Sandwich-type Electrochemiluminescence Immunosensor Research Articles

FeNi-MIL-88B-based electrochemiluminescence immunosensor for ultra-sensitive detection of CD44 protein via dual-quenching strategy

BackgroundCluster of Differentiation 44 (CD44) is considered an important biomarker for various cancers, and achieving highly sensitive detection of CD44 is crucial, which plays a significant role in tumor invasion and metastasis, providing essential information for clinical tumor diagnosis. Commonly used methods for analysis include fluorescence spectroscopy (FL), photoelectrochemical analysis (PEC), electrochemical analysis (EC), and commercial ELISA kits. Although these methods offer high sensitivity, they can be relatively complex to perform experimentally. Electrochemiluminescence (ECL) has gained widespread research attention due to its high sensitivity, ease of operation, effective spatiotemporal control, and close to zero background signal. ResultsIn this work, a sandwich-type ECL immunosensor for detecting CD44 was constructed using luminol as a luminophore. In this sensing platform, bimetallic MOFs (Pd@FeNi-MIL-88B) loaded with palladium nanoparticles (Pd NPs) were used as a novel enzyme mimic, exhibiting excellent catalytic performance towards the electroreduction of H2O2. The hybrids provided a strong support platform for luminol and antibodies, significantly enhancing the initial ECL signal of luminol. Subsequently, core-shell Au@MnO2 nanocomposites were synthesised by gold nanoparticles (Au NPs) encapsulated in manganese dioxide (MnO2) thin layers, as labels. In the luminol/H2O2 system, Au@MnO2 exhibited strong light absorption in the broad UV–vis spectrum, similar to the black body effect, and the scavenging effect of Mn2+ on O2•−, which achieved the dual-quenching of ECL signal. Under the optimal experimental conditions, the immunosensor demonstrated a detection range of 0.1 pg mL−1 − 100 ng mL−1, with a detection limit of 0.069 pg mL−1. SignificanceBased on Pd@FeNi-MIL-88B nanoenzymes and Au@MnO2 nanocomposites, a dual-quenching sandwich-type ECL immunosensor for the detection of CD44 was constructed. The proposed immunosensor exhibited excellent reproducibility, stability, selectivity, and sensitivity, and provided a valuable analytical strategy and technical platform for the accurate detection of disease biomarkers, and opened up potential application prospects for early clinical treatment.

Europium Metal-Organic Framework with a Tetraphenylethylene-Based Ligand: A Dual-Mechanism Quenching Immunosensor for Enhanced Electrochemiluminescence via the Coordination Trigger.

The effective applications of electrochemiluminescence (ECL) across various fields necessitate ongoing research into novel luminophores and ECL strategies. In this study, self-luminous flower-like nanocomposites (Eu-tcbpe-MOF) were prepared by coordination self-assembly using the aggregation-induced emission material 1,1,2,2-tetrakis(4-carboxyphenyl)ethylene (H4TCBPE) and Eu(III) ions as the precursors. Compared with the monomers and aggregates of H4TCBPE, Eu-tcbpe-MOF exhibits stronger ECL emission. Such enhanced electrochemiluminescence is due to coordination as the coordination-triggered electrochemiluminescence (CT-ECL) enhancement effect. In this study, a cubic-structured nanocomposite (Co9S8@Au@MoS2) was used as an efficient quencher, and a more sensitive ECL detection platform was achieved by two quenching mechanisms: resonance energy transfer and competitive consumption of coreactants. N,N-Diethylethanolamine (DBAE) was used as a coreactant, and DBAE has a faster electron transfer rate and stronger energy supply efficiency than the traditional anodoluminescent coreactant tripropylamine, which effectively improves the ECL signal intensity of Eu-tcbpe-MOF. Hence, a sandwich-type ECL immunosensor was prepared by employing a dual-quenching mechanism, utilizing Eu-tcbpe-MOF as the detection probe and Co9S8@Au@MoS2 as the quencher, achieving precise detection of carcinoembryonic antigen from 0.1 pg·mL-1 to 100 ng·mL-1 with a detection limit of 35.1 fg·mL-1.

