SERS Immunoassay
Based on an Enzyme-Catalyzed Cascade
Reaction and Metal–Organic Framework/Alkaline Phosphatase for
Ultrasensitive Detection of Adenosine Triphosphate
Herein, an adenosine triphosphate (ATP)-induced enzyme-catalyzed
cascade reaction system based on metal–organic framework/alkaline
phosphatase (MOF/ALP) nanocomposites was designed to establish a surface-enhanced
Raman spectroscopy (SERS) biosensor for use in rapid, sensitive ATP
detection. Numerous ALP molecules were first encapsulated using ZIF-90
to temporarily deactivate the enzyme activity, similar to a lock.
Au nanostars (AuNSs), as SERS-enhancing substrates, were combined
with o-phenylenediamine (OPD) to form AuNSs@OPD,
which could significantly improve the Raman signal of OPD. When the
target ATP interacted with the MOF/ALP nanocomposites, ATP could act
as a key to open the MOF structure, releasing ALP, which should further
catalyze the conversion of OPD to oxOPD with the aid of ascorbic acid
2-phosphate. Therefore, with the increasing concentrations of ATP,
more ALP was released to catalyze the conversion of OPD, resulting
in the reduced intensity of the Raman peak at 1262 cm–1, corresponding to the level of OPD. Based on this principle, the
ATP-induced enzyme-catalyzed cascade reaction SERS biosensor enabled
the ultrasensitive detection of ATP, with a low detection limit of
0.075 pM. Consequently, this study provides a novel strategy for use
in the ultrasensitive, rapid detection of ATP, which displays considerable
potential for application in the fields of biomedicine and disease
diagnosis.