Yifeng Tu

A sensitive colorimetric detection toward tyrosinase activity was developed. Rod-shaped manganese-doped cerium oxide (Mn/CeO2) nanozyme was synthesized through a simple hydrothermal process. This complex exhibited a peroxidase-like activity, which was able to accelerate the conversion of a colorless chromogenic substrate TMB (3,3',5,5'-tetramethylbenzidine) into a blue product. It was found that a substrate for tyrosinase, catechol, significantly inhibited this catalysis and the subsequent color change. The further introduction of tyrosinase facilitated an oxidation of catechol into a benzoquinone product without the inhibiting capability, and a recovery of the catalysis from the nanozyme was rendered. This response presented a turn-on colorimetric signal toward tyrosinase in the range 1-3000 U/L, with a detection limit at 0.3 U/L. The scheme was successfully applied onto practical samples.

Alzheimer's disease (AD) is a degenerative condition of the nervous system that causes severe damage to patients’ daily activities and quality of life. Amyloid beta 1–40 protein (Aβ₄₀), which is involved in the formation of cerebral plaques, is one of the crucial biomarkers related to AD. Herein, a novel and highly sensitive immunosensor for the detection of Aβ₄₀ is developed. Using a reinforced indium tin oxide-coated glass with a nanocomposite of gold nanoparticle-enhanced CoSn(OH)₆ (AuNPs@CoSn(OH)₆) to trigger the electrochemiluminescence (ECL) of luminol as the sensing signal, the immunosensor is fabricated by immobilizing the Aβ₄₀ antibody onto it. By integrating the high immune specificity, excellent conductivity and catalytic activity of the nanocomposite, the resultant immunosensor can be successfully employed to detect the target in real samples. The formation of the immune complex leads to increased steric hindrance and electron transfer resistance, which in turn causes a declined ECL output when the target Aβ₄₀ binds to the antibody on the sensor surface. Under optimized conditions, the developed ECL immunosensor exhibits a linear response for Aβ₄₀ ranging from 1 to 800 pg mL⁻¹ and a low detection limit of 0.47 pg mL⁻¹. Experimentally, it is demonstrated to be highly sensitive, specific, reproducible and stable. This work extends the application of the perovskite CoSn(OH)₆ and AuNPs in the field of ECL immunosensing and provides a novel strategy for clinical research on Alzheimer's disease.

Flash phase engineering (FPE) enables the fabrication of heterophase MoS₂ nanofilms that efficiently transition from the 1T to the 2H phase by controlled laser irradiation. This offers large-area fabrication of site-selective heterophase structures.

To simply and rapidly detect the highly phosphorylated tau protein at threonine 217 (p-tau217) as a precautionary measure against Alzheimer's disease and distinguish it from other neurodegenerative diseases, a novel immunosensor was prepared using luminol as the electrochemiluminescent (ECL) sensing probe reinforced by Au-Cu nanoparticles (Au-Cu NPs). The Au-Cu alloy NPs were prepared via a co-reduction reaction, exhibiting excellent conductivity and catalytic activity. These properties remarkably enhanced the ECL of luminol, providing a suitable background for the sensing response. After the Au-Cu NPs were decorated on the surface of indium tin oxide glass using 3-amino-propyl trimethoxysilane, the antibody of p-tau217 was immobilized via dominant Au-N bonding to enable the biological specificity of the immunosensor. When p-tau217 specifically interacted with an antibody to form an immune complex on the sensing interface, the ECL signal of the sensor was considerably inhibited by the resulting giant biomolecular complex. This complex prevented luminol diffusion to the electrode surface and electron transfer. The resulting immunosensor showed remarkable sensitivity to p-tau217, with a wide linear detection range from 5 to 600 pg/mL. A detection limit of 0.56 pg/mL was achieved, with recoveries in human serum ranging from 92.3 to 109%. This ECL immunosensor demonstrated high sensitivity and specificity toward p-tau217, along with good reproducibility and stability, providing a new approach for clinical research on Alzheimer's disease.

