科研之友
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摘要
We now present a novel signal amplification strategy of the photoswitchable enzyme cascade that can be used for versatile biosensing applications. Specifically, the biocatalysis of alkaline phosphatase (ALP) allows the formation of a nano-trigger of catechol coordinated TiO2 nanoparticles (NPs), which subsequently activates the activity of horseradish peroxidase (HRP) for oxidizing its typical substrate of 3,3',5,5'-tetramethylbenzidine (TMB) under visible light irradiation. This photoswitchable enzyme cascade has powerful signal amplification effect, enabling us to construct advanced colorimetric sensing platform for probing ALP-based bioassays with ultra-high sensitivity. A low detection limit of 4 x 10(-4) U/L was obtained for probing the activity of ALP. In addition, an immunoassay protocol to detect the cancer biomarker of human antigen alpha-fetoprotein (AFP, taken as a model) with the detection limit as low as 0.02 pg/mL also validated the versatility of the biocatalytic cascade as the amplified signaling transducer. Different from the conventional enzyme cascades in which the product of one enzyme is the substrate of the other, this study sets up the first example of nanomaterial mediated photoswitchable enzyme cascade, which may find wide applications in bioassays that relying on enzymatic catalysis for signal readout.
