Ni-C@MOF-Apt microspheres with enzyme activity and photodynamic properties for capture and clearance of MCF-7 cells.

Circulating tumor cells (CTCs) carry a migration risk, prone to forming metastatic foci and exacerbating the disease. Therefore, it is of great importance to improve the capture efficiency and killing effect of CTCs. First, Ni-doped covalent organic framework (Ni-COF) is used as a precursor for calcination at 900 °C, which reduces Ni2+ to magnetic Ni nanoparticles, and COF evolve into carbon nanospheres exhibiting enzyme activity (Ni-C-900). Then, with the photosensitizer meso-Tetrakis (4-carboxyphenyl) porphyrin (TCPP) as the first ligand and (2,5-dicarboxyphenyl) boronic acid (DCBA) as the second ligand, a metal-organic framework shell is in-situ grown on the surface of Ni-C-900 to obtain Ni-C@MOF. Finally, the aptamers are orderly linked via DCBA ligands to obtain Ni-C@MOF-Apt microspheres. Ni-C@MOF-Apt exhibits excellent targeting towards MCF-7 cancer cells, with a capture efficiency of 82.6% in whole-blood samples (1000 cells per milliliter), and the capture efficiency can still be maintained at 71% within a relatively low cell-concentration range (50 cells per milliliter). In addition, under weakly acidic conditions, Ni-C@MOF-Apt exhibits peroxidase (POD) and oxidase (OXD) activities, which can generate reactive oxygen species (ROS) to eliminate MCF-7 cells in synergy with photodynamic effects. This strategy combines nanozyme activity with photodynamic effects and improves the killing efficacy against MCF-7 cells.