Aggregation-induced electrochemiluminescence based on intramolecular charge transfer and twisted molecular conformation for label-free Immunoassay.

Organic emitters with exceptional properties exhibit significant potential in the field of aggregation-induced electrochemiluminescence (AIECL); however, their practicality is impeded by limited ECL efficiency (ΦECL). This paper investigates a novel type of AIECL emitter (BDPPA NPs), where an efficient intramolecular charge transfer (ICT) effect and highly twisted conformation contribute to a remarkable enhancement of ECL. The ICT effect reduces the electron transfer path, while the twisted conformation effectively restricts π-π stacking and intramolecular motions. Intriguingly, compared to the standard system of [Ru(bpy)32+]/TPrA, bright emissions with up to 54 % ΦECL were achieved, enabling direct visual observation of ECL through the co-reactant route. The label-free immunosensor exhibited distinguished performance in detecting SARS-CoV-2 N protein across an exceptionally wide linear range of 0.001-500 ng mL-1, with a remarkably low detection limit of 0.28 pg mL-1. Furthermore, this developed ECL platform exhibited excellent sensitivity, specificity, and stability characteristics, providing an efficient avenue for constructing platforms for bioanalysis and clinical diagnosis analysis.

Role of Machine Learning Assisted Biosensors in Point-of-Care-Testing For Clinical Decisions.

Point-of-Care-Testing (PoCT) has emerged as an essential component of modern healthcare, providing rapid, low-cost, and simple diagnostic options. The integration of Machine Learning (ML) into biosensors has ushered in a new era of innovation in the field of PoCT. This article investigates the numerous uses and transformational possibilities of ML in improving biosensors for PoCT. ML algorithms, which are capable of processing and interpreting complicated biological data, have transformed the accuracy, sensitivity, and speed of diagnostic procedures in a variety of healthcare contexts. This review explores the multifaceted applications of ML models, including classification and regression, displaying how they contribute to improving the diagnostic capabilities of biosensors. The roles of ML-assisted electrochemical sensors, lab-on-a-chip sensors, electrochemiluminescence/chemiluminescence sensors, colorimetric sensors, and wearable sensors in diagnosis are explained in detail. Given the increasingly important role of ML in biosensors for PoCT, this study serves as a valuable reference for researchers, clinicians, and policymakers interested in understanding the emerging landscape of ML in point-of-care diagnostics.

Low-potential anodic electrochemiluminescence of terbium metal-organic frameworks for selective microRNA-155 detection.

High excitation potential is recognized as a harmful factor for the biological activity of biomacromolecules, such as proteins and nucleic acids, in electrochemiluminescence (ECL) biosensing. Developing low-potential ECL luminophores is vital for improving ECL accuracy in actual sample sensing. In this work, based on porous metal-organic framework (MOF) structure with multiple active sites and energy transfer between the excited ligands and Ln nodes, we designed a series of Ln-MOFs and observed ECL emission at low potential, providing a novel method to realize low-potential ECL. The MOF nanoemitters were prepared using 1,3,5-tri (4-carboxyphenyl)benzene ligand and several lanthanide ions as nodes through mild hydrothermal reaction. Interestingly, strong ECL emission at +0.75 V of peak potential was observed in the ECL-potential curve of Tb-based MOF using 2,2',2″-nitrilotriethanol as coreactant, which was beneficial for reducing background interference in biosensing, and this ECL emission was attributed to the energy transfer between Tb and excited ligand. This low-potential ECL was then applied to construct an ECL biosensor with newly developed Cas12a-based method for selective detection of microRNA-155 without the help of strand displacement or reverse transcription. For this ECL system, the limit of detection was 0.78 nM, and the overall detection time was 2.5 h. The Ln-MOF nanoemitter provides a robust ECL platform to selectively detect various targets by integrating new bio-related techniques.

Solid electrochemiluminescence sensor by immobilization luminol in Zn-Co-ZIF CNFs for sensitive detection of procymidone in vegetables.

