Fabrication of Noncoplanar Molecule Aggregates with Inherent Porous Structures for Electrochemiluminescence Signal Amplification

Recent Advances in Electrochemiluminescence Biosensors for MicroRNA Detection

Electrochemiluminescence (ECL) as an analytical technology with a perfect combination of electrochemistry and spectroscopy has received considerable attention in bioanalysis due to its high sensitivity and broad dynamic range. Given the selectivity of bio-recognition elements and the high sensitivity of the ECL analysis technique, ECL biosensors are powerful platforms for the sensitive detection of biomarkers, achieving the accurate prognosis and diagnosis of diseases. MicroRNAs (miRNAs) are crucial biomarkers involved in a variety of physiological and pathological processes, whose aberrant expression is often related to serious diseases, especially cancers. ECL biosensors can fulfill the highly sensitive and selective requirements for accurate miRNA detection, prompting this review. The ECL mechanisms are initially introduced and subsequently categorize the ECL biosensors for miRNA detection in terms of the quenching agents. Furthermore, the work highlights the signal amplification strategies for enhancing ECL signal to improve the sensitivity of miRNA detection and finally concludes by looking at the challenges and opportunities in ECL biosensors for miRNA detection.

Pyrenecarboxaldehyde@Graphene Oxide Acted as a Highly Efficient ECL Emitter and Target-Triggered the Recyclable Cascade System as an Amplifier for Ultrasensitive APE1 Activity Detection

Herein, pyrenecarboxaldehyde@graphene oxide (Pyc@GO) sheets with highly efficient electrochemiluminescence (ECL) as emitters were prepared by a noncovalent combination to develop a neoteric ECL biosensing platform for the ultrasensitive assessment of human apurinic/apyrimidinic endonuclease1 (APE1) activity. Impressively, the pyrenecarboxaldehyde (Pyc) molecules were able to form stable polar functional groups on the surface of GO sheets through the noncovalent π-π stacking mechanism to prevent intermolecular restacking and simultaneously generate Pyc@GO sheets. Compared with the tightly packed PAH nanocrystals, the Pyc@GO sheets significantly reduced internal filtering effects and diminished nonactivated emitters to enhance ECL intensity and achieve strong ECL emission. Furthermore, the APE1-activated initiators could trigger the recyclable cascade amplified system based on the synergistic cross-activation between catalytic hairpin assembly (CHA) and DNAzyme, which improved the signal amplification and transduction ability. Consequently, the developed ECL platform for the detection of APE1 activity displayed exceptional sensitivity with a low detection limit of 4.6 × 10-9 U·mL-1 ranging from 10-8 to 10-2 U·mL-1. Therefore, the proposed strategy holds great promise for the future development of sensitive and reliable biosensing platforms for the detection of various biomarkers.

Vesicles as a Multifunctional Microenvironment for Electrochemiluminescence Signal Amplification

Vesicles as a typical interface-rich microenvironment can promote the reaction rate and the intermediate stability, which are promising for introduction in electrochemiluminescence (ECL) signal amplification. In this work, a kind of multilamellar vesicle obtained from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was used to modify the electrode surface. The AOT vesicle-modified microenvironment could significantly enhance the ECL performances for the luminol/O2 system in a neutral medium. The mechanism study demonstrated that the nanoscale multilamellar vesicles could maintain the vesicle structure on the electrode surface, which substantially improved the electron transfer and reaction rate, luminescence efficiency of the excited-state 3-aminophthalate anion, and stability of the superoxide anion radical. Alternatively, such a multifunctional microenvironment was also able to enhance the ECL signals from the tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+)/tripropylamine (TPrA) system. Moreover, another dodecyl dimethyl(3-sulfopropyl) ammonium hydroxide inner salt (DSB)-based vesicle was constructed to further verify the versatility of the vesicle-modified microenvironment for ECL signal amplification. Our work not only provides a versatile microenvironment for improving the efficiency of various ECL systems but also offers new insights for the microenvironment construction using the ordered assemblies in ECL fields.

