Electrochemiluminescence (ECL)-functionalized metal–organic frameworks (MOFs) have attracted increasing attention in biosensing in virtue of their diverse and tunable optical properties. A famous ECL luminophore, carboxyl-rich tris­(4,4′-dicarboxylic acid-2,2′-bipyridyl) ruthenium­(II) (Ru­(dcbpy)3 2+), possesses the characteristics of good water solubility and excellent ECL performance and also has the potential to be the organic ligand of metal–organic frameworks. Herein, functionalized MOF nanosheets (RuMOFNSs) containing plenty of Ru­(dcbpy)3 2+ in the frameworks were synthesized in aqueous solution by a simple one-pot method. In this protocol, Ru­(dcbpy)3 2+ acted as organic ligand to coordinate with Zn2+ originated from Zn­(NO3)2, and polyvinylpyrrolidone (PVP) was used as structure-directing agent to control the formation of sheetlike structure. For practical application, a “signal-on” ECL immunosensor was designed for cardiac troponin I (cTnI) detection by employing RuMOFNSs as ECL probe. The immunosensor exhibited high sensitivity and excellent selectivity for cTnI detection in the range from 1 fg/mL to 10 ng/mL with a detection limit as low as 0.48 fg/mL. Finally, the biosensor was successfully applied for the detection of cTnI in human serum sample with satisfactory results, demonstrating its potential application in bioanalysis and clinical diagnosis.

Ratiometric electrochemiluminescence (ECL) has attracted special focus in the biological analysis field, because it could eliminate the environmental interference and allow for precise measurement. Herein, a dual-wavelength ratiometric ECL biosensor was designed for the detection of cardiac troponin I (cTnI), where (4,4′-dicarboxylic acid-2,2′bipyridyl) ruthenium(II) (Ru(dcbpy) 3 2+ ) and Au nanoparticle-loaded graphene oxide/polyethylenimine (GPRu− Au) nanomaterial acts as an acceptor, and Au nanoparticlemodified graphitic phase carbon nitride nanosheet composite (Au−CNN) acts as donor. Au−CNN shows a high and steady ECL signal centered at 455 nm, which is well-matched with the adsorption of GPRu−Au; thereby, a highly efficient electrochemiluminescent resonance energy transfer (ECL-RET) sensing platform is designed. AuNPs facilitate the immobilization of antibody on the nanomaterials through a Au−N bond. The high surface area of graphene oxide/polyethylenimine allows a large number of Ru(dcbpy) 3 2+ to be loaded, immensely amplifying the ECL signal. This sensing platform exhibits outstanding analytical performance toward cTnI with a detection limit of 3.94 fg/mL (S/N = 3). The high reliability, selectivity, and sensitivity of this ratiometric ECL biosensor provides a versatile sensing platform for the bioanalysis.

In recent years, self-enhanced tris­(bipyridine) ruthenium­(II)-based luminescence systems have achieved great development in electrochemiluminescence (ECL) but are seldom mentioned in chemiluminescence (CL). Herein, a self-enhanced CL luminophore with excellent CL behavior was synthesized by covalently cross-linking tris­(4,4′-dicarboxylic acid-2,2′-bipyridyl) ruthenium­(II) dichloride ([Ru­(dcbpy)3]­Cl2) with branched polyethylenimine (BPEI) in one molecule (BPEI-Ru­(II)), which then self-assembled into nanoparticles (BRuNPs). The nanoparticles exhibited stable and strong CL emission with potassium persulfate (K2S2O8) as the oxidant. After the redox reaction between K2S2O8 and BRuNPs, and the subsequent intramolecular electron-transfer reaction, excited state luminophores were generated to emit light. This self-enhanced CL system shortened the electron transfer distance and reduced energy loss, thus improving the luminous efficiency. In addition, the CL lifetime of BRuNPs/K2S2O8 was longer than classical luminophores such as N-(4-aminobutyl)-N-ethylisoluminol (ABEI), indicating the potential application of this system in CL imaging. Surprisingly, Ag+ was found to greatly improve the CL efficiency of BRuNPs/K2S2O8 by catalyzing the decomposition of K2S2O8 to generate SO4 •–. On the basis of the enhancement effect of Ag+, a simple and rapid CL method was proposed for Ag+ detection. The chemosensor showed a wide linear range from 25 to 3000 nM and low detection limit of 9.03 nM, as well as good stability and excellent selectivity. More importantly, this result indicated that Ag+ can be used as a coreaction accelerator to develop a ternary self-enhanced CL system, BRuNPs/K2S2O8/Ag+.

