to reduce the direct interaction between the aptamer and the interface and avoid the inactivation of the aptamer. The cell affinity of the engineered cell capture interface had a total increase of ~100-fold compared with that of free aptamer. In addition, due to the reversible boronate conjugation, the captured CTCs can be gently released by acid fructose with high viability. The capture efficiency of CTCs in whole blood was 91.85% and the release efficiency was 92.41% by using this interface. We achieved the direct isolation of CTCs from the peripheral blood of cancer patients and tumor-bearing mice and successfully achieved downstream mutation analysis and drug susceptibility test. In conclusion, our method can efficiently isolate highly active CTCs, which provides the possibility for the early diagnosis of cancer and the design of personalized treatment regimens.

Magnetic boronic acid-functionalized g-C3N4 nanosheets for capture and nondestructive release of circulating tumor cells

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