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The accurate diagnosis of diseases can be improved by detecting multiple biomarkers simultaneously. This study presents the development of a magnetic photoelectrochemical (PEC) immunosensor array for the simultaneous detection of amyloid-β 42 (Aβ) and microtubule-associated protein (Tau), which are markers for neurodegenerative disorders. A metal-organic framework (MOF) derivative, Fe 2 O 3 @FeS 2 magnetic composites with exceptional photoelectric and ferromagnetic properties was synthesized while preserving the original structure and advantages. Thus, the immunoassembly process of the sensor can be carried out in homogeneous solution and recovered by magnetic separation. For simultaneous detection, a chip is divided into multiple independent sensing sites, which have the same preparation and detection environment, allowing for the implementation of a self-calibration method. The sensor array demonstrates considerable detection ranges of 0.01-100 ng mL -1 for Aβ and 0.05-100 ng mL -1 for Tau, with low detection limits of 2.1 pg mL -1 for Aβ and 7.9 pg mL -1 for Tau. The PEC sensor array proposed in this study exhibits exceptional stability, selectivity, and reproducibility, providing a new method for detecting multiple markers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The successful application of electrochemiluminescence (ECL) in immunoassay for clinical diagnosis requires improving sensitivity and accuracy. Herein was reported an ECL analytical model based zinc-based metal-organic frameworks of ruthenium hybrid (RuZn MOFs) as the signal emitter. To enlarge the output difference, the quenching effect of three different noble metal nanoparticles included palladium seeds (Pd seeds ), palladium octahedrons (Pd oct ), and Pt-based palladium (Pd@Pt oct ) core-shell were researched. Among them, Pd@Pt oct core-shell possessed higher activity and improved durability than Pd-only (NPs), they could load more protein macromolecules amicably and stabilized in the analysis system. Furthermore, since the charge redistribution owing to the hybridization of the Pt and Pd atoms in Pd@Pt oct , it could generate the electron flow maximumly from the emitter RuZn MOFs to Pd@Pt oct and result in the enhancement of quenching ECL. And the UV absorption of noble metal nanoparticles overlapped with the ECL emission of RuZn MOFs to varying degrees, which caused the behavior of resonance energy transfer (RET) reaction at the same time. This would greatly promote the sensitivity of this ECL system compared with the traditional single quenching mechanism. Based on this, a signal-off immunsensor was constructed to sensitive detection of D-dimer with linearity range from 0.001 to 200 ng mL -1 , limit of detection (LOD) was 0.20 pg mL -1 and provide a further theoretical basis for the clinical application of ECL technology., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

As an inflammatory marker, procalcitonin (PCT) is more representative than other traditional inflammatory markers. In this work, a highly efficient photoelectrochemical (PEC) immunosensor was constructed based on the photoactive material Bi 2 S 3 /Ag 2 S to realize the sensitive detection of PCT. Bi 2 S 3 was prepared by a hydrothermal method, and Ag 2 S quantum dots were deposited on the ITO/Bi 2 S 3 surface via in situ reduction. Bi 2 S 3 is a kind of admirable photoelectric semiconductor nanomaterial on account of its moderate bandgap width and low binding rate of photogenerated electron holes, which can effectively convert light energy into electrical energy. Therefore, based on the energy level matching principle of Bi 2 S 3 and Ag 2 S, a labeled Bi 2 S 3 /Ag 2 S PEC immunosensor was constructed, and the sensitive detection of PCT was successfully established. The linear detection range of the PEC immunosensor was 0.50 pg∙mL -1 to 50 ng∙mL -1 , and the minimum detection limit was 0.18 pg∙mL -1 . Compared with the traditional PEC strategy, the proposed PEC immunosensor is simple, convenient, and has good anti-interference, sensitivity, and specificity, which could provide a meaningful theoretical basis and reference value for the clinical detection of PCT.

