The theory of aggregation-induced electrochemiluminescence (AIECL) has introduced new vitality into preparing new electrochemiluminescence (ECL) emitters. However, the progress in the application of biosensing analysis has been slow owing to the lack of AIECL-based functional nanomaterials. Herein, a biosensor was fabricated using mesoporous silica nanosphere (MSN) matrix-confined 1,1,2,2-tetra(4carboxylphenyl)ethylene (TPE) as a well-ordered ECL emitter and selfdesigned WHPWSYC (WC-7) heptapeptide as the target capturer for CD44 detection. TPE and its co-reactant, triethylamine (TEA), were encapsulated in the MSN nanomatrix to enhance the radiation transition by limiting the intramolecular rotation of TPE molecule benefit from the spatial confinement effect, and the ECL intensity is self-enhanced by replacing electron free diffusion in the conventional ECL system. MSN−TPE−TEA can act as satisfactory sensing substrates that improve the reproducibility and batch-to-batch consistency of biosensors and functions as a stable signal label for trace analysis of biomarkers. As a substitute for antibody and hyaluronic acid, the WC-7 heptapeptide significantly reduced the steric hindrance of the sensing interface in CD44 affinity tests. Combined with the DNA strand displacement reaction, this strategy shows a good ECL response to standard CD44 antigen and MCF-7 cells with different concentrations, which is another feasible method for detecting CD44 in body fluids or living cells.

It is significantly vital to develop a convenient assay method in clinical treatment due to an atypically low abundance (∼5 μM) of bleomycin (BLM) used in clinics. Herein, an electrochemiluminescence (ECL) biosensor using a zirconium-based metal−organic frameworks (Zr-MOFs) as an intramolecular coordination-induced electrochemiluminescence (CIECL) emitter was proposed for sensitive detection of BLM. Zr-MOFs were synthesized using Zr(IV) as metal ions and 4,4′,4″-nitrilotribenzoic acid (H 3 NTB) as ligands for the first time. The H 3 NTB ligand not only acts as coordination units bonding with Zr(IV) but functions as a coreactant to enhance ECL efficiency rooted in its tertiary nitrogen atoms. Specifically, a long guanine-rich (G-rich) single-stranded DNA (ssDNA) was released by the target-BLMcontrolled DNA machine that could perform π−π stacking with another G-quadruplex, ssDNArhodamine B (S-RB), by shearing DNA's fixed sites 5′-GC-3′ and the auxiliary role of exonuclease III (Exo III). Finally, due to the quenching effect of rhodamine B, a negative correlation trend was obtained between ECL intensity and BLM concentration in the range from 5.0 nM to 50 μM and the limit of detection was 0.50 nM. We believe that it is a promising approach to guide the preparation of CIECL-based functional materials and establishment of analytical methods.

Herein, a novel dual mode detection system of split-type photoelectrochemical (PEC) and visual immunoassay was developed to detect neuron specific enolase (NSE), which achieved simultaneous and reliable NSE detection due to the completely different signal readouts and transduction mechanism. Specifically, specific reactions of antigens and antibodies were performed in 96-microwell plates. Gold nanoparticle (Au NP)-loaded Fe3O4 (Au@Fe3O4) NPs were used as secondary antibody markers and signal regulators, which could produce a blue-colored solution in the presence of 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 because of its peroxidase-like activity. Therefore, the visual detection of NSE was realized, making the results more intuitive. Meanwhile, the above biological process could also be used as part of the split-type PEC sensing platform. Oxidized TMB and Fe3+ were consumptive agents of the electron donor, which both realized the double quenching of PEC signal generated by the SnO2/MgIn2S4/Zn0.1Cd0.9S composites. Owing to the waterfall band structure, SnO2/MgIn2S4/Zn0.1Cd0.9S composites partially absorb visible light and effectively inhibit the electron–hole recombination, thereby providing significantly enhanced and stable initial signal. On the basis of the multiple signal amplification strategy and the split-type mode, NSE could be sensitively detected with a low detection limit of 14.0 fg·mL–1 (S/N = 3) and a wide linear range from 50.0 fg·mL–1 to 50.0 ng·mL–1.

Improving the sensitivity and accuracy of bioimmunoassays has been the focus of research into the development of electrochemiluminescence (ECL) sensing platforms, as this is a critical factor in their application to practical analysis. In this work, an electrochemiluminescence−electrochemistry (ECL−EC) dual-mode biosensing platform based on an "off−on−super on" signals pattern strategy was developed for the ultrasensitive detection of Microcystin-LR (MC-LR). In this system, sulfur quantum dots (SQDs) are a novel class of ECL cathode emitter with almost no potentially toxic effects. The sensing substrate is made from rGO/Ti 3 C 2 T x composites, whose huge specific surface area greatly reduces the possibility of aggregation-caused quenching of SQDs. The ECL detection system was constructed based on the ECL-resonance energy transfer (ERET) strategy, where methylene blue (MB) with an ECL receptor function was bound to the aptamer of MC-LR by electrostatic adsorption and the center actual distance between the donor and the acceptor was calculated to be 3.84 nm, which was verified to be in accordance with the ERET theory. Meanwhile, the introduction of Ag + as an ECL signal-amplifying molecule greatly improved the sensitivity of sensing analysis. Based on the specific binding of MC-LR to the aptamer, the concentration of MC-LR was found to have a positive correlation with the ECL signal. Also, EC detection was realized with the benefit of the excellent electrochemical properties of MB. The dual-mode biosensor greatly improves the confidence of the detection, examination areas of 0.001−100 pg/ mL with MC-LR for ECL and EC were obtained, and the detection limits are 0.17 and 0.24 pg/mL, respectively.