Label-free Electrochemiluminescence Research Articles

AgTCNQ nanoshuttle as a novel organic electrochemiluminescence emitter for ultrasensitive label-free detection of aflatoxin B1

The search for novel efficient organic electrochemiluminescence (ECL) emitters is still an active and ongoing topic. Herein, a well-known metal–organic semiconducting charge transfer structure, AgTCNQ, is identified as a promising organic ECL emitter. AgTCNQ nanoshuttles were synthesized and used for the first time to demonstrate robust cathodic ECL emission with K2S2O8 as a coreactant. The ECL mechanism of the AgTCNQ nanoshuttles was investigated, revealing a red-shifted ECL emission attributed to surface states. Leveraging the strong and stable ECL of AgTCNQ nanoshuttles, a label-free ECL immunosensor was developed for the sensitive detection of aflatoxin B1 (AFB1) in Chinese herbal medicine. The immunosensor demonstrated excellent analytical performance with a linear range of 3.16 × 10−15–3.16 × 10−13 g/mL, a low detection limit of 9.33 × 10−16 g/mL, and good stability and reproducibility. Selectivity tests and detection in Chinese herbal medicines validate the specificity and feasibility of the proposed ECL immunosensor for AFB1 detection. The precision and accuracy of the immunosensor are verified by comparison with the standard high-performance liquid chromatography method. Overall, this study introduces a novel type of organic ECL nanoemitter and highlights the potential of AgTCNQ nanoshuttles in the development of sensitive and selective ECL biosensors for diverse analytical applications.

AuPt Nanodonuts as a Novel Coreaction Accelerator and Luminophore for a Label-free Electrochemiluminescence Aptasensor.

Novel and effective coreaction accelerators are of great importance in electrochemiluminescence (ECL) systems. In this work, novel AuPt nanodonuts, i.e., SnS2 quantum dots (QDs)/Cys-AuPt heterogeneous nanorings (NRs), serve as both a highly effective coreaction accelerator and the luminophore in a label-free ECL aptasensor. The novel AuPt nanodonuts were formed by decorating SnS2 QDs onto AuPt NR surfaces, which would promote the production of more coreactant intermediate in the SnS2 QDs/K2S2O8 system. As a result, the ECL performance was greatly improved. Meanwhile, l-cysteine (l-Cys) played an important role in the combination between AuPt NRs and SnS2 QDs, and the nanodonuts served as the matrix to load numerous lincomycin (Lin) aptamers. Under optimal conditions, the ECL aptasensor exhibited ultrasensitive detection of Lin from 1 to 0.1 pg/mL with a limit of detection (LOD) of 0.7 fg/mL (1.72 fM)..

An In Situ Investigation of the Protein Corona Formation Kinetics of Single Nanomedicine Carriers by Self-Regulated Electrochemiluminescence Microscopy.

Protein coronas are present extensively at the bio-nano interface due to the natural adsorption of proteins onto nanomaterials in biological fluids. Aside from the robust property of nanoparticles, the dynamics of the protein corona shell largely define their chemical identity by altering interface properties. However, the soft coronas are normally complex and rapidly changing. To real-time monitor the entire formation, we report here a self-regulated electrochemiluminescence (ECL) microscopy based on the interaction of the Ru(bpy)3 3+ with the nanoparticle surface. Thus, the heterogeneity of the protein corona is in situ observed in single nanoparticle "cores" before and after loading drugs in nanomedicine carriers. The label-free, optical stable and dynamic ECL microscopy minimize misinterpretations caused by the variation of nanoparticle size and polydispersity. Accordingly, the synergetic actions of proteins and nanoparticles properties are uncovered by chemically engineered protein corona. After comparing the protein corona formation kinetics in different complex systems and different nanomedicine carriers, the universality and accuracy of this technique were well demonstrated via the protein corona formation kinetics curves regulated by competitive adsorption of Ru(bpy)3 3+ and multiple proteins on surface of various carriers. The work is of great significance for studying bio-nano interface in drug delivery and targeted cancer treatment.

Study of an Ultrasensitive Label-Free Electrochemiluminescent Immunosensor Fabricated with a Composite Electrode for Detecting the Glutamate Decarboxylase Antibody.