Herein, a novel dual mode detection system of split-type photoelectrochemical (PEC) and visual immunoassay was developed to detect neuron specific enolase (NSE), which achieved simultaneous and reliable NSE detection due to the completely different signal readouts and transduction mechanism. Specifically, specific reactions of antigens and antibodies were performed in 96-microwell plates. Gold nanoparticle (Au NP)-loaded Fe 3 O 4 (Au@Fe 3 O 4 ) NPs were used as secondary antibody markers and signal regulators, which could produce a blue-colored solution in the presence of 3,3',5,5'-tetramethylbenzidine (TMB) and H 2 O 2 because of its peroxidase-like activity. Therefore, the visual detection of NSE was realized, making the results more intuitive. Meanwhile, the above biological process could also be used as part of the split-type PEC sensing platform. Oxidized TMB and Fe 3+ were consumptive agents of the electron donor, which both realized the double quenching of PEC signal generated by the SnO 2 /MgIn 2 S 4 /Zn 0.1 Cd 0.9 S composites. Owing to the waterfall band structure, SnO 2 /MgIn 2 S 4 /Zn 0.1 Cd 0.9 S composites partially absorb visible light and effectively inhibit the electron-hole recombination, thereby providing significantly enhanced and stable initial signal. On the basis of the multiple signal amplification strategy and the split-type mode, NSE could be sensitively detected with a low detection limit of 14.0 fg·mL -1 (S/N = 3) and a wide linear range from 50.0 fg·mL -1 to 50.0 ng·mL -1 .

The preparation of highly efficient electrochemiluminescence (ECL) illuminants is an effective method to improve the sensitivity and repeatability of ECL immunoassay. In this study, we prepared an ECL immunoassay for efficient and sensitive detection of neuron-specific enolase (NSE) by linking carboxylated Ru(bpy) 3 2+ to an iron-based metal-organic framework (NH 2 -MIL-88 (Fe)) via an amide bond as an ECL signal probe. NH 2 -MIL-88 (Fe) possesses a large number of amino groups that can catalyze the co-reactant S 2 O 8 2- , which generates abundant reaction intermediates SO 4 •- around Ru(dcbpy) 3 2+ , reduces the loss of material transport and energy transfer between SO 4 •- and Ru(dcbpy) 3 2+ , and significantly enhances the ECL signal. We used polyaniline-intercalating vanadium oxide (PVO) nanosheets as the substrates to capture NSE owing to the large specific surface area and extraordinary conductivity of the nanosheets. Similarly, PVO nanosheets also possess abundant amino groups, which can act as co-reaction promoters to catalyze the reaction of S 2 O 8 2- to SO 4 •- , enhancing the ECL signal of the immunoassay. Therefore, we constructed a dual-enhanced ECL immunoassay with Ru(dcbpy) 3 2+ /NH 2 -MIL-88 (Fe) and PVO as the signal probe and substrate, respectively, which exhibited excellent sensitivity and selectivity for detecting NSE. This study offers an effective strategy for ultrasensitive detection of trace proteins using ECL immunoassays., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The successful application of electrochemiluminescence (ECL) in various fields required continuous exploration of novel ECL signal emitters. In this work, we have proposed a pristine ECL luminophor named NiRu MOFs, which owned extremely high and stable ECL transmission efficiency and was synthesized via a straightforward two-step hydrothermal pathway. The foundation framework of pure Ni-MOFs with the initial structure was layered-pillared constructed by the coordinated octahedrally divalent between nickel and terephthalic acid (BDC). The terephthalates were coordinated and pillared directly to the nickel hydroxide layers and the three-dimensional framework was formed, which had a weak ECL response strength. Then, the ruthenium pyridine complex was recombined with pure Ni-MOFs to produce NiRu MOFs and part of the introduced ruthenium was atomically dispersed in the layered-pillared structure through an ion-exchange method, which led to the ECL luminous efficiency being significantly boosted more than pure Ni-MOFs. In order to verify the superiority of this newly synthesized illuminant, an ECL immunoassay model has been designed, and the results demonstrated that it had extremely strong and steady signal output in practical application. This study realized an efficient platform in ECL immunoassay application with the limit of detection of 0.32 pg mL -1 for neuron-specific enolase (NSE). Therefore, the approach which combined the pristine pure Ni-MOFs and the star-illuminant ruthenium pyridine complex would provide a convenient and meaningful solution for exploring the next-generation ECL emitters.

