Electrogenerated chemiluminescence of luminol on wireless conducting polymer films

Regio selective deposition of conducting polymers using wireless electropolymerisation

The ability to induce different potentials in different regions of a (bipolar) electrode could transform applications such as on-demand drug delivery, the electrostimulation of biological cells, the development of advanced electroceuticals, and multi-analyte detection devices where different analytes could be wirelessly detected in different regions of a single sensing surface dramatically simplifying the device design. Here, we demonstrate the use of multiple feeder electrodes to control the electric field distribution in solution thus changing the potential induced in different regions of the bipolar electrode depending on the feeder voltage, polarity and feeder electrode position. The principle is demonstrated for the deposition of films of the conducting polymer, Poly(3,4-EthyleneDiOxyThiophene) (PEDOT), without the need for a physical template to control the regions in which polymer deposits.

Bright luminol electrochemiluminescence mediated by a simple TEMPO radical for visualized multiplex detection

In this work, a series of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) radicals bearing different functional groups were exploited as a simple catalyst to promote electrochemiluminescence (ECL) generation in luminol/H2O2 system. These TEMPO radicals were found to facilitate the electrochemical oxidation of H2O2 and luminol through different catalytic mechanisms, as well as the subsequent ECL generation of luminol/H2O2 system. The electrochemical oxidation and luminol ECL generation could be tuned by the functional group on the para-position of TEMPO, for which the structure/activity relationship was revealed. Finally, with the combination of enzymatic system, luminol ECL enhancement up to 9.6-fold was obtained through the catalysis of 4-hydroxyl-TEMPO. The enhanced luminol ECL allows acquiring brighter ECL images in a single-electrochemical system (SEES) for multiplex detection of cholesterol, H2O2 and glucose.

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.

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).

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.

Wireless rotating bipolar electrochemiluminescence for enzymatic detection

New dynamic, wireless and cost-effective analytical devices are developing rapidly in biochemical analysis. Here, we report on a remotely-controlled rotating electrochemiluminescence (ECL) sensing system for enzymatic detection of a model analyte, glucose, on both polarized sides of an iron wire acting as a bipolar electrode. The iron wire is controlled by double contactless mode, involving remote electric field polarization, and magnetic field-induced rotational motion. The former triggers the interfacial polarization of both extremities of the wire by bipolar electrochemistry, which generates ECL emission of the luminol derivative (L-012) with the enzymatically produced hydrogen peroxide in presence of glucose, at both anodic and cathodic poles, simultaneously. The latter generates a convective flow, leading to an increase in mass transfer and amplifying the corresponding ECL signals. Quantitative glucose detection in human serum samples is achieved. The ECL signals were found to be a linear function of the glucose concentration within the range of 10-1000 μM and with a limit of detection of 10 μM. The dynamic bipolar ECL system simultaneously generates light emissions at both anodic and cathodic poles for glucose detection, which can be further applied to biosensing and imaging in autonomous devices.

Optimization and miniaturization of SE-ECL for potential-resolved, multi-color, multi-analyte detection

Electrochemiluminescence (ECL) is a bioanalytical technique with numerous advantages, including the potential for high temporal and spatial resolution, a high signal-to-noise ratio, a broad dynamic range, and rapid measurement capabilities. To reduce the complexity of a multi-electrode approach, we use a single-electrode electrochemiluminescence (SE-ECL) configuration to achieve the simultaneous emission and detection of multiple colors for applications that require multiplexed detection of several analytes. This method exploits intrinsic differences in the electric potential applied along single electrodes built into electrochemical cells, enabling the achievement of distinct colors through selective excitation of ECL luminophores. We present results on the optimization of SE-ECL intensity for different channel lengths and widths, with sum intensities being 5 times larger for 6 cm vs. 2 cm channels and linearly increasing with the width of the channels. Furthermore, we demonstrated for the first time that applying Alternating Current (AC) voltage within the single electrode setup for driving the ECL reactions has a dramatic effect on the emitted light intensity, with square waveforms resulting in higher intensities vs sine waveforms. Additionally, multiplexed multicolor SE-ECL on a 6.5 mm × 3.6 mm CMOS semiconductor image sensor was demonstrated for the first time, with the ability to simultaneously distinguish four different colors, leading to the ability to measure multiple analytes.

Nitrogen-Doped Graphene Quantum Dots as Electrochemiluminescence-Emitting Species for Sensitive Detection of KRAS G12C Mutation via PET-RAFT

The levels of KRAS G12C point mutation is recognized to be closely related to the earlier diagnosis of non-small cell lung cancer (NSCLC). Here, based on nitrogen-doped graphene quantum dots (NGQDs) and photo-induced electron/energy transfer reversible addition-fragment chain transfer (PET-RAFT) signal amplification strategy, we fabricated a novel electrochemiluminescence (ECL) biosensor for the detection of KRAS G12C mutation for the first time. NGQDs as ECL-emitting species with cathodic ECL were prepared by a simple calcination method. Firstly, KRAS G12C mutation DNA, i. e., target DNA (tDNA), was captured by specific identification with hairpin DNA (hDNA). Then, PET-RAFT was initiated by blue light, and large numbers of monomers were successfully polymerized to form controllable polymer chains. Lastly, massive NGQDs was introduced via amidation reaction with N-(3-aminopropyl)methacrylamide hydrochloride (APMA), which significantly amplified the ECL signal intensity. Under optimal conditions, this biosensor achieved a good linear relationship between ECL intensity and logarithm of the levels of KRAS G12C mutation in the range from 10 fM to 10 nM. Moreover, this strategy exhibited high selectivity and excellent applicability for KRAS G12C mutation detection in the serum samples. Therefore, this biosensor has great potential in clinical diagnosis and practical application.

