Electrogenerated chemiluminescence and its biorelated applications

Tetrahedral DNA nanostructures, graphene and carbon nanodots-based electrochemiluminescent biosensor for BRCA1 gene mutation detection

In this study, we present a novel electrochemiluminescent DNA biosensor designed for detecting breast cancer type 1 (BRCA1) gene mutations. The biosensor integrates graphene nanosheets (Graph-NS), tetrahedral DNA nanostructures (TDNs), and carbon nanodots (CNDs) to enhance sensitivity and specificity. Graph-NS are employed to structure the transducer and serve as a platform for DNA immobilization. TDNs are engineered with a BRCA1 gene-specific capture probe located at the apex (TDN-BRCA1), facilitating efficient biorecognition. Additionally, the basal vertices of TDNs are functionalized with amino groups, enabling their attachment to the CSPE/Graph-NS surface via amino-graphene interaction. This platform effectively identifies single-base mutations in the BRCA1 gene utilizing synthesized CNDs as a coreactant and [Ru(bpy)3]2+ as the luminophore through the coreactant pathway. The developed biosensor demonstrates exceptional sensitivity and can detect a single mutation in the BRCA1 gene. Furthermore, it has been successfully validated in real samples obtained from breast cancer patients, showcasing a remarkable detection limit of 1.41 aM.

Photoluminescent and Electrochemiluminescent Detection of Fe3+ Using Cyclometalated Iridium Complexes via Fe3+-Catalyzed Hydrolysis

Ferric ion (Fe3+) is a biologically abundant and important metal ion. We developed several cyclometalated iridium complex-based molecular sensors (1, ppy-1, 1-phen, 1 a, and 1_OMe) for the detection of Fe3+ using an acetal moiety as the reaction site. The acetal moiety in iridium complexes undergoes Fe3+-catalyzed hydrolysis and subsequent formation of a formyl group, resulting in turn-off photoluminescent and electrochemiluminescent responses. Sensor 1 showed excellent selectivity toward Fe3+ over other biologically important metal ions. Furthermore, we compared the performance of the sensors based on the structural differences of the iridium complexes, and revealed a relationship between the structure and chemical properties through electrochemical experiments and computational calculations.

Laser-Treated Screen-Printed Carbon Electrodes for Electrochemiluminescence imaging

Electrochemiluminescence (ECL) is nowadays a powerful technique widely used in biosensing and imaging, offering high sensitivity and specificity for detecting and mapping biomolecules. Screen-printed electrodes (SPEs) offer a versatile and cost-effective platform for ECL applications due to their ease of fabrication, disposability, and suitability for large-scale production. This research introduces a novel method for improving the ECL characteristics of screen-printed carbon electrodes (SPCEs) through the application of CO2 laser treatment following fabrication. Using advanced ECL microscopy, we analyze three distinct carbon paste-based electrodes and show that low-energy laser exposure (ranging from 7 to 12 mJ·cm-2) enhances the electrochemical performance of the electrodes. This enhancement results from the selective removal of surface binders and contaminants achieved by the laser treatment. We employed ECL microscopy to characterize the ECL emission using a bead-based system incorporating magnetic microbeads, like those used in commercial platforms. This approach enabled high-resolution spatial mapping of the electrode surface, offering valuable insights into its electrochemical performance. Through quantitative assessment using a photomultiplier tube (PMT), it was observed that GST electrodes could detect biomarkers with high sensitivity, achieving an approximate detection limit (LOD) of 11 antibodies per μm2. These findings emphasize the potential of laser-modified GST electrodes in enabling highly sensitive electrochemiluminescent immunoassays and various biosensing applications.

Ru-OH-Zr Site over Metal-Organic Frameworks Boosts Coreactant Activation for Efficient Electrochemiluminescence

Metal-organic frameworks (MOFs) are promising electrochemiluminescent (ECL) nanoemitters. Great endeavors have been made to optimize the inherent luminescent properties, yet most MOFs suffer from poor coreactant activation ability, resulting in limited ECL. Therefore, it is urgent to integrate and design efficient catalytic centers within MOFs. Herein, we decorate atomically dispersed Ru onto the Zr-nodes of NU-1000, constructing Ru-OH-Zr centers to synergistically activate coreactants. The proposed NU-Ru enables 7.8 times enhancement in ECL efficiency. Theoretical investigations reveal that Ru atoms with strong electronegativity not only accelerate the charge transfer but also provide superior Lewis acid sites for promoting peroxysulfate binding and activation. Assisted by Bro̷nsted acid groups, the Ru-OH-Zr centers efficiently split the O-O bonds to enrich radicals through a proton-coupled electron transfer process. Furthermore, a direct mode sensor was established for sensitive organophosphorus pesticide analysis based on the interaction between the P═O bond and Lewis acid sites.

Enhanced Electrochemiluminescence Detection of Dopamine Using Antifouling PEDOT-Modified SPEs for Complex Biological Samples

Detecting medically important biomarkers in complex biological samples without prior treatment or extraction poses a major challenge in biomedical analysis. Electrochemical methods, specifically electrochemiluminescence (ECL), show potential due to their high sensitivity, minimal background noise, and straightforward operation. This study investigates the ECL performance of screen-printed electrodes (SPEs) modified with the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and its derivatives for dopamine (DA) detection. PEDOT modification significantly enhances ECL intensity, improves sensitivity, and expands the linear range for DA detection. Functionalizing PEDOT with ethylene glycol (EG) further enhances stability, specificity, and resistance to interferences for DA detection. These modified SPEs demonstrate the linear range of 1-200 μM and a detection limit as low as 0.887 nM (S/N = 3), surpassing many previous studies using SPEs. Moreover, the PEDOT-EG4-OMe-modified SPEs can reliably detect DA in solutions with high protein concentrations or artificial cerebrospinal fluid. These results suggest that the PEDOT derivative-modified SPE can serve as reusable and sensitive DA sensors in complex biological environments, highlighting the potential of the ECL system for a range of challenging applications.

Recent advances and future prospects in oxidative-reduction low-triggering-potential electrochemiluminescence strategies based on nanoparticle luminophores

The oxidative-reduction electrochemiluminescence (ECL) potential of a luminophore is one of the most significant parameters during light generation processes when considering the growing demand for anti-interference analysis techniques, electrode compatibility and the reduction of damage to biological molecules due to excessive excitation potential. Nanoparticle luminophores, including quantum dots (QDs) and metal nanoclusters (NCs), possess tremendous potential for forming various ECL sensors due to their adjustable surface states. However, few reviews focused on nanoparticle luminophore-based ECL systems for low-triggering-potential (LTP) oxidative-reduction ECL to avoid the possible interference and oxidative damage of biological molecules. This review summarizes the recent advances in the LTP oxidative-reduction ECL potential strategy with nanoparticle luminophores as ECL emitters, including matching efficient coreactants and nanoparticle luminophores, doping nanoparticle luminophores, constructing donor-acceptor systems, choosing suitable working electrodes, combining multiplex nanoparticle luminophores, and employing surface-engineering strategies. In the context of the different LTP ECL systems, potential-lowering strategies and bio-related applications are discussed in detail. Additionally, the future trends and challenges of low ECL-triggering-potential strategies are discussed.

