Label-free Electrochemiluminescence Immunosensor Research Articles

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.

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 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.

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.

Copper-Doped Terbium Luminescent Metal Organic Framework as an Emitter and a Co-reaction Promoter for Amplified Electrochemiluminescence Immunoassay

This work designed a signal amplification strategy for construction of a highly sensitive electrochemiluminescence (ECL) biosensor by doping Cu2+ in a terbium luminescent metal organic framework (Cu:Tb-MOF) to act as a co-reaction promoter, which enhanced the generation of SO4•- radical during the cathodic process in the presence of K2S2O8 as a co-reactant. The porous and hollow morphology and the size of Cu:Tb-MOF could be efficiently tuned via changing the molar ratio of Cu2+ and Tb3+ and the reaction time, which were related to the specific surface area, pore diameter, and the ECL intensity of the MOF structure. To further improve the sensitivity of the ECL biosensor, H2O2 was introduced into the ECL system to act as another co-reaction promoter, leading to a new ECL mechanism involving dual co-reaction promoters. In view of the low electron transfer resistance of Cu:Tb-MOF, a label-free ECL immunosensor was conveniently constructed by co-immobilizing Cu:Tb-MOF and the capture antibody on the electrode surface. Using pro-gastrin-releasing peptide (ProGRP, a biomarker of small-cell lung cancer) as the model target, the proposed immunosensor exhibited excellent performance with a detection range of 1.0 pg·mL-1 to 50 ng·mL-1 and a limit of detection down to 0.68 pg·mL-1 (3σ). This work demonstrated a strategy to use the MOF structures as both an emitter and a co-reaction promoter for amplified ECL emission and proposed an innovative route to extend the application of lanthanide MOFs.

Development of a ZnCdS@ZnS quantum dots-based label-free electrochemiluminescence immunosensor for sensitive determination of aflatoxin B1 in lotus seed.

In this study, we designed a ZnCdS@ZnS quantum dots (QDs)-based label-free electrochemiluminescence (ECL) immunosensor for sensitive determination of aflatoxin B1 (AFB1). A Nafion solution assembled abundant QDs on the surface of aAu electrode as ECL signal probes, with specially coupled anti-AFB1 antibodies as the capturing element. As the reduction reaction between S2O82- in the electrolyte and QDs on the electrode led to ECL emission, the decreased ECL signals resulting from target AFB1 in the samples were recorded for quantification. We evaluated electrochemical impedance spectroscopy and ECL measurements along each step in the construction of the proposed immunosensor. After systematic optimization of crucial parameters, the ECL immunosensor exhibited a good sensitivity, with a low detection limit of 0.01ng/mL for AFB1 in awide concentration range of 0.05-100ng/mL. Testing with lotus seed samples confirmed the satisfactory selectivity, stability, and reproducibility of the developed ECL immunosensor for rapid, efficient, and sensitive detection of AFB1 at trace levels in complex matrices. This study provides a powerful and universal analytical platform for a variety of analytes that can be used in broad applications for real-time analysis, such as food and traditional Chinese medicine safety testing, environmental pollution monitoring, and disease diagnostics. Graphical abstract Development of a ZnCdS@ZnS quantum dots based label-free electrochemiluminescence immunosensor for sensitive detection of aflatoxin B1 in lotus seed.

Versatile NiCo2O4 nanosheets hybrids-based label-free immunosensor for thyroglobulin using photothermal amplification

Herein, an ultrasensitive label-free electrochemiluminescence (ECL) immunosensor based on electrocatalytic and photothermal amplification was constructed and was applied to detect Thyroglobulin (Tg). Single-walled carbon nanotube (SWCNTs) with charming merits was used as supporter for porous NiCo2O4 nanosheets (pNiCo2O4 NSs), the formed pNiCo2O4 NSs/SWCNTs hybrids was utilized as an effective matrix and realized multiple signal amplification. To be specific, pNiCo2O4 NSs/SWCNTs hybrids on the one hand can facilitate the electron transfer and enhance ECL signal. On the other hand can catalyze the oxygen evolution reaction (OER) to increase the concentration of dissolved O2 for further strengthening ECL signal. What’s more, the pNiCo2O4 NSs/SWCNTs hybrids had a strong near-infrared harvesting capability, can convert laser energy into heat to increase the electrode surface temperature, resulting in the significant enhancement in ECL signal. Based on excellent properties of pNiCo2O4 NSs/SWCNTs hybrids, a highly-efficient label-free ECL immunosensor was developed and exhibited a wide linear range (10−5 ng/mL to 100 ng/mL) and a low detection limit (3.3 × 10−6 ng/mL) for Tg determination, which was approximately 7.1 fold-lower than at room temperature. This work provided a new thought for high-performance ECL sensing platform construction.