Gold modified thiol graphene (Au@HS-rGO) was prepared and applied as sensing platform for constructing the electrochemical aptasensor. While gold-palladium modified zirconium metal-organic frameworks (AuPd@UiO-67) nanozyme was employed as signal enhancer for detecting mercury ions (Hg 2+ ) sensitively. Herein, gold nanoparticles (Au NPs) were modified on HS-rGO to form the thin Au@HS-rGO layer. Then the substrate strand (Apt1) was modified on the platform through Au-S bond. The signal strand (Apt2) was further decorated on the platform in the presence of Hg 2+ . Herein, the Apt2 was labeled with AuPd@UiO-67 nanozyme, which exhibited catalase-like properties to catalyze H 2 O 2 , thereby generating the electrical signal. With the concentration of Hg 2+ increased, the amount of modified Apt2-AuPd@UiO-67 increased, leading to the rise of current response. Since the current responses were linear with concentration of Hg 2+ , the detection of Hg 2+ can be achieved. Under the optimum conditions, the prepared electrochemical aptasensor exhibited wide linear range from 1.0 nmol/L to 1.0 mmol/L, along with a low detection limit of 0.16 nmol/L. Moreover, the electrochemical aptasensor showed excellent selectivity, reproducibility and stability, together with superior performance in actual water sample analysis. Therefore, this proposed electrochemical aptasensor may have promising applications and provide references for environmental monitoring and management., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

In this paper, we constructed a sandwich-type photoelectrochemical (PEC) immunosensor for the quantitative detection of procalcitonin (PCT) based on the sensitization of Mn 2+ doped CdS (CdS:Mn) nanocomposites to Bi 2 WO 6 and the signal amplification effect of an upconversion material NaYF 4 :Yb,Tm. Bi 2 WO 6 was synthesized with a three-dimensional flowered structure. CdS:Mn reduced the recombination of photogenerated carriers, and significantly improved photocurrent response. Lanthanide-doped upconversion nanomaterials were used as the label of secondary antibody. NaYF 4 :Yb,Tm have two functions, not only connected with the secondary antibody, but also can further amplify the photocurrent response. The proposed immunosensor for detecting PCT provided a desired linear range of 0.5 pg mL -1 -100 ng mL -1 and a detection limit of 0.13 pg mL -1 under optimal experimental conditions. Besides, the PEC immunosensor demonstrated good reproducibility, specificity and stability. The results of determination of PCT in real human serum samples were satisfactory. Thus, the immunosensor may be applied in the clinical diagnosis of PCT and other biomarkers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Based on the necessity and urgency of detecting infectious disease marker procalcitonin (PCT), a novel unlabeled photoelectrochemical (PEC) immunosensor was prepared for the rapid and sensitive detection of PCT. Firstly, SnO 2 porous nanoflowers with good photocatalytic performance were prepared by combining hydrothermal synthesis and calcining. BiOI nanoflowers were synthesized by facile ultrasonic mixed reaction. Ag 2 S quantum dots were deposited on SnO 2 /BiOI composites by in situ growth method. The SnO 2 /BiOI/Ag 2 S composites with excellent photoelectric properties were employed as substrate material, which could provide significantly enhanced and stable signal because of the energy level matching of SnO 2 , BiOI and Ag 2 S and the good light absorption performance. Accordingly, a PEC immunosensor based on SnO 2 /BiOI/Ag 2 S was constructed by using the layered modification method to achieve high sensitivity analysis of PCT. The linear dynamic range of the detection method was 0.50 pg·mL -1 ~100 ng·mL -1 , and the detection limit was 0.14 pg·mL -1 . In addition, the designed PEC immunosensor exhibited satisfactory sensitivity, selectivity, stability and repeatability, which opened up a new avenue for the analyzation of PCT and further provided guidance for antibiotic therapy.

