Electrochemiluminescence Resonance Energy Transfer Research Articles

Hexagonal Prism-Shaped AIE-Active MOFs as Coreactant-Free Electrochemiluminescence Luminophores Coupled with Hollow Cu2-xO@Pd Heterostructures as Efficient Quenching Probes for Sensitive Biosensing.

For most self-luminous metal-organic framework (MOF)-involved electrochemiluminescence (ECL) systems, the integration of exogenous coreactants is indispensable to promote ECL efficiency. However, the introduction of a coreactant into an electrolyte would result in poor stability, thereby inevitably affecting analytical accuracy. Herein, by employing aggregation-induced emission luminogens as ligands, we first synthesized one hexagonal prism-shaped MOF that displays robust and steady ECL signal without an exogenous coreactant. Furthermore, adenosine triphosphate (ATP), as the target analyte, can be fixed on the electrode surface directly owing to the strong coordination between Zr4+ and phosphate groups. According to the ECL resonance energy transfer effect, hollow Cu2-xO@Pd heterostructures are conveniently prepared and act as efficient quenching probes. Remarkably, the resultant urchin-like hollow structure could provide more active sites to anchor ATP aptamers, thus enhancing the ECL quenching efficiency. In this manner, an elaborate coreactant-free ECL system was developed to detect ATP, which demonstrates a remarkable detection limit of 0.17 nM, as well as excellent stability and reproducibility. The present work offers significant enlightenment for the further evolution of advanced ECL systems integrated with MOF-based luminophores.

Multi-quenching electrochemiluminescence system based on resonance energy transfer from self-enhanced Ce(III, IV)-MOF@Ru to CuO@PDA@AuNPs for ultrasensitive detection of HER2

This study presents an innovative approach based on electrochemiluminescence resonance energy transfer (ECL-RET) through the introduction of a new pattern donor-acceptor couple. The donor of self-enhanced Ce(III, IV)-MOF@Ru is created by immobilizing Ru(bpy)32+ on Ce-based metal-organic frameworks (Ce(III, IV)-MOF). The acceptor of CuO@PDA@AuNPs is the CuO nanospheres polydopamine (PDA) framework grafted with gold nanoparticles (AuNPs). An ultrasensitive detection of human epidermal growth factor receptor-2 (HER2) was achieved through the development of a quenched ECL immunosensor. Ce(III, IV)-MOF, a unique 3D infinite extension framework, was recognized for its excellent nanostructure and remarkable capacity to greatly activate tripropylamine (TPrA) and generate abundant radicals. Fortunately, it was simultaneously utilized as a highly effective coreactant accelerator and encapsulation agent, thereby facilitating the immobilization of Ru(bpy)32+ and the generation of radicals for creating a self-enhanced emitter of Ce(III, IV)-MOF@Ru. Consequently, by effectively reducing the distance of electron transmission and minimizing the loss of energy, Ce(III, IV)-MOF@Ru achieved a significantly high efficiency in ECL. More importantly, CuO@PDA@AuNPs was prepared as a perfect quenching agent. The ultraviolet-visible (UV–vis) spectra of CuO@PDA@AuNPs exhibited partial overlap with ECL spectra of Ce(III, IV)-MOF@Ru, thus efficiently initiating the ECL-RET interaction between the donor and acceptor. With the purpose of demonstrating the superiority of newly obtained self-enhanced nanoemitter and donor-acceptor couple, an ECL immunoassay was proposed for the analysis of HER2 with range of 0.2 fg/mL ∼ 10 ng/mL and the limit of detection of 0.067 fg/mL. Therefore, this method supplies convenient and significant strategy for the clinical analysis.

Dual-signal immunosensor based on aggregation-induced electrochemiluminescence resonance energy transfer of La-MOF and low cathodic excitation potential of g-C3N4@AuNPs for the quantitation of human serum amyloid A

We report on the development of a dual-signal electrochemiluminescence (ECL) immunosensor for the quantitation of human serum amyloid A (SAA). The immunosensor comprises g-C3N4@AuNPs as the cathode and a lanthanum-based metal organic framework (La-MOF) as the anode, the latter of which utilizes aggregation-induced electrochemiluminescence (AIECL) to overcome the otherwise poor ECL intensity of H4TBAPy ligands at the electrode surface. Furthermore, the rigid MOF structure significantly improved the fluorescence quantum yield, as well as the fluorescence and ECL emission, of the La-MOF compared to H4TBAPy. The g-C3N4@AuNPs exhibits an ultrathin nanosheet structure with a low cathodic excitation potential of −0.72V. When the dual-signal ECL immunosensor was employed to detect SAA, the difference between the anodic and cathodic ECL signals exhibited a strong linear relationship with the logarithm of the SAA concentration in the range of 100 fg/mL–200ng/mL, with a detection limit of 24.5 fg/mL.

