The sensitive detection of biomarkers
is crucial for the early
identification and treatment of cancer. In this study, a cysteine–histidine–Cu-modified
jujube-like Cu2O (CH-Cu@J-Cu2O) nanozyme was
synthesized and used to fabricate an electrochemical sensor for mucin-1
(MUC1) sensitive detection. Gold-modified reduced graphene oxide and
CH-Cu@J-Cu2O for the sensor were prepared and also characterized
by transmission electron microscopy (TEM), scanning electron microscopy
(SEM), high-resolution transmission electron microscopy (HRTEM), X-ray
diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The
CH-Cu@J-Cu2O nanozyme was used as a signal probe, containing
two catalytic units of cysteine–histidine–Cu and jujube-like
Cu2O. The CH-Cu@J-Cu2O nanozyme can potently
catalyze the H2O2-driven oxidation of dopamine
to aminochrome, leading to a high-level electrochemical signal. This
electrochemical sensor was used to detect MUC1 with a linear range
from 0.5 to 5000 pg·mL–1, and the limit of
detection was 0.085 pg·mL–1, owing to the excellent
catalytic activity of CH-Cu@J-Cu2O. The expression of MUC1
on the surface of MCF-7 cells was further analyzed, and the results
indicate that the proposed strategy is practical for the detection
of biomarkers.
A Faraday-cage-type electrochemical
aptasensor based on two-dimensional
(2D) nanomaterials was developed for the sensitive detection of Escherichia coli O157:H7. In this electrochemical aptasensor,
2D titanium carbide (Ti3C2T
x
) MXene was used for electrode modification. 2D Ti3C2T
x
could immobilize aptamers
via chelation between titanium and phosphate groups and provide a
large electroactive surface for signal transduction. Another 2D zirconium
ferrocene-based metal–organic framework (Zr-Fc MOF) combined
with gold nanoparticles (AuNPs) and 4-mercaptophenylboronic acid (4-MPBA)
(Zr-Fc MOF/AuNPs/4-MPBA) was used as an electrochemical signal label,
in which Fc was a signal molecule and AuNPs could improve the electroactivity
and combine with 4-MPBA via Au–S bonds. 4-MPBA could bind with E. coli O157:H7 via covalent bonding between boronic acid
and the cis-diol of lipopolysaccharides on bacteria
cell walls. So, the signal labels could immobilize on the electrode
to form a Faraday-cage-type structure owing to the large surface area
of Zr-Fc MOF. In this structure, electrons flowed directly between
the electrode and ferrocene, and the electrochemical signal could
be amplified. When the application of 2D nanomaterials and the Faraday-cage
strategy were combined, E. coli O157:H7 was sensitively
detected with a detection limit of 3 CFU·mL–1. The aptasensor was applied for milk sample detection. This aptasensor
has practical application potential because of its properties of satisfactory
sensitivity, specificity, and stability.
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