Enhancing the Electrochemiluminescence of Porphyrin via Crystalline Networks of Metal-Organic Frameworks for Sensitive Detection of Cardiac Troponin I.

Porphyrins easily aggregate due to unfavorable π-π accumulation, causing luminescent quenching in the aqueous phase and subsequently reducing luminescent efficiency. It is a feasible way to immobilize porphyrin molecules through metal-organic framework materials (MOFs). In this study, 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) was introduced into the metal-organic skeleton (PCN-224) as a ligand. The result showed that the electrochemiluminescence (ECL) and photoluminescence (PL) efficiency of the MOF skeleton was 8.2 and 6.5 times higher than TCPP, respectively. Impressively, the periodic distribution of porphyrin molecules in the MOF framework can overcome the bottleneck of porphyrin aggregation, resulting in the organic ligand TCPP participating in the electron transfer reaction. Herein, based on the PCN-224, a sandwich-type ECL immunosensor was constructed for the determination of cardiac troponin I (cTnI). It provided sensitive detection of cTnI in the range of 1 fg/mL to 10 ng/mL with a detection limit of 0.34 fg/mL. This work not only innovatively exploited a disaggregation ECL (DIECL) strategy via the crystalline framework of MOF to enhance the PL and ECL efficiency of porphyrin but also provided a promising ECL platform for the ultrasensitive monitoring of cTnI.

Electrochemiluminescence resonance energy transfer between Ru(bpy)32+@Cu3(HHTP)2 and GO-Au composites for C-reactive protein detection

Designing innovative electrochemiluminescence (ECL) immunosensors is critical for the detection of biomarkers with a low concentration and the precise evaluation of clinical diseases. Herein, a Cu3(hexahydroxytriphenylene)2 (Cu3(HHTP)2) nanoflake-based sandwich-type ECL immunosensor was constructed for C-Reactive Protein (CRP) detection. The Cu3(HHTP)2 nanoflake, an electronically conductive metal–organic framework (MOF), has a periodically arranged porous structure with a cavity size of 2 nm, which not only accommodates a large amount of Ru(bpy)32+ but also confines the spatial diffusion of active species. Therefore, the Ru(bpy)32+-loaded Cu3(HHTP)2 nanocomplex (Ru@CuMOF) as an ECL emitter exhibits an enhanced ECL efficiency. The ECL resonance energy transfer (ECL-RET) was accomplished by combining Ru@CuMOF used as a donor with gold nanoparticles-functionalized graphene oxide nanosheets (GO-Au) utilized as an acceptor. This should be ascribed to the fact that the ECL emission spectrum of Ru@CuMOF shows the strongest signal intensity at 615 nm, overlapping with the absorption spectrum of GO-Au at 580–680 nm. Targeted detection of CRP in human serum samples was achieved by the sandwich-type immunosensor based on the ECL-RET mechanism with a 0.26 pg mL−1 detection limit. The electro-activated hybrids of Cu3(HHTP)2 and ECL emitters provide a new sensing strategy for the high-sensitivity detection of disease markers.

Electrochemiluminescence immunosensor for cancer antigen 125 detection based on novel resonance energy transfer between graphitic carbon nitride and NIR CdTe/CdS QDs