Dual metal-organic-frameworks mediated resonance energy transfer for ultrasensitive electrochemiluminescence immunosensing.

Anelectrochemiluminescence (ECL) biosensor for carcinoembryonic antigen (CEA) based on electrochemiluminescence resonance energy transfer (ECL-RET) was designed. Tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+) was used as an energy donor for ECL-RET, and an Au nanoparticle-modified MOF framework (AuCoFe MOF) was used as an energy receptor for ECL-RET. The ECL emission spectra of Ru(bpy)32+ were in the range 550 to 680nm, and a zinc oxalate MOF encapsulating Ru(bpy)32+ (Ru@ Zn oxalate MOF) was prepared. The UV-vis absorption spectrum of AuCoFe MOF ranges from 280 to 700nm and overlaps with emission spectra of Ru@Zn oxalate MOF, which is critical for RET. The AuCoFe MOF-Ab2 bioconjugate, target CEA antigen, and the Ru@Zn oxalate MOF-Ab1 bioconjugate together form a sandwich structure, resulting in quenching of the ECL signal of Ru@Zn oxalate MOF by AuCoFe MOF. Under the optimized experimental conditions, the ECL-RET sensor exhibited excellent analytical performance in CEA detection with a linear range of 1.0 × 10-13 to 1.0 × 10-8mgmL-1; the minimum limit of detection is 1.4 × 10-14mgmL-1 (S/N = 3); and its recoveries of spiked samples ranging from 99.1 to 100.7%. The developed sensor has excellent stability, reproducibility, and specificity and is suitable for the detection of CEA in human serum and has the potential to provide sensitive detection of other biomarkers of diseases.

Self-Enhanced Electrochemiluminesence of Dye-Doped Polymer Dots for Coreactant-Free Visualized Detection of Iodide Ions.

The monitoring of radioactive iodide levels is of great significance in environmental science and cancer radiotherapy. In this work, a high-throughput, radiation-resistant, and visualized electrochemiluminescence (ECL) strategy was developed for detection of iodide ions. Herein, the hydrophobic ruthenium derivative (Ru(bpy)3[B(C6F5)4]2) (bpy = bipyridyl) was doped in tertiary amine-coupled polymer dots (N-PFO Pdots) to synthesize self-enhanced Pdots (Ru@Pdots), which showed extremely high ECL intensity in absence of coreactant. Due to the efficient ECL resonance energy transfer between Ru(bpy)3[B(C6F5)4]2 and N-PFO, the Ru@Pdots exhibited 18 times higher ECL intensity compared with bare N-PFO Pdots. Besides, Ru@Pdots also showed 220-times higher ECL intensity compared with Ru(bpy)3[B(C6F5)4]2 doped coreactant-dependent Pdots (Ru@PFO Pdots). Using Ru@Pdots as ECL emitters, an ECL imaging array was designed for iodide ion detection, which exhibited a detection range of 0.8 nM-4 μM and a limit of detection of 0.1 nM. In this strategy, iodide ions were oxidized as iodide free radicals on the surface of the electrode, which could further consume the nitrogen radical of Ru@Pdots and effectively quench the ECL signal. This method also showed good specificity, radiation-resistant performance, and accuracy in actual seawater sample testing, which indicated its value in marine environmental monitoring, nuclear security, and cancer radiotherapy.