A solid-state electrochemiluminescence (ECL) sensor was fabricated by immobilizing luminol, a classical luminescent reagent, on a Zn-Co-ZIF carbon fiber-modified electrode for the rapid and sensitive detection of procymidone (PCM) in vegetable samples. The sensor was created by sequentially modifying the glassy carbon electrode with Zn-Co-ZIF carbon fiber (Zn-Co-ZIF CNFs), Pt@Au NPs, and luminol. Zn-Co-ZIF CNFs, prepared through electrospinning and high-temperature pyrolysis, possessed a large specific surface area and porosity, making it suitable as carrier and electron transfer accelerator in the system. Pt@Au NPs demonstrated excellent catalytic activity, effectively enhancing the generation of active substances. The ECL signal was significantly amplified by the combination of Zn-Co-ZIF CNFs and Pt@Au NPs, which can subsequently be diminished by procymidone. The ECL intensity decreased proportionally with the addition of procymidone, displaying a linear relationship within the concentration range 1.0 × 10-13 to 1.0 × 10-6 mol L-1 (R2 = 0.993). The sensor exhibited a detection limit of 3.3 × 10-14 mol L-1 (S/N = 3) and demonstrated outstanding reproducibility and stability, making it well-suited for the detection of procymidone in vegetable samples.

Novel biomimetic hybrid plasmonic nanocavity-based ECL strategy for the detection of extracellular vesicles.

Tumor-derived extracellular vesicles detection has emerged as an important clinical liquid biopsy approach for cancer diagnosis. In this work, we developed a novel hybrid plasmonic nanocavity consisting of hexagonal Au nanoplates nanoarray, SnS2/Au nanosheet layer and biomimetic lipid bilayer. Firstly, the hybrid plasmonic nanocavity combined the optical confinement for the ECL regulation and the biological recognition for the detection of extracellular vesicles. Secondly, MXene-derived Ti2N QDs have been prepared as ECL nanoprobe to label extracellular vesicles. Moreover, biomimetic lipid bilayer with specific aptamer was used to identify extracellular vesicles and integrate Ti2N QDs into the nanocavity with membrane fusion strategy. Due to the significant electromagnetic field enhancement at the cavity region, the hybrid plasmonic nanocavity provided strong field confinement to concentrate and redistribute the ECL emission of QDs with a 9.3-fold enhancement. The hybrid plasmonic nanocavity-based ECL sensing system improved the spatial controllability of EVs analysis and the accurate resolution of specific protein. It achieved the sensitive detection of extracellular vesicles in ascites and successfully distinguished the peritoneal metastasis of gastric cancer.

Electrochemiluminescence assay for the impact of Ganoderma lucidum polysaccharides on resisting arsenic-induced apoptosis.

Ganoderma lucidum (G. lucidum) is a traditional edible fungus with strong medicinal value. G. lucidum polysaccharides (GLP) encapsulate many of the key beneficial properties of this species, providing a valuable tool for the treatment of a range of diseases. The present study was developed to explore the protective benefits of GLP treatment in the context of arsenic poisoning. Through microscopy and flow cytometry experiments, NaAsO2 was found to induce rat tracheal epithelial (RTE) cell apoptosis, together with reductions in cell surface epidermal growth factor receptor (EGFR) expression. GLP treatment, however, was able to reduce apoptosis rates and elevate the expression of EGFR relative to NaAsO2-treated cells. GLP extracts (50, 100, 200 mg·mL-1) prepared from four types of G. lucidum were administered to RTE cells damaged with arsenic, revealing limited differences in position resistance among these varieties. This work provides reference for the pharmaceutical and medical research of G. lucidum.

Confinement-enhanced electrochemiluminescence of copper nanoclusters on 3D layered double hydroxide for ultrasensitive detection of GFAP.

In this work, the copper nanoclusters (Cu NCs) were confined on 3D layered double hydroxide (3D-LDH) to form Cu NCs@3D-LDH with outstanding electrochemiluminescence (ECL) for constructing ultrasensitive biosensor to detect of glial fibrillary acidic protein (GFAP) implicated in Alzheimer's Disease (AD). More importantly, compared to the individual Cu NCs, Cu NCs@3D-LDH presented strong and stable ECL response, since 3D-LDH could not only gather more Cu NCs but also limit the intramolecular free motion to reduce nonradiative transition for obtaining high ECL intensity. In addition, the improved cascade amplification method combining proximity ligation assay (PLA) with DNAzyme could transform tiny amount of target protein into a large amount of output DNA to improve sensitivity of biosensor. The ECL biosensor realized ultrasensitive detection of GFAP with the detection limit of 2 ag/mL and it had been successfully applied to the evaluation of GFAP in the serum of patients with neurological diseases. This research offered a general and facile method to improve ECL performance of Cu NCs for sensitive detection of biomarkers for disease diagnosis.