Antibody testing for the glutamic acid decarboxylase 65 antibody (GADA) is widely used as a golden standard for autoimmune diabetes diagnosis, while current methods for antibody testing are not sensitive enough for clinical usage. Here, a label-free electrochemiluminescent (ECL) immunosensor for detecting GADA in autoimmune diabetes is fabricated and investigated. In the designed immunosensor, a composite film including the multiwalled carbon nanotubes (MWCNTs), zinc oxide (ZnO), and Au nanoparticles (AuNPs) was prepared through nanofabrication processes to improve the performance of sensor. The MWCNTs, which can provide a larger specific surface area, ZnO as a good photocatalytic material, and AuNPs that can enhance the ECL signal of luminol and immobilize the GAD65 antigen were applied to prefunctionalize indium tin oxide (ITO) glass based on a nanofabrication process. The GADA concentration was detected using the ECL immunosensor after incubating with GAD65 antigen-coated prefunctionalized ITO glass. After a direct immunoreaction, it is found that the degree of decreased ECL intensity has a good linear regression toward the logarithm of the GADA concentration in the range of 0.01 to 50 ng mL-1 with a detection limit down to 10 pg mL-1. Human serum samples positive or negative for GADA all nicely fell in the expected area. The fabricated immunosensor with excellent sensitivity, specificity, and stability has potential capability for clinical usage in GADA detection.

Label-free electrochemiluminescence sensor based on magnetic nanoparticles modified with G-quadruplex DNA for detecting lead ions

Developing rapid and renewable sensors to detect heavy metal lead ions is a crucial and promising area of research. Herein, we constructed a label-free electrochemiluminescence (ECL) sensor for detecting Pb2+ using magnetic nanoparticles that were modified with a G-quadruplex probe. The aptamer probe was created by immobilizing a double-stranded DNA (dsDNA) onto the surface of Fe3O4@Au magnetic nanoparticles, with Ru(phen)32+ being intercalated into the dsDNA structure. Upon introduction of Pb2+, the dsDNA structure opened up to form the Fe3O4@Au-G-quadruplex-Pb2+ structure, resulting in the dissociation of single-stranded DNA (ssDNA) and Ru(phen)32+. The dissociated Ru(phen)32+ acted as an ECL probe, allowing for the construction of a highly sensitive sensing system that quantitatively relates Pb2+ concentrations to ECL signals. In the presence of the strong chelating agent EDTA, the hybridization of the two ssDNA strands back into the dsDNA structure allowed for the re-insertion of Ru(phen)32+ into the dsDNA structure, endowing the sensor with excellent renewability. The adapter sensor was characterized using cyclic voltammetry, electrochemiluminescence, and fluorescence spectroscopy. Over the range of 50 pM to 9 nM, the Pb2+ concentration exhibited a linear relationship with its corresponding ECL signal, with a detection limit of 1.2 pM. In addition, the biosensor demonstrated outstanding selectivity, stability, reproducibility, and potential for use in real-world sample applications.

Spatial Confinement-Enhanced electrochemiluminescence of Gold nanoclusters in chitosan nanogels and its application for ultrasensitive detection of Aflatoxin B1

Gold nanoclusters (AuNCs), as a category of promising electrochemiluminescence (ECL) emitter, hold great potential for sensing applications. However, its application is still restricted by the relatively low ECL quantum yield and difficult to purification. In this work, AuNCs were confined in a soft chitosan (CS) nanogel matrix (AuNCs@CS) with good biocompatibility via a facile one-pot approach. The as-fabricated AuNCs@CS nanogels showed 2.4-fold ECL intensity relative to that of bare AuNCs without chitosan. The ECL enhancement was attributed to the increased percentage of Au(0) in AuNCs@CS nanogels, the confinement effect of chitosan nanogels, as well as chitosan as a polymer could reduce the diffusion of the radicals and prolong the excited state lifetime of AuNCs in ECL reaction. Moreover, the obtained AuNCs@CS nanogels are stable and easy to be purified by centrifugation. On this basis, a label-free ECL immunosensor for ultrasensitive detection of aflatoxin B1 (AFB1) was developed by using AuNCs@CS nanogels modified fluorine doped tin oxide (FTO) electrode as a sensing interface. The linear range of the proposed immunosensor for AFB1 detection was 3.16 × 10-14 to 3.16 × 10-12 g/mL with a detection limit of 9.3 × 10-15 g/mL, which was at least one order of magnitude lower than the reported ECL biosensor of AFB1. The proposed strategy may be used for the determination of other toxins in the Aflatoxin family if corresponding antibodies are available, which is of great significance for the quality control of Chinese herbal medicine and food safety.