Coronary heart disease (CHD) poses an important threat to human health, and its pathogenesis is the formation of atheromatous plaques in coronary ventricles. Compared to other biomarkers, lipoprotein-associated phospholipase A2 (Lp-PLA2), which is involved in multiple processes of atherosclerosis, is a noticeable inflammatory biomarker related to CHD. Herein, using a multifunctional nanocomposite containing a CoFe Prussian blue analogue (PBA) and Au nanoparticles (AuNPs) (AuNPs@CoFe PBA) as a sensing substrate, an electrochemiluminescent (ECL) immunosensor was developed for the highly sensitive detection of Lp-PLA2. Benefiting from the synergistic effect of the PBA and AuNPs, the nanocomposite exhibits excellent peroxidase-like activity and can catalyze the luminol-ECL reaction, amplifying the ECL signal by ∼29-fold. Meanwhile, the enlarged specific surface area of the nanocomposite and the presence of abundant AuNPs allow the immobilization of more antibody proteins, thereby improving the sensing response of the immunosensor. When the target Lp-PLA2 is captured by the antibody on the sensor surface, the sensor emits a reduced ECL signal because of the increased mass and electron transfer resistance due to the formation of the immune complex. Under optimized conditions, the constructed ECL immunosensor exhibits a broad linear range from 1 to 2200 ng/mL and a low detection limit of 0.21 ng/mL. Additionally, the ECL immunosensor exhibits high specificity, stability, and reproducibility. This work provides a new approach to diagnose CHD and broadened the application of the PBA in the field of ECL sensors.

The sensitive quantification of cardiac troponin I (cTnI) and myoglobin (Myo) in blood is essential for an early emergency diagnosis of acute myocardial infarction (AMI). Attributed to AuNPs and a titanium element on the surface of the AuNPs/Ti₃C₂-MXenes hybrid, each respective aptamer strand can be immobilized on. In this work, a nanohybrid was deposited on amino-functionalized indium tin oxide (ITO) via an Au–N bond; thereafter, it could catch cTnI-specific, thiol-functionalized DNA aptamer through Au–S self-assembly or Myo-aptamer via adsorption and metal chelate interaction between phosphate groups and titanium for specific recognition. Both using [Fe(CN)₆]^3−/4− as a signaling probe, the differential pulse voltammetric (DPV) current of the cTnI-aptasensor decreased after binding with cTnI, while the other responded to Myo via the impedimetric measurement. These developed biosensors enable the response to the femtogram/mL level cTnI or nanogram/mL level Myo. Remarkably, the proposed aptasensors exhibit high sensitivity and specificity for targets and display great potential for applications in clinic diagnosis.

Amyloid-β (Aβ) protein is considered to be a key biomarker that is closely associated with Alzheimer's disease (AD). The level of Aβ, particularly its subtle fluctuation, indicates early neuropathological changes, which poses a considerable challenge in predicting AD, considering the detection limit of sensing technologies. Herein, a new label-free sensor based on luminol electrochemiluminescence (ECL) was proposed by developing a close-packed monolayered-SiO₂ array with gold (Au) nanoparticles (NPs) entrapped in their gaps as the basal electrode. The well-organized SiO₂ NPs with a quasiphotonic crystal structure amplified the ECL signal via light scattering, while Au NPs amplified the signal by directly catalyzing luminol oxidation. Owing to the dual signal amplification, the proposed electrode furnished an ∼64-fold-intensified ECL signal of luminol as the sensing background. Further, the as-prepared ECL electrode served as the substrate to develop an aptasensor for the sensitive detection of Aβ. The inhibition of the ECL signal due to the suppressed diffusion of luminol to the sensor surface acts as an indicator to quantify the amount of Aβ. The transfer dynamics mechanism provides a label-free sensing strategy and facilitates the high sensitivity of the aptasensor for Aβ detection. Under optimal conditions, the developed aptasensor exhibits an ultrasensitive performance for Aβ with a very low limit of detection of 5 fM, providing a new prospect for clinical research on Aβ and a promising approach in the field of ECL sensing.