Sonochemiluminescence Using Apertureless USB Piezoelectric Ultrasonic Transducer and Its Applications for the Detection of Hydrogen Peroxide, Glucose, and Glucose Oxidase Activity

The mesh-type USB piezoelectric ultrasonic transducer (USB-PUT) used in household humidifiers and inhalation therapy devices is very cheap, small, and energy saving. It holds great promise for sonochemistry. However, the microtapered apertures in the center of the stainless steel substrate of mesh-type USB-PUT can lead to rapid atomization of solution, leakage of solutions containing surfactants and organic solvent through the apertures, and high background emission. Herein, we design a new type of USB-PUT by replacing the meshed stainless steel substrate with an apertureless stainless steel substrate. We have found that this apertureless USB-PUT can not only induce intense sonochemiluminescence (SCL) but can also enable sensitive luminol SCL detection of hydrogen peroxide which is practically impossible using mesh-type PUT because of the strong background SCL emission. By using this apertureless device to induce SCL and using smart phone as a detector, a visual hydrogen peroxide SCL detection method with a linear range of 0.5-50 μM and a detection limit of 0.32 μM is established. Moreover, the device can achieve the detection of glucose oxidase (GOD) activity and glucose by enzymatic conversion of glucose to hydrogen peroxide. The linear range of GOD detection is 1-200U/L with a detection limit of 0.86 U/L. The linear range of glucose detection is 0.5-70 μM with a detection limit of 0.43 μM. The cheap (a few dollars) and user-friendly apertureless USB-PUT is promising for sonochemistry applications and chemical education.

Plasmon-Boosted Cu-Doped TiO2 Oxygen Vacancy-Rich Luminol Electrochemiluminescence for Highly Sensitive Detection of Alkaline Phosphatase

In this study, an effective oxygen vacancy (O_v)-involved luminol-dissolved oxygen (O₂) electrochemiluminescence (luminol-DO ECL) system was developed and exploited for ECL sensing applications through significant plasmon enhancement of the O_v-involved weak luminol-DO ECL signals by the combined use of Cu-doped TiO₂ oxygen vacancy and a Au@SiO₂ nanomembrane. The results disclosed that the ECL response of the corresponding system could be synergistically boosted, and the plausible underlying mechanism has been discussed. Furthermore, for the first time, the developed system has been successfully applied for the highly sensitive detection of alkaline phosphatase with a low limit of detection of 0.005 U/L, with an excellent linear range from 0.005 to 10 U/L, as well as good stability and reproducibility.

All-sealed paper-based electrochemiluminescence platform for on-site determination of lead ions

Lab-on-paper (LOP) devices are urgently required for the rapid development of point-of-care diagnoses and environmental assays. Herein, an all-sealed paper-based electrochemiluminescence (ECL) platform was developed to achieve lead ions (Pb²⁺) sensitive analysis via incorporating convenient plastic package technology. Benefiting from transparent plastic encapsulation, the sealed devices effectively avoided the interference of O₂. Meanwhile, myrica rubra-like Pt nanomaterials (MPNs) prepared by an economical and easy-to-operate ultrasound method were employed to catalyze H₂O₂ decomposition. With the help of Pb²⁺-specific DNAzymes, the oligonucleotide probe functionalized via MPNs could be detached from the device in the presence of target, resulting in the reduced ECL intensity. Moreover, the combination of modified paper electrode with functional regions separated by multiple layers of wax enhanced the practicability of the LOP device for rapid detection. Under the optimal conditions, the all-sealed platform achieved wide linear relationship ranging from 0.01 nM to 0.05 μM with a low detection limit of 0.004 nM for sensitive detecting Pb²⁺. It is believed that this platform could provide a robust, simple and versatile strategy for sensitive determination of heavy metal ions, and be applied in on-site contamination analysis in the future.

