Biominerized gold-Hemin@MOF composites with peroxidase-like and gold catalysis activities: A high-throughput colorimetric immunoassay for alpha-fetoprotein in blood by ELISA and gold-catalytic silver staining

Catalytic hemin was first remolded with biomineralized gold to form Hemin-Au core and further encapsulated into the Tb metal organic framework (MOF) matrix. The so obtained Hemin-Au@MOF composites could possess high environmental stability and especially double catalysis activities of enhanced peroxidase-like and gold catalysis. Steady state kinetics studies indicate that Hemin-Au@MOF could present much higher intrinsic catalysis and substrate affinity (lower Michaelis constants) than native hemin and even natural peroxidase . Furthermore, the catalytic composites were employed for labeling antibodies towards the sandwiched immunoassays for alpha-fetoprotein (AFP) as a model biomarker of cancers. The results indicate that the Hemin-Au@MOF-based immunoassays could be conducted by two signal amplification ways of hemin-catalyzed chromogenic reaction and gold-catalyzed silver staining, enabling the detection of AFP in blood with the level down to 0.020 ng mL −1 . Importantly, the proposed fabrication protocol combining the gold biomineralization and MOF encapsulation routes may be extended for the fabrication of a variety of enzymes or enzymatic mimics with the improved environmental stability and multiple catalysis activities for the wide catalysis applications.