Boron nitride quantum dots as electrochemiluminescence coreactants of rGO@Au@Ru–SiO2 for label-free detection of AFP in human serum

A label-free electrochemiluminescence (ECL) immunosensor is developed to detect alpha-fetoprotein (AFP). Ru (bpy)32+-doped silica nanoparticles (Ru–SiO2) and gold nanoparticle-modified reduced graphene oxide (rGO@Au) are integrated to form an rGO@Au@Ru–SiO2 composite. The composite is employed as a carrier for immobilizing the target antibody, and a label-free ECL immunosensor is constructed via antigen–antibody interaction. Owing to the numerous Ru (bpy)32+ molecules in the Ru–SiO2, a high ECL signal is acquired. With excellent conductivity and a large surface area, the rGO@Au composite not only accelerates electron transfer but also improved the ECL signal and captures antibodies, thus enhancing ECL response and sensitivity. Moreover, boron nitride quantum dots (BNQDs) are used as rGO@Au@Ru–SiO2 coreactants, achieving high ECL intensity. The proposed ECL system exhibits significant potential in bioanalysis, which is attributed to the excellent biocompatibility and good stability of BNQDs. Under optimal experimental conditions, the sensor has a linear range of 0.0001 ng mL−1 to 100 ng mL−1 and a limit of detection equal to 0.03 pg mL−1 (S/N = 3). The proposed technique is successfully applied in the susceptible detection of AFP in human serum. The recovery ranges from 99% to 100%, and the RSD is less than 2.8%. The constructed ECL immunosensor exhibits acceptable performance during actual application.

In situ H2O2 generation with gold nanoflowers as the coreactant accelerator for enzyme-free electrochemiluminescent immunosensing

In traditional electrochemiluminescence (ECL) analysis, gold nanomaterials are commonly used as a tool for signal amplification and linking antibodies due to their good electrical conductivity and biocompatibility. Here, we found that multitipped gold nanoparticles—gold nanoflowers (AuNFs) as coreactant accelerator have good catalytic activity for the reduction of dissolved oxygen (O2) to hydrogen peroxide (H2O2) using tris (hydroxymethyl) aminomethane (Tris) as electron donor. Based on this, a new enzyme-free and label-free ECL immunosensor have been constructed for the detection of α-fetoprotein (AFP). In this system, due to the unique geometric and spatial effects of AuNFs, the dissolved O2 as endogenous coreactant was catalyzed by AuNFs to produce H2O2 using Tris as an electron donor. The in situ generated H2O2 can more efficiently produce various electrogenerated reactive oxygen species (ROSs) as the important intermediates on the electrode surface. Then, oxidation of luminol reacts with ROSs significantly amplifies the luminol ECL signal. Under optimal experimental conditions, the proposed ECL immunosensor was able to detect the AFP concentration from 0.01 to 100 ng mL−1, with a low detection limit of 3.4 pg mL−1 (S/N = 3). In addition, the prepared ITO-based sensor is similar to a micro-test chip and convenient to use, thus making it suitable for clinical use as a disposable device in point-of-care tests (POCTs).

