Bismuth Nano-Nest/Ti3CN Quantum Dot-Based Surface Plasmon Coupling Electrochemiluminescence Sensor for Ascites miRNA-421 Detection.

In this study, a novel surface plasmon-coupled electrochemiluminescence (SPC-ECL) biosensor was developed based on bismuth nano-nest and Ti3CN quantum dots (Ti3CN QDs). First, MXene derivative QDs (Ti3CN QDs) with excellent luminescence performance were prepared as the ECL luminescent. The N doping in Ti3CN QDs can effectively improve the luminescence performance and catalytic activity. Therefore, the luminescence performance of QDs has been effectively improved. Furthermore, the bismuth nano-nest structure with a strong localized surface plasmon resonance effect has been designed as the sensing interface via the electrochemical deposition method. It was worth noticed that the morphology of bismuth nanomaterials can be controlled effectively on the electrode surface by the step potential method. Due to the abundant surface plasmon hot spots generated between the bismuth nano-nests, the isotropic ECL signal of Ti3CN QDs can be not only significantly enhanced by 5.8 times but also converted into polarized emission. Finally, the bismuth nano-nest/Ti3CN QD-based SPC-ECL sensor was used to quantify miRNA-421 in the range of 1 fM to 10 nM. The biosensor has been successfully used for miRNA in ascites samples from gastric cancer patients, which indicated that the SPC-ECL sensor developed in this study has great potential for clinical analysis.

Accurate Capture and Identification of Exosomes: Nanoarchitecture of the MXene Heterostructure/Engineered Lipid Layer.

Recently, exosome detection has become an important breakthrough in clinical diagnosis. However, the effective capture and accurate identification of cancer exosomes in a complex biomatrix are still a tough task. Especially, the large size and non-conductivity of exosomes are not conducive to highly sensitive electrochemical or electrochemiluminescence (ECL) detection. Therefore, we have developed a Ti3C2Tx-Bi2S3-x heterostructure/engineered lipid layer-based nanoarchitecture to overcome the limitations. The engineered lipid layer not only specifically captured and efficiently fused CD63 positive exosomes but also showed excellent antifouling property in the biological matrix. Moreover, the MUC1 aptamer-modified Ti3C2Tx-Bi2S3-x heterostructure further identified and covered the gastric cancer exosomes that have been trapped in the engineered lipid layer. In the self-luminous Faraday cage-type sensing system, the Ti3C2Tx-Bi2S3-x heterostructure with sulfur vacancies extended the outer Helmholtz plane and amplified the ECL signal. Therefore, this sensor can be used to detect tumor exosomes in ascites of cancer patients without additional purification. It provides a new pathway to detect exosomes and other large-sized vesicles with high sensitivity.

MoS2 QDs-MXene heterostructure-based ECL sensor for the detection of miRNA-135b in gastric cancer exosomes.

Exosomes play an important role in the proliferation, adhesion and migration of cancer cells. In this study, we have developed a novel electrochemiluminescence (ECL) sensor based on MoS2 QDs-MXene heterostructure and Au NPs@biomimetic lipid layer to detect exosomal miRNA. MoS2 QDs-MXene heterostructure had been prepared as the luminescence probe. Ti3C2Tx MXene nanosheets possessed the large specific surface area, excellent flexibility and superior conductivity. MoS2 QDs on the MXene nanosheets worked as the radiation center to generate strong ECL signal. Meanwhile, Au NPs with biomimetic lipid layer have been modified on the electrode, which retained the lipid dynamics and excellent antifouling property. When miRNA-135b was recognized on the Au NPs@biomimetic lipid layer, MoS2 QDs-MXene heterostructure was linked on the electrode and further extended the outer Helmholtz plane. As a result, the self-luminous Faraday cage-mode sensing system has been used to detect miRNA-135b from 30 fM to 20 nM with a detection limit of 10 fM. Furthermore, gastric cancer exosomal miRNA in the ascites of clinical patients has been detected successfully. The sensing system can be served as a versatile platform with huge application potential in the field of exosome detection.

3D Plasmonic Nanostructure-Based Polarized ECL Sensor for Exosome Detection in Tumor Microenvironment.