Emerging trends and recent advances in MXene/MXene-based nanocomposites toward electrochemiluminescence sensing and biosensing.

Electrochemiluminescence (ECL) sensing systems have surged in popularity in recent years, making significant strides in sensing and biosensing applications. The realization of high-throughput ECL sensors hinges on the implementation of novel signal amplification strategies, propelling the field toward a new era of ultrasensitive analysis. A key strategy for developing advanced ECL sensors and biosensors involves utilizing novel structures with remarkable properties. The past few years have witnessed the emergence of MXenes as a captivating class of 2D materials, with their unique properties leading to exploitation in diverse applications. This review provides a comprehensive summary of the latest advancements in MXene-modified materials specifically engineered for ECL sensing and biosensing applications. We thoroughly analyze the structure, surface functionalization, and intrinsic properties of MXenes that render them exceptionally suitable candidates for the development of highly sensitive ECL sensors and biosensors. Furthermore, this study explores the broad spectrum of applications of MXenes in ECL sensing, detailing their multifaceted roles in enhancing the performance and sensitivity of ECL (bio)sensors. By providing a comprehensive overview, this review is expected to promote progress in related areas.

Novel electrochemiluminescence sensing platform for ultrasensitive detection of malathion residue in tea based on SiO2NSs doped Luminol/AgNPs as a signal amplification strategy.

To address the potential hazards of organophosphorus pesticides (OPs) residues in tea, an electrochemiluminescence (ECL) aptasensor based on functionalized nanomaterials was constructed in this work. Firstly, gold nanoparticles (AuNPs) were attached on the surface of multi-walled carbon nanotubes (MWCNTs) by the constant potential electrodeposition to form a compound, and it was utilized to provide excellent immobilization sites for complementary DNA (cDNA). Subsequently, composite nanomaterials were synthesized by a one-pot method with aminated Luminol/silver nanoparticles@silica nanospheres (NH2-Luminol/Ag@SiO2NSs). Finally, NH2-Luminol/Ag@SiO2NSs was combined with a malathion aptamer (Apt) to obtain signal probes (SPs) for the construction of an aptasensor. The aptasensor had a wide linear range (1×10-3-1×103 ng/mL) and a low limit of detection (LOD) (0.3×10-3 ng/mL). It had the virtues of high sensitivity, wonderful stability and excellent specificity, which could be used for the detection of malathion residue in tea. The work provides a proven way for the construction of a rapid and ultrasensitive aptasensor with low-cost.

An intense cathodic electrochemiluminescence from carbon-nanosheets in situ grown on glassy carbon electrode and application in immunoanalysis via biometallization strategy.

An intense cathodic electrochemiluminescence (ECL) is reported from a polarized glassy carbon electrode (GCE) in peroxydisulfate solution. After the polarization in 1 M Na2SO4 at the potential of - 3.7 V for 3 s, carbon nanosheets (C-NSs) were in situ grown on the surface of the GCE. Measured in 100 mM K2S2O8 solution, the ECL intensity of the GCE/C-NSs is 112-fold that of a bare GCE. The ECL spectrum revealed that the true ECL luminophore in the GCE/C-NSs-peroxydisulfate system is O2/S2O82- which is promoted by C-NSs. When Cu2+ was electrochemically enriched and reduced to Cu(0) on the catalytic sites of C-NSs, the ECL from GCE/C-NSs/Cu in K2S2O8 solution was decreased with increasing logarithmic concentration of Cu2+ in the range from 10 pM to 1 µM, with a limit of detection (LOD) of 3 pM. An immunoanalysis method is proposed via a biometallization strategy using CuS nanoparticles as the tags and carcinoembryonic antigen (CEA) as the model analyte. After the immune recognition in the microplate, the CuS tags in the immunocomplex were dissolved and the resultant Cu2+ was electrochemically enriched and reduced on the catalytic sites of C-NSs, quenching the ECL intensity of GCE/C-NSs-O2/S2O82- system. The proposed ECL immunoanalysis method was used to quantify CEA in actual serum samples with an LOD of 1.0 fg mL-1, possessing the advantages of simple electrode modification, high sensitivity and good reproducibility.