Label-free electrochemiluminescence immunosensor for mucoprotein 1 using a graphene oxide-Ru(Bpy)3 2+-polyaniline nanocomposite

A graphene oxide-Ru(bpy)3 2+-polyaniline-nanocomposite (GO-Ru(bpy)3 2+-PANI) was prepared to develop a sensitive label-free electrochemiluminescence (ECL) immunosensor for mucoprotein 1 (MUC1). Ru(bpy)3 2+ and PANI were decorated together on graphene oxide for the first time. The GO-Ru(bpy)3 2+-PANI material was characterized by scanning electron microscopy (SEM), absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), fluorescence, electrochemical impedance spectroscopy (EIS), and ECL. The GO-Ru(bpy)3 2+-PANI exhibited excellent stability. The ECL immunosensor for MUC1 was fabricated by covalently immobilizing anti-MUC1 upon GO-Ru(bpy)3 2+-PANI modified indium-doped tin oxide (ITO) electrode. In the presence of MUC1, a decrease of ECL was observed due to the formation of the anti-MUC1/MUC1 complex. The immunosensor showed a linear relationship from 1 × 10−13 to 1 × 10−7 mg/mL with a detection limit of 8.2 × 10−14 mg/mL. The immunosensor was applied to the determination of MUC1 in human serum.

Bimodal Electrochemiluminescence Microscopy of Single Cells.

Electrochemiluminescence (ECL) microscopy is an emerging technique with new applications such as imaging of single entities and cells. Herein, we have developed a bimodal and bicolor approach to record both positive ECL (PECL: light-emitting object on dark background) and shadow label-free ECL (SECL: nonemissive object shadowing the background luminescence) images of single cells. This bimodal approach is the result of the simultaneous emissions of [Ru(bpy)3]2+ used to label the cellular membrane (PECL) and [Ir(sppy)3]3- dissolved in solution (SECL). By spectrally resolving the ECL emission wavelengths, we recorded the images of the same cells in both PECL and SECL modes using the [Ru(bpy)3]2+ (λmax = 620 nm) and [Ir(sppy)3]3- (λmax = 515 nm) luminescence, respectively. PECL shows the distribution of the [Ru(bpy)3]2+ labels attached to the cellular membrane, whereas SECL reflects the local diffusional hindrance of the ECL reagents by each cell. The high sensitivity and surface-confined features of the reported approach are demonstrated by imaging cell-cell contacts during the mitosis process. Furthermore, the comparison of PECL and SECL images demonstrates the differential diffusion of tri-n-propylamine and [Ir(sppy)3]3- through the permeabilized cell membranes. Consequently, this dual approach enables the imaging of the morphology of the cell adhering on the surface and can significantly contribute to multimodal ECL imaging and bioassays with different luminescent systems.

An electrochemiluminescence immunosensor based on signal magnification of luminol using OER-activated NiFe2O4@C@CeO2/Au as effective co-reaction accelerator

In this work, a novel, label-free electrochemiluminescence (ECL) immunosensor was constructed for the ultrasensitive detection of carbohydrate antigen 15–3 (CA15-3) by the combined use of NiFe2O4@C@CeO2/Au hexahedral microbox and luminol luminophore. The synthesis of the co-reaction accelerator (NiFe2O4@C@CeO2/Au) was related to the calcination of FeNi-based metal–organic framework (MOF), as well as the ingrowth of CeO2 nanoparticles and modification of Au nanoparticles. To be specific, the electrical conductivity will be boosted due to the Au nanoparticles, the synergetic effect generated between CeO2 and calcination FeNi-MOF could offer better activity of oxygen evolution reaction (OER). Herein, the NiFe2O4@C@CeO2/Au hexahedral microbox as a co-reaction accelerator has excellent OER activity and production of reactive oxygen species (ROS), thus increasing the ECL intensity of luminol in a neutral medium without other co-reactants such as H2O2. Because of these benefits, the constructed ECL immunosensor was applied to detect CA15-3 as an example under optimum conditions, the designed ECL immunosensor exhibited high-level selectivity and sensitivity for CA15-3 biomarker within a linear response range of 0.01–100 U mL−1 and an ultralow detection limit of 0.545 mU mL−1 (S/N = 3), demonstrating its potentially valuable application in the area of clinical analysis.