Sensitive detection of bisphenol A based on resonance energy transfer between zinc oxide nanoparticles enhanced luminol ECL and silver nanoparticles decorated TiVC MXene

This present work developed a highly sensitive electrochemiluminescence (ECL) sensor based on resonance energy transfer between ZnO nanoparticles (ZnONPs) enhanced luminol ECL as the energy donor and silver nanoparticle-modified TiVC MXene (AgNPs@TiVC) as the energy acceptor. ZnONPs were employed as catalysts to facilitate the reaction between luminol and dissolved oxygen, which could amplify the ECL signal of luminol without the need of additional co-reactants. The AgNPs@TiVC composite functioned as the energy acceptor, participating in ECL resonance energy transfer to quench the ECL emission. In the presence of bisphenol A (BPA), the specific recognition by the aptamer could detach the energy acceptor from the electrode surface, resulting in the recovery of ECL signal. The variation of ECL intensity exhibited a good linear relationship with the logarithm of BPA concentration in the range of 0.06 nM–0.08 μM, with a detection limit of 8.9 pM (3σ). This sensor owned satisfactory sensitivity and selectivity, which could further expand the utility of various MXenes in ECL sensing applications.

A sensitive electrochemiluminescence immunosensor for CEA detection based on the ECL-RET between zinc-based metal–organic frameworks and ZiF-8@PDA

In this study, we developed a new system that using zinc-based metal–organic frameworks NH2-Zn-PTC as the donor and ZiF-8@PDA as the acceptor to achieve highly sensitive detection of carcinoembryonic antigen (CEA), using the fundamentals of electrochemiluminescence resonance energy transfer (ECL-RET). Firstly, the aggregation-induced quenching effect (ACQ) was eliminated by the coordination of PTC in MOF and the ECL signal was improved. Secondly, the ECL signal was further amplified by using Au NPs and amino groups as co-reaction promoters to generate more SO4.−. In addition, the introduction of ZiF-8@PDA as an acceptor and NH2-Zn-PTC as a donor took advantage of the feature of partial overlap of the UV–vis absorption spectrum and ECL emission spectra between the two, thereby effectively initiating the ECL-RET behavior, which improved the detection sensitivity of the sensor. The prepared immunosensor showed good linearity in the concentration range of 10−4 to 80 ng/mL with a detection limit of 18.20 fg/mL. This makes it promising for clinical testing of tumor markers.

Electrochemiluminescence sensor for organophosphorus pesticides based on the regulation of resonance energy transfer between negative charged gold nanorods and Ru(bpy)32+

Combined the electrostatic interaction of the negatively charged gold nanorods (AuNRs) (as acceptor) and Ru(bpy)32+ (as donor), an electrochemiluminescence resonance energy transfer (ECL-RET) sensor was constructed and applied for the detection of organophosphorus pesticides (OPs). Negatively charged AuNRs were synthesized by modifying AuNRs with polystyrene sulfonate (PSS) firstly, which can bind to Ru(bpy)32+ through electrostatic interaction so that the luminophore was absorbed by the acceptor, the resonance energy transfer occurred and only low ECL signal had been detected. Thiocholine can be produced by the hydrolysis process of acetylthiocholine (ATCh) with the help of acetylcholinesterase (AChE), which can bond with PSS-modified AuNRs (PSS-AuNRs) through gold-sulfur interaction, this caused the releasing of the adsorbed Ru(bpy)32+ into the solution and resulting in the restoration of the ECL intensity. However, the activity of AChE was inhibited by OPs, and the recovery process of the ECL signal was thus suppressed as well. In this study, chlorpyrifos was chosen as model target, the results indicated that the correlation between the ECL intensity and the logarithm of chlorpyrifos concentration showed remarkable linearity across 1 ng/mL to 1 mg/mL, achieving a detection limit of 0.51 ng/mL. The proposed system has been utilized for detecting OPs in real samples with satisfied results.

Bifunctional silver-metal organic gels with catalytic and electrochemiluminescence properties applied for ratio detection of I27L gene