A novel electrochemiluminescence aptasensor for ultrasensitive lincomycin detection using Ti3C2-TiO2-Ru probe.

The presence of lincomycin (LIN) residues in food poses significant health risks to humans, necessitating a highly sensitive and specific detection method for LIN. This study used a self-enhancing Ti3C2-TiO2-Ru probe to develop an electrochemiluminescence aptasensor to detect LIN. The Ti3C2-TiO2 was synthesized in situ by harnessing the unique reducibility of Ti3C2, with TiO2 serving as a co-reaction accelerator. Moreover, Ti3C2-TiO2 served as a carrier with an excellent negative charge, allowing for the immobilization of a substantial amount of Ru(bpy)32+ through electrostatic adsorption, thus forming a self-enhancing Ti3C2-TiO2-Ru probe. Furthermore, the specific affinity of LIN toward the aptamer and the chelating interaction between the Ti and phosphate groups ensured highly precise LIN detection. This sensor demonstrated excellent performance, with a detection limit of 0.025 ng mL-1 and a detection range of 1.0 × 10-1-1.0 × 104 ng mL-1. The LIN detection in milk showed commendable recovery rates, ranging from 94.4% to 106.0%.

An integrated bipolar electrode with shared cathode for dual-mode detection and imaging of CEA.

In this paper, we designed a novel shared cathode bipolar electrode chip based on Ohm 's law and successfully constructed a dual-mode dual-signal biosensor platform (DD-cBPE). The device integrates ELISA, ECL, and ECL imaging to achieve highly sensitive detection and visual imaging of carcinoembryonic antigen (CEA). The unique circuit structure of the device not only realizes the dual signal detection of the target, but also breaks the traditional signal amplification concept. The total resistance of the system is reduced by series-parallel connection of BPE, and the total current in the circuit is increased. In addition, Au@NiCo2O4@MnO2 nanozyme activity probe was introduced into the common cathode to enhance the conductivity of the material. At the same time, due to the excellent peroxidase (POD) activity of NiCo2O4@MnO2, the decomposition of H2O2 was accelerated, so that more electrons flowed to the BPE anode, and finally the dual amplification of the ECL signal was realized. The device affects the current in the circuit by regulating the concentration of the co-reactant TPrA, thereby affecting the resistance of the system. Finally, different luminescent reagents emit light at the same potential and the luminous efficiency is similar. In addition, the chip does not need external resistance regulation, which improves the sensitivity of the immunosensor and meets the needs of timely detection. It provides a new idea for the deviceization of bipolar electrodes and has broad application prospects in biosensors, clinical detection, and environmental monitoring.

Solid-Phase Electrochemiluminescence Enzyme Electrodes Based on Nanocage Arrays for Highly Sensitive Detection of Cholesterol.

The convenient and sensitive detection of metabolites is of great significance for understanding human health status and drug development. Solid-phase electrochemiluminescence (ECL) enzyme electrodes show great potential in metabolite detection based on the enzyme-catalyzed reaction product hydrogen peroxide (H2O2). Herein, a solid-phase ECL enzyme sensor was fabricated based on a confined emitter and an immobilized enzyme using electrostatic nanocage array, constructing a platform for the sensitive detection of cholesterol. The electrostatic cage nanochannel consists of a bipolar and bilayer vertically aligned mesoporous silica film (bp-VMSF). The upper layer of bp-VMSF is an amino-modified, positively charged VMSF (p-VMSF), and the lower layer is a negatively charged VMSF (n-VMSF). The most commonly used ECL probe tris(bipyridine)ruthenium(II) (Ru(bpy)32+) is fixed in n-VMSF by electrostatic adsorption from n-VMSF and electrostatic repulsion from the upper p-VMSF, generating significantly enhanced and stable ECL signals. The successful preparation of the electrostatic cage was characterized by scanning electron microscopy (SEM) and electrochemical methods. After amino groups on the outer surface of bp-VMSF were derivatized with aldehyde, cholesterol oxidase (ChOx) molecules were covalently immobilized. The successful construction of the enzyme electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). When the corresponding enzyme substrate, cholesterol, was present in the solution, the ECL signal of Ru(bpy)32+ was quenched by the enzyme-catalyzed reaction product H2O2, enabling the high-sensitivity detection of cholesterol. The linear range for detecting cholesterol was from 0.05 mM to 5.0 mM, with a limit of detection (LOD) of 1.5 µM.