Resonance energy transfer (RET), as an efficient strategy, has been widely used for exploring a variety of biological processes and achieving sensitive bioanalysis. In this work, fluorescence and electrochemiluminescence (ECL) RET between graphitic carbon nitride (g-C3N4) and NIR CdTe/CdS QDs was reported firstly. Based on this novel RET system, a sensitive sandwich-type ECL immunosensor was constructed to detect cancer antigen 125 (CA125). In this strategy, the ECL of Au NPs-functionalized graphitic carbon nitride nanohybrids (Au-g-C3N4 NHs) was efficiently quenched by near-infrared CdTe/CdS quantum dots (NIR CdTe/CdS QDs), where NIR CdTe/CdS QDs acts as acceptors, and Au-g-C3N4 NHs acts as donors. Au NPs improved the intensity and stability of ECL and provided sites to immobilize the antibody. Silica nanospheres carried abundant NIR CdTe/CdS QDs (QDs-SiO2) labeling secondary antibodies, further enhancing the quenching effect. Under the optimum conditions, the constructed immunosensor showed excellent analytical performance with a linear concentration of CA125 from 0.0001 U mL−1 to 10 U mL−1 and the limit of detection reached 0.034 mU mL−1 (S/N = 3). Meanwhile, the immunosensor also revealed great stability, reproducibility, and selectivity and it could be applied in human serum samples successfully. This strategy provided a useful analytical method for the sensitive detection of biomarkers in the early stages of the disease and an innovative reference for developing more efficient and sensitive RET bioanalysis.

A sandwich-type ECL immunosensor based on signal amplification using a ZnO nanorods-L-cysteine-luminol nanocomposite for ultrasensitive detection of prostate specific antigen

An ultrasensitive sandwich-type electrochemiluminescence (ECL) immunosensor was developed for detection of prostate specific antigen (PSA) using an amplification strategy based on ZnO nanorods-l-cysteine-luminol nanocomposites and the biotin-streptavidin system. The biotin-streptavidin system served as a capture probe to increase the number of antibodies. ZnO nanorods not only acted as a nanocarrier that increased the number of luminol molecules and secondary antibodies, but also enhanced the ECL signal of luminol-H2O2 system by promoting H2O2 decomposition, which can further increase ECL intensity. Under optimized conditions, the proposed immunosensor demonstrated excellent analytical performance with a wide linear detection range of 0.03 pg mL−1 to 30 ng mL−1 and a detection limit of 0.01 pg mL−1 (the detection limit in real samples was 0.021 pg mL−1). This method exhibited excellent stability, reproducibility, and selectivity. In addition, the results of PSA determinations in human serum samples obtained using the proposed immunosensor were consistent with data collected using the commercial chemiluminescence immunoassay analyzer.

CuS as co-reaction accelerator in PTCA-K2S2O8 system for enhancing electrochemiluminescence behavior of PTCA and its application in detection of amyloid-β protein

In this work, 3,4,9,10-perylenetetracar-boxylic acid (PTCA) as luminophor was grafted on the surface of graphene oxide (PTCA-GO) directly. GO exhibited large specific surface area and excellent electrical conductivity which can immobilize large amounts of PTCA to improve the electrochemiluminescence (ECL) efficiency. Moreover, gold nanoparticles (Au NPs) were anchored on the surface of PTCA-GO to immobilize primary antibodies (Ab1) via Au-NH2 bond and enhance the electron transport of PTCA-GO. CuS was used as a novel co-reaction accelerator in PTCA-K2S2O8 system to label secondary antibodies (Ab2), which can react with the coreactant (K2S2O8) to produce more SO4•-. SiO2 nanospheres with large specific surface area were used to load a mass of CuS and Au NPs, which can directly combine with Ab2 and accelerate the ECL emission remarkably. Therefore, a novel sandwich-type ECL immunosensor was fabricated successfully for amyloid-β protein (Aβ) detection. Under the optimal condition, a wide detection range from 50 fg/mL to 25 ng/mL and a low detection limit of 18 fg/mL (S/N = 3) were obtained. Featuring favorable specificity, stability and reproducibility, the strategy can be a powerful analytical tool in sensitive trace detection of biomolecules in clinical analysis.