Ultrasensitive Imaging of Cells and Sub-Cellular Entities by Electrochemiluminescence.

Here we report on a label-free electrochemiluminescence (ECL) microscopy using exceptionally low concentrations of the [Ru(bpy)3 ]2+ luminophore. This work addresses the central point of the minimal concentration of the ECL luminophore required to image single entities. We demonstrate the possibility to record ECL images of cells and mitochondria at concentrations down to nM and pM. This is 7 orders of magnitude lower than classically-used concentrations and corresponds to a few hundreds of luminophores diffusing around the biological entities. Yet, it produces remarkably sharp negative optical contrast ECL images, as demonstrated by structural similarity index metric analyses and supported by predictions of the ECL image covering time. Finally, we show that the reported approach is a simple, fast, and highly sensitive method, which opens new avenues for ultrasensitive ECL imaging and ECL reactivity at the single molecule level.

Label-free electrochemiluminescence immunosensor based on conductive PANI to synergistically amplify electrodeposited AuNPs luminophore signal for ultrasensitive detection of 3-nitrotyrosine

As an appropriate biomarker for oxidative stress, 3-nitrotyrosine (3-NT) in biological samples is associated with many neurodegenerative disorders and inflammatory diseases. Herein, a novel and rapid electrochemiluminescence (ECL) immunosensor was successfully fabricated for ultrasensitive detection of 3-NT. Electrodeposited gold nanoparticles (AuNPs) being used as the luminophore and polyaniline being electropolymerized to promote the luminescence of AuNPs, a stable and efficient ECL system was obtained with an ECL intensity 28 times higher than that of bare electrodes. Taking advantage of the good biocompatibility and large specific surface area of AuNPs, the antibody was effectively immobilized on the electrode, achieving high selectivity for 3-NT detection. Under the optimal conditions, the immunosensor exhibited good analytical performance for 3-NT with a wide linear detection in the range of 1 × 10−11–1 × 10−8 mol/L and a low detection limit of 2.57 × 10−12 mol/L. Furthermore, the established sensor had a high recovery rate (85.29%–103.94%) in practical sample applications. The sensor had simple preparation method, high sensitivity and good stability, providing a promising sensing platform for the detection of 3-NT.

Charge-Dependent Signal Changes for Label-Free Electrochemiluminescence Immunoassays.

Label-free electrochemiluminescence (ECL) immunoassays (lf-ECLIA), based on biomarker-induced ECL signal changes, have attracted increasing attention due to the simple, rapid, and low-cost detection of biomarkers without secondary antibodies and complicated labeling procedures. However, the interaction rule and mechanism between analytical interfaces and biomarkers have rarely been explored. Herein, the interactions between biomarkers and analytical interfaces constructed by assembly of a nanoluminophore and antibody-functionalized gold nanoparticles on an indium tin oxide electrode were studied. The nanoluminophore was synthesized by mixing Cu2+/l-cysteine chelate and N-(4-Aminobutyl)-N-ethylisoluminol-bifunctionalized gold nanoparticles with chitosan. It was found that positively charged biomarkers increased the ECL intensity, whereas negatively charged biomarkers decreased the ECL intensity. The assembly pH influenced the biomarker charges, which determined the ECL enhancement or inhibition. The detection pH only affected the ECL intensity but not the ECL changing trends. Based on the ECL signal changes, a charge-dependent lf-ECLIA was established, which exhibited inhibition responses to negatively charged human immunoglobulin G and copeptin and enhancement responses to positively charged cardiac troponin I, heart-type fatty acid binding protein, brain natriuretic peptide, and SARS-CoV-2 N protein. The linear range was 0.1-1000 pg/mL, and the detection limits were distributed in 0.024-0.091 pg/mL. Besides, a mechanism of the charge-dependent ECL enhancement and inhibition effects is proposed, which is very important for the development of new lf-ECLIA methodologies.