The rate of maturity-onset diabetes of the young (MODY) is significantly increased by the common I27L gene variant of the hepatocyte nuclear factor-1α (HNF1A), hence achieving sensitive and precise I27L gene detection is the focus of early monitoring and diagnosis of HNF1A-MODY. In this study, we developed a silver-metal organic gels (Ag MOGs)/ K2S2O8-O2 system-based electrochemiluminescence resonance energy transfer (ECL-RET) ratio biosensor for detecting the I27L gene. The novel Ag MOGs were synthesized by simply mixing Ag+ and Luminol at ambient temperature. On the one hand, Ag MOGs could generate excellent anodic ECL signals in phosphate buffer without requiring exogenous co-reactants, which were derived from the Luminol ligand. On the other hand, Ag MOGs facilitated the electrocatalytic reduction of K2S2O8 by providing stable catalytic active sites and enhancing electron transfer rates, thereby leading to enhanced cathodic ECL emission from K2S2O8-O2. We constructed an ECL-RET ratio biosensor utilizing a DNA walker cycle amplification strategy. The biosensor leveraged the anodic ECL emission from the Ag MOGs/K2S2O8-O2 system as a donor and Atto 425 as a receptor, achieving ultra-sensitive detection of the I27L gene within a linear range of 100 amol/L to 100 pmol/L, and featuring a detection limit of 72 amol/L. Therefore, a direct synthesis technique of bifunctional materials with catalysis and electrochemiluminescence has been developed. Additionally, the ECL-RET ratio biosensor provided a universal platform for the detection of diabetes subtypes.

Detection of urokinase based on ECL resonance energy transfer between block copolymers encapsulated iridium complex and ReS2 nanosheets

The encapsulation of water insoluble iridium complex in SiO2 nanoparticles can be used to fabricate aqueous electrochemiluminescence (ECL) sensor, however, the ECL signal is greatly reduced. It is urgent to explore more suitable method to encapsulate iridium complex and improve its ECL efficiency. Pluronic block copolymers has good biocompatibility and high load capacity, which might be used to encapsulate iridium complex. In the present work, one kind of concentric nanospheres were assembled by encapsulating iridium complexes into block copolymers using poly (styrene-co-maleicanhydride) (PSMA@Ir). Strong anodic ECL signal was obtained at PSMA@Ir nanospheres modified electrode without additional coreactant. The light absorption character of ReS2 nanosheets (ReS2NS) endowed it the ability to accept energy from PSMA@Ir ECL. As a result, a novel ECL resonance energy transfer (ECL-RET) system was constructed with PSMA@Ir as energy donor while ReS2NS as energy acceptor. Based on the above results, an ECL aptasensor was designed to detect urokinase (UPA). The ECL intensity changed linearly with the logarithm of UPA concentration in the range of 1.0 × 10−16–1.0 × 10−12 mol/L with a detection limit of 2.95 × 10−17 mol/L. The prepared sensor owned high sensitivity and selectivity, and provided new avenue for the application of water insoluble iridium complex in ECL sensing.

Aptamer responsive DNA Functionalized hydrogels electrochemiluminescence biosensor for the detection of adenosine triphosphate

DNA hydrogel represents a noteworthy biomaterial. The preparation of biosensors by combining DNA hydrogel with electrochemiluminescence can simplify the modification process and raise the experimental efficiency. In this study, an electrochemiluminescence (ECL) biosensor based on DNA hydrogel was fabricated to detect adenosine triphosphate (ATP) simply and quickly. CdTe–Ru@SiO2 nanospheres capable of ECL resonance energy transfer (RET) were synthesized and encapsulated CdTe–Ru@SiO2 in the DNA hydrogel to provide strong and stable ECL signals. DNA hydrogel avoided the labeling of ECL signal molecules. The aptamer of ATP as the linker of the hydrogel for the specificity of ATP detection. The cross-linked structure of the aptamer and the polymer chains was opened by ATP, and then the decomposition of the DNA hydrogel initiated the escape of CdTe–Ru@SiO2 to generate an ECL signal. The designed biosensor detected ATP without too much modification and complex experimental steps on the electrode surface, with good specificity and stability, and a wide linear range. The detection range was 10–5000 nM, and the detection limit was 6.68 nM (S/N = 3). The combination of DNA hydrogel and ECL biosensor provided a new way for clinical detection of ATP and other biomolecule.

