Considering the enormous demand for meat in people’s
daily
lives, the development of efficient meat freshness assays is of great
significance for safeguarding food safety. Here, a novel bimetallic
nanozyme Fe@CeO2 with high peroxidase-like activity was
first synthesized by embedding ferrocenecarboxylic acid (Fc) into
hollow CeO2 nanospheres, which combined with xanthine oxidase
(XOD) to develop a self-supplying H2O2-facilitated
enzymatic cascade catalytic system of XOD + Fe@CeO2, yielding
a meat freshness indicator hypoxanthine (Hx)-responsive colorimetric
and photothermal dual-mode analytical platform for judging meat freshness
upon the assistance of 3,3′,5,5′-tetramethylbenzidine
(TMB). Owing to the catalytic activity of XOD to convert Hx into H2O2, Fe@CeO2 rapidly dissociated it into •OH via a peroxidase activity-triggered Fenton-like
reaction, emerging a typical enzymatic cascade catalytic reaction.
As a result, the colorless TMB was oxidized to be the product of dark-blue
oxTMB by •OH, with a chromogenic reaction-driven
absorption enhancement at 652 nm, which endowed it with a significant
photothermal effect under 660 nm laser irradiation. On this basis,
an Hx concentration-dependent colorimetric and photothermal dual-mode
signal cascade catalytic enhancement sensing platform was proposed
by integrating with a Color Picker App-installed smartphone and a
660 nm laser-equipped handheld thermal imager, achieving the onsite
quantitative, reliable, and visual detection of Hx in real meat samples
for judging meat freshness with acceptable results. Notably, the colorimetric
and photothermal dual-mode signal cascade catalytic enhancement improved
not only the reliability but also the sensitivity of the assay, which
provided new insights for efficient onsite visual monitoring of meat
freshness to safeguard food safety.