Remote On-Paper Electrochemiluminescence-Based High-Safety and Multilevel Information Encryption

The escalating needs in information protection underscore the urgency of developing advanced encryption strategies. Herein we report a novel chemical approach that enables information encryption by on-paper electrochemiluminescence (ECL). Dendritic porous silica nanospheres modified with polyetherimide and bovine serum albumin were prepared as the chemical ink to write the secret message on a paper. Attaching the paper to an electrode, immersing it in a solution containing tris(2,2'-bipyridyl)ruthenium (Ru(bpy)3 2+) and then applying a suitable voltage, a remote "catalytic route" electrochemical reaction produces ECL that functions as the key to decrypt and visualize the message by imaging. In addition, proteins can be also used as the biological ink to write the secret message, which is then decrypted by a combined use of immunochemistry and ECL imaging as two keys. We believe the ECL-based strategy holds great promise in high-safety and multilevel information encryption, as it is protected not only by encoding, like conventional invisible inks, but also by the unique ECL decoding approach.

Coordination-Based Site-Specific Labeling Strategy for Electrogenerated Chemiluminescence Biosensing of Matrix Metalloproteinase 2

Matrix metalloproteinase 2 (MMP-2) is an important biomarker for some diseases. Herein, one first-case coordination-based site-specific labeling strategy is proposed for electrogenerated chemiluminescence (ECL) biosensing of MMP-2 by employing an iridium(III) solvent complex as a signal reagent and a histidine (His)-containing peptide as a molecular recognition substrate. One ECL probe was prepared via coordination labeling of the His-containing peptide with one iridium(III) solvent complex ([(3-(2-pyridyl)benzoic acid)2Ir(DMSO)Cl], Ir1-DMSO). High ECL efficiency and good cleavage ability by MMP-2 were obtained for the ECL probe. By combining the high sensitivity of the ECL method, the good specificity of the peptide, and the simpleness of the magnetic bead-based assay, one "cleavage-magnetic enrichment type" ECL biosensing method was developed to detect MMP-2. MMP-2 can be sensitively detected in the linear range of 1.0-10 ng/mL with a limit of quantification of 1.0 ng/mL and a limit of detection of 0.3 ng/mL. Moreover, the ECL biosensing method was successfully applied for the determination of MMP-2 in serum samples with recoveries from 98.0% ± 8.0% to 108.0% ± 6.0%. Further, high affinity (Kd = 0.11 nM) was obtained for the Ir1-DMSO-labeled His-containing peptide and MMP-2. This work may pave the way for the labeling of His-containing biomolecules with an iridium(III) solvent complex and provides a promising method in point-of-care testing of MMP-2.

Proline-Selective Electrochemiluminescence Detecting a Single Amino Acid Variation Between A1 and A2 β-Casein Containing Milks

The proline amino acid and prolyl residues of peptides/proteins confer unique biological and biochemical properties that motivates the development of proline-selective analysis. The study focuses on one specific class of problem, the detection of single amino acid variants involving proline, and reports a Pro-selective electrochemiluminescence (ECL) method. To develop this method, the A1-/A2- variants of milk's β-casein protein are investigated because it is a well-established example and abundant samples are readily available. Specifically, β-casein has 209 amino acids with 34 (or 35) proline residues: the A1-variant has a Pro-to-His substitution at position 67 (relative to the A2 variant). The study shows that proline's strong luminescence allows the generic discrimination of: Pro from other amino acids; an A2-oligopeptide from an A1-oligopeptide; the A2-β-casein variant from the A1-variant; and commercially-available A2 milks from A1-containing regular milks. The evidence indicates that luminescence depends on proline content and accessibility, as well as signal quenching. Compared to conventional immunoassays, the ECL method is simple, rapid, and inexpensive. Further, the ECL-method is Pro-selective (vs molecularly-selective like typical immunoassays) which should make it broadly useful for studying the role of proline in biology and especially useful for tracking the digestion of proline-rich proteins in the diet.

Recent Advances in Electrochemiluminescence Visual Biosensing and Bioimaging

Electrochemiluminescence (ECL) is one of the most powerful techniques that meet the needs of analysis and detection in a variety of scenarios, because of its highly analytical sensitivity and excellent spatiotemporal controllability. ECL combined with microscopy (ECLM) offers a promising approach for quantifying and mapping a wide range of analytes. To date, ECLM has been widely used to image biological entities and processes, such as cells, subcellular structures, proteins and membrane transport properties. In this review, we first introduced the mechanisms of several classic ECL systems, then highlighted the progress of visual biosensing and bioimaging by ECLM in the last decade. Finally, the characteristics of ECLM were summarized, as well as some of the current challenges. The future research interests and potential directions for the application of ECLM were also outlooked.

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.

Electrogenerated chemiluminescence from luminol-labelled microbeads triggered by in situ generation of hydrogen peroxide

We developed a sensing strategy that mimics the bead-based electrogenerated chemiluminescence immunoassay. However, instead of the most common metal complexes, such as Ru or Ir, the luminophore is luminol. The electrogenerated chemiluminescence of luminol was promoted by in situ electrochemical generation of hydrogen peroxide at a boron-doped diamond electrode. The electrochemical production of hydrogen peroxide was achieved in a carbonate solution by an oxidation reaction, while at the same time, microbeads labelled with luminol were deposited on the electrode surface. For the first time, we proved that was possible to obtain light emission from luminol without its direct oxidation at the electrode. This new emission mechanism is obtained at higher potentials than the usual luminol electrogenerated chemiluminescence at 0.3-0.5 V, in conjunction with hydrogen peroxide production on boron-doped diamond at around 2-2.5 V (vs Ag/AgCl).

Biocompatible WSe2@BSA Dots with Merged Catalyst and Coreactant for Efficient Electrochemiluminescence

Electrochemiluminescence (ECL) is a powerful tool for clinical diagnosis due to its exceptional sensitivity. However, the standard tripropylamine (TPrA) coreactant for Ru(bpy)3Cl2, the most widely studied and used ECL system, is highly toxic. Despite extensive research on alternative coreactants, they often fall short in poor efficiency. From a reaction kinetics perspective, accelerating electrooxidation rate of Ru(bpy)3Cl2 is an essential way to compensate the efficiency limitation of coreactants, but is rarely reported. Here, a hybrid electrocatalyst@coreactant dots for the ECL of Ru(bpy)3Cl2 is reported. The as-prepared WSe2@bovine serum albumin (WSe2@BSA) dots is biocompatible, and demonstrate dual functions, i.e., the BSA shell works as a coreactant, meanwhile, the WSe2 core effectively catalyzes Ru(bpy)3Cl2 oxidation. As a result, WSe2@BSA dots exhibit an exceptionally high efficiency comparable to TPrA for the ECL of Ru(bpy)3Cl2. In addition, the procedure for synthesizing WSe2@BSA dots is facile (room temperature, atmospheric conditions), rapid (5 min), and scalable (for millions of bioassays). A biosensor utilizing WSe2@BSA dots shows promise for highly sensitive detecting glypican-3 in clinical liver cancer serum samples, especially for alpha-fetoprotein-negative patients. This work opens a new avenue for developing a highly efficient ECL system for biosensing and clinical diagnosis.

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.