A novel pH-responsive electrochemiluminescence immunosensor for ALV-J detection based on hollow MnO2 encapsulating Ru(bpy)3Cl2

A novel pH-responsive sandwich-type electrochemiluminescence immunosensor was successfully developed for the detection of avian leukosis virus subgroup J (ALV-J). The immunosensor consisted of graphene oxide functionalized with tannic acid (rGO-TA) and primary antibodies (Ab1) as the main ALV-J sensing platform. For signal amplification, pH-responsive hollow MnO2 (hMnO2) nanospheres encapsulating Ru(bpy)3Cl2 and carrying secondary antibodies (Ab2) were employed. Under optimal conditions, the immunosensor exhibited a wide ALV-J detection range of 101.80 to 104.30 TCID50/mL (TCID50: 50% tissue culture infective dose) and a low detection limit of 101.71 TCID50/mL (S/N = 3). Importantly, the immunosensor showed high sensitivity, good reproducibility and excellent operational stability. Finally, the immunosensor was evaluated using a real avian serum sample containing ALV-J, with excellent results being achieved.

Quenching Electrochemiluminescence Immunosensor Based on Resonance Energy Transfer between Ruthenium (II) Complex Incorporated in the UiO-67 Metal-Organic Framework and Gold Nanoparticles for Insulin Detection.

This work describes a sandwich-type electrochemiluminescence (ECL) strategy for insulin detection by using Ru(bpy)32+ as the luminophore which was encapsulated in the UiO-67 metal-organic framework (UiO-67/Ru(bpy)32+). Because UiO-67 possesses the characteristics of large specific surface area and porosity, more Ru(bpy)32+ could be loaded onto its surface and holes, thus greatly improving the ECL efficiency. Furthermore, the ECL resonance energy transfer (ECL-RET) could occur between UiO-67/Ru(bpy)32+ (ECL donor) and Au@SiO2 nanoparticles (ECL acceptor), resulting in a conspicuously decreased ECL response. The ECL spectrum of UiO-67/Ru(bpy)32+ which exhibited strong ECL intensity has suitable spectral overlap with the absorption spectrum of Au@SiO2, which further proved the occurrence of the ECL-RET action. The ECL intensity decreased with the increase of the concentration of insulin. In addition, the sandwich-type ECL immunosensor was applied to insulin detection, and the ECL decrease efficiency was found to be logarithmically related to the concentration of the insulin antigen in the range of 0.0025 to 50 ng mL-1 with the limit of detection of 0.001 ng mL-1. Meanwhile, this work provides an important reference for the application of metal-organic frameworks in the ECL and ECL-RET study and also exhibits potential capability in the detection of other hormones.

A dual-amplified electrochemiluminescence immunosensor constructed on dual-roles of rutile TiO2 mesocrystals for ultrasensitive zearalenone detection

Herein, a new sandwich-type electrochemiluminescence (ECL) immunosensor was established on the dual-roles of tetragonal rutile TiO2 mesocrystals (TRM) to realize the sensitive detection of zearalenone (ZEA). On the one hand, the poly (amidoamine) dendrimers (PAAD)-functionalized TRM, combining the advantages of hyper-branched of PAAD and the high nanoporosity, large surface area of TRM, was served as the sensing matrix to immobilize enough capturing antibody, realizing the signal amplification. On the other hand, TRM was applied as an effective probe platform to absorb Ru (bpy)32+ and simultaneously immobilize the secondary antibody (Ab2). Here, based on the superior properties of TRM and the new bridge of 4-Mercaptophenylboronic acid (4-MPBA) for the high affinity of Ab2 and TRM, a strong and stable ECL emission was realized. Additionally, cysteamine first emerging as a blocker was proved to sensitize the ECL response of Ru (bpy)32+, which further amplified the ECL signal, avoiding addition of exogenous coreactants into testing solution. Finally, the sandwich-type ECL immunosensor enabled the real samples detection of ZEA with a lower detection limit and wider linear range.

