Coreactant-Free Zirconium Metal-Organic Framework with Dual Emission for Ratiometric Electrochemiluminescence Detection of HIV DNA.

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 Zr4+ 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 (O2), 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.

Dual-emission Tb-based coordination polymer as a ratiometric fluorescence probe for the detection of phosphate.

A simple, sensitive dual-emission probe was developed for the detection of phosphate (Pi). The probe Tb-BTB/DPA was synthesized by mixing dual-ligand, 1,3,5-tri(4-carboxyphenyl) benzene (H3BTB) and dipicolinic acid (DPA), with metal ions Tb3+ in ethanol-water solution at 40℃ for 2 h. Tb-BTB/DPA exhibits two emission peaks, the emission at 362 nm is attributed to H3BTB, an energy transfer between Tb3+ nodes, and DPA further enhances the fluorescence of Tb3+ at 544 nm. Pi competes with ligand H3BTB to coordinate Tb3+, resulting in partial collapse of the Tb-BTB/DPA structure and interrupting the electron transfer between H3BTB and Tb3+. Therefore, the emission at 362 nm is enhanced, while the emission at 544 nm is unchanged, and a ratiometric fluorescence method is developed to detect Pi. Tb-BTB/DPA exhibits good linearity within the Pi concentration range (0.1-50 µmol/L), and the detection limit was 25.8 nmol/L. This study provides a new way to prepare probes with dual emission sensing properties.

Coreactant-free aggregation-induced electrochemiluminescence system based on the novel zinc-luminol metal-organic gel for ultrasensitive detection of PiRNA-823.

Aggregation-induced electrochemiluminescence (AIECL) technology has aroused widespread interest due to the significant improve in ECL response by solving the problems of aggregation-caused quenching and poor water solubility of the luminophore. However, the existing AIECL emitters still suffer from low ECL efficiency, additional coreactants and complex synthesis steps, which greatly limit their applications. Herein, luminol, as a kind of AIE molecule, was assembled with Zn2+ nodes to obtain a novel microflower-like Zinc-luminol metal-organic gel (Zn-MOG) by one-step method. In the light of the strong affinity of N atoms in luminol ligand to Zn2+, Zn-MOG with vigorous viscosity and stability can be formed immediately after vortex oscillation, overcoming the main difficulties of the complicated synthesis steps and poor film-forming performance encountered in current AIECL materials. Impressively, an AIECL resonance energy transfer (RET) biosensor was constructed using Zn-MOG as a donor and Alexa Fluor 430 as an acceptor in combination with DNA-Fuel-driven target recycling amplification for the ultrasensitive detection of PiRNA-823. The fabricated biosensor exhibited a wide linear relationship in the range of 100 aM to 100 pM and a detection limit as low as 60.0 aM. This work is the first to realize the construction of ECL emitters using the AIE effect of luminol, which provides inspiration for the design of AIECL systems without adding coreactants.

Facile synthesis of dual-ligand europium-metal organic gels for ratiometric electrochemiluminescence detecting I27L gene.

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 Eu3+ 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 K2S2O8 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.

Ratiometric Electrochemiluminescence of Zirconium Metal-Organic Framework as a Single Luminophore for Sensitive Detection of HPV-16 DNA.

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.

High-Efficiency Aluminum-Metal Organic Framework/HEPES Electrochemiluminescence System for Ultrasensitive Detection of HBV DNA.

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 Al3+ 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)32+ 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.

Controlled synthesis of zinc-metal organic framework microflower with high efficiency electrochemiluminescence for miR-21 detection.

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.