A novel “on-off-on” electrochemiluminescence aptasensor based on resonance energy transfer as signal amplification strategy for ultrasensitive detection of sulfadiazine in different samples

The misuse of antibiotics may contaminate the environment and cause harm to human health. Therefore, rapid and accurate detection of antibiotics is essential. In this study, a novel electrochemiluminescence resonance energy transfer (ECL-RET) pair was designed using a new ECL emitter (CPM, Ce-TBAPy) as the donor and Co-MOF@AuPt as the acceptor. Moreover, a highly sensitive and specific “on-off-on” ECL aptasensor was constructed for detecting sulfadiazine (SDZ). The aptasensor exhibited a broad linear range (from 10.0 fg mL−1 to 100 ng mL−1) for the SDZ concentration, with limit of detection and limit of quantification values of 1.14 fg mL−1and 3.75 fg mL−1, respectively. The aptasensor achieved good results in spiking experiments with milk and egg samples, and successfully quantified SDZ in fish meal quality control sample. The prepared aptasensor presents great potential for food and environmental safety by detecting antibiotics.

Sensitive detection of kanamycin based on ECL resonance energy transfer between iridium complex doped SiO2 nanospheres and Au nanoparticles decorated TiVC MXene

Herein, a novel sandwich electrochemiluminescence (ECL) aptasensor was developed based on the resonance energy transfer (RET) with iridium complex doped silicate nanoparticles (SiO2@Ir) as energy donor and gold nanoparticles modified TiVC MXene (AuNPs@TiVC) as energy acceptor. Strong anodic ECL signal of SiO2@Ir was obtained through both co-reactant pathway and annihilation pathway. Electrochemical results showed that SiO2@Ir has good electron transfer rate and large specific surface area to immobilize more aptamers. AuNPs@TiVC apparently quenched the ECL signal of SiO2@Ir due to the ECL resonance energy transfer between them. In the presence of kanamycin (KAN), a sandwich type sensor was formed with the aptamer probes as connecters between the donor and the acceptor, resulting in the decrease of ECL intensity. Under the optimal condition, KAN could be sensitively detected in the range of 0.1 pg/mL to 10 ng/mL with a low detection limit of 24.5 fg/mL. The proposed ECL system exhibited satisfactory analytical performance, which can realize the detection of various biological molecules by adopting suitable aptamer.

An intra-stimuli resonance energy transfer-based electrochemiluminescence biosensor for DNA methylation detection

Aberrant DNA methylation, as one of the promising biomarkers, is intimately connected to a variety of genetic and tumor diseases. Herein, we constructed an innovative intra-stimuli electrochemiluminescence resonance energy transfer (ECL-RET) biosensor for methylated DNA detection with high sensitivity and accuracy. Glucose oxidase (GOD) was modified at the terminal of assist DNA as functional conjugation (assist DNA-GOD), which then hybridized with methylated target DNA and hairpin DNA to form Y-shaped DNA ternary conjugate. Ru(bpy)32+ encapsulated silica nanospheres (RuSiO2 NPs) were uniformly coated with silver nanoparticles (Ag NPs) and the formed RuSiO2@Ag nanocomposites were introduced to the terminal of hairpin DNA via amide bond. The combination of the ECL donor (RuSiO2 NPs) and acceptor (Ag NPs) on one nanostructure yielded an intra-molecular ECL-RET. Afterward, the presence of H2O2 as the product of GOD catalyzing glucose induced the etching of Ag NPs and subsequent recovery of ECL signal from RuSiO2 NPs. Thus, due to the dependence of the ECL enhancement on the target concentration, this method achieved the quantitative analysis of methylated target DNA with good selectivity, repeatability, and practical utility.

DNA tetrahedral nanostructure-corbelled DNA walker for intramolecular electrochemiluminescence resonance energy transfer sensing of tumor exosomes

Exosomes as new noninvasive biomarkers play a prominent role in early cancer diagnosis, but tumor-derived exosomes are difficult to detect upon tumor initiation because of their low levels. Herein, we proposed a novel and stable strategy for exosomes detection based on intramolecular electrochemiluminescence resonance energy transfer (ECL-RET) and DNA tetrahedral nanostructures (DTNs)-corbelled DNA walker. To enhance the ECL efficiency of luminophores, abundant Ru(bpy)32+ molecules were coordinatively immobilized on Zr12-adb nanoplates (NPs) to form Ru-Zr12-adb NPs. So, high ECL-RET efficiency based on the combination of Zr12-adb NPs (donor) and Ru(bpy)32+ (acceptor) into one nanostructure resulted in considerably enhanced ECL response. Impressively, DNA walker with six track strands supported by DTNs demonstrated enhanced walking speed and high reaction efficiency because of the improved local concentration and space confinement effect of DTNs. In consequence, this as-designed ingenious ECL biosensor exhibited excellent sensing performance for exosomes.