Unary Au Nanocrystal with Prestored Electrons and Intrinsic Low Hole-Injected Potential for Low-Triggering Potential Electrochemiluminescence

Screening a novel electrochemiluminescence (ECL) system and lowering the ECL triggering potential are essential to ECL evolution. Herein, the near-infrared (NIR) ECL system with low-triggering potential ECL was constructed with weakly reductive tert-butylamine borane as coreactant and mercaptosuccinic acid/citrate (MSA/Cit)-capped Au (MSA/Cit@AuNCs) as luminophores. Toxic-element-free and dual-ligand MSA/Cit@AuNCs were prepared via ligand exchange and utilized as a model for developing unary metal NCs-based luminophores with more enhanced ECL performance than monoligand Au nanocrystals (AuNCs), which exhibited a two hole-injected process at around 0.48 and 0.80 V, respectively. Beneficial to the intrinsic low hole-injected potential of AuNCs, MSA/Cit@AuNCs exhibited similar low-triggering ECL potential at around 0.57 V with the participation of series coreactants or not, originating from the recombination of an internal prestored electron within the conduction band (CB) and electroinjected holes at around 0.25 V. Furthermore, the enhanced low-triggering potential around 0.57 V and NIR ECL around 835 nm of MSA/Cit@AuNCs was eventually obtained with the reductive tert-butylamine borane or N2H4·H2O containing a -C-N single-bond structure merely as coreactant. The low-triggering potential ECL of MSA/Cit@AuNCs/tert-butylamine borane system at 0.57 V can be harnessed to selectively determine a carcinoembryonic antigen (CEA) with one linear range spanning from 2 to 20000 fg/mL and a limit of detection of 0.33 fg/mL (S/N = 3). This study will contribute to a more comprehensive understanding of the ECL mechanism in terms of both regulating NCs and selecting coreactants.

Donor-Acceptor MOF Enabling Efficient Electrochemiluminescence Based on TSCT-TADF

Electrochemiluminescence (ECL) is an extensively studied luminescence technique recognized for its efficacy in investigating surface energy states. Effective utilization of ECL to explore and probe the charge transfer mechanisms facilitated by novel luminescent materials is crucial. In this study, we demonstrate thermally activated delayed fluorescence (TADF) based on spatial charge transfer through the precisely controlled synthesis of luminescent materials, which is achieved by incorporating phenyl-carbazole derivatives as donor guests within acceptor-hosted metal-organic frameworks (D-A MOFs). These hybrid structures exhibit superior ECL intensities compared with their monomeric counterparts. Mechanistic investigation by DFT calculation reveals that the physically separated yet spatially closed D-A configuration induces efficient intermolecular through-spatial charge transfer (TSCT), leading to efficient ECL through tuning of the dihedral angle of the guest molecules to enhance π-π interactions. This study introduces a strategy for precise modulation of spatial charge transfer at the molecular level in the programmable synthesis of ECL luminophores.

Metal-Organic Frameworks (MOFs): Classification, Synthesis, Modification, and Biomedical Applications

Metal-organic frameworks (MOFs) are a new variety of solid crystalline porous functional materials. As an extension of inorganic porous materials, it has made important progress in preparation and application. MOFs are widely used in various fields such as gas adsorption storage, drug delivery, sensing, and biological imaging due to their high specific surface area, porosity, adjustable pore size, abundant active sites, and functional modification by introducing groups. In this paper, the types of MOFs are classified, and the synthesis methods and functional modification mechanisms of MOFs materials are summarized. Finally, the application prospects and challenges of metal-organic framework materials in the biomedical field are discussed, hoping to promote their application in multidisciplinary fields.

Ultralow Potential Cathodic Electrochemiluminescence Aptasensor for Detection of Kanamycin Using Copper Nanoribbons as Coreaction Accelerator

An ultralow cathodic potential electrochemiluminescence (ECL) aptasensor was designed, employing DNA nanoribbon template self-assembly copper nanoclusters (DNR-CuNCs) as a novel coreaction accelerator within the luminol-H2O2 system for the sensitive detection of kanamycin (KANA). Mechanistic investigations revealed that the DNR-CuNCs preferred to generate highly active hydroxyl radicals by facilitating the reduction of the coreactant H2O2 under neutral pH conditions, consequently enhancing cathodic luminescence. By the strong π-π stacking effect of KANA aptamer and graphene as a signal modulation switch, DNR-CuNCs were displaced from the electrode surface due to the affinity of KANA and its aptamer, resulting in the inhibition of the luminol-H2O2 system and a decrease in the ECL signal. Under optimal experiments, the aptasensor demonstrated exceptional sensitivity in detecting KANA within the concentration range from 1 × 10-2 to 5 × 105 pg/mL, with the detection limit as low as 0.18 fg/mL. This innovative strategy provided a novel approach to designing effective ECL emitters for monitoring food safety.

The electrochemical modulation of single molecule fluorescence

Recently it has been shown that electrochemistry, instead of using high intensity lasers, can be used to modulate the intensity of emission of fluorophores and even switch fluorophores between their ON and OFF states as required for single molecule localisation microscopy. This modulation of fluorescence does not necessarily correlate with direct oxidation and reduction of the dyes. Questions arise from this unexpected observation related to what is the electrochemistry that occurs, what are the important variables in switching fluorophores electrochemically and what range of dyes can be modulated with electrochemistry. Herein we seek to answer some of these questions. We demonstrate how to effectively modulate the fluorescence intensity of organic dye-labelled cell samples on an indium tin oxide surface using electrochemistry with redox-active mediators present in an oxygen scavenger buffer. We showed the electrochemical fluorescence modulation is sensitive to the applied potential and the excitation laser intensity, indicating the possibility of coupled photochemical and electrochemical reactions occurring. We also compared the electrochemical fluorescence modulation of representative oxazine, rhodamine, and cyanine dyes using ATTO 655, Alexa Fluor 488, and Alexa Fluor 647. Different dyes with distinctly different structural cores show fluorescence modulation to different extents. The electrochemical fluorescence modulation will be applicable in fluorescence imaging techniques as well as biosensing.

Effect of the Imidazole π-Extension on TADF Emitters in Electrochemiluminescence

Already known molecules which exhibit good electrochemiluminescence (ECL) efficiencies and high photoluminescence quantum yields (PLQY) have been structurally modified in order to increase their performance. The followed strategy is to stiffen the structures to limit the rotational and vibrational freedom degrees and favour radiative decay processes once excited. Molecules under investigation consist of donor-acceptor systems in which the acceptor fraction is a benzonitrile with an imidazole in para position, while the donor fraction consists of four diphenylamine (NPh2) or 3,6-di(tert-butyl)-9H-carbazole (t-BuCz) groups in the remaining positions on the central benzene ring. Therefore, in order to stiffen these systems and restrict the intramolecular rotations (RIR), the imidazole in the para position has been replaced with more extended π-systems, i. e., benzimidazole and phenanthro[9,10-d]imidazole. The restriction of the intramolecular rotation can be clearly observed by 1H NMR analysis. We expected to observe an increase in ECL efficiency and PLQY with the rigidity. Surprisingly, we observed a generally opposite trend: molecules with the smallest imidazole fraction showed the best performance in ECL and higher PLQY. Notably, NPh2 derivatives with benzimidazole and phenanthro[9,10-d]imidazole showed an hypsochromic shift of the emission spectra with concomitant increase of the PLQY as the solvent polarity increases.

