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Owing to the limitations of dual-signal luminescent materials and coreactants, constructing a ratiometric electrochemiluminescence (ECL) biosensor based on a single luminophore is a huge challenge. This work developed an excellent zirconium metal-organic framework (MOF) Zr-TBAPY as a single ECL luminophore, which simultaneously exhibited cathodic and anodic ECL without any additional coreactants. First, Zr-TBAPY was successfully prepared by a solvothermal method with 1,3,6,8-tetra(4-carboxyphenyl)pyrene (TBAPY) as the organic ligand and Zr 4+ cluster as the metal node. The exploration of ECL mechanisms confirmed that the cathodic ECL of Zr-TBAPY originated from the pathway of reactive oxygen species (ROS) as the cathodic coreactant, which is generated by dissolved oxygen (O 2 ), while the anodic ECL stemmed from the pathway of generated Zr-TBAPY radical itself as the anodic coreactant. Besides, N , N -diethylethylenediamine (DEDA) was developed as a regulator to ECL signals, which quenched the cathodic ECL and enhanced the anodic ECL, and the specific mechanisms of its dual action were also investigated. DEDA can act as the anodic coreactant while consuming the cathodic coreactant ROS. Therefore, the coreactant-free ratiometric ECL biosensor was skillfully constructed by combining the regulatory role of DEDA with the signal amplification reaction of catalytic hairpin assembly (CHA). The ECL biosensor realized the ultrasensitive ratio detection of HIV DNA. The linear range was 1 fM to 100 pM, and the limit of detection (LOD) was as low as 550 aM. The outstanding characteristic of Zr-TBAPY provided new thoughts for the development of ECL materials and developed a new way of fabricating the coreactant-free and single-luminophore ratiometric ECL platform.

Metal organic gels (MOGs) are a new kind of intelligent soft materials with excellent luminescence properties. However, MOGs with dual electrochemiluminescence (ECL) properties have not been reported. In this study, using Eu 3+ as metal node, 4'-(4-carboxyphenyl)-2,2':6',2″-terpyridine (Hcptpy) and Luminol as organic ligands, a novel dual-ligand Europium-organic gels (Eu-L-H MOGs) were prepared by simple mixing at room temperature. On the one hand, Eu-L-H MOGs could exhibit strong and stable anodic ECL signals in the phosphate buffered saline (PBS) without the addition of co-reactants, which came from the blue emission of Luminol. On the other hand, using K 2 S 2 O 8 as a cathodic co-reactant, Eu-L-H MOGs produced cathodic signals, which were derived from the red emission of Eu sensitized by Hcptpy through the antenna effect. Based on the independent dual ECL signals of Eu-L-H MOGs, we selected Alexa Flour 430 as the receptor and anodic ECL emission of Eu-L-H MOGs as the donor to construct the ECL resonance energy transfer (ECL-RET) ratio biosensor, which utilized exonuclease III assisted DNA cycle amplification to achieve ultrasensitive detection of the I27L gene. The detection linearity of I27L ranged from 1 fM to 10 nM, with a detection limit as low as 284 aM. This study developed a straightforward technique for obtaining a single luminescent material with dual signals, and further broadened the analytical application of MOGs in the realm of ECL., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

This study developed a new zirconium metal-organic framework (MOF) luminophore named Zr-DPA@TCPP with dual-emission electrochemiluminescence (ECL) characteristics at a resolved potential. First, Zr-DPA@TCPP with a core-shell structure was effectively synthesized through the self-assembly of 9,10-di( p -carboxyphenyl)anthracene (DPA) and 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (TCPP) as the respective organic ligands and the Zr cluster as the metal node. The reasonable integration of the two organic ligands DPA and TCPP with ECL properties into a single monomer, Zr-DPA@TCPP, successfully exhibited synchronous anodic and cathodic ECL signals. Besides, due to the impressively unique property of ferrocene (Fc), which can quench the anodic ECL but cannot affect the cathodic ECL signal, the ratiometric ECL biosensor was cleverly designed by using the cathode signal as an internal reference. Thus, combined with DNA recycle amplification reactions, the ECL biosensor realized sensitive ratiometric detection of HPV-16 DNA with the linear range of 1 fM-100 pM and the limit of detection (LOD) of 596 aM. The distinctive dual-emission properties of Zr-DPA@TCPP provided a new idea for the development of ECL luminophores and opened up an innovative avenue of fabricating the ratiometric ECL platform.

