Wireless label-free electrochemical detection of cancer cells by MnO2-Decorated polymer dots

The development of an optical biosensor for cancer diagnosis has encountered roadblocks and challenges because of some limitations including a high limit of detection (LOD), low sensitivity, time-consuming procedures, and expensive instrumentation. In this study, we designed a novel wireless electrochemical biosensor based on polymer dot-manganese oxide complexes (PD/MnO2) that provided not only a fluorescence-based approach but also an electrochemical response for the detection of cancer cells on a coated surface. The electroconductive PDs exhibited strong fluorescent emission, which was quenched when the PDs were loaded onto MnO2. This decreased the resistance of the biosensor. In the presence of the extracellular alkaline phosphatase (ALP) expressed by cancer cells and after the addition of 2-phospho-L-ascorbic acid (AAP), the PD/MnO2 complex showed MnO2 cleaving because of the formation of ascorbic acid (AA) as a result of the hydrolysis of AAP by ALP. This phenomenon caused the recovery of PD fluorescence and a change in the biosensor resistance, which was used as an indicator for cancer cell detection. The LOD of the PD/MnO2 biosensor using the electrochemical approach was 3.98 cells/mL, whereas that of the biosensor using the fluorescence approach was 1995 cells/mL. Furthermore, the electrochemical signals could be collected by a wireless electronic device, which allowed realtime cancer detection directly using a smartphone. Thus, the wireless electrochemical biosensor developed in this study was suitable for cancer detection for biomedical and practical applications.