Exosomes of cancer cells play an important role in the proliferation, adhesion, and migration of tumors. Especially, exosomes in the tumor microenvironment can reflect the proliferation of tumors directly, thus serving as ideal referenced markers of the possibility and grade of malignancy in neoplasms. However, the sensitive and accurate detection of exosomes remains challenging. In this work, a novel three-dimensional (3D) plasmonic nanostructure was constructed for exosomal miRNA detection. It combined the advantages of Au nanostar monolayer and Ag nanowire monolayer to provide multiple hot spots. Moreover, Au nanostar monolayer changed the isotropic electrochemiluminescence (ECL) into polarized emission. The Ag nanowire monolayer worked as waveguides for the light direction. As a result, the polarized resolution and intensity of ECL signal were improved. The polarized ECL emission was significantly increased by 47.1 times. This high-resolution polarized ECL sensor was used for detecting exosomal miRNA-146b-5p in the thyroid tumor microenvironment. This sensor showed the linear range from 1 fM to 1 nM with a detection limit of 0.3 fM. The satisfactory results indicated the developed 3D plasmonic nanostructure-based ECL sensor had great potential in biosensing and clinical diagnosis.

In situ synthesis of Cu nanoclusters/CeO2 nanorod as aggregated induced ECL probe for triple-negative breast cancer detection.

Cu nanoclusters (NCs) have attracted a lot of attention due to the excellent properties. However, the low luminescence and poor stability limited the Cu NC-based sensing research. In this work, Cu NCs were in situ synthesized on CeO2 nanorods. On the one hand, the aggregated induced electrochemiluminescence (AIECL) of Cu NCs has been observed on the CeO2 nanorods. On the other hand, the substrate of CeO2 nanorods acted as catalysis, which reduced the excitation potential and further enhanced the ECL signal of Cu NCs. It was noticed that CeO2 nanorods also greatly improved the stability of Cu NCs. The resulted high ECL signals of Cu NCs can be kept constant for several days. Furthermore, MXene nanosheets/Au NPs has been employed as electrode modification materials to construct the sensing platform to detect miRNA-585-3p in triple negative breast cancer tissues. Au NPs@MXene nanosheets not only enlarged the specific interface area of the electrodes and the number of reaction sites, but also modulated electron transfer to amplify the ECL signal of Cu NCs. The biosensor had a low detection limit (0.9 fM) and a wide linear range (1 fM to 1 µM) for the detection of miRNA-585-3p in the clinic tissues.

The controllable assembly of Cu nanocluster-based aggregation induced ECL strategy for miRNA detection.

Copper nanoclusters (Cu NCs) were a new class of non-toxic and economical nanoprobe. However, the low luminescence performance and instability of Cu NCs limited the actual application. Herein, this work developed the novel controllable assembly of Cu NCs aggregation as the electrochemiluminescence (ECL) emitter. Firstly, the hydrophilic Cu NCs was located into the micelles in the reverse microemulsion system. Due to the uniform size of micelles, the number of Cu NCs in each micelle can be controlled exactly. Cerium ions were added to induce Cu NCs to accumulate in micelles. The strong aggregation induced ECL (AIECL) signal can be observed in the controllable assembly of Cu NCs aggregation. The nano-sized Cu NCs assembly not only possessed more strong luminescence and better stability than original Cu NCs, but also kept the good dispersibility over the aggregated bulk. Furthermore, SnS2 nanosheets increased the specific surface area of the electrode and the number of reactive sites, which further modulated electron transfer to amplify the ECL signal. The ECL sensing system was used to detect miRNA-455-3p in the triple-negative breast cancer tumor tissues. The work provided the new pathway to prepare Cu NCs assembly and expanded AIECL-based sensing application.

A novel nanosponge-hydrogel system-based electrochemiluminescence biosensor for uric acid detection.