A novel electrochemiluminescence immunosensor based on functional β-cyclodextrin-ferrocene host-guest complex with multiple signal amplification

Abstract The shortened distance between luminophor and coreactant can effectively enhance luminous efficiency in electrochemiluminescence (ECL) system owing to the improvement of electron transfer rate. Here, a novel sandwich-type ECL immunosensor based on N-(aminobutyl)-N-(ethylisoluminol) (ABEI) as luminophor was constructed by integrating hollow gold nanoparticles (HAuNPs), l -cysteine ( l -Cys) and ferrocene (Fc) in a complex for multiple signal amplification. The HAuNPs with large specific surface areas and superior conductivity were first used as scaffolds to load abundant coreactant l -Cys, aiming to further assemble catalyzer Fc stably. Through host-guest recognition, the β-cyclodextrin (β-CD) functionalized ABEI thus subsequently decorated on Fc, bringing in shortened distance between luminophor ABEI and coreactant l -Cys with high ECL signal. Moreover, the catalyzer Fc and HAuNPs could dramatically promote decomposition of another coreactant H2O2 to produce abundant superoxide radical (O2 ˉ) and hydroxyl radical (OH ) for further signal amplification. Taking β2-microglobulin (β2 M) as model analyte, the developed immunosensor exhibited a superior performance for detection β2 M in the range of 1.0 × 10−3–1.0 × 103 ng mL−1 with a detection limit of 2.6 × 10−1 pg mL−1. The developed strategy realized solid-state ECL detection and multiple ECL signal amplification, providing a novel sensitive detection method for β2 M, which may show a great promise for the clinical application.

3D Nanostructured Palladium-Functionalized Graphene-Aerogel-Supported Fe3O4 for Enhanced Ru(bpy)32+-Based Electrochemiluminescent Immunosensing of Prostate Specific Antigen.

We developed a novel Ru(bpy)32+-based electrochemiluminescence (ECL) immunosensor utilizing palladium nanoparticle (Pd NP)-functionalized graphene-aerogel-supported Fe3O4 (FGA-Pd) for real-sample analysis of prostate specific antigen (PSA). 3D nanostructured FGA-Pd, as a novel ECL carrier, was prepared by in situ reduction. Large amounts of Ru(bpy)32+ could combine with FGA-Pd via electrostatic interaction to establish a brand-new ECL emitter (Ru@FGA-Pd) for improving ECL efficiency. The obtained Ru@FGA-Pd composite was utilized to label the secondary antibody, which generated strong ECL signals with tripropylamine (TPrA) as a coreactant. Furthermore, we demonstrated that the participation of Pd NPs endowed FGA with favorable electrocatalytic ability in the luminescence process to produce more excited state [Ru(bpy)32+]* for realizing desirable signal amplification. In addition, the primary antibody was captured by gold nanoparticle (Au NP)-functionalized Fe2O3 nanodendrites (Au-FONDs), which possessed good electrical conductivity and favorable biocompatibility. Under optimum conditions, the fabricated sandwich-type ECL immunosensor showed a sensitive response to PSA with a low detection limit of 0.056 pg/mL (S/N = 3) and a calibration range of 0.0001-50 ng/mL. Featuring favorable selectivity, stability, and repeatability, the proposed immunosensor is expected to blaze a novel trail for the real sample detection of PSA and other biomarkers.

A Novel Electrochemiluminescence Immunosensor for the Analysis of HIV-1 p24 Antigen Based on P-RGO@Au@Ru-SiO₂ Composite.