Design and application of an ultrasensitive and selective tobromycin electrochemiluminescence aptasensor using MXene /Ni/Sm-LDH-based nanocomposite.

Using a chemiluminescence reaction between luminol and H2O2 in basic solution, an ultrasensitive electrochemiluminescence (ECL) aptasensor was developed for the determination of tobramycin (TOB), as an aminoglycoside antibiotic. Ti3C2/Ni/Sm-LDH-based nanocomposite effectively catalyzes the oxidation of luminol and decomposition of H2O2, leading to the formation of different reactive oxygen species (ROSs), thus amplifying the ECL signal intensity of luminol, which can be used for the determination of TOB concentration. To evaluate the performance of the electrochemiluminescence aptasensor and synthesized nanocomposite, different methods such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses were performed. The considerable specific area, large number of active sites, and enhanced electron transfer reaction on this nanocomposite led to the development of an ECL aptasensor with high sensitivity and electrocatalytic activity. After optimizing the preparation method and analysis conditions, the aptasensor revealed a wide linear response ranging from 1.0 pM to 1.0 µM with a detection limit of 18 pM, displaying outstanding accuracy, specificity, and response stability. The developed ECL sensor was found to be applicable to the determination of TOB in human serum samples and is anticipated to possess excellent clinical potentials for detecting other antibiotics, as well.

Analysis of okadaic acid using electrochemiluminescence imaging on microfluidic biosensing chip.

The sensitivity and specificity of electrochemiluminescence (ECL)-based biosensor directly rely on the property of luminophor, the type of sensing carriers and the effectiveness of signal amplification used in the sensor design, which poses a major challenge to manage these elements simultaneously. In this work, an aggregation-induced electrochemiluminescence (AIECL) microfluidic sensing chip using 4',4″,4‴,4‴'-(ethene-1,1,2,2-tetrayl)tetrabiphenyl-4-carboxylic acid (TPE)-derived hafnium-based metal-organic framework (Hf-MOF) as emitter was developed. An easily overlooked marine pollutant, okadaic acid (OA) with different concentrations ranging from 5.00 ng/mL to 1.50 × 104 ng/mL at the electrode is visualized imaging benefit from high luminescence efficiency of Hf-MOF coupled the rolling circle amplification strategy assisted by trans-cleavage activity of CRISPR/Cas12a. These highlights will solve the long-lasting task in the accurate analysis of small molecule pollutants, which can be able to provide more worthy reference solution about construction of novel ECL luminophor and signal extraction of low-abundance disease-related biomarkers.

Enhanced electrochemiluminescence of dual-defect graphite carbon nitride for ultrasensitive detection of CEA.

Herein, a dual-defective graphite carbon nitride (DDCN) was prepared by polymerization under N2 atmosphere combined with oxidation treatment. The luminous intensity of dual-defect graphite phase carbon nitride based on defect state luminescence is significantly improved compared to CN-air. On this basis, a biosensor for CEA detection was constructed based on specific immunobinding of antigen-antibody. It is noted that the biosensor exhibits a wide linear range of 1 × 10-5 âˆ¼ 1 × 102 ng•mL-1, a low detection limit of 3.3 × 10-4 pg•mL-1, a recovery of 94 %∼105 % and RSD less than 4.41 %. In addition, there was no significant difference to the clinical results, indicating that this work has good clinical application prospects.

Self-Powered Electrochemiluminescence for Imaging the Corrosion of Protective Coating of Metal and Quantitative Analysis.

In almost all electrochemical systems for electrochemiluminescence (ECL) analysis, electrodes are connected with an external power source, either directly or via wireless energy transfer circuit. That is inconvenient and makes some applications impossible. Herein, we both use galvanized iron with two different metals as both power source and electrodes to achieve a self-powered ECL and exploit ECL for the imaging of the corrosion of protective coating of widely used metal (e.g. galvanized iron) for the first time. The self-powered ECL enables the visualization of the deterioration of galvanic coating on iron using a smartphone and the detection of ascorbic acid with a linear range of 0.5-100 µM and a limit of detection of 0.31 µM. The devices based on self-powered approach do not require external power supply, thus effectively reducing their volume and cost. The self-powered ECL holds great promise for metal corrosion imaging and analytical applications.

