Construction of a dual-mode biosensor for electrochemiluminescent and electrochemical sensing of alkaline phosphatase

We demonstrate the construction of a dual-mode biosensor based on fully-π conjugated covalent organic framework (COF) and cobalt oxyhydroxide (CoOOH) nanoflakes for electrochemiluminescent (ECL) and electrochemical sensing of alkaline phosphatase (ALP). The fully-π conjugated COF with sp2 carbon-linkage is synthesized through Knoevenagel polycondensation of 2, 5-dimethoxy-terephthalaldehyde (DMTA) and 1,3,5-tris(4-cynomethylphenyl)benzene (TCPB), and it acts as an efficient ECL emitter whose signal is 41 and 125-fold higher than those of TCPB and DMTA. The ECL signal of TCPB-DMTA-COF may be quenched by CoOOH nanoflakes through electrochemiluminescent resonance energy transfer, and meanwhile CoOOH promotes the oxidation of o-phenylenediamine (o-PD) to generate a high differential pulse voltammetry (DPV) signal. When ALP is present, it hydrolyzes L-ascorbic acid-2-phosphate (AAP) to produce L-ascorbic acid (AA). AA can reduce CoOOH to Co2+, resulting in the decomposition of the CoOOH nanoflakes and consequently the recovery of ECL signal and the decrease of DPV peak current. This dual-mode biosensor can efficiently eliminate the errors associated with personnel operation and experimental factors, leading to more reliability and accuracy than single-mode biosensor. Moreover, this dual-mode biosensor can be applied for specifically sensing ALP in human serums and screening the inhibitors, with potential applications in biomedical researches.