Label-free electrochemiluminescent immunosensor for prostate specific antigen ultrasensitive detection based on novel luminophore Ag3PO4 decorated GO

A label-free electrochemiluminescence (ECL) sensor having high sensitivity was operated for detection of prostate specific antigen (PSA) by using silver/silver orthophosphate/graphene oxide composites (Ag/Ag3PO4/GO) as antibody carriers and sensing platform. Firstly, nanoparticles of Ag3PO4 were employed as luminescent materials for solid-state ECL detection and to propose possible luminescence route in this study. GO, having the ultrahigh specific surface area and superior conductivity, was utilized as a loading matrix for nanoparticles of Ag3PO4. It was employed not only to contribute for the enhancement of electrons transfer for the whole ECL system, but also further improvement of the sensitivity of the immunosensor. Given that the spectacular biocompatibility of silver nanoparticles (Ag NPs) was used to immobilize PSA antibody (anti-PSA) via the covalent coupling between silver and amino group, to improve immunosensor sensitivity. The proposed sensing platform presented tremendous cathodic ECL performance and better response to the PSA. Under optimized experimental conditions, the proposed immunosensor displayed a calibration range of 0.001–80ng/mL and low detection limit of 0.3pg/mL (S/N=3) for PSA determination. Featuring encouraging selectivity, repeatability, and stability, the fabricated Ag/Ag3PO4/GO is anticipated to glare novel ECL biosensor platform for PSA and other biomarkers detection in the real sample.

Enhancing Luminol Electrochemiluminescence by Combined Use of Cobalt-Based Metal Organic Frameworks and Silver Nanoparticles and Its Application in Ultrasensitive Detection of Cardiac Troponin I.

Electrochemiluminescence (ECL) has emerged as one of the most important methods for in vitro diagnosis and detection, but it is still limited in sensitivity for ultrasensitive biodetections. Fast and ultrasensitive detection of biomolecules is critical, especially for the clinical detection of cardiac troponin I (cTnI) for cardiac infarction diagnosis. In this study, an effective tactic was developed to enhance ECL efficiency of the luminol system, by combined use of Co2+-based metal organic frameworks (MOF), zeolitic imidazolate frameworks (ZIF-67), and luminol-capped Ag nanoparticles (luminol-AgNPs). The integration leads to a pronounced ∼115-fold enhancement in luminol ECL. On the basis of this fascinating sensing platform, a robust label-free ECL immunosensor was constructed for ultrasensitive detection of cTnI, the main marker of myocardial infarction, with good stability and a detection limit as low as 0.58 fg mL-1 (S/N = 3).

Label-free electrochemiluminescent immunosensor for detection of prostate specific antigen based on mesoporous graphite-like carbon nitride

In this paper, mesoporous graphite-like carbon nitride (mpg-C3N4) combined with gold nanoparticles (Au NPs) was conducted to construct a luminol-hydrogen peroxide (H2O2) based electrochemiluminescent (ECL) immunosensor for prostate specific antigen (PSA) detection. The mpg-C3N4 exhibited large specific surface area and high porosity was synthesized from a simple precursor, which possessed abundant active sites to load Au NPs and luminol (mpg-C3N4/Au-luminol). After that, Au NPs linked mpg-C3N4 (mpg-C3N4/Au) could hatch with the primary antibody (Ab1) via Au-NH2 bond, which reinforced the sensitivity of immunosensor. The mpg-C3N4 and Au shows excellent catalytic enhancement effect on the ECL intensity of luminol. Under optimal conditions, the constructed ECL immunosensor exhibited sensitive response to PSA in a wide linear range of 0.001 ~ 15 ng mL−1 with a lower detection limit of 0.927 pg mL−1. Meanwhile, the proposed ECL immunosensor endows the good reproducibility and stability. Therefore, the results could open another avenue for detection of PSA and other biomarkers.

A label-free electrochemiluminescent immunosensor for glutamate decarboxylase antibody detection on AuNPs supporting interface

In this paper, we will describe a novel lable-free electrochemiluminescent (ECL) immunosensor for the detection of glutamate decarboxylase antibody (GADA) in which Au nanoparticles (AuNPs) had pre-functionalized the indium tin oxide (ITO) glass to support the sensing interface. The preparation of the basal electrode only need a simple two-step drop coating, a thin polymer of hydrolyzed 3-aminopropyl trimethoxysilane, and the AuNPs gel on the ITO substrate. The AuNPs not only enhanced the ECL signal of luminol, but also acted to immobilize the glutamate decarboxylase (GAD) to build the sensing host. This immunosensor exhibits excellent specificity, reproducibility and stability. On resultant sensor, after the direct immunoreaction, the decreased ECL intensity has a good linear regression toward the logarithm of GADA concentration in the range of 0.30 ng mL−1 to 50 ng mL−1 with a detection limit of 0.10 ng mL−1. The proposed senor has prospective capability for the clinical detection of GADA in human serums, which had important value for diagnosis and precaution of type-1 diabetes or latent autoimmune diabetes in adult (LADA).

