Constructing 2D Nanosheet-Assembled MnCo₂O₄ Nanotubes for Pressure and Colorimetric Dual-Signal Readout Detection of Cancer Cells in Serum Samples

Developing a facile and reliable strategy for detecting cancer cells in early stages in aqueous systems remains a challenge, although this strategy is crucial in biomedicine. Here, a green approach is proposed for synthesis of MnCo2O4 nanotubes. The resulting nanotubes have been shown to have peroxidase activity that catalyzes the oxidation of 3,3′,5,5′-tertamethylbenzidine (TMB) by O2, resulting in a typical color reaction from colorless to blue. Moreover, such nanotubes exhibit excellent catalytic properties for the decomposition of H2O2 into O2, resulting in a significant increase in pressure in the bottle. Thus, a new sensor system using MnCo2O4 nanotubes as an artificial peroxidase, generating O2 as pressure signal, and TMB as a color change reporter molecule for dual-mode pressure-based (pressuremeter) and colorimetric (naked eye) detection of cancer cells was established. By using folic acid (FA) as a recognition element, a total of 50 folate receptor (FR) positive cancerous cells can be distinguished by naked-eye observation and pressuremeter. The clinical applicability of such a dual-mode strategy has been tested in detecting cancer cells in serum samples. We envisaged that such a dual-signal readout dual-mode strategy based on MnCo2O4 nanotubes offers a promising biosensing platform for early clinical diagnosis.