Ratiometric electrochemiluminescence sensing and intracellular imaging of ClO- via resonance energy transfer.

Electrochemiluminescence resonance energy transfer (ECL-RET) is a versatile signal transduction strategy widely used in the fabrication of chem/biosensors. However, this technique has not yet been applied in visualized imaging analysis of intracellular species due to the insulating nature of thecell membrane. Here, we construct a ratiometric ECL-RET analytical method for hypochlorite ions (ClO-) by ECL luminophore,with a luminol derivative (L-012) as the donor and afluorescence probe (fluorescein hydrazide) as the acceptor. L-012 can emit astrong blue ECL signal and fluorescein hydrazide has negligible absorbance and fluorescence signal in the absence of ClO-. Thus, theECL-RET process is turned off at this time. In the presence of ClO-, however, the closed-loop hydrazide structure in fluorescein hydrazide is opened via specific recognition with ClO-, accompanied with intensified absorbance and fluorescence signal. Thanks to the spectral overlap between theECL spectrum of L-012 and theabsorption spectrum of fluorescein, theECL-RET effect isgradually recovered with the addition of ClO-. Furthermore, the ECL-RET system has been successfully applied to image intracellular ClO-. Although the insulating nature of thecell itself can generate ashadow ECL pattern in the cellular region, extracellular ECL emission penetrates thecell membrane and excites intracellular fluorescein generated by the reactions between fluorescein hydrazide and ClO-. The cell imaging strategy via ECL-RET circumvents the blocking of thecell membrane and enables assays of intracellular species. The importance of theECL-RET platform lies in calibrating the fluctuation from theexternal environment and improving the selectivity by using fluorescent probes. Therefore, this ratiometric ECL sensor has shown broad application prospects in the identification of targets in clinical diagnosis and environmental monitoring.

Potential-Resolved Ratiometric Aptasensor for Sensitive Acetamiprid Analysis Based on Coreactant-free Electrochemiluminescence Luminophores of Gd-MOF and "Light Switch" Molecule of [Ru(bpy)2dppz]2.

For conventional potential-resolved ratiometric electrochemiluminescence (ECL) systems, the introduction of multiplex coreactants is imperative. However, the undesirable interactions between different coreactants inevitably affect analytical accuracy and sensitivity. Herein, through the coordination of aggregation-induced emission ligands with gadolinium cations, the self-luminescent metal-organic framework (Gd-MOF) is prepared and serves as a novel coreactant-free anodic ECL emitter. By the intercalation of [Ru(bpy)2dppz]2+ with light switch effect into DNA duplex, one high-efficiency cathodic ECL probe is obtained using K2S2O8 as a coreactant. In the presence of acetamiprid, the strong affinity between the target and its aptamer induces the release of [Ru(bpy)2dppz]2+, resulting in a decreasing cathode signal and an increasing anode signal owing to the ECL resonance energy transfer from Gd-MOF to [Ru(bpy)2dppz]2+. In this way, an efficient dual-signal ECL aptasensor is constructed for the ratiometric analysis of acetamiprid, exhibiting a remarkably low detection limit of 0.033 pM. Strikingly, by using only one exogenous coreactant, the cross interference from multiple coreactants can be eliminated, thus improving the detection accuracy. The developed high-performance ECL sensing platform is successfully applied to monitor the residual level of acetamiprid in real samples, demonstrating its potential application in the field of food security.

Ultrasensitive Detection of SARS-CoV-2 Nucleocapsid Protein Based on Porphyrin-Based Metal-Organic Gels with Highly Efficient Electrochemiluminescence at Low Potential.

