Label-Free Electrochemiluminescent Determination of DNA Using Luminol and Hemin Functionalized Nanoparticles

Development of a P-tau217 Electrochemiluminescent Immunosensor Reinforced with Au-Cu Nanoparticles for Alzheimer's Disease Precaution

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.

A Sensitive Signal-on Supersandwich DNA Biosensor Based on the Enhancement of Poly(aniline-luminol) Nanowires Electrochemiluminescence by Ferrocene

A signal-on supersandwich type of electrochemiluminescence (ECL) DNA biosensor was developed based on the poly(aniline-luminol) nanowires (PALNWs) modified electrode and enhancement of ferrocene (Fc) on ECL of luminol. Aminated capture DNA was covalently linked to the PALNWs on the electrode surface by the crosslinking of glutaraldehyde. In presence of target DNA, its 3' terminus hybridizes with the capture probe and the 5' terminus hybridizes with ferrocene labeled DNA (Fc-DNA) to form a long DNA concatamer supersandwich structure. The ECL intensity of the prepared biosensor was clearly improved by increasing the concentration of target DNA due to the enhancement of ferrocene on luminol ECL. The difference of the ECL intensity in the absence and presence of target DNA was used to monitor the hybridization event. The difference of ECL linearly increased with the logarithm of target DNA concentration in the range from 1.0  ×  10^-16 - 1.0  ×  10^-8 mol L^-1 with a detection limit of 5.8  ×  10^-17 mol L^-1. The sensor had high sensitivity and wide linear relationship for the detection of target DNA.