Sensitive detection of uric acid based on low-triggering-potential cathodic luminol electrochemiluminescence achieved by ReS2 nanosheets.

The majority of previously reported cathodic electrochemiluminescence (ECL) systems often required very negative potential to be carried out, which has greatly limited their applications in the sensing field. Screening high-performance cathodic ECL systems with low triggering potential is a promising way to broaden their applications. In this work, rhenium disulfide nanosheets (ReS2 NS) have been revealed as an efficient co-promoter to realize low-triggering-potential cathodic luminol ECL. One strong cathodic ECL signal appeared at a potential of -0.3 V and one anodic ECL peak was obtained at -0.15 V under the reverse potential scan, which were caused by electrogenerated reactive oxygen species (ROS) from hydrogen peroxide. The generation of strong luminol ECL at low potential was the result of the electrocatalytic effect of ReS2 NS on the reduction of H2O2. The scavenging effect of uric acid (UA) on the ROS could significantly inhibit the cathodic ECL. As a result, an ECL sensor was proposed, which showed outstanding performance for the detection of UA in the range of 10 nM to 0.1 mM with a low detection limit of 1.53 nM. Moreover, the ECL sensor was successfully applied in the sensitive detection of UA in real samples. This work provides a new avenue to establish a low-potential cathodic ECL system, which will sufficiently expand the potential application of cathodic ECL in the sensing field.

Recent Advances in Electroluminescent Metallic Nanoclusters: From Materials to Devices.

Metallic nanoclusters (MNCs) were developed rapidly in recent decades, owing to their unique electronic structures and excited state characteristics, leading to their wide applications. Luminescence as one of the most important functions for MNCs has also been used to realize biodetection, displays, and lighting, through either electrochemiluminescence (ECL) or electroluminescence (EL). Both emissive properties and electrochemical activities of MNCs were utilized to enhance ECL and EL through facilitating exciton formation and radiation, rendering the rapid emerging of the latter in the last ten years. Through ligand modification, radiative excited-state components were increased to realize state-of-the-art photo- and electroluminescence efficiencies up to ∼100% and ∼30%, as well as ultralow biodetection limits. Nonetheless, material selection space and processing technologies are still limited. Herein, we overview and discuss recent advances of MNCs-based ECL and EL, through both aspects of materials/systems and devices, which would enlighten continuous innovations in optoelectronic MNCs.

Novel cathodic and anodic dual-emitting electrochemiluminescence of Ru(bpy)32+/α-keto acid system.

Novel cathodic and anodic dual-emitting electrochemiluminescence (ECL) of Ru(bpy)32+ and α-keto acids system are studied for the first time. Based on their cathodic and anodic ECL intensity, α-keto acids including oxalate, glyoxylic acid, pyruvic acid, and phenylglyoxylic acid can be directly sensitively detected. The limits of detection (LOD) of oxalate, glyoxylic acid, pyruvic acid, and phenylglyoxylic acid are 31.25 nM, 23.26 µM, 36.36 µM, and 18.52 µM, respectively. Possible mechanism of ECL produced is also proposed. Electrochemical results show that the reduction of oxygen at the cathode to produce ·OH is a vital step for cathodic and anodic dual-emitting ECL. Furthermore, using the enhancement strategy of S2O82-/Ag+ as coreactant accelerators is proposed considering that decarboxylation of α-keto acids to produce acyl radical can be achieved via S2O82- or Ag+. Using the S2O82-/Ag+ enhancement strategy, the LOD of oxalate, glyoxylic acid, pyruvic acid, and phenylglyoxylic acid are improved and are 2.12 nM, 0.37 µM, 3.23 µM, and 0.28 µM, respectively. Coreactants of Ru(bpy)32+ with dual-emitting ECL are expanded, which includes additional substances with organic carboxylic acid characterized by the keto group in α-position. It also provides an effective way to enhance ECL and improve sensitivity. More importantly, cathodic and anodic dual-emitting ECL greatly improves the selectivity.