Au Nanorings/TiO2 NPs@MXene-Based Metasurfaces with a Magnetic Mirror-Modulated ECL Strategy for Extracellular Vesicle Detection

A metasurface as an artificial electromagnetic structure can concentrate optical energy into nanometric volumes to strongly enhance the light-matter interaction, which has been becoming a powerful platform for optical sensing, nonlinear effects, and quantum optics. Herein, we developed a novel hybrid plasmonic-dielectric metasurface consisting of Au nanorings (Au NRs) and TiO2 nanoparticles derived from MXene (TiO2 NPs@MXene). The hybrid metasurface simultaneously benefited from the high near-field enhancement effect of plasmonic materials and the low loss of dielectric materials. Furthermore, the optical modulation efficiency of the hybrid metasurface can be regulated by a magnetic mirror configuration. The magnetic mirror acted like a mirror, confining the electrons to a limited region and increasing the density of the surface plasmon. Moreover, the electrochemiluminescence (ECL) of the Cu2BDC metal-organic framework (Cu2BDC-MOF) served as a light source for the Au NRs/TiO2 NPs@MXene metasurface. Due to the exceptional light manipulation capability of the hybrid metasurface and the coordination of the magnetic mirror, the isotropic ECL signal can be dynamically amplified and converted into polarized emission. Finally, a metasurface-regulated ECL (MECL)-based biosensor with a dual-positive membrane protein recognition strategy was developed for the accurate identification of gastric cancer-derived extracellular vesicles. The novel MECL research opened up a new route in the realization of dynamically tunable metasurfaces for optical sensing and novel nanophotonic devices.

Recent Advances in Luminophores for Enhanced Electrochemiluminescence Analysis

Electrochemiluminescence (ECL) detection is widely applied in many fields, including chemical measurement, biological analysis, and clinic tests, due to its high sensitivity. Currently, the fast development of many new electrochemical luminophores is continuously improving the ECL-based detection ability. Besides the enhancement of luminescence emission for a high detection sensitivity, minimizing the effect of co-reactants on ECL detection and achieving multiple analysis in one sample are also the main directions in this field. This review focuses on a summary of recently prepared new luminophores to achieve the three aims mentioned above. Especially, the review is composed by three parts, focusing on the luminophores or materials with high ECL efficiency, self-enhancing properties, and multi-color ECL luminophores. The fabrication of biosensors using these molecules is also reviewed to exhibit the advances in biological applications.

Recent Advances in On-Line Mass Spectrometry Toolbox for Mechanistic Studies of Organic Electrochemical Reactions

Electrochemical reactions are very complex and involve a variety of physicochemical processes. Accurate and systematic monitoring of intermediate process changes during the reaction is essential for understanding the mechanism of electrochemical reactions and is the basis for rational design of new electrochemical reactions. On-line electrochemical analysis based on mass spectrometry (MS) has become an important tool for studying electrochemical reactions. This technique is based on different ionization and sampling means and realizes on-line analysis of electrochemical reactions by establishing electrochemistry-MS (EC-MS) coupling devices. In particular, it provides key evidence for elucidating the reaction mechanism by capturing and identifying the reactive reaction intermediates. This review will categorize various EC-MS devices and the organic electrochemical reaction systems they study, highlighting the latest research progress in recent years. It will also analyze the properties of various devices and look forward to the future development of EC-MS.

Spotting d-band centers of single-atom catalysts by oxygen intermediate-boosted electrochemiluminescence

Catalytic activities of single-atom catalysts are strongly dependent on their d-band centers. However, it is a long-standing challenge to provide a cost-effective and accurate evaluation for the positions of d-band centers of these catalysts due to the fact that the widely applicable photoelectron spectroscopy methodologies require complicated sampling and spectral unfolding processes. In this contribution, we have proposed oxygen intermediate-boosted electrochemiluminescence (ECL) for rapid spotting of the d-band centers of single-atom catalysts, involving single atomic Au, Ag, Cu and Fe. It was disclosed that the d-band centers of single-atom catalysts closer to the Fermi level could facilitate the interaction between catalysts and oxygen intermediates, leading to higher luminol ECL intensities as a result of the promoted adsorption and reduction ability towards oxygen intermediates. Moreover, this correlation was also adapted for other metal catalysts such as Au and Ag nanoparticles. This correspondence could be utilized for an accurate identification of d-band centers of single-atom catalysts. It is anticipated that the proposed strategy could be beneficial for a deep understanding of microstructure studies of single-atom catalysts to achieve advanced catalytic performances.

A simple and cost-effective strategy for electrochemiluminescence spectral determination

BACKGROUND

Electrochemiluminescence (ECL), as a unique and powerful analytical technique, has been widely used in various fields. The determination of ECL spectra plays a crucial role in understanding ECL reaction mechanisms and conducting spectra-resolved ECL analysis. ECL intensity is typically detected using a photomultiplier tube, which offers high sensitivity for detecting extremely weak light signals but does not allow for spectral identification. Due to the time-dependent variation of ECL intensity caused by the applied potential and electrochemical reaction processes, it is challenging to perform ECL spectral detection using conventional wavelength-scanning spectrometers.

RESULTS

In this study, we present a straightforward and cost-effective ECL spectral detection strategy by incorporating an automatically controlled tunable optical filter device between a commonly used PMT detector and a specially designed ECL reaction cell. The effectiveness of this approach was confirmed through initial validation, where the spectrum of a green LED spotlight was measured and compared with a commercial spectrometer. In a dynamic system with stable ECL signals, the ECL spectrum of the typical Ru(bpy)32+/TPA system was rapidly acquired by adjusting the bandpass filters. To account for time-varying ECL signals in practical measurements, time-based correction algorithms were implemented to rectify variations in ECL intensity. By integrating time-based correction algorithms and an automatically controlled tunable optical filter device into a commonly utilized PMT detector, the rapid and sensitive ECL spectra determination was achieved. Experimental results demonstrated the reliability of the proposed strategy.

SIGNIFICANCE

This strategy is based on the widely used high-sensitivity PMT detection component, enabling the rapid and sensitive measurement of ECL spectra without altering the ECL detection hardware. It is simple, fast, efficient, and cost-effective, with the potential to be widely used for rapid ECL spectral detection and spectra-resolved ECL analysis.

COVID-19 diagnosis on the basis of nanobiosensors' prompt interactivity: A holistic review

The fast spread and severe consequences of novel coronavirus disease 2019 (COVID-19) have once again underscored the critical necessity of early detection of viral infections. Several serology-based techniques, including as point-of-care assays and high-throughput enzyme immunoassays that support the diagnosis of COVID-19 are utilized in the detection and identification of coronaviruses. A rapid, precise, simple, affordable, and adaptable diagnostic tool is required for controlling COVID-19 as well as for outbreak management, since the calculation and monitoring of viral loads are crucial for predicting the infection stage and recovery time. Nowadays, the most popular method for diagnosing COVID-19 is reverse transcription polymerase chain reaction (RT-PCR) testing, and chest computed tomography (CT) scans are also used to determine the disease's phases. This is all because of the fact that RT-PCR method caries with itself a number of downsides comprising of being immovable, expensive, and laborious. RT-PCR has not well proven to be capable of detection on the very early infection stages. Nanomaterial-based diagnostics, together with traditional clinical procedures, have a lot of promise against COVID-19. It is worthy of attention that nanotechnology has the mainstay capacity for purposes of developing even more modern stratagems fighting COVID-19 by means of focusing on state-of-the-art diagnostics. What we have centered on in this review, is bringing out even more efficient detection techniques whereby nanobiosensors are employed so that we might obstruct any further development and spreading of SARS-CoV-2.

