Label-free tri-luminophores electrochemiluminescence sensor for microRNAs detection based on three-way DNA junction structure

Photoelectrochemical analysis of Pb2+ based on Au@PTCA Schottky junction with Pb2+-G quadruplex structure

Herein, a novel photoelectrochemical (PEC) aptasensor using gold nanoparticles@3,4,9,10-perylene tetracarboxylic (Au@PTCA) Schottky junction as the effective optoelectronic material and lead ion (Pb2+)-G quadruplex structure as the efficient quencher was constructed for the detection of Pb2+ with high sensitivity and excellent selectivity. Au@PTCA Schottky junction, which was proposed by the in situ reduction of Au NPs on the PTCA surface, exhibited a strong unidirectional conductivity, which could generate a significantly enhanced PEC signal compared with the pure PTCA. The Pb2+-G quadruplex structure with a large spatial hindrance effect was formed when the target Pb2+ was present owing to the occurrence of the specific recognition between Pb2+ and its aptamer S1. The formation of a Pb2+-G quadruplex structure effectively quenched the initial signal generated by the Au@PTCA Schottky junction, which was derived from restricted electron transport and light transmission. The obtained prominently decreased PEC signal could achieve the quantitative detection of Pb2+ from 0.5 pM to 500 nM, with a low detection limit of 0.17 pM. The preparation time of this PEC aptasensor was 13 h, and the time for PEC measurement depended on the illumination time, which switched off-on-off for 10 s-20 s-10 s. The study proposed here with high sensitivity and excellent selectivity for Pb2+ analysis offered a novel and reliable tool for environmental monitoring related to heavy metal ions.

Highly sensitive biosensor for specific miRNA detection based on cascade signal amplification and magnetic electrochemiluminescence nanoparticles

Herein, magnetic electrochemiluminescence (ECL) nanoparticle Fe3O4@PtPd/Ru(bpy)32+ had been synthesized then been coupled with CRISPR/Cas13a system and Zn2+ dependent DNAzyme to design a novel ECL biosensor for specific detection of microRNA-145 (miRNA). The synthesized multifunctional magnetic nanoluminescent materials Fe3O4@PtPd/Ru(bpy)32+ not only load Ru(bpy)32+ to provide ECL signals, but also can quickly achieve separation and enrichment from complex matrices. In addition, ferrocene (Fc) was used as a quencher in the Ru(bpy)32+/tripropylamine (TPA) system. Fc was modified on DNA bound to Fe3O4@PtPd. Benefited from the highly specific recognition ability of CRISPR/Cas13a, the target miRNA induces CRISPR/Cas13a trans-cleavage to trigger the Zn2+-dependent DNAzyme cyclic cleavage to realize the dual signal amplification. DNA modified by Fc was split by target miRNA-induced cleaving, and then magnetic separation was performed to keep Fc away from the surface of the nanoparticles. Thus, the enhanced ECL signal was obtained to detect miRNA-145. Under optimized conditions, the prepared sensor showed a wide linear range (1 fM to 1 nM) and a low limit of detection (LOD) down to 0.41 fM. Furthermore, it shows excellent selectivity and good reproducibility. The proposed ECL platform has huge potential applications in the development of various sensitive sensors for detecting the other miRNA.

Bioanalytical Applications of Graphene Quantum Dots for Circulating Cell-Free Nucleic Acids: A Review

Graphene quantum dots (GQDs) are carbonaceous nanodots that are natural crystalline semiconductors and range from 1 to 20 nm. The broad range of applications for GQDs is based on their unique physical and chemical properties. Compared to inorganic quantum dots, GQDs possess numerous advantages, including formidable biocompatibility, low intrinsic toxicity, excellent dispensability, hydrophilicity, and surface grating, thus making them promising materials for nanophotonic applications. Owing to their unique photonic compliant properties, such as superb solubility, robust chemical inertness, large specific surface area, superabundant surface conjugation sites, superior photostability, resistance to photobleaching, and nonblinking, GQDs have emerged as a novel class of probes for the detection of biomolecules and study of their molecular interactions. Here, we present a brief overview of GQDs, their advantages over quantum dots (QDs), various synthesis procedures, and different surface conjugation chemistries for detecting cell-free circulating nucleic acids (CNAs). With the prominent rise of liquid biopsy-based approaches for real-time detection of CNAs, GQDs-based strategies might be a step toward early diagnosis, prognosis, treatment monitoring, and outcome prediction of various non-communicable diseases, including cancers.