N-heterocyclic Ir(III) complex targeting G-quadruplex structure to boost label-free and immobilization-free electrochemiluminescent sensing

Development of simple, low-cost and highly sensitive electrochemiluminescence (ECL) sensors for various targets is urgent but remains challenging. It is because most of emitters were required to be dissolved in organic solvent or immobilized at electrode's surface to display ECL emission, and suffered from complicated tagging procedures and short emission wavelength. Herein, we synthesize an iridium (III) complex (Ir-ECL) and applied it as a ECL emitter for improved target sensing. ECL emission of Ir-ECL originated from the sensitization of N-heterocyclic ligands on Ir (III). Impressively, Ir-ECL exhibited ECL emission wavelength at 590 nm, and displayed a superior intercalation ability into G-quadruplex DNA against single-stranded DNA and double-stranded DNA (dsDNA). Using such properties, Ir-ECL was applied to enzyme-free, label-free, sensitive and homogeneous ECL analysis of pesticide acetamiprid (Ace) based on aptamer-target recognition-driven hybridization chain reaction (HCR). The recognition of H1 by Ace switched HCR of H2 and H3 to generate a long-chain dsDNA with abundant G-quadruplex DNAs, in which large numbers of Ir-ECL were locked, resulting in falling diffusion toward electrode, declining ECL signal and eventually improving Ace ECL sensing.

A sensitive electrochemiluminescence immunosensor for the detection of CA15-3 based on CeO2/Pt/rGO as a novel co-reaction accelerator

In this work, we successfully constructed a label-free electrochemiluminescence (ECL) immunosensor for the detection of breast cancer marker antigen (CA15-3). In particular, 3,4,9,10-perylenetetracarboxylic acid (PTCA) is cleverly attached to the surface of silica spheres as a luminophore (NH2-SiO2-PTCA), which greatly alleviates the disadvantage of PTCA anti-induced aggregated luminescence and improves the ECL performance. Furthermore, Pt nanoparticles were used to dope CeO2 and introducing reduced graphene oxide (rGO) to prepare CeO2/Pt/rGO composites as a novel co-reaction accelerator. Among them, Pt nanoparticles were used to improve the electrical conductivity of CeO2, and the use of rGO as a substrate allows for a more uniform dispersion of CeO2 to increase the catalytic surface area, which effectively improves the performance of the co-reaction accelerator and thus increasing the ECL intensity of the PTCA/S2O82− system. Under the optimal conditions, the designed ECL immunosensor showed satisfactory results in the determination of CA15-3 with a linear range of 12.00 mU mL−1 - 120.00 U mL−1 and a low detection limit of 1.348 mU mL−1. Importantly, the resulting biosensor has good stability, high sensitivity and reliable reproducibility, suggesting its potential application in clinical research.

Interfacial DNA/RNA duplex-templated copper nanoclusters as a label-free electrochemiluminescence strategy for the detection of ribonuclease H

• Interfacial DNA/RNA duplexes templated Cu nanoclusters are successfully synthesized with excellent electrochemiluminescence (ECL) performance. • The well-designed DNA/RNA duplexes can serve as a target-trigger, exhibiting superior selectivity towards RNase H. • Interfacial DNA/RNA duplexes templated Cu nanoclusters are used to construct ECL biosensor for the first time. • This label-free electrochemiluminescence biosensor can accurately detect RNase H in human serum, demonstrating potentially clinical applicability. Ribonuclease H (RNase H) has been proven to be an attractive biomarker for anti-human immunodeficiency virus (HIV) therapeutics. Herein, a novel label-free electrochemiluminescence (ECL) biosensor is developed for the ultrasensitive detection of RNase H activity by employing DNA/RNA duplex-templated copper (Cu) nanoclusters (NCs). Specifically, interfacial DNA/RNA duplex-templated Cu NCs, as novel excellent ECL luminophores, were successfully synthesized by electroreduction. Meanwhile, the DNA/RNA duplexes can also serve as a target-trigger, exhibiting superior selectivity toward RNase H. Benefitting from the well-designed DNA/RNA duplexes, the label-free ECL biosensor exhibits an admired linear relationship in the concentration range from 3 × 10 −3 U/mL to 20 U/mL with a detection limit of detection of 1.97 × 10 −3 U/mL. Importantly, the detection of RNase H in human serum using the developed ECL biosensor represents satisfactory accuracy, demonstrating that the ECL biosensor possesses tremendous potential for further development in clinical diagnosis.