Dual-signal ratiometric electrochemiluminescence biosensor based on Au NPs-induced low-potential emission of PFO Pdots and LSPR-ECL mechanism for ultra-sensitive detection of microRNA-141

In this study, we have for the first time constructed a ratiometric ECL biosensor for the ultrasensitive detection of microRNAs (miRNAs) using gold nanoparticles (Au NPs) to trigger both the low-potential emission from conjugated polymer poly(9,9-dioctylfluorene-2,7-diyl) dots (PFO Pdots) and the LSPR-ECL effect with sulfur-doped boron nitride quantum dots (S-BN QDs). PFO Pdots were first applied to the Au NPs-modified electrode, followed by covalent binding to capture the hairpin H1. Immediately thereafter, a small amount of miRNA-141 was able to generate a large amount of output DNA (OP) by traversing the target cycle. OP, H3-S-BN QDs, and H4-glucose oxidase (H4-GOD) were then added sequentially to the Au NPs-modified electrode surface, and the hybridization chain reaction (HCR) was initiated. This resulted in the introduction of a large amount of GOD into the system, which catalyzed the in situ formation of the co-reactant hydrogen peroxide (H2O2) from the substrate glucose. Due to the electron transfer effect, the production of H2O2 led to the ECL quenching of PFO Pdots. Meanwhile, H2O2 served as a co-reactant of S-BN QDs, resulting in strong ECL emission of S-BN QDs at the cathode. Furthermore, the cathodic ECL intensity of S-BN QDs was further enhanced by an LSPR-ECL mechanism between Au NPs and S-BN QDs. By measuring the ratio of ECL intensities at two excitation potentials, this approach could provide sensitive and reliable detection of miRNA-141 in the range of 0.1 fM ∼10 nM, with a detection limit of 0.1 fM.

Electroprecipitating the Sulfate Radical Anion Amplifies Electrochemiluminescence in Space and Time

We have discovered a strategy to synthesize reactive radical salts, effectively bottling up radicals in space and time for future use. We apply this new principle to electrochemiluminescence (ECL) through the simultaneous electro-reduction of peroxydisulfate, S2O82-, and tris(bipyridine)ruthenium(II), [Ru(bpy)3]2+ in a water/acetonitrile mixture. The electrode generates a concentration profile exceeding the solubility of the cation and anion pair, promoting precipitation. After the application of a potential, leads are disconnected, and the crystals electrolessly chemiluminesce during dissolution and can be transported to other solutions for later chemiluminescence uses. Our method extends ECL hundreds of micrometers from the electrode surface and increases the ECL lifetime by orders of magnitude. Control experiments, including electron spin resonance, validate the crystallization of SO4•-, allowing detailed mechanistic insight. We demonstrate platform generalizability by precipitating a radical salt made of calcium and SO4•-, and we demonstrate the salt's ability to drive chemiluminescence. Our results emphasize the elegant chemical tenet that extremely reactive radicals can be bottled up as solids to be used as future reagents if precipitation occurs more quickly than the radical lifetime.

Emerging electrochemical biosensors for lung cancer-associated protein biomarker and miRNA detection

Lung cancer remains a major driver of global morbidity and mortality, and diagnosing lung tumors early in their development is vital to maximizing treatment efficacy and patient survival. Several biomarkers, including CYFRA 21-1, NSE, ProGRP, CEA, and miRNA, have been identified as reliable indicators for early lung cancer detection and monitoring treatment progress. However, the minute changes in the levels of these biomarkers during the early stages of disease necessitate advanced detection platforms. In this space, electrochemical biosensors have currently emerged as robust tools for early lung cancer screening and diagnosis owing to their low costs, rapid responses, and superior sensitivity and selectivity. This review provides an up-to-date overview of the application of electrochemiluminescence, photoelectrochemical, and other electrochemical analytical strategies for detecting lung cancer-associated protein biomarkers, and miRNA. This review compares these techniques to provide a concise overview of the principles underlying these electrochemical analytical methods, the preparation of their components, and the performance of the resulting biosensors. Lastly, a discussion of the challenges and opportunities associated with electrochemical biosensors detection of lung cancer-associated biomarkers are provided.

Optical Image Sensors for Smart Analytical Chemiluminescence Biosensors

Optical biosensors have emerged as a powerful tool in analytical biochemistry, offering high sensitivity and specificity in the detection of various biomolecules. This article explores the advancements in the integration of optical biosensors with microfluidic technologies, creating lab-on-a-chip (LOC) platforms that enable rapid, efficient, and miniaturized analysis at the point of need. These LOC platforms leverage optical phenomena such as chemiluminescence and electrochemiluminescence to achieve real-time detection and quantification of analytes, making them ideal for applications in medical diagnostics, environmental monitoring, and food safety. Various optical detectors used for detecting chemiluminescence are reviewed, including single-point detectors such as photomultiplier tubes (PMT) and avalanche photodiodes (APD), and pixelated detectors such as charge-coupled devices (CCD) and complementary metal-oxide-semiconductor (CMOS) sensors. A significant advancement discussed in this review is the integration of optical biosensors with pixelated image sensors, particularly CMOS image sensors. These sensors provide numerous advantages over traditional single-point detectors, including high-resolution imaging, spatially resolved measurements, and the ability to simultaneously detect multiple analytes. Their compact size, low power consumption, and cost-effectiveness further enhance their suitability for portable and point-of-care diagnostic devices. In the future, the integration of machine learning algorithms with these technologies promises to enhance data analysis and interpretation, driving the development of more sophisticated, efficient, and accessible diagnostic tools for diverse applications.

Dual-Enhancement Electrochemiluminescence Device for Ultratrace Uranium Visualized Monitoring in Fish, Hair, and Nail Samples

Uranium is a nuclear fuel but also a hazardous contaminant due to its radioactivity and chemical toxicity. To prevent and mitigate its potential threat, the accurate monitoring of ultratrace uranium (orders of magnitude of pg g-1) in practical environmental samples has become an important scientific problem. To meet this challenge, we developed an efficient electrochemiluminescence (ECL) UO22+ detection device by a novel dual-enhancement mechanism. In detail, poly[(9,9-dioctylfuor-enyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1,3}-thiadiazole)] polymer dots (Pdots) are modified by the UO22+ DNA aptamer, and rhodamine B (RhB) is combined with dsDNA to quench the ECL signal via a resonance energy transfer (RET) process. UO22+ can cut off the DNA aptamer to release RhB, which generates an ECL enhancement process, and then, UO22+ continuously combines with the DNA chain, inducing another ECL enhancement by the RET process from UO22+ to Pdots. This device achieves an ultralow detection limit (12 pg L-1) and a wide linear range (113 pg L-1-11.3 mg L-1), which can successfully give accurate determination results to the ultratrace uranium in biosamples (<1 pg g-1) to monitor the uranium simulation of fish. This work presents an efficient strategy for ultratrace uranium determination in the environment, highlighting its significance in public health and environmental fields.