In this work, a highly efficient electrochemiluminescence (ECL) biosensor was developed based on the nanosponge-hydrogel system for uric acid (UA) detection. First, the nanosponge consisted of polylactic acid glycolic acid (PLGA) nanoparticles immobilized with MoS2 quantum dots (QDs) and urate oxidase (UAO). The marked loading capability of PLGA nanoparticles enables loading many biomolecules and QDs for the specific recognition of UA. Urate oxidase on the nanosponge can catalyze UA to generate H2 O2 in situ, which further triggers the ECL signal for the MoS2 QDs. Furthermore, the biocompatible acrylamide-based hydrogel not only effectively retained the functionalities of the chimeric nanosponge-hydrogel, but also provided structural integrity and engineering flexibility on the electrode for ECL sensing applications. In addition, there were many ester groups and amide bonds in the nanosponge-hydrogel structure. Therefore, many electron can be excited in the ECL process due to the large number of lone electron pairs on oxygen and nitrogen atoms. This resulted in a seven-fold ECL enhancement of the MoS2 QDs. Finally, the nanosponge-hydrogel structure-based ECL biosensor was successfully used in real clinical serum assays. This showed a good analytical performance for UA detection (100-500 µmol/L) with a limit of detection of 20 µmol/L.

Confined Gold Single Atoms-MXene Heterostructure-Based Electrochemiluminescence Functional Material and Its Sensing Application.

Herein, based on electronic metal-support interaction (EMSI), a gold single atom confined MXene (AuSA/MXene) heterostructure was developed as the highly efficient electrochemiluminescence (ECL) functional material, which greatly improved the electrochemical properties and broadened the sensing application of MXenes. Gold single atoms were confined into the vacancy defects of Ti3C2Tx MXene, which could effectively avoid the masking of catalytic active sites. Meanwhile, electron transport could be accelerated with the assistance of titanium dioxide on the MXene nanosheets. Therefore, the AuSA/MXene heterostructure had high catalytic activity and electrical activity to promote hydrogen peroxide to generate free radicals, which achieved high-efficiency ECL. Eventually, the AuSA/MXene heterostructure was used to construct a Faraday cage-type ECL sensor with fluid nanoislands to detect miRNA-187 in triple-negative breast cancer tumor tissues.

A practical guide to scanning light-field microscopy with digital adaptive optics.

With the development of a wide variety of animal models in recent years, there is a rapidly growing demand for long-term, high-speed intravital fluorescence imaging to observe intercellular and intracellular interactions in their native states. Scanning light-field microscopy (sLFM) with digital adaptive optics provides a compact computational solution by imaging the entire volume in a tomographic way with orders-of-magnitude improvement in spatiotemporal resolution and reduction in phototoxicity, as compared to traditional intravital microscopy. Here, we present a step-by-step protocol for both hardware and software implementation of multicolor sLFM as an add-on to a normal wide-field fluorescence microscope by using off-the-shelf lenses and devices at low cost. The procedure can be easily applied to other LFM variants, which can be advantageous in certain experimental contexts. Owing to the strong reliance of sLFM on algorithmic post-processing for high-quality data, the protocol describes various kinds of artefacts and corresponding parameters used for correcting and performance optimization. To increase the tolerance to system misalignment and differences in device fabrication, we describe a one-step calibration method for robust imaging performance up to the diffraction limit. An open-source graphical user interface is presented for hardware synchronization and real-time rendering of multiview images. The whole procedure including optical setup, software installation, system calibration and 3D reconstruction can be executed in 3-4 d with basic knowledge in optics and electronics.

Gold Nanorod Vertical Array-Based Electrochemiluminescence Polarization Assay for Triple-Negative Breast Cancer Detection.

In this work, a polarization-resolved electrochemiluminescence (ECL) sensor for microRNA-155 (miRNA-155) detection has been constructed based on the surface plasmon coupling effect. In the sensing system, nitrogen dots (N dots) were employed as ECL emitters. As a surface-enhanced structure, a gold nanorod vertical array was constructed on the electrode surface by the volatilization-induced self-assembly. The coupling of the adjacent gold nanorods in the array can generate significant local electromagnetic fields. Due to the anisotropy of gold nanorods and the hot spot effect of the vertical array, the ECL signal of N dots was greatly improved at a specific polarization angle. In addition, the catalytic hairpin self-assembly strategy was used to amplify the nucleic acid analyte signal. As a result, the polarization-resolved ECL sensor can detect miRNA-155 sensitively, which is related to triple-negative breast cancer.

Luminous MoS2 nanosheet-based electrochemiluminescence biosensor with biomimetic vesicle for miRNA-210 detection.

