An amperometric nanobiosensor using a biocompatible conjugate for early detection of metastatic cancer cells in biological fluid.

Metastasis is the major cause of cancer-associated death in humans, and its early diagnosis will help clinicians to develop suitable therapeutic strategies which may save life of cancer patients. In this direction, we designed an amperometric biosensor using a biocompatible conjugate to diagnose cancer metastasis by detecting epithelial cell adhesion molecule expressing metastatic cancer cells (Ep-MCCs). The sensor probe is fabricated by immobilizing monoclonal capture antibody (CapAnti) on the gold nanoparticles (AuNPs)/conducting polymer composite layer. The detection relies on a sandwich-type approach using a bioconjugate composed of reporter antibody (RepAnti), nanostructured collagen (nCOL), AuNPs, and hydrazine (Hyd) which served as a nonenzymatic electrocatalyst for the reduction of H2O2. The binding of Ep-MCCs with the sensor probe was confirmed using electrochemical impedance spectroscopy, cyclic voltammetry, and chronoamperometry. A dynamic range for the Ep-MCCs detection is determined between 45 and 100,000 Ep-MCCs/mL with the detection limit of 28±3 Ep-MCCs/mL. The proposed immunosensor is successfully applied to detect Ep-MCCs in serum and mixed cell samples and interferences due to nontarget cells and molecules present in the real sample matrix are also examined. The early stage of Ep-MCCs was examined by fluorescence-activated cell sorting assay, which confirms that the developed biosensor has detected Ep-MCCs in its early stage.