Ru(bpy)3(2+)-doped silica (Ru-SiO2) nanoparticles and gold-nanoparticle-decorated graphene (P-RGO@Au) were combined to form a P-RGO@Au@Ru-SiO2 composite. The composite was used to develop a novel sandwich-type electrochemiluminescence immunosensor for the analysis of HIV-1 p24 antigen. The composite worked as carrier to immobilize target antibody and to build a sandwich-type electrochemiluminescence immunosensor through an interaction between antigen and antibody. Importantly, high ECL signal could be obtained due to the large amounts of Ru(bpy)3(2+) molecules per Ru-SiO2 nanoparticle. The P-RGO@Au composite with good conductivity and high surface area not only accelerated the electron transfer rate but also improved the loading of both ECL molecules and capture antibody, which could further increase the ECL response and result in high sensitivity. Taking advantage of both Ru-SiO2 nanoparticles and the P-RGO@Au composite, the proposed immunosensor exhibited a linear range from 1.0 × 10(-9) to 1.0 × 10(-5) mg mL(-1) with a detection limit of 1.0 × 10(-9) mg mL(-1) for HIV-1 p24 antigen. The proposed ECL immunosensor was used to analyze HIV-1 p24 antigen in human serum, and satisfactory recoveries were obtained, indicating that the proposed method is promising for practical applications in the clinical diagnosis of HIV infection.

A novel sandwich electrochemiluminescence immunosensor for ultrasensitive detection of carbohydrate antigen 19-9 based on immobilizing luminol on Ag@BSA core/shell microspheres.

A novel sandwich-type electrochemiluminescence immunosensor based on immobilizing luminol on Ag@BSA core/shell microspheres (Ag@BSA-luminol) for ultrasensitive detection of tumor marker carbohydrate antigen 19-9 (CA19-9) has been developed. Herein, magnetic carbon nanotubes (MAGCNTs) decorated with polyethylenimine (PEI) was used to construct the base of the immunosensor. MAGCNTs with prominent electrical conductivity and high surface area could be beneficial for promoting the electron transfer and loading plenty of primary antibodies (Ab1) via glutaraldehyde (GA). Meanwhile, the magnetic property of MAGCNTs makes it easy to be attached to the surface of magnetic glass carbon electrode (MGCE) through magnetism interaction, which provides an outstanding platform for this immunosensor. Moreover, Ag@BSA microspheres with large surface area, good stability, and excellent biocompatibility were desirable candidates for effective cross-link of CA19-9 detection antibodies (Ab2). A more interesting thing was that ELISA color reaction was used as an ultrasensitive strategy for identifying Ab2 was successfully coated on Ag@BSA with the naked eye. Additionally, we immobilized the luminol on the surface of Ag@BSA to prepare the target immunosensor. Immobilization of luminol on the surface of Ag@BSA could decrease the distance between luminophores and the electrode surface, leading to great enhancement of the ECL intensity of luminol in the present of hydrogen peroxide (H2O2). Under the optimal conditions, the intensity of the ECL immunosensor increased linearly with the logarithm of CA19-9 concentration in a wide linear range from 0.0005 to 150UmL(-1) with a detection limit of 0.0002UmL(-1) (S/N=3). All the results suggested the prepared CA19-9 immunosensor displayed high sensitivity, excellent stability and good specificity. The developed method opened a new avenue to clinical bioassay.

An ultrasensitive quenched electrochemiluminescent immunoassay based on the peroxidase-like activity of ZnFe2O4@Au nanoparticles

We reported here the synthesis of zinc ferrite (ZnFe2O4), which was further fabricated into gold nanoparticles (AuNPs) functionalized ZnFe2O4 (ZnFe2O4@Au) through a layer-by-layer (LBL) self-assembly method. The prepared ZnFe2O4@Au showed excellent catalytic performance to the reduction reaction procedure of hydrogen peroxide (H2O2), and the coated AuNPs provided the nanoparticles with good biocompatibility. In addition, the CdTe quantum dots dotted graphene (G–CdTe) was prepared and was found with good electrochemiluminescence (ECL) property. The prepared ZnFe2O4@Au and G–CdTe were applied in a simple sandwich-type ECL immunosensor for carcinoembryonic antigen (CEA). In the immunosensor, G–CdTe acted as the solid support for CEA primary antibody and ZnFe2O4@Au was employed as the supporter of CEA secondary antibody. The ZnFe2O4@Au could quench the ECL signal of the G–CdTe and the quenching ECL intensity could be obtained. The proposed immunosensor enabled CEA concentrations to be determined in the 0.01–50ngmL−1 concentration range, with a detection limit of 4pgmL−1.