High-Sensitivity Electrochemiluminescence Probe with Molybdenum Carbides as Nanocarriers for α-Fetoprotein Sensing.

Suitably designed electrochemiluminescence (ECL) carrying group acting as high-efficiency solid-state probe has attracted a lot of attention. Herein, molybdenum carbides with the two-dimensional ultrathin nanosheet structure on the surface and excellent conductivity were successfully employed as the nanocarriers for the capture of ECL reagent of luminol-capped Au nanoparticles (luminol-AuNPs). Notably, the luminol-AuNPs in the hybrid (luminol-AuNPs@Mo2C) exhibited enhanced ECL performance (∼6-fold) as compared to individual luminol-AuNPs because of the facilitated electron transfer process. Ultimately, the as-prepared ECL label was used to construct a label-free ECL immunosensor for the detection of α-fetoprotein (AFP). The immunosensor shows high selectivity and high sensitivity to AFP detection with a wide linear range of 0.1 pg·mL-1 to 30 ng·mL-1 and an extremely low detection limit of 0.03 pg·mL-1 (S/N = 3). Moreover, the fabricated ECL immunosensor exhibit satisfied performance in the practical application. This novel sensing strategy not only broadens the application of molybdenum carbides but also provides a new efficient approach to detect various biomolecules.

An ultrasensitive label-free electrochemiluminescent immunosensor for measuring Cry1Ab level and genetically modified crops content

The development of genetically modified (GM) insect-resistant crops has aroused great public concern about the risks on the eco-environment resulting from a release of toxic Cry proteins (such as Cry1Ab) to the soil. Therefore, it is of crucial importance to measure the Cry proteins level and the GM crops content. Here, we have tested for the first time a method that uses novel carbon nanospheres (CNPs) label-free electrochemiluminescent (ECL) immunosensor for the ultrasensitive quantification of Cry1Ab and GM crops. In this work, novel CNPs were prepared from printer toner with a very facile approach, and linked with anti-Cry1Ab antibodies to modify a golden working electrode. The immunoreaction between Cry1Ab and its antibody formed an immunocomplex on the bioreceptor region of the sensor, which inhibited electron transfer between the electrode surface and the ECL substance, leading to a decrease of ECL response. Under the optimal conditions, the fabricated label-free ECL immunosensor determined Cry1Ab down to 3.0pgmL−1 within a linear range of 0.010−1.0ngmL−1, showing significant improvement of sensitivity than that of most previous reports. Meanwhile, the proposed method was successfully applied for GM rice BT63 and GM maize MON810 detections down to 0.010% and 0.020%, respectively. Due to its outstanding advantages such as high sensitivity, ideal selectivity, simple fabrication, rapid detection, and low cost, the developed method can be considered as a powerful and pioneering tool for GM crops detection. Its use can also be extended to other toxin protein sensing in foods.

Macroporous graphene capped Fe3O4 for amplified electrochemiluminescence immunosensing of carcinoembryonic antigen detection based on CeO2@TiO2

A novel electrochemiluminescence (ECL) signal-amplified immunosensing strategy was proposed by using gold nanoparticles (Au NPs) functionalized reduced graphene oxide (rGO) capped Fe3O4 (Au-FrGO). In this work, CeO2@TiO2 was prepared by a sol-gel method to wrap CeO2 with TiO2. In the presence of CeO2, CeO2@TiO2 exhibited better ECL activity than TiO2 with peroxydisulfate as coreactant. In addition, FrGO with macroporous structure was synthesized by self-assembly of rGO sheets capped cationic Fe3O4 nanoparticles, exhibiting larger specific surface area than rGO. Due to the low toxicity and magnetism of Fe3O4, FrGO owned more favorable biocompatibility and the application of magnetic-separation simplified the preparation procedure. After hybridizing with Au NPs, FrGO exhibited more excellent electrical conductivity and could immobilize more CeO2@TiO2 and antibodies. Therefore, a novel label-free ECL immunosensor based on Au-FrGO-CeO2@TiO2 was constructed which generated higher ECL response. To investigate the performance of the immunosensor, carcinoembryonic antigen (CEA) was chosen as a model target analyte. Under optimal conditions, the immunosensor had sensitive response to CEA in a wide linear range of 0.01pgmL−1 to 10ngmL−1 with a detection limit of 3.28 fg mL−1. The proposed ECL immunosensor exhibited excellent stability, repeatability and selectivity, which opened another promising avenue for CEA determination in real serum samples.