In this work, a novel aluminum metal-organic framework (Al-MOF)/ N -2-hydroxyethylpiperazine- N '-ethane-sulfonic acid (HEPES) system with an excellent electrochemiluminescence (ECL) property was developed. First, Al-MOF was successfully synthesized through a one-pot solvothermal method by using 9,10-di( p -carboxyphenyl)anthracene (DPA) as the organic luminescence ligand and Al 3+ as the metal node. Compared with DPA, Al-MOF showed high ECL intensity and excellent stability without an additional coreactant in the HEPES buffer. The corresponding ECL mechanism was studied in detail, verifying HEPES was not only the buffer in the system but also the coreactant of Al-MOF. In particular, the system of Al-MOF/HEPES showed a high ECL efficiency of 30.0%, taking the Ru(bpy) 3 2+ system as the standard. In addition, the ECL signal of Al-MOF was effectively quenched by dopamine (DA). The biosensor for HBV DNA detection was constructed through the ECL signal on-off-on mode of DNA specific recognition integrated with the DNA walker signal amplification strategy. The ultrasensitive detection for HBV DNA was achieved with a linear range of 100 aM to 10 pM and a limit of detection (LOD) of 62.1 aM. This work proposed a high-efficiency Al-MOF/HEPES system, providing a new viewpoint for a coreactant-free system in the field of ECL.

In this study, as the self-enhanced electrochemiluminescence (ECL) emitter, the dual ligand metal-organic framework microflower was successfully synthesized via a facile one-pot method by integrating 9,10-di(pcarboxyphenyl) anthracene (DPA) ligand and N, N-Diethylethylenediamine (DEAEA) ligand into zinc ions metal node, denoted as Zn-DPA/DEAEA (d-MOF). The DPA ligand was a typical ECL luminophore. The DEAEA ligand not only could be used as an effective co-reactant but also a morphologic regulator. The morphology of d-MOF changed from a thick sheet to a thin sheet and finally a microflower by controlling the dosage of DEAEA. Linking emitter and co-reactant in a MOF structure, the d-MOF exhibited an efficient intramolecular electron transfer process, with a strong and ultra-stable ECL performance without any extra co-reactants compared with the DPA ligand or the Zn-DPA single ligand MOF (s-MOF). Furthermore, an ECL resonance energy transfer (ECL-RET) biosensor was fabricated using d-MOF as donor, and 6-carboxy-4', 5'-dichloro-2', 7'-dimethoxyfluorescein (JOE) as accepter for the ultra-sensitive detection of miR-21 without additional co-reactant. And with a detection linear range of miR-21 was 100.0 aM to 10.0 pM, with a detection limit of 61.7 aM. This work offers a new perspective for the future design of stable self-enhanced ECL materials., (Copyright © 2022 Elsevier B.V. All rights reserved.)

As a class of electrochemiluminescence (ECL) enhancers, silver-based materials have broad application prospects. In this work, a novel silver metal-organic framework (AgMOF) was developed as a self-enhanced ECL emitter by one-step mixing and standing at room temperature. The AgMOF could produce strong and stable ECL emissions based on a double-amplification method, which originated from the aggregation-induced ECL emission of ligands and catalyzing S 2 O 8 2- to produce more SO 4 •- by silver. Moreover, an ECL resonance energy transfer (ECL-RET) biosensor with AgMOF as a donor and BHQ2 as an acceptor was fabricated by duplex-specific nuclease (DSN)-assisted target recycling amplification to detect miRNA-107. The biosensor exhibited a strong ECL-RET effect due to the higher ECL emission of the AgMOF and perfect match of spectra between the AgMOF and BHQ2. Upon the introduction of DSN and target miRNAs, the specific DNA-RNA binding and nuclease cleaving could trigger the detachment of BHQ2, resulting in an increased ECL signal of AgMOF. Benefiting from the ECL-RET and DSN-assisted target recycling amplification methods, this biosensor achieved a wide linear relationship range from 20 to 120 fM with a low limit of detection (4.33 fM). This research presents an effective emitter for self-enhanced ECL systems, which broadens the potential ECL applications of silver-based nanomaterials.

Developing a coreactant-free ratiometric electrochemiluminescence (ECL) strategy based on a single luminophore to achieve more accurate and sensitive microRNA (miRNA) detection is highly desired. Herein, utilizing zinc-metal organic frameworks (Zn-MOFs) as the single luminophore, a novel dual-potential ratiometric ECL biosensor was constructed for ultrasensitive detection of miRNA-133a. The as-prepared Zn-MOFs exhibited simultaneous cathode and anode ECL emission. Furthermore, the Zn-MOFs were confirmed to be a multichannel ECL sensing platform with excellent annihilation and coreactant ECL emission. The corresponding ECL behaviors were investigated in detail. Benefiting from the hybridization chain reaction (HCR) amplification technology, N , N -diethylethylenediamine (DEAEA) was modified on hairpin DNA, and the gained products loaded with quantities of DEAEA enhanced the anodic ECL intensity of Zn-MOFs. In the presence of miRNA-133a, the ECL intensity ratio of anode to cathode ( I a / I c ) was significantly increased, which realized the ultrasensitive ratiometric detection of miRNA-133a. In addition, without an exogenous coreactant, the biosensor revealed superb accuracy and stability. Under optimal conditions, the detection linearity of miRNA-133a was from 50 aM to 50 fM with a low detection limit of 35.8 aM (S/N = 3). This is the first work to use Zn-MOFs as a single emitter for reliable ratiometric ECL bioanalysis, which provides a new perspective for fabricating a ratiometric ECL biosensor platform.