Chromium-based metal-organic framework embedded with cobalt phthalocyanine for the sensitively impedimetric cytosensing of colorectal cancer (CT26) cells and cell imaging

In this study, we have prepared the series of nanohybrids of Cr-based metal-organic framework (Cr-MOF) and cobalt phthalocyanine (CoPc) nanoparticles (denoted as Cr-MOF@CoPc) and investigated them as novel platforms of electrochemical cytosensors for determining colorectal cancer (CT26) cells. The developed Cr-MOF@CoPc nanohybrids were composed of irregularly small nanoparticles, mixed metal valence states of Cr2+/Cr3+/Cr5+ and Co2+/Co3+, rich functional groups of C–O and COO and strong fluorescence performance, as well as high specific area and large pore volume. These intrinsic features of Cr-MOF@CoPc nanohybrids endowed them with strong immobilization ability toward aptamer strands via π- π* stacking, electrostatic interaction, and van der Waals force, excellent electrochemical property, strong fluorescence intensity, and good biocompatibility. Compared with cytosensors based on the sole metal MOFs (Cr-MOF and CoPc) and other reported bulk MOF-based sensors, the constructed Cr-MOF@CoPc-based cytosensor exhibited low detection limit toward CT26 cells, for which the sensing performance was modulated by changing the dosage of CoPc nanoparticles. Electrochemical impedance spectroscopy and differential pulse voltammetry results showed extremely low detection limits of 36 and 8 cells mL−1, respectively, within the concentration range of the CT26 cell suspension (50–1 × 107 cells mL−1), along with high selectivity, excellent stability, and acceptable reproducibility. Thus, the prepared cytosensor can be extensively applied for the analysis of other kinds of cancer cells when anchored their corresponding aptamer strands, providing great potential applications in the biosensor and biomedical fields.