Endogenous and exogenous wireless multimodal light-emitting chemical devices

Multimodal imaging is a powerful and versatile approach that integrates and correlates multiple optical modalities within a single device. This concept has gained considerable attention due to its potential applications ranging from sensing to medicine. Herein, we develop several wireless multimodal light-emitting chemical systems by coupling two light sources based on different physical principles: electrochemiluminescence (ECL) occurring at the electrode interface and a light-emitting diode (LED) switched on by an electrochemically triggered electron flow. Endogenous (thermodynamically spontaneous redox process) and exogenous (requiring an external power source) bipolar electrochemistry acts as a driving force to trigger both light emissions at different wavelengths. The results presented here interconnect optical imaging and electrochemical reactions, providing a novel and so far unexplored alternative to design autonomous hybrid systems with multimodal and multicolor optical readouts for complex bio-chemical systems.

SE-ECL on CMOS: a miniaturized electrochemiluminescence biosensor

Biosensors exhibit high potential for the detection of analytes of interest at the point-of-need. Over the past two decades, the combination of novel biosensing systems - such as electrochemiluminescence (ECL) biosensors - and advances in microfluidic techniques has allowed the development of lab-on-a-chip devices with enhanced overall performance and simplified sample handling. However, recording data with conventional platforms requires advanced and complicated instruments, such as sensitive photodetectors coupled to microscopes, to capture the photons from the chemiluminescent reaction. In this work, we integrated microfluidic and luminol/hydrogen peroxide ECL systems on a complementary metal-oxide-semiconductor (CMOS) chip for sample handling and data collection on the same platform. This was achieved by the adaptation of a single electrode as an electrochemical transducer and a CMOS chip as a built-in detector. We demonstrated the application of this platform for the detection of uric acid (UA), a biomarker of gout disease. A linear detection range was observed from 25 to 300 μM, with a detection limit (LOD) as low as 26.09 μM. The device showed high reusability and reproducibility within the linear detection range while maintaining high selectivity for UA detection. The analytical performance has also been evaluated in simulated saliva and urine samples, demonstrating the potential utility in medical diagnosis at the point-of-need. Compared to other ECL imaging platforms, this device showed an eightfold increase in photon collection efficiency. Overall, this approach has promising potential as an inexpensive, portable, and efficient ECL platform for measuring analytes at the point-of-need.

Dye-functionalized metal-organic frameworks with the uniform dispersion of MnO2 nanosheets for visualized fluorescence detection of alanine aminotransferase

The wide applications of metal-organic framework (MOF) luminescent materials in the field of optics have attracted the general attention of researchers. Therefore, the development of simple and multifunctional MOF light-emitting platforms have become a research hotspot. The composites (MnO2@ZIF-8-luminol) were prepared by an in situ synthesis method and room-temperature covalent reaction. The composites and o-phenylenediamine (OPD) constitute a dual emission sensor for detecting alanine aminotransferase (ALT). OPD can be oxidized by MnO₂ to 2,3-diaminophenazine (DAP) with yellow fluorescence emission, which inhibits the blue emission of luminol through fluorescence resonance energy transfer (FRET). The presence of tiopronin (TP) will destroy the FRET process, extinguishing the yellow fluorescence emission and restoring the blue fluorescence emission. The special effect between ALT and TP will further reverse the changes in the two fluorescent signals. Moreover, in the detection process, when the blue and yellow fluorescence energies in the system are within a certain range, a new white light emission will be generated, which causes the sensing of ALT to present ternary visualization. In addition, a high-security anti-counterfeiting platform is constructed by using the prepared materials and agarose hydrogels. The anti-counterfeiting platform can encrypt information on demand according to the luminous characteristics of different materials. This study not only provides a typical case of ternary visualization sensing by MOF-based materials but also develops a possible method for the construction of a MOF-based hydrogel anti-counterfeiting platform.

Hybrid light-emitting devices for the straightforward readout of chiral information

Bipolar electrochemistry has gained increasing attention in recent years as an attractive transduction concept in analytical chemistry in general and, more specifically, in the frame of chiral recognition. Herein, we use this concept of wireless electrochemistry, based on the combination of the enantioselective oxidation of a chiral probe with the emission of light from a light-emitting diode (LED), as an alternative for an easy and straightforward readout of the presence of chiral molecules in solution. A hybrid polymer-microelectronic device was designed, using an inherently chiral oligomer, that is, oligo-(3,3'-dibenzothiophene) and a polypyrrole strip as the anode and cathode of a miniaturized LED. The wireless induced redox reactions trigger light emission when the probe with the right chirality is present in solution, whereas no light emission is observed for the opposite enantiomer. The average light intensity shows a linear correlation with the analyte concentration, and the concept opens the possibility to quantify the enantiomeric excess in mixtures of the molecular antipodes.