Abstract
Circulating tumor cells (CTCs) are important tumor markers that indicate early metastasis, tumor recurrence, and treatment efficacy. To identify and separate these cells from the blood, new nanomaterials need to be developed. The present study explored the potential application of ZnFe2O4 magnetic nanoparticles in capturing CTCs with cell surface markers. Folic acid was coupled to L-cysteine-capped ZnFe2O4 nanoparticles (ZC) to provide binding sites on ZnFe2O4 nanoparticles for the recognition of folate bioreceptors, which are highly expressed in MCF-7 breast cancer cells. The cytotoxicity of ZnFe2O4 nanoparticles and ZC against MCF-7 was analyzed with the MTT assay. After 24 h of incubation, there were IC50 values of 702.6 and 805.5 µg/mL for ZnFe2O4 and ZC, respectively. However, after 48 h of incubation, IC50 values of ZnFe2O4 and ZC were reduced to 267.3 and 389.7 µg/mL, respectively. The cell quantification was conducted with magnetically collected cells placed on a glassy carbon electrode, and the differential pulse voltammetry (DPV) responses were analyzed. This cost-effective ZnFe2O4-based biosensing platform allowed cancer cell detection with a limit of detection of 3 cells/mL, ranging from 25 to 104 cells/mL. In future, these functionalized zinc ferrites may be used in electrochemical cell detection and targeted cancer therapy.