A molecularly imprinted electrochemiluminescence nanoprobe based on complexes consisting of CdTe and multiwall carbon nanotube for sensitive determination of clenbuterol

An electrochemiluminescence (ECL) nanoprobe was fabricated for the determination of clenbuterol (CLB). A molecularly imprinted polymer (MIP) film was coated on the surface of the glassy carbon electrode modified with CdTe-doped multiwall carbon nanotubes. The MIP film with CLB as the template molecule improves the selectivity of the nanoprobe, CdTe is used as ECL signal amplifier, and MWCNT works as the carrier. The ECL intensity is altered by elution and reabsorption of CLB. The possible reaction mechanism and experimental parameters of the nanoprobe are discussed. Under optimized conditions, the quenched ECL intensity and the CLB concentration have a linear relationship in the range 2.3 × 10^-9 to 1.5 × 10^-5 mol·L^-1, and the detection limit is 1.0 × 10^-9 mol·L^-1 (S/N = 3). The nanoprobe was successfully applied to the determination of CLB in pork samples. Graphical abstract Schematic representation of the molecularly imprinted electrochemiluminescence nanoprobe based on complexes consisting of CdTe and multiwall carbon nanotube used to determinate clenbuterol.

Tetraphenylenthene-Based Conjugated Microporous Polymer for Aggregation-Induced Electrochemiluminescence

We demonstrate the aggregation-induced electrochemiluminescence (AIECL) generated by 1,1,2,2-tetrakis(4-bromophenyl)ethane (TBPE)-based conjugated microporous polymers (TBPE-CMPs) and its biosensing application. We synthesized three TBPE-CMPs (i.e., TBPE-CMP-1, -2, -3) using three different molecules including tris(4-ethynylphenyl)amine (TEPA), 4,4'-diethynylbiphenyl (DEP), and 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (TEPT). The TBPE-CMPs can act as electrochemiluminescence (ECL) emitters to generate AIECL. Among them, TBPE-CMP-1 exhibits the highest ECL efficiency (1.72%) due to the improved electron-hole recombination efficiency and efficient suppression of nonradiative transition. Moreover, the ECL properties of TBPE-CMPs can be tuned by the introduction of different conjugated molecules that can decrease the energy gap to facilitate the injection of an electron into the conjugated polymer backbone. Importantly, TBPE-CMP-1 can be used to construct an ECL sensor for the detection of dopamine, whose electro-oxidation products (e.g., leucodopaminechrome (LDC), dopaminechrome (DC), 5,6-dihydroxyindole (DHI), and 5,6-indolequinone (IDQ)) may function as energy acceptors to quench the ECL emission of TBPE-CMP-1. This ECL sensor exhibits high sensitivity and good anti-interference capability against ascorbic acid and uric acid.

A label-free and signal-on electrochemiluminescence strategy for sensitive amyloid-beta assay

Development of a simple, cost-effective and sensitive biosensing strategy is highly desirable to advance the applications in Alzheimer's disease diagnosis. In this paper, we present a simple, label-free and signal-on electrochemiluminescence (ECL) aptasensor for the detection of amyloid-beta (Aβ) peptide using luminol as ECL emitter and in-situ generated reactive oxygen species (ROS) as coreactant via catalytic reaction between Cu²⁺-Aβ and the dissolved O₂ in the presence of ascorbic acid (AA). Aβ₁₆, the binding site of Cu²⁺ in the monomeric full-length Aβ, was used as a model in present study. As a result, this signal-on ECL aptasensor has exhibited favorable analytical performance for Aβ₁₆ monomer with a linear range of 1.0 × 10^-13 mol/L-1.0 × 10^-8 mol/L and a limit of detection of 3.5 × 10^-14 mol/L (S/N=3). Furthermore, the proposed biosensor was also able to detect the full length Aβ₄₀ not only in the phosphate buffer saline (PBS) solution but also in human serum. The presented biosensor represents a promising, simple, turn-on and label-free diagnostic tool for blood analysis.

Rapid screening of the hydrogen bonding strength of radicals by electrochemiluminescent probes

In this study, we discovered that a clear decrease in the electrochemiluminescence (ECL) intensities of luminol occurred upon increasing the electron donating capacity of amides. Therefore, herein, a novel ECL probe was used for the first time to screen the strength of the hydrogen bonds formed between HOO˙ radicals and amides. This proposed hydrogen bonding strength-sensitive ECL probe has a significant prospect in distinguishing the hydrogen bonding strength of different radicals.