Fibrous nanoaggregates of a new benzoxazole-based derivative have been reported. This derivative exhibits not only H-aggregates but also strong yellow fluorescence, which is different from the traditional understanding of H-aggregates.

A novel ratiometric electrochemiluminescence–electrochemical hybrid biosensor with high accuracy and reproducibility was fabricated for the ultrasensitive detection of miRNA-133a.

Until now, despite the great success acquired in scientific research and commercial applications, magnetic beads (MBs) have been used for nothing more than a carrier in most cases in bioassays. In this work, highly chemiluminescent magnetic beads containing N-(4-aminobutyl)-N-ethyl isoluminol (ABEI) and Co (Co/ABEI/MBs) were first synthesized via a facile strategy. ABEI and Co were grafted onto the surface of carboxylated MBs by virtue of a carboxyl group and electrostatic interaction. The as-prepared Co/ABEI/MBs exhibited good paramagnetic properties, satisfactory stability, and intense chemiluminescence (CL) emission when reacted with HO, which was more than 150 times that of ABEI functionalized MBs. Furthermore, it was found that 2,4,6-trinitrotoluene (TNT) aptamer could attach to the surface of Co/ABEI/MBs via electrostatic interaction and coordination interaction between TNT aptamer and Co, leading to a decrease in CL intensity due to the catalytic site Co being blocked by the aptamer. In the presence of TNT, TNT would bind strongly with TNT aptamer and detach from the surface of Co/ABEI/MBs, resulting in partial restoration of the CL signal. Accordingly, label-free aptasensor was developed for the determination of TNT in the range of 0.05-25 ng/mL with a detection limit of 17 pg/mL. This work demonstrates that Co/ABEI/MBs are easily connected with recognition biomolecules, which are not only magnetic carriers but also direct sensing interfaces with excellent CL activity. It provides a novel CL interface with a magnetic property which easily separates analytes from the sample matrix to construct label-free bioassays.

In this study, we proposed a ratiometric electrochemiluminescent (ECL)/electrochemical (EC) biosensor based on duplex-specific nuclease (DSN)-assisted target recycling and multilayer catalytic hairpin assembly (CHA) amplification cascades for the detection of microRNA (miRNA). The DSN-assisted target recycling transformed miRNAs into a large number of ssDNA, which then catalyzed a multilayer CHA amplification cascade to produce numerous long dsDNA duplexes H n /H n+1 (n = 2, 4, 6, ...). Then the H n /H n+1 displaced the ferrocene (Fc)-labeled ssDNA (S x+1 , x = 1, 3, 5, ...) to hybridize with the S x sequence on the gold electrode surface. Consequently, a great number of long S x /H n / H n+1 duplexes were immobilized for binding Ru(phen) 3 2+ to obtain an amplified ECL signal. Meanwhile, the EC signal of Fc was reduced, and the quenching effect of Fc to ECL signal also decreased. By measuring the ratio of the ECL signal of Ru(phen) 3 2+ to the EC signal of Fc, quantitative analysis of miRNA-499 with high accuracy and reproducibility was obtained. The ratiometric biosensor shows high sensitivity and a wide linear range of 6 orders of magnitude. With the help of DSN-assisted target recycling, this strategy can be easily extended to detect other miRNAs without redesigning the CHA cascade system. The proposed "hybrid" ratiometric ECL/EC strategy enriches the ratiometric sensors and can find extensive applications in bioanalysis, especially for multiplex detection.

Measurement of cardiac troponin I in the blood is crucial for the early diagnosis of acute myocardial infarction. Herein, a novel and ultrasensitive electrochemiluminescence (ECL) immunosensor has been developed for determination of cardiac troponin I (cTnI) by using Au nanoclusters and hybridization chain reaction (HCR) signal amplification. In this ECL immunosensor, Au nanoclusters were dual-labeled at each end of hairpin DNA (H 1 and H 2 ) and acted as the luminophore. DNA initiator strands (T 1 ) and secondary antibody (Ab 2 ) were conjugated on Au nanoparticles (AuNPs) to obtain a smart probe