Homogeneous label-free electrochemiluminescence biosensor based on double-driven amplification and magnetic graphene platform

Traditional DNA-based electrochemiluminescence (ECL) biosensors generally require a laborious and time-consuming process of electrode modification. Although immobilization-free homogeneous electrochemical approaches have been proposed, the problems of low detectable signals from indicators and high background interferences resulting from label-free sensors remain unsolved. Herein, a new type of homogeneous label-free ECL biosensor for aflatoxin B1 (AFB1) is designed based on a double-driven signal-amplifying strategy (combination of entropy-driven and nuclease-driven) and a background reduction by magnetic graphene oxide (M-GO). The target of AFB1 competitively binds the aptamer in the duplex DNA, leading to the release of the catalyst strand which would further bind the Ru(bpy)32+-Probe (Ru-Probe) absorbed in M-GO based on the principle of entropy increase. In the presence of exonuclease III, the Ru-Probe is degraded to release Ru(bpy)32+ for detection, and the catalyst strand is preserved to trigger much more Ru(bpy)32+ released. So the nuclease-driven combined with entropy-driven amplifying strategy greatly enhances the ECL signal. Moreover, the unreacted Ru-Probes adsorbed in M-GO are removed by the magnetic separation, providing the background signal was reduced as far as possible. Under the optimum conditions, the enhanced ECL signal exhibits a linear relationship with the AFB1 concentration in the range of 1 pM–100 nM with a detection limit of 20 fM. The homogeneous ECL biosensor is successfully applied to determine AFB1 in corn samples with high sensitivity and selectivity. By altering the probes employed, this type of novel ECL biosensor is promising for further determination of diverse targets which are trace contaminants in food, environment, and the disease biomarkers.

Inhibiting effect of molybdenum disulfide nanosheets on cathodic Ru(bpy)32+ electrochemiluminescence in ionic liquids and its sensing application

Strong cathodic electrochemiluminescence (ECL) behavior of needle-like structure Ru(bpy) 3 2+ was obtained in 1-(2-hydroxyethyl)-3-methimidazole tetrafluoroborate without the need of additional coreactant. Molybdenum disulfide nanosheets (MoS 2 NSs) exhibited apparent inhibiting effect on the cathodic ECL signal through energy transfer and charge transfer process. As a result, a label-free ECL aptasensor was fabricated for the detection of lysozyme in HomimBF 4 . • Strong cathodic Ru(bpy) 3 2+ ECL was obtained in ionic liquid without coreactant. • MoS 2 nanosheets exhibited greatly inhibiting effect of ECL. • A “off-on” mode aptasensor for lysozyme was fabricated. Electrochemiluminescence (ECL) behaviors of needle-like structure Ru(bpy) 3 2+ was investigated in three room temperature ionic liquids with different cations such as 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate (HomimBF 4 ), 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF 4 ), and 1-hexyl-3-methylimidazolium tetrafluoroborate (HmimBF 4 ). The results revealed that both cathodic ECL and anodic ECL could be obtained in ionic liquids without the need of additional coreactant, which could simplify the fabricating process of biosensor. Strongest cathodic ECL signal can be obtained in HomimBF 4 which was selected as medium in biosensing investigation. Several experimental parameters, such as potential window, potential scan rate and direction, different atmosphere, and ECL spectrum were studied and the possible ECL mechanisms were proposed. Apparent inhibiting effect of molybdenum disulfide nanosheets (MoS 2 NSs) on the cathodic ECL signal was observed and used to fabricate “off-on” mode ECL sensor for lysozyme in HomimBF 4 . In the range of 1.0 × 10 -12 to 5.0 × 10 -9 mol L -1 , the ECL intensity varied linearly with the logarithmic of lysozyme concentration with a detection limit of 0.163 pM. The fabricated ECL sensor showed high sensitivity and good selectivity in the detection of lysozyme, revealing that ionic liquid is the potential promising medium for ECL sensor.