Electrochemiluminescence of luminol enhanced by the synergetic catalysis of hemin and silver nanoparticles for sensitive protein detection

A novel and ultrasensitive electrochemiluminescence (ECL) immunosensor, which was based on the amplifying ECL of luminol by hemin-reduced graphene oxide (hemin-rGO) and Ag nanoparticles (AgNPs) decorated reduced graphene oxide (Ag-rGO), was constructed for the detection of carcinoembryonic antigen (CEA). For this proposed sandwich-type ECL immunosensor, Au nanoparticles electrodeposited (DpAu) onto hemin-rGO (DpAu/hemin-rGO) constructed the base of the immunosensor. DpAu had outstanding electrical conductivity to promote the electron transfer at the electrode interface and had good biocompatibility to load large amounts of primary antibody (Ab1), which provided an excellent platform for this immunosensor. Moreover, AgNPs and glucose oxidase (GOD) functionalized graphene labeled secondary antibody (Ag-rGO–Ab2–GOD) was designed as the signal probe for the sandwiched immunosensor. Not only did the hemin-rGO improve the electron transfer of the electrode surface, but hemin also further amplified the ECL signal of luminol in the presence of hydrogen peroxide (H2O2). With the aid of Ag-rGO–Ab2–GOD, enhanced signal was obtained by in situ generation of H2O2 and catalysis of AgNPs to ECL reaction of the luminol–H2O2 system. The as-prepared ECL immunosensor exhibited excellent analytical property for the detection of CEA in the range from 0.1pgmL−1 to 160ngmL−1 with a detection limit of 0.03pgmL−1 (SN−1=3).

Sandwich-type electrochemiluminescence immunosensor based on poly(acrylic acid) coated Fe3O4 composite for human chorionic gonadotrophin detection using quantum dots functionalized CNTs as labels

In this work, an easy approach was reported to synthesize novel poly(acrylic acid) coated Fe3O4 magnetic nanoparticles which showed high water solubility and biocompatibility. Primary antibodies were immobilized onto the surface of the prepared nanoparticles using cysteine as a coupling agent. A large number of negatively charged CdTe quantum dots were coated on the poly(diallyldimethylammonium chloride) coated carbon nanotubes via self-assembly electrostatic reactions, and used as carriers of secondary antibodies, which could significantly amplify the electroluminescence signal. Coupled with a microfluidic strategy, the electroluminescence immunosensors could be easily separated and assembled on the surface of indium tin oxide glass with external magnetic forces. With a sandwich-type immunoassay format, the electroluminescence intensity increased linearly with the logarithm of the human chorionic gonadotrophin concentration in the range of 0.005–50 ng cm−3 and the detection limit was 2.8 pg cm−3. In particular, this approach has the advantages of high sensitivity, specificity, and stability and could become of great promise for clinical application. .

3D microfluidic origami electrochemiluminescence immunodevice for sensitive point-of-care testing of carcinoma antigen 125