Graphitic carbon nitride nanosheet supported silica nanochannel film for enhanced electrochemiluminescence sensing of 2,4,6-trichlorophenol and prochloraz

The development of simple, rapid, and sensitive methods for detecting pesticide in environmental and food samples holds significant importance. Electrochemiluminescence (ECL) sensing platforms with high resistance to interference and contamination, and reduced consumption of ECL emitters, are highly desirable for such applications. In this work, we present an ECL sensing platform based on a graphitic carbon nitride nanosheets (CNNS) supported vertically ordered mesoporous silica film (VMSF) modified glassy carbon electrode (GCE) for the highly sensitive detection of the environmental pollutant 2,4,6-trichlorophenol (TCP) and the broad-spectrum insecticide prochloraz. Two-dimensional (2D) CNNS were synthesized by exfoliating bulk graphitic carbon nitride (g-C3N4) using concentrated sulfuric acid, serving as a novel conductive and adhesive layer for the growth of a stable VMSF on GCE via an electrochemical assistance self-assembly (EASA) method to prepare VMSF/CNNS/GCE. The electrostatic enrichment capability of VMSF nanochannels for the positively charged ECL emitter tris(2,2'-bipyridyl)ruthenium(ii) (Ru(bpy)3 2+) realized stable and significantly enhanced ECL signals at a low concentration of Ru(bpy)3 2+ (10 μM). Based on the quenching effect of TCP on the ECL signal of Ru(bpy)3 2+, highly sensitive ECL detection of TCP was achieved by the VMSF/CNNS/GCE with a linear range from 10 nM to 0.7 mM and a low detection limit (DL) of 2.2 nM. As the metabolic end product of prochloraz is TCP, indirect ECL detection of prochloraz was also accomplished by measuring the produced TCP. Combined with anti-fouling and anti-interference abilities, as well as signal amplification of VMSF, the developed VMSF/CNNS/GCE sensor enabled the sensitive ECL detection of TCP in pond water and prochloraz in orange peel extract.

Multicolor Electrochemiluminescence of Binary Microcrystals of Iridium and Ruthenium Complexes

We here report the multicolor electrochemiluminescence (ECL) of binary microcrystals prepared from a blue-emissive iridium complex 1 and an orange-emissive ruthenium complex 2. These materials display a plate-like morphology with high crystallinity, as demonstrated by microscopic and powder X-ray diffraction analyses. Under light excitation, these microcrystals exhibit gradient emission color changes as a result of the efficient energy transfer between two complexes. When modified on glass carbon electrodes, these microcrystals exhibit tunable ECLs with varied emission colors including sky-blue, white, orange, and red, depending on the doping ratio of complex 2 and the applied potential. Furthermore, organic amines with different molecular sizes are used as the co-reactant to examine their influences on the ECL efficiency of the porous microcrystals of 1. The analysis on the luminance and RGB values of ECL suggests the existence of energy transfer in the generation of multicolor ECLs in these binary crystals.

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.

MoS2/MXene Van der Waals heterojunction-based electrochemiluminescence sensor for triple negative breast cancer detection

The van der Waals heterojunction is able to combine the advantages of different materials and has potential to be used in biosensing researches. In this study, we developed a novel van der Waals heterojunction by combining MXene and MoS2 nanosheets for the electrochemiluminescence (ECL) sensing applications. This van der Waals heterojunction material not only possessed the superior conductivity of MXene, but also regulated the electron transport. Additionally, the incorporation of MoS2 nanosheets into the MXene interlayers significantly enhances the material stability. Meanwhile, nitrogen-rich quantum dots (N dots) were synthesized as ECL tags with an impressive nitrogen content of up to 75 %. By integrating the ECL response of N dots within the van der Waals heterojunction, we established a highly efficient sensing system for miRNA-373, which overexpressed in triple negative breast cancer tissues. The van der Waals heterojunction-based biosensor can enhance the ECL signal of N dots effectively to detect miRNA-373 from 1 fM to 1 μM. Consequently, the developed sensing system holds promise for the early detection of metastasis of the triple-negative breast cancer, paving the way for the effective clinical interventions.

Iridium(III) solvent complex-based electrogenerated chemiluminescence method for the detection of 3-methylhistidine in urine

3-Methylhistidine (3-MeHis) is increasingly used as an indicator of muscle protein breakdown. The development of a sensitive, simple, and non-invasive method for 3-MeHis assay is important in clinical practice. Herein, a sensitive, simple, and non-invasive electrogenerated chemiluminescence (ECL) method was proposed for the quantitation of 3-MeHis in urine by using an iridium(III) solvent complex ([Ir(dfppy)2(DMSO)Cl], dfppy = 2-(2,4-difluorophenyl)pyridine, Ir-DMSO) as a signal reagent. The photoluminescence (PL) and ECL responses of Ir-DMSO to 3-MeHis were studied. The ECL intensity of Ir-DMSO was enhanced in the presence of 3-MeHis because of the coordination recognition between Ir-DMSO and the imidazole group of 3-MeHis. Based on the enhancement of ECL intensity, 3-MeHis can be sensitively detected in the range of 5 to 25 μM. The detection limit was 0.4 μM. This is the first report of an ECL method for the quantitation of 3-MeHis. Further, to investigate the feasibility of the Ir-DMSO-based ECL method in practical applications, the developed ECL method was applied for 3-MeHis assay in urine samples of 28 healthy volunteers and 2 patients. The urine samples from patients hospitalized with obesity and kidney disease and healthy individuals were distinguished by the ECL responses of Ir-DMSO. The proposed ECL method based on the coordination recognition between iridium(III) solvent complex and the imidazole group of 3-MeHis allows inexpensive, fast, non-invasive, and sensitive detection of 3-MeHis in urine, which is promising for assessing large volumes of patients for routine analysis in clinical practices.

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.

Mass spectrometry in measurement of thyroid biomarkers

In 2022, the number of patients with thyroid disease in China exceeded 200 million (10 million with hyperthyroidism, 90 million with hypothyroidism, and 100 million with other thyroid disease such as goiter, thyroid nodules, and thyroid cancer). Well-established markers include FT3, FT4, TT3, TT4, and TSH tested by a number of immunoassay methods. This approach is based on the primary binding of antigen with antibody and a subsequent secondary chemical reaction that provides an indirect measure. The use of traceable standards for quantitation remains an important factor to ensure inter-assay reliability and precision. Recently, mass spectrometry (MS) has received considerable attention as an analytic tool due to high resolution and quantitative accuracy. In addition, MS allows for sensitive determination of low-abundance markers making it ideal for development of traceable standards. Furthermore, this technology will allow for the development of highly accurate thyroid biomarker assays to facilitate diagnosis, enable early treatment and improve outcomes. Herein, we provide a systematic review and summary of MS in enhancing the analysis of thyroid biomarkers.

Dual-Mode Immunoassay Constructed by Water-Induced Perylene Diimide Supramolecular Self-Assembly and Enzymatic Biocatalytic Precipitation Strategy

A water-induced electron-deficient dye, the supramolecule perylene diimide (PDI), has been identified recently. PDI possesses advantages such as easy reduction, nontoxicity, low cost, and simple preparation, making it a promising candidate for electrochemiluminescence (ECL) sensing platforms. In this study, a series of PDI supramolecular systems with morphological changes were prepared by utilizing water molecules to induce PDI self-assembly. This method improves the π-π stacking interactions between PDI molecules and effectively mitigates the aggregation-caused quenching (ACQ) effect on the luminous efficiency of the coplanar polycyclic aromatic hydrocarbon PDI. It is noteworthy that excellent ECL emission performance of the PDI supramolecular system was observed at -0.4 V. This low excitation potential aids in preserving antigen-antibody bioactivity and ensures accurate identification of the immune response. As a proof of concept, a dual-mode immunosensing platform for carcinoembryonic antigen (CEA) detection was constructed using an enzymatic biocatalytic precipitation (EBCP) strategy. The dual-mode immunosensor exhibited good detection performance in the concentration range of 0.001-80 ng·mL-1, presenting an advanced bioprotective analytical method for CEA detection.