Label-Free Ratiometric Electrochemiluminescent (ECL) Immunosensor for the Determination of Prostate Specific Antigen (PSA) in Serum

A spatial- and potential-resolved ratiometric electrochemiluminescent (ECL) immunosensor was developed for prostate specific antigen detection in a label-free mode. CdS quantum dots (CdS QDs) and luminol-gold nanoparticles (luminol-Au NPs) were the potential-resolved electrochemiluminescence emitters and H2O2 was used as a co-reactant. The cathodic signal from the CdS QD electrode served as the working signal and the anodic signal from luminol-Au NPs as the reference. For prostate specific antigen detection, several concentrations of prostate specific antigen were immobilized on the CdS QDs modified electrode and a fixed concentration of the prostate specific antigen was modified on the luminol-Au NPs modified electrode. The prostate specific antigen levels were quantified by the electrochemiluminescence signal ratio of the cathodic and anodic (ECLcathodic/ECLanodic). Under the optimized conditions, the ratio of the cathodic and anodic signals (ECLcathodic/ECLanodic) had a linear relationship with the logarithm of (C, g mL−1) of prostate specific antigen concentration from 1.0 × 10−11 to 1.0 × 10−7 g mL−1. The detection limit was 5.0 × 10−12 g mL−1. Prostate specific antigen was determined in human serum and the recoveries were from 80.0% to 107.0%. The label-free electrochemiluminescence immunosensor offers simplicity and reliability for human serum with potential for clinical application.

Functionalized 3D H-SnS2-APTES-PTCA complexes with 3D hollow SnS2 as effective co-reaction accelerator for label-free electrochemiluminescence immunosensor

In this work, a novel, label-free, and self-enhanced electrochemiluminescence (ECL) immunosensor, based on 3,4,9,10-perylenetetracarboxylic acid (PTCA) and three dimensional hollow SnS2 (3D H-SnS2), was constructed to sensitively detect cardiac troponin I (cTnI). The 3D H-SnS2 was employed as an effective co-reaction accelerator in an ECL system, with the 3D H-SnS2 and PTCA cross-linked through (3-aminopropyl) triethoxysilane (APTES) to form a self-reinforcing ECL system. Functionalized 3D H-SnS2-APTES-PTCA complexes were then prepared and applied for the subsequent experiments. This system had plenty of active sites on the surface of insert-like SnS2 nanosheets within the 3D H-SnS2 and as such, it could strongly induce S2O82- to produce more SO4•- radicals. Furthermore, since the luminescent substance and the co-reaction accelerator were connected together, the distance between the SO4•- radicals and the luminescent PTCA could be effectively shortened, thus enabling SO4•- to act immediately on PTCA for significantly enhancing the ECL intensity. By analyzing the mechanism involved, it was found that the conversion between the ion pairs of Sn4+/2+ played a very important role in enhancing the signal. Based on the above work, the constructed biosensor was used to detect cTnI, a signaling molecule associated with acute myocardial infarction disease. And the sensor, with its linear response range of 16 fg mL−1-16 ng mL−1 and its low detection limit of 1.19 fg mL−1, displayed potential application value in the field of clinical analysis.

A novel label-free electrochemiluminescence aptasensor using a tetrahedral DNA nanostructure as a scaffold for ultrasensitive detection of organophosphorus pesticides in a luminol-H2O2 system.

In this work, a new type of Au-tetrahedral DNA nanostructure (Au-TDN) was originally proposed and successfully applied in an electrochemiluminescence aptasensor to detect organophosphorus pesticides (Ops). The aptamers modified with -SH could be covalently bonded with gold nanoparticles (AuNPs) to form a tetrahedron structure, and there were independent probes at each vertex of the tetrahedron, which could increase the probability of specific binding with Ops. The originally designed structure could not only maintain a stable tetrahedral configuration, but also combined with the target to improve the sensitivity of the sensor. Meanwhile, silver nanoparticles (AgNPs) could catalyze the chemical reaction between luminol and H2O2 to generate a variety of intermediates called reactive oxygen species (ROS) for signal enhancement. Factors that had important influences on the aptasensor, such as the concentration of Au-TDN, the incubation time, and the pH value of the buffer, were optimized in this trial. According to the final results, the limit of detection (LOD) of 3 pg mL-1 (S/N = 3) for methyl parathion, the LOD of 0.3 pg mL-1 (S/N = 3) for parathion and the LOD of 0.03 pg mL-1 (S/N = 3) for phoxim were obtained, respectively. Moreover, the novel tetrahedral structure could be replaced by different types of aptamers to expand its application range and lay a foundation for the development of portable rapid detection devices for pesticide residues.