Artificial control of cell adhesion on smart surface is an on-demand technique in areas ranging from tissue engineering, stem cell differentiation, to the design of cell-based diagnostic system. In this paper, we report an electrochemical system for dynamic control of cell catch-and-release, which is based on the redox-controlled host-guest interaction. Experimental results reveal that the interaction between guest molecule (ferrocene, Fc) and host molecule (β-cyclodextrin, β-CD) is highly sensitive to electrochemical stimulus. By applying a reduction voltage, the uncharged Fc can bind to β-CD that is immobilized at the electrode surface. Otherwise, it is disassociated from the surface as a result of electrochemical oxidation, thus releasing the captured cells. The catch-and-release process on this voltage-responsive surface is noninvasive with the cell viability over 86%. Moreover, because Fc can act as an electrochemical probe for signal readout, the integration of this property has further extended the ability of this system to cell detection. Electrochemical signal has been greatly enhanced for cell detection by introducing branched polymer scaffold that are carrying large quantities of Fc moieties. Therefore, a minimum of 10 cells can be analyzed. It is anticipated that such redox-controlled system can be an important tool in biological and biomedical research, especially for electrochemical stimulated tissue engineering and cell-based clinical diagnosis.

Pro-metastatic cell signaling controls the switch to distant metastasis and the final cancer death. In hepatocellular carcinoma (HCC), this death switch is turned on by the multiprotein interactions of β-catenin with many transcription factors, so a method to assay the bioactivity of β-catenin to participate in these pro-metastatic protein/protein interactions has been proposed in this work. This method employs cost-effective peptide-based protein targeting ligands, while the electrochemical catalytic cross-linking in this method also "finalize" the noncovalent molecular recognition, so that the robustness can be improved to enable detection of relatively more complex biosamples. In studying clinical samples with the proposed method, the cellular distribution and overall expression of β-catenin show a parallel with the pathological grade of the sample, particularly, nuclear translocation. The pro-metastatic activation of β-catenin can also be observed as evidently correlated with higher-grade cases, suggesting the active role of β-catenin in promoting metastasis. According to these results, the proposed method may have the prospective use as a prognostic tool for evaluating the potential of invasion and metastasis in cancer.

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