In this work, a novel electrochemiluminescence (ECL) sensor has been developed to detect miRNA-210 in the serum of triple negative breast cancer (TNBC) patients. The luminous MoS2 nanosheets were synthesized via the solvothermal method and served as ECL emitters for the first time. As a result, the ECL properties of as-prepared MoS2 nanosheets were significantly improved. Furthermore, the biomimetic magnetic vesicles were used as capture platform in the ECL sensing strategy. Due to the highly efficient fluidity and magnetic property, the biomimetic vesicles with hairpin aptamers can capture target gene in the serum. After magnetic separation, the captured miRNA-210 can trigger the target-catalyzed hairpin assembly (CHA) sensing process on the magnetic electrode and hybridize MoS2 nanosheets labeled probe DNA. The concentration of miRNA-210 can be quantified by the ECL enhancement of the MoS2 nanosheets. This approach has achieved the sensitive detection for miRNA-210 in a range from 1 fM to 100 pM with the detection limit of 0.3 fM. The luminous MoS2 nanosheets-based ECL sensing system with the biomimetic vesicles would provide a new pathway to explore 2D nanomaterials for developing a wide range of bioanalytical applications.

MXene-Derived Quantum Dot@Gold Nanobones Heterostructure-Based Electrochemiluminescence Sensor for Triple-Negative Breast Cancer Diagnosis.

MXene material has been gradually studied in recent years due to its fascinating characteristics. This work developed a novel MXene-derived quantum dots (MQDs) @gold nanobones (Au NBs) heterostructure as the electrochemiluminescence (ECL) sensor. First, MXene and MQDs were synthesized via the green preparation process, which avoided the harm of hydrofluoric acid to humans and the environment. There was a strong ECL signal enhancement in the MQD@Au NBs heterostructure. On the one hand, Au NBs with surface plasmon resonance (SPR) effect acted as an "electronic regulator" that can transfer electrons to itself to control over-injection of electrons into the conduction band of MQDs. The luminous signal of MQDs can be efficiently generated and significantly amplified in the ECL sensing process. On the other hand, the work function of MQDs with excellent conductivity was relatively close to that of Au NBs in the heterostructure. So, ECL quenching caused by short-distance electron transfer between luminophore and Au nanomaterial has been effectively suppressed. The MQD@Au NBs heterostructure-based ECL sensing system was applied to determine miRNA-26a in the serum of patients with triple-negative breast cancer. It not only provides ideas for the green synthesis of MXene but also provides a guide for the application of MQD@Au NBs heterostructure in the field of ECL sensing.

Polarization-Resolved Electrochemiluminescence Sensor Based on the Surface Plasmon Coupling Effect of a Au Nanotriangle-Patterned Structure.

This work focused on the construction of a nanomaterial-patterned structure for high-resolved ECL signal modulation. Due to the surface coupling effect, the different shapes and distribution states of surface plasmonic nanomaterials not only affect the luminescence intensity enhancement but also decide the electrochemiluminescence (ECL) polarization characteristics. Herein, tin disulfide quantum dots were synthesized via a solvothermal method as ECL emitters. Compared with other nanostructures, Au nanotriangle (Au NT) displayed both the localized surface plasmon resonance electromagnetic enhancement effect and the tip amplification effect, which had significant hot spot regions at three sharp tips. Therefore, self-assembled Au NT-based patterned structures with high density and uniform hot spots were constructed as ideal surface plasmonic materials. More importantly, the distribution states of the hot spots affect the polarization characteristics of ECL, resulting in directional ECL emission at different angles. As a result, a polarization-resolved ECL biosensor was designed to detect miRNA 221. Moreover, this polarization-resolved biosensor achieved good quantitative detection in the linear range of 1 fM to 1 nM and showed satisfactory results in the analysis of the triple-negative breast cancer patients' serum.

Rational Fabrication of a Smart Electrochemiluminescent Sensor: Synergistic Effect of a Self-Luminous Faraday Cage and Biomimetic Magnetic Vesicles.