Abstract In this paper, a 3D microfluidic origami device combined with electrochemiluminescence (ECL) immunosensor was introduced for sensitive point-of-care testing of carcinoma antigen 125 in clinical serum samples for the first time. This microfluidic origami device was fabricated by directly screen-printing carbon working, counter electrodes and Ag/AgCl reference electrode including their conductive pads on wax-patterned pure cellulose paper, and was activated by folding to form a 3D electrochemical cell. To construct a sensitivity-enhanced sandwich-type ECL immunosensor, gold nanoparticles (AuNPs) was synthesized to modify the working electrode to provide a good pathway of electron transfer and enhance the immobilized amount of capture antibody (McAb1), and luminol functionalized gold nanoparticles (Lu-AuNPs) was synthesized to label signal antibody (McAb2). With the aid of a facile device-holder, cyclic voltammetry was applied on microfluidic origami ECL immunodevice to trigger ECL. Under optimal conditions, this microfluidic origami ECL immunodevice provided a good linear response range from 0.01 to 100 U mL−1 with a detection limit of 0.0074 U mL−1. The proposed ECL immunodevice presented high sensitivity and stability, and could be applied in point-of-care testing of other tumor markers for remote regions and developing countries.

The sandwich-type electrochemiluminescence immunosensor for α-fetoprotein based on enrichment by Fe3O4-Au magnetic nano probes and signal amplification by CdS-Au composite nanoparticles labeled anti-AFP

A novel and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was fabricated on a glassy carbon electrode (GCE) for ultra trace levels of α-fetoprotein (AFP) based on sandwich immunoreaction strategy by enrichment using magnetic capture probes and quantum dots coated with Au shell (CdS-Au) as the signal tag. The capture probe was prepared by immobilizing the primary antibody of AFP (Ab1) on the core/shell Fe3O4-Au nanoparticles, which was first employed to capture AFP antigens to form Fe3O4-Au/Ab1/AFP complex from the serum after incubation. The product can be separated from the background solution through the magnetic separation. Then the CdS-Au labeled secondary antibody (Ab2) as signal tag (CdS-Au/Ab2) was conjugated successfully with Fe3O4-Au/Ab1/AFP complex to form a sandwich-type immunocomplex (Fe3O4-Au/Ab1/AFP/Ab2/CdS-Au), which can be further separated by an external magnetic field and produce ECL signals at a fixed voltage. The signal was proportional to a certain concentration range of AFP for quantification. Thus, an easy-to-use immunosensor with magnetic probes and a quantum dots signal tag was obtained. The immunosensor performed at a level of high sensitivity and a broad concentration range for AFP between 0.0005 and 5.0ngmL−1 with a detection limit of 0.2pgmL−1. The use of magnetic probes was combined with pre-concentration and separation for trace levels of tumor markers in the serum. Due to the amplification of the signal tag, the immunosensor is highly sensitive, which can offer great promise for rapid, simple, selective and cost-effective detection of effective biomonitoring for clinical application.

Sandwich-type electrochemiluminescence immunosensor based on Ru-silica@Au composite nanoparticles labeled anti-AFP

A simple and sensitive sandwich-type electrochemiluminescence immunosensor for α-1-fetoprotein (AFP) on a gold nanoparticles (nano-Au) modified glassy carbon electrode (GCE) was developed by using Ru-silica (Ru(bpy) 3 2+-doped silica) doped Au (Ru-silica@Au) composite as labels. The primary antibody, anti-AFP was first immobilized on the gold nanoparticles modified electrode due to the covalent conjugation, then the antigen and the Ru-silica@Au composite nanoparticles labeled secondary antibody was conjugated successively to form a sandwich-type immunocomplex through the specific interaction. The surfaces of Ru-silica nanoparticles were modified via the assemble of Au nanoparticles. The prepared Ru-silica@Au composite nanoparticles own the large surface area, good biocompatibility and highly effective electrochemiluminescence properties. The morphologies of the Ru-silica@Au composite nanoparticles were investigated by using transmission electronic microscope (TEM). The Ru-silica@Au composite nanoparticles labeled anti-AFP/AFP/bovine serum albumin (BSA)/anti-AFP/nano-Au modified GCE electrode was evaluated by means of cyclic voltammetry (CV) and electrogenerated chemiluminescence (ECL). The immunosensor performed high sensitivity and wide liner for detection AFP in the range of 0.05–50 ng/mL and the limit detection was 0.03 ng/mL (defined as S/ N = 3).