Dynamic Monitoring of Time-Dependent Evolution of Biomolecules Using Quantum Dots-Based Biosensors Assemblies

The dynamic monitoring of biomolecules that are part of cell membranes generally constitutes a challenge. Electrochemiluminescence (ECL) biosensor assemblies provide clear advantages concerning microscopic imaging. Therefore, this paper proposes and analyzes a quantum dots-based biosensor assembly. Thus, particular attention is granted to biomolecules that are part of cell membranes. Additionally, this paper describes and analyzes a quantum dots-based biosensor assembly, which is used to implement a fully functional color ECL visualization system that allows for cellular and biomolecular structures to be accurately visualized. The related nano-emitter allows the implementation of real-time bioimaging scenarios. Consequently, the proposed approach is thoroughly evaluated relative to the time-dependent evolution of biomolecules. It has been demonstrated that traditionally problematic structures, like the biomolecules that are part of cell membranes, can be studied and monitored relative to their time-dependent dynamic evolution using the proposed solution. The reported research process has been conducted in the realm of cooperation with a specialized biomedical engineering company, and the described results are expected to substantially support a better understanding of the biomolecules' time-dependent dynamic evolution.

Critical Aspects and Challenges in the Design of Small Molecules for Electrochemiluminescence (ECL) Application

Electrochemiluminescence (ECL) has gained renewed interest due to the strong parallel development of luminophores in the field of organic light emitting diodes (OLEDs) with which this technique shares several aspects. In this perspective review we discuss the most relevant advances of the past 15 years in the study of organic and organometallic compounds as ECL emitters, by dividing them in three different classes: i) fluorescent emitters, ii) phosphorescent emitters and iii) Thermally Activated Delayed Fluorescence (TADF) emitters; then, water-soluble organic luminophores will be also discussed. We focus on how their design, their photo- and electrochemical properties and, in particular, the nature of the emitter, affect their efficiency in ECL. Regardless of the type of luminophore or the photoluminescence quantum yield (PLQY), the literature converges on the fact that the most determining aspect is the stability of the oxidized/reduced form of the emitter. Even if phosphorescent emitters can show outstanding efficiency, this often requires the absence of oxygen. In the case of TADFs, there is also a strong dependence of photoluminescence both in terms of PLQY and emission energy on the polarity of the media, so compounds, that appear promising in organic solvents, may be very inefficient in aqueous media.

Tailored Cis-Trans Isomeric Metal-Covalent Organic Frameworks for Coordination Configuration-Dependent Electrochemiluminescence

Precise manipulation of the coordination configuration within substances can modulate the band structure and catalytic properties of the target material. Metal-covalent organic frameworks (MCOFs), a crystal material amalgamating the benefits of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), can integrate a predetermined coordination environment into the frameworks for amplifying the catalytic effect. In this study, we delicately synthesize isomeric MCOFs using bis(glycinato)copper as the aminoligand via kinetically and thermodynamically favorable pathways to yield cis-MCOF and trans-MCOF products, respectively, thereby introducing a cis-trans isomeric coordination field into the framework. Moreover, the twisted skeleton derived from the flexibility of amino acid and β-ketoenamine linkages endows trans-MCOF with surprising water dispersibility. Compared to cis-MCOF, the trans isomerism displays a significant enhancement in cathodic electrochemiluminescence via the catalysis of Cu nodes toward K2S2O8. The density of states analysis shows that the d-band center of trans-MCOF is closer to the Fermi level, leading to more stable adsorption binding to promote the catalysis. This study is the first report on constructing predesign coordination configuration MCOFs via an easy-handling method, which gives the guidelines for the design of amino acid-based MCOF materials.

Direct Comparative Studies Revealing the Contribution of TADF Activity of Organic Emitters Towards Efficient Electrochemiluminescence

Electrochemiluminescence (ECL) featuring thermally activated delayed fluorescence (TADF) properties has attracted considerable interest, showcasing their potential for 100 % exciton harvesting, which marks a significant advancement in the realm of organic ECL. However, the challenge of elucidating the precise contribution of TADF to the enhanced ECL efficiency arises due to the lack of comparative studies of organic compounds with or without efficient TADF properties. In this study, we present four carbazole-benzonitrile molecules possessing similar chemical structures and comparable exchange energy (ΔEST). Despite their comparable properties, these compounds exhibited varying TADF efficiencies, warranting a closer examination of their underlying structural and electronic characteristics governing the optical properties. Consequently, intense ECL emission was only observed from 4CzBN with a remarkable TADF efficiency, underscoring the substantial difference in the ECL signal among molecules with comparable ΔEST and similar spectral properties but varying TADF activity.

Recent progress on charge transfer engineering in reticular framework for efficient electrochemiluminescence

Electrochemiluminescence (ECL) is a luminescence production technique triggered by electrochemistry, which has emerged as a powerful analytical technique in bioanalysis and clinical diagnosis. During ECL, charge transfer (CT) is an important process between electrochemical excitation and luminescent emission, and dramatically affects the efficiency of exciton generation, playing a pivotal role in the light-emitting properties of nanomaterials. Reticular framework materials with intramolecular/intermolecular interactions offer a promising platform for regulating CT pathways and enhancing luminescence efficiency. Deciphering the role of intramolecular/intermolecular CT processes in reticular framework materials allows for the targeted design and synthesis of emitters with precisely controlled CT properties. This sheds light on the microscopic mechanisms of electro-optical conversion in ECL, propelling advancements in their efficiency and breakthrough applications. This mini-review focuses on recent advancements in engineering CT within reticular frameworks to boost ECL efficiency. We summarized strategies including intra-reticular charge transfer, CT between the metal and ligands, and CT between guest molecules and frameworks within reticular frameworks, which holds promise for developing next-generation ECL devices with enhanced sensitivity and light emission.

Portable, intelligent MIECL sensing platform for ciprofloxacin detection using a fast convolutional neural networks-assisted Tb@Lu2O3 nanoemitter

Environmental pollution caused by ciprofloxacin is a major problem of global public health. A machine learning-assisted portable smartphone-based visualized molecularly imprinted electrochemiluminescence (MIECL) sensor was developed for the highly selective and sensitive detection of ciprofloxacin (CFX) in food. To boost the efficiency of electrochemiluminescence (ECL), oxygen vacancies (OVs) enrichment was introduced into the flower-like Tb@Lu2O3 nanoemitter. With the specific recognition reaction between MIP as capture probes and CFX as detection target, the ECL signal significantly decreased. According to, CFX analysis was determined by traditional ECL analyzer detector in the concentration range from 5 × 10-4 to 5 × 102 μmol L-1 with the detection limit (LOD) of 0.095 nmol L-1 (S/N = 3). Analysis of luminescence images using fast electrochemiluminescence judgment network (FEJ-Net) models, achieving portable and intelligent quick analysis of CFX. The proposed MIECL sensor was used for CFX analysis in real meat samples and satisfactory results, as well as efficient selectivity and good stability.

