Herein, a highly sensitive electrochemical immunosensor was presented for the cardiac troponin I (cTnI) determination using a multifunctional covalent organic framework-based nanocomposite (HRP-Ab2-Au-COF) as the signal amplification probe. The spherical COF with a large surface area was synthesized in a short time by a simple solution-based method at room temperature. The good biocompatibility, low toxicity, and high stability in water of the COF guarantee its application in biosensing. Besides, its high porosity makes it an excellent carrier for loading abundant horseradish peroxidase (HRP). The modified gold nanoparticles on the surface of COF not only provide a load platform for secondary antibody (Ab2) but also improve the conductivity of COF. Under the synergistic effect of the hydrogen peroxide (H 2 O 2 ) and HRP, hydroquinone (HQ) in the solution is catalytically oxidized to benzoquinone (BQ), which is then reduced on the electrode surface to generate the electrochemical signal. The designed probes not only show the specific recognition behavior of Ab2 to cTnI but also improve the sensitivity of the biosensing system due to the signal amplification caused by the excellent enzyme catalytic performance of HRP. Based on the H 2 O 2 -HRP-HQ signal amplification system, the biosensor for cTnI was fabricated and exhibited a linear response as a function of logarithmic cTnI concentration ranging from 5 pg/mL to 10 ng/mL, and the detection limit was 1.7 pg/mL. Moreover, the biosensor exhibited excellent recovery and reproducibility in the actual sample testing. This work provided a simple approach to determine cTnI quantitatively in practical samples and broadened the utilization scope of the COF-based nanocomposite in the electrochemical immunosensor.
The
early and rapid diagnosis of acute myocardial infarction (AMI)
is of great significance to its treatment. Here, we developed an electrochemiluminescence
biosensor based on an entropy-driven strand displacement reaction
(ETSD) and a tetrahedral DNA nanostructure (TDN) for the detection
of the potential AMI biomarker microRNA-133a. In the presence of the
target, numerous Ru(bpy)3
2+-labeled signal probes
(SP) were released from the preformed three-strand complexes through
the process of ETSD. The ETSD reaction cycle greatly amplified the
input signal of the target. The released SP could be captured by the
TDN-engineered biosensing interface to generate a strong ECL signal.
The rigid structure of TDN could significantly improve the hybridization
efficiency. With the assistant of double amplification of TDN and
ETSD, the developed biosensor has a good linear response ranging from
1 fM to 1 nM for microRNA-133a, and the detection limit is 0.33 fM.
Additionally, the constructed biosensor has excellent repeatability
and selectivity, demonstrating that the biosensor possesses a great
application prospect in clinical diagnosis.
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