A smart electrochemiluminescent (ECL) sensor has been designed in this work. The sensing system consisted of Ag NPs-Ti3AlC2 nanosheets (Ag-TACS) as the self-luminous Faraday cage and biomimetic magnetic vesicles as the functional substrate. By engineering the structure and properties of Ti3AlC2 nanosheets to induce the Faraday-cage effect, the outer Helmholtz plane (OHP) was extended to contribute to ECL enhancement. Compared with the Faraday cage that further incorporated luminous materials, the self-luminous Faraday cage in the "direct label" model kept all the luminous materials on the OHP. Meanwhile, biomimetic magneticvesicles with highly efficient fluidity were used to improve the sensing efficiency and obtain a perfect Faraday-cage structure to enhance the ECL signals. The highest ECL enhancement (ca. 25 times) has been achieved by the synergistic effect of the Faraday cage and biomimetic magnetic vesicles. This sensing system was used to detect the wild-type K-ras gene in the colorectal tumor tissue. It provides not only an important guide for the novel ECL sensing concept but also a smart modulation system of the electromagnetic field.

Multiplex Electrochemiluminescence Polarization Assay Based on the Surface Plasmon Coupling Effect of Au NPs and Ag@Au NPs.

A novel multiplex electrochemiluminescence (ECL) polarization assay was developed to detect breast cancer-related genes BRCA1 and BRCA2 simultaneously based on the polarization characteristics of surface plasmon-coupled electrochemiluminescence (SPC-ECL). In this work, boron nitride quantum dots (BN QDs) were used as ECL emitters, and gold nanoparticles (Au NPs) and gold-coated silver nanoparticles (Ag@Au NPs) were employed as surface plasmon materials. The surface plasmon coupling resonance of different metal NPs not only enhanced the ECL intensity but also converted the isotropic emission into directional emission. This study revealed the relation between the structure of metal nanomaterials and SPC-ECL, and a high polarization-resolved sensing system was designed to detect multitarget DNA from 100 aM to 1 nM simultaneously. Polarization-based multiple ECL analysis has broad prospects in related cancer diagnosis and treatment evaluation.

Ag3PO4 NP@MoS2 nanosheet enhanced F, S-doped BN quantum dot electrochemiluminescence biosensor for K-ras tumor gene detection.

In this research, a novel Ag3PO4 NPs@MoS2 nanosheet-based electrochemiluminescence (ECL) sensing system was developed to provide an effective method for tumor gene detection. At first, fluorine, sulfur-doped BN quantum dot (F, S-BN QD) were prepared as ECL emitter. Sulfur dopant can provide more reactive sites in the ECL reaction. Fluorine atoms in the QD structure further improved the stability of the crystal. Furthermore, Ag3PO4 NP@MoS2 nanosheets were fabricated via a hydrothermal route as ECL reaction catalyst. On the one hand, Ag3PO4 NP@MoS2 nanosheets promoted the generation of more oxidant of coreactant in the F, S-BN QD/H2O2 coreactant ECL pathway. On the other hand, the excellent conductivity of Ag3PO4 NP@MoS2 nanosheets facilitated the electron transfer and effectively reduce the damage of F, S-BN QD by excessive hot electrons. Finally, the proposed biosensor was designed to accurately quantify K-ras tumor gene from 10 fM to 100 pM with a limit of detection (LOD) of 0.2 fM. The sensing system was used to detect K-ras gene in human colorectal cancer tumor and tumor-adjacent tissues samples with satisfactory results. The amplified ECL sensing strategy with Ag3PO4 NPs@MoS2 nanosheet has significant potential value in the clinical detection.

Construction of a Sensing Platform Based on DNA-Encoded Magnetic Beads and Copper Nanoclusters for Viral Gene Analysis with Target Recycling Amplification.

The rapid and accurate monitoring of viral genes plays an important role in the area of disease diagnosis, biomedical research, and food safety. Herein, we successfully designed a sensing system that combined the technologies of target DNA recycling amplification, magnetic separation, and in situ formation of fluorescent copper nanoclusters (CuNCs) for viral DNA analysis. In the presence of target viral DNA (tDNA), a large quantity of output DNA (oDNA) was produced from hairpin DNA (hDNA) through an exonuclease III-assisted target recycling amplification strategy. Magnetic beads (MBs) labeled with capture DNA (cDNA) were hybridized with oDNA, and the partially complementary oDNA served as a bridge that could link AT-rich dsDNA on the surface of MBs, which led to a decrease of AT-rich dsDNA in solution after magnetic separation. On account of the lack of AT-rich dsDNA as a template in solution, in situ formation of fluorescent CuNCs was blocked, which resulted in a decrease in the fluorescence intensity at 590 nm. Therefore, taking advantage of one-step magnetic separation and in situ formation of CuNCs, the target viral DNA was sensitively and specifically detected in a linear range from 5 pM to 5 nM with a detection limit of 1 pM. The MB-based platform was not only reusable but also achieved magnetic separation, which could eliminate interferences in complex samples. The assay combining the MB-based probe with fluorescent CuNCs provided a universal, label-free, and reusable platform for viral DNA detection.