Automatic Electrochemiluminescence Method for the Detection of Cancerous Exosomes Incorporating Specific Aptamer-Magnetic Beads and Signal Nanoprobes

Exosomes, as an emerging biomarker, have exhibited remarkable promise in early cancer diagnosis. Here, a highly sensitive, selective, and automatic electrochemiluminescence (ECL) method for the detection of cancerous exosomes was developed. Specific aptamer-(EK)4 peptide-tagged magnetic beads (MBs-(EK)4-aptamer) were designed as a magnetic capture probe in which the (EK)4 peptide was used to reduce the steric binding hindrance of cancerous exosomes with a specific aptamer. One new universal ECL signal nanoprobe (CD9 Ab-PEG@SiO2ϵRu(bpy)32+) was designed and synthesized by using microporous SiO2 nanoparticles as the carrier for loading ECL reagent Ru(bpy)32+, polyethylene glycol (PEG) layer, and anticluster of differentiation 9 antibody (CD9 Ab). A "sandwich" biocomplex was formed on the surface of the magnetic capture probe after mixing the capture probe, target exosomes, and ECL signal nanoprobe, and then it was introduced into an automated ECL analyzer for rapid and automatic ECL measurement. It was found that the designed signal nanoprobe shows a 270-fold improvement in the signal-to-noise ratio than that of the ruthenium complex-labeled CD9 antibody signal probe. The relative ECL intensity was proportional to MCF-7 exosomes as a model in the range of 102 to 104 particle/μL, with a detection limit of 11 particle/μL. Furthermore, the ECL method was employed to discriminate cancerous exosomes based on fingerprint responses using the designed multiple magnetic capture probes and the universal ECL signal nanoprobe. This work demonstrates that the utilization of a designed automated ECL tactic using the MBs-(EK)4-aptamer capture probe and the CD9 Ab-PEG@SiO2ϵRu(bpy)32+ signal nanoprobe will provide a unique and robust method for the detection and discrimination of cancerous exosomes.

Ratiometric fluorescence and colorimetric strategies for assessing activity of butyrylcholinesterase in human serum using g-C3N4 nanosheets, silver ion and o-phenylenediamine

Ratiometric fluorescence and colorimetric strategies for detecting activity of butyrylcholinesterase (BChE) in human serum were developed by using g-C3N4 nanosheets, silver ion (Ag+) and o-phenylenediamine (OPD) as chromogenic agents. The oxidation-reduction reaction of OPD and Ag+ generates 2,3-diaminophenazine (oxOPD). Under exciation at 370 nm, g-C3N4 nanosheets and oxOPD emit fluorescence at 440 nm (F440) and 560 nm (F560), respectively. Additionally, oxOPD exhibits quenching ability towards g-C3N4 nanosheets via photoinduced electron transfer (PET) process. Thiocholine (TCh), as a product of BChE-catalyzed hydrolysis reaction of butylthiocholine iodide (BTCh), can coordinate with Ag+ intensively, and consequently diminish the amount of free Ag+ in the testing system. Less amount of free Ag+ leads to less production of oxOPD, resulting in less fluorescence quenching towards g-C3N4 nanosheets as well as less fluorescence emission of oxOPD. Therefore, by using g-C3N4 nanosheets and oxOPD as fluorescence indicators, the intensity ratio of their fluorescence (F440/F560) was calculated and employed to evaluate the activity of BChE. Similarly, the color variation of oxOPD indicated by the absorbance at 420 nm (ΔA420) was monitored for the same purpose. These strategies were validated to be sensitive and selective for detecting BChE activity in human serum, with limits of detection (LODs) of 0.1 U L-1 for ratiometric fluorescence mode and 0.7 U L-1 for colorimetric mode.

Boosting Electrochemiluminescence Performance of a Dual-Active Site Iron Single-Atom Catalyst-Based Luminol-Dissolved Oxygen System via Plasmon-Induced Hot Holes

Due to the commonly low content of biomarkers in diseases, increasing the sensitivity of electrochemiluminescence (ECL) systems is of great significance for in vitro ECL diagnosis and biodetection. Although dissolved O2 (DO) has recently been considered superior to H2O2 as a coreactant in the most widely used luminol ECL systems owing to its improved stability and less biotoxicity, it still has unsatisfactory ECL performance because of its ultralow reactivity. In this study, an effective plasmonic luminol-DO ECL system has been developed by complexing luminol-capped Ag nanoparticles (AgNPs) with plasma-treated Fe single-atom catalysts (Fe-SACs) embedded in graphitic carbon nitride (g-CN) (pFe-g-CN). Under optimal conditions, the performance of the resulting ECL system could be markedly increased up to 1300-fold compared to the traditional luminol-DO system. Further investigations revealed that duple binding sites of pFe-g-CN and plasmonically induced hot holes that disseminated from AgNPs to g-CN surfaces lead to facilitate significantly the luminous reaction process of the system. The proposed luminol-DO ECL system was further employed for the stable and ultrasensitive detection of prostate-specific antigen in a wide linear range of 1.0 fg/mL to 1 μg/mL, with a pretty low limit of detection of 0.183 fg/mL.

SERS-based microdevices for use as in vitro diagnostic biosensors

Advances in surface-enhanced Raman scattering (SERS) detection have helped to overcome the limitations of traditional in vitro diagnostic methods, such as fluorescence and chemiluminescence, owing to its high sensitivity and multiplex detection capability. However, for the implementation of SERS detection technology in disease diagnosis, a SERS-based assay platform capable of analyzing clinical samples is essential. Moreover, infectious diseases like COVID-19 require the development of point-of-care (POC) diagnostic technologies that can rapidly and accurately determine infection status. As an effective assay platform, SERS-based bioassays utilize SERS nanotags labeled with protein or DNA receptors on Au or Ag nanoparticles, serving as highly sensitive optical probes. Additionally, a microdevice is necessary as an interface between the target biomolecules and SERS nanotags. This review aims to introduce various microdevices developed for SERS detection, available for POC diagnostics, including LFA strips, microfluidic chips, and microarray chips. Furthermore, the article presents research findings reported in the last 20 years for the SERS-based bioassay of various diseases, such as cancer, cardiovascular diseases, and infectious diseases. Finally, the prospects of SERS bioassays are discussed concerning the integration of SERS-based microdevices and portable Raman readers into POC systems, along with the utilization of artificial intelligence technology.

From theory to practice: understanding the challenges in the implementation of electrogenerated chemiluminescence for analytical applications

Electrogenerated chemiluminescence (ECL) stands out as a remarkable phenomenon of light emission at electrodes initiated by electrogenerated species in solution. Characterized by its exceptional sensitivity and minimal background optical signals, ECL finds applications across diverse domains, including biosensing, imaging, and various analytical applications. This review aims to serve as a comprehensive guide to the utilization of ECL in analytical applications. Beginning with a brief exposition on the theory at the basis of ECL generation, we elucidate the diverse systems employed to initiate ECL. Furthermore, we delineate the principal systems utilized for ECL generation in analytical contexts, elucidating both advantages and challenges inherent to their use. Additionally, we provide an overview of different electrode materials and novel ECL-based protocols tailored for analytical purposes, with a specific emphasis on biosensing applications.