Metal-organic gels (MOGs) are a new type of intelligent soft material, which are bridged by metal ions and organic ligands through noncovalent interactions. In this paper, we prepared highly stable P-MOGs, using the classical organic electrochemiluminescence (ECL) luminescence meso-tetra(4-carboxyphenyl)porphine as the organic ligand and Fe3+ as the metal ion. Surprisingly, P-MOGs can stably output ECL signals at a low potential. We introduced P-MOGs into the ECL resonance energy transfer strategy (ECL-RET) and constructed a quenched ECL immunosensor for the detection of the SARS-CoV-2 nucleocapsid protein (SARS-CoV-2-N). In the ECL-RET system, P-MOGs were used as energy donors, and Au@Cu2O@Fe3O4 were selected as energy acceptors. The ultraviolet-visible spectrum of Au@Cu2O@Fe3O4 partially overlaps with the ECL spectrum of P-MOGs, which can effectively touch off the ECL-RET behavior between the donors and receptors. Under the ideal experimental situation, the linear detection range of the SARS-CoV-2-N concentration was 10 fg/mL to 100 ng/mL, and the limit of detection was 1.5 fg/mL. This work has broad application prospects for porphyrin-MOGs in ECL sensing.

Exogenous Co-Reactant-Free Electrochemiluminescent Biosensor for Ratiometric Measurement of α-Glucosidase Based on a ZIF-67-Regulated Hydrogen-Bonded Organic Framework.

The development of highly sensitive and selective analytical approaches for monitoring enzymatic activity is critical for disease diagnosis and biomedical research. Herein, we develop an exogenous co-reactant-free electrochemiluminescence (ECL) biosensor for the ratiometric measurement of α-glucosidase (α-Glu) based on a zeolitic imidazolate framework (ZIF-67)-regulated pyrene-based hydrogen-bonded organic framework (HOF-101). Target α-Glu can hydrolyze maltose to α-d-glucose, which can subsequently react with GOx to produce gluconic acid. The resultant gluconic acid can dissolve ZIF-67, leading to the recovery of the HOF-101 cathodic ECL signal and the decrease of the luminol anodic ECL signal. The long-range ordered structure of HOF-101 can speed up charge transfer, resulting in a stable and strong cathodic ECL signal. Moreover, ZIF-67 can not only efficiently quench the ECL signal of HOF-101 due to ECL resonance energy transfer between HOF-101 and ZIF-67 as well as the steric hindrance effect of ZIF-67 but also enhance the anodic ECL emission of luminol in dissolved O2 system because of its ordered and porous crystalline structure and the atomically dispersed Co2+. Notably, HOF-101 possesses a higher ECL efficiency (32.22%) compared with the Ru(bpy)32+ standard. Importantly, this ratiometric ECL biosensor shows high sensitivity (a detection limit of 0.19 U L-1) and a broad linear range (0.2-50 U L-1). This biosensor can efficiently eliminate systematic errors and enhance detection reliability without the involvement of exogenous co-reactants, and it displays good assay performance in human serum samples, holding great promise in biomedical research studies.

Dual-Mechanism-Driven Ratiometric Electrochemiluminescent Biosensor for Methicillin-Resistant Staphylococcus aureus.

Design of a ratiometric method is a promising pathway to improve the sensitivity and reliability of electrochemiluminescent (ECL) assay, for which the signals produced at two distinct potentials change reversely as it is applied to the target analyte. Herein, a biosensor for ECL assay of methicillin-resistant Staphylococcus aureus (MRSA) was constructed by immobilizing porcine IgG for capturing MRSA onto an electrode that was precoated with β-cyclodextrin-conjugated luminol nanoparticles (β-CD-Lu NPs) as an anodic luminophore. MOF PCN 224 loaded with an atomically distributed Zn element (PCN 224/Zn) was conjugated with phage recombinant cellular-binding domain (CBD) to act as a cathodic luminophore for tracing MRSA. After the formation of the sandwich complex of β-CD-Lu NPs-porcine IgG/MRSA/PCN 224/Zn-CBD on the biosensor, two ECL reactions were triggered with cyclic voltammetry. The anodic process of the β-CD-Lu NPs-H2O2 system and the cathodic process of the PCN 224/Zn-S2O82- system competed to react with reactive oxygen species (ROS) for producing ECL emission, which led to a reverse change of the two signals. Meanwhile, the overlap of the β-CD-Lu NPs emission spectrum and PCN 224/Zn absorption spectrum effectively triggered ECL resonance energy transfer between the donor (β-CD-Lu NPs) and the acceptor (PCN 224/Zn). Thus, a ratiometric ECL method was proposed for assaying MRSA with a dual-mechanism-driven mode. The detection limit for assaying MRSA is as low as 12 CFU/mL. The biosensor was applied to assay MRSA in various biological samples with recoveries ranging from 84.9 to 111.3%.