Tunable plasmon-assisted electrochemiluminescence strategy for determination of the rapidly accelerated fibrosarcoma B-type (BRAF) gene using concave gold nanocubes.

A tunable plasmon-assisted electrochemiluminescence (ECL) strategy is reported using concave Au nanocubes (Au CBs) for rapidly accelerated fibrosarcoma B-type (BRAF) detection. Concave Au CBs exhibit a strong surface plasmon coupling (SPC) effect between its sharp apexes and edges. The high spectral overlap with graphite phase carbon nitride quantum dots (g-C3N4 QDs) is achieved by tuning surface plasmon absorption peak of the concave Au CBs. It maximizes the SPC effect and enhances the ECL signal of g-C3N4 QDs 3-fold. The SPC effect of Au CBs is twice as high as with Au NPs. We also employed a toehold-mediated strand displacement (TMSD) strategy for sensitive target recycling amplification. Under optimal conditions, this sensor can determine BRAF gene from 1 pM to 1 nM with a detection limit of 3.06 × 10-5 nM (S/N = 3) and RSD 3.67%. With the aid of the TMSD strategy and tunable plasmon-assisted ECL sensing mode, this sensor also exhibits good analytical performance in human serum with satisfactory recovery of 90.2~109%. The proposed strategy provides a promising method to effectively enhance spectral overlap and detect BRAF gene.

Fe3O4 NP@ZIF-8/MoS2 QD-based electrochemiluminescence with nanosurface energy transfer strategy for point-of-care determination of ATP.

Herein, Fe3O4 NP@ZIF-8/MoS2 QD-based electrochemiluminescence (ECL) biosensor with nanosurface energy transfer strategy was successfully developed for point-of-care determination of ATP. With the porous structure and poor electron transfer ability, Fe3O4 NP@ZIF-8 complex was first used as an excellent catalyst in ECL. The complex catalyzed the coreactant for more free radicals and hindered the quenching effect of Fe3O4 nanoparticles (NPs) on quantum dots (QDs). In ECL-nanosurface energy transfer (NSET) system, through the specific binding of complementary DNA linked to MoS2 QDs (QDs-cDNA) and aptamer linked to Au NPs, interaction between the point dipole of MoS2 QDs and the collective dipoles of Au NPs quenched ECL signal. When ATP was captured by aptamer, the ECL-NSET system was taken apart, which resulted in the recovery of ECL signal. Moreover, changes of the ECL imaging can be captured by a smartphone, which enabled point-of-care determination of ATP from 0.05 nmol L-1 to 200 nmol L-1 with LOD of 0.015 nmol L-1. With superior specificity and stability, the sensing system showed significant potential about the application of catalysts coated with ZIF and NSET in point-of-care ECL determination.

Polarized-Electrochemiluminescence Biosensor Based on Surface Plasmon Coupling Strategy and Fluorine-Doped BN Quantum Dots.

The first polarized-electrochemiluminescence (ECL) biosensor is reported in this work. Surface plasmon coupling ECL (SPC-ECL) strategy is developed for the amplified polarization light of fluorine-doped BN quantum dot (F-BN QD) emitters. The generation of polarized-ECL is attributed to the characteristic of polarization-angle-dependent SPC effect. A polarized sandwich-type biosensor based on F-BN QDs and Au nanoparticles (Au NPs) is established to detect the K-ras gene. The polarized-ECL sensor is more sensitive with lower detection limit than the isotropic ECL sensing system. The sensor can quantify the K-ras gene from 0.1 fM to 10 nM, with the detection limit as 0.03 fM. This work not only explores polarized SPC-ECL, but also offers a new analytical method for clinical diagnosis. The generation of polarized-ECL and the amplification strategy of the SPC effect opens a new path for ECL-resolved analyses.