Ferrocene covalently confined in porous MOF as signal tag for highly sensitive electrochemical immunoassay of amyloid-β

Here a new type of ferrocene confined in a metal–organic framework (Fc-Zn-MOF) as an electrochemical signal tag has been synthesized and applied in an immunosensor for highly sensitive amyloid-β (Aβ, as a model protein) detection. In the present work, an electrochemically active molecule of Fc was covalently bonded in a Zn-MOF via postsynthetic modification to obtain a flower-like Fc-Zn-MOF, in which the high-content Fc signal units were periodically arranged in a well-defined porous structure, showing enhanced electrochemical activity. As noticed, Fc molecules are chemically anchored on the Zn-MOF, which avoids leakage of signal molecules, protects those electrochemical activities from potential damage and exhibits good stability. The Fc-Zn-MOF signal tag was further explored in constructing an electrochemical immunosensor for Aβ detection, with a linear range from 0.0001 to 100 ng mL−1 and a detection limit of 0.03 pg mL−1, showing improved analytical performance. This work presents an example of an Fc-MOF as a signal tag for Aβ detection, which would encourage atypical research lines for MOFs in bioassays where the introduction of ordered structures promises new opportunities.