Single-step cycle pulse operation of the label-free electrochemiluminescence immunosensor based on branched polypyrrole for carcinoembryonic antigen detection.

A novel label-free electrochemiluminescence (ECL) immunosensor based on luminol functional-Au NPs@polypyrrole has been developed for the detection of carcinoembryonic antigen (CEA). In this work, polypyrrole prepared by chemical polymerization provided a large surface area to load amounts of gold nanoparticles (Au NPs). Au NPs could not only attach abundant luminol for the enhancement of ECL signal, but also provide a friendly microenvironment for the immobilization of antibodies. Moreover, 1-butylpyridinium tetrafluroborate ([BPy]BF4) were used to disperse luminol functional-Au NPs@polypyrrole nanocomposites, resulting in the film-formation of composites on the electrode, which could improve the stability of immunosensor. In particular, employment of single-step cycle pulse could limit the consecutive reaction between luminol and H2O2 efficiently, thus leading to stable and strong signals. The proposed method presents good ECL response for the detection of CEA allowing a wide linear range from 0.01 pg/mL to 10 ng/mL and a limit of detection as low as 3 fg/mL. The immunosensor would be a promising tool in the early diagnosis of CEA due to its high sensitivity, simplicity and cost-effective.

Label-free Electrochemiluminescent Immunosensor for Detection of Prostate Specific Antigen based on Aminated Graphene Quantum Dots and Carboxyl Graphene Quantum Dots.

Prostate-specific antigen (PSA) was used as the model, an ultrasensitive label-free electrochemiluminescent immunosensor was developed based on graphene quantum dots. Au/Ag-rGO was sythsized and used as electrode material to load a great deal of graphene quantum dots due to the large surface area and excellent electron conductivity. After aminated graphene quantum dots and acarboxyl graphene quantum dots were modified onto the electrode, the ECL intensity was much high using K2S2O8 as coreactant. Then, antibody of PSA was immobilized on the surface of modified electrode surface through the adsorption of Au/Ag toward proteins, leading to the decrease of the ECL intensity. As proven by ECL spectra test and electrochemical impedance spectroscopy (EIS) analysis, the fabrication process of the immunosensor is successful. Under the optimal conditions, the ECL intensity decreased linearly with the logarithm of PSA concentration in the range of 1 pg/mL ~ 10 ng/mL. The detection limit achieved is 0.29 pg/mL. The immunosensor results were validated through the detection of PSA in serum samples with satisfactory results. Due to excellent stability, high sensitivity, acceptable repeatability and selectivity, the immunosensor has promising applications in disease and drug analysis.

A label-free electrochemiluminescence immunosensor based on EuPO4 nanowire for the ultrasensitive detection of Prostate specific antigen

EuPO4 nanowire, which exhibited strong and stable cathodic electrochemiluminescence (ECL) activity, was used for the first time to fabricate an immunosensor for the detection of prostate specific antigen (PSA). EuPO4 has some inherent excellent properties such as long luminescence lifetime, narrow emission band, high quantum yield and low toxicity. Based on these properties, a novel label-free ECL immunosensor was developed using EuPO4 as a sensing matrix. Chitosan solution was used to disperse EuPO4 nanowires and the amino groups on chitosan enabled the covalent attachment of capture antibodies. After the modification of the electrode surface with EuPO4 nanowires, anti-PSA was then immobilized on them, forming a label-free immunosensing interface. The specific binding of PSA on the electrode inhibited the ECL reaction of EuPO4 nanowires with the coreactant due to the steric hindrance effect (Deng et al., 2013). Under the optimum conditions, a good linear relationship between ECL intensity and the logarithm of PSA concentration was obtained in the range of 0.0005–80ng/mL with a detection limit of 177.33fg/mL. The proposed ECL immunosensor showed good stability, acceptable selectivity and reproducibility.