Molecularly imprinted polymers (MIPs) based on electrochemical sensors (MIP-EC sensors) have obtained ideal achievements in recent years. However, some challenges are still need to be addressed, such as adjustable preparation, unstable sensing interface and great signal-to-noise ratio. Here, based on the ingenious combination of the MIP and the self-supported CoN nanowire arrays grown on carbon cloth (CoN NWs/CC), a robust MIP-EC sensor was developed, in which the MIP film was uniformly coated on the CoN NWs/CC via a bulk polymerization crosslinking process. Especially, CoN NWs/CC were prepared via in-situ transformation of their oxide precursors and then directly as a candidate of EC electrode. Under the optimal conditions, the MIP-EC sensor can detect Tylosin (TS) in the concentration range from 8.6 × 10 -11 to 6.7 × 10 -5 mol L -1 , and the low detection limit (LOD) is 5.5 × 10 -12 mol L -1 (S/N = 3). Furthermore, the MIP-EC sensor showed high selectivity, reproducibility and stability. The practicability of the MIP-EC sensor was tested in the actual samples of surface water and soil with the comparison of the traditional ELISA method. The developed MIP-EC sensor with simple and fabrication process can provide a versatile and reliable method, which has great potential application value for the detection of small hazardous molecules., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this study, a sensitive label-free electrochemical immunosensor was designed based on nanoporous Fe3O4 and a biotin-streptavidin system to specifically detect zearalenone (ZEN). Herein, nanoporous Fe3O4 was employed to carry streptavidin to prepare the highly sensitive immunosensor. The application of nanoporous Fe3O4 and the biotin-streptavidin reaction provided large amounts of antibodies on each conjugate, thus amplifying the detected signal. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were conducted to characterize the modification with ZEN. Factors which might influence the properties of the immunosensor, including concentration of nanoporous Fe3O4, pH of the buffer, incubation time and temperature were studied. Under the best conditions, the immunosensor displayed a highly sensitive response toward ZEN, ranging in concentration from 10.0 pg mL-1 to 3.00 ng mL-1 and 3.00 ng mL-1 to 12.0 ng mL-1, with a low detection limit of 3.7 pg mL-1. The results for analysis of human urine samples were satisfactory. Furthermore, this proposed method may find promising applications in the detection of other mycotoxins.

An ultrasensitive label-free photoelectrochemical (PEC) immunosensor was developed to detect amyloid β-protein (Aβ) based on CdS/CdTe-cosensitized SnO2 nanoflowers. Specifically, SnO2 with a flower-like porous nanostructure was utilized as a perfect substrate for the construction of PEC immunosensors, and the SnO2-modified electrode was first coated with CdTe quantum dots (QDs) and then further deposited with CdS by successive ionic layer adsorption and reaction techniques. The formed SnO2/CdS/CdTe-cosensitized structure exhibited excellent photocurrent intensity and was employed as an excellent photoactive matrix to immobilize Aβ antibody to further construct the immunosensor. Under optimal conditions, the as-constructed PEC immunosensor was used to detect Aβ and exhibited a wide linear concentration range from 0.5 pg mL-1 to 10 ng mL-1, with a low limit of detection (LOD, 0.18 pg mL-1, S/N = 3). Meanwhile, it also presented good reproducibility, specificity, and stability and may open a new promising platform for the clinical detection of Aβ or other biomarkers.

A sandwich-type electrochemical immunosensor for prostate-specific antigen (PSA) detection was constructed. In this sensing platform, palladium nanoparticles (Pd NPs) loaded electroactive amino-zeolitic imidazolate framework-67 (Pd/NH 2 -ZIF-67) nanocomposite is utilized as a novel redox mediator. Pd NPs, as the labeling signal molecule, owns good biocompatibility and excellent catalytic performance. Meanwhile, the electroactive ZIF-67 with lamellar structures serves not only as a carrier of Pd NPs but also as a synergistic catalyst of palladium to decompose H 2 O 2 . Amperometric method is used to determine the current signal generated on the electrode surface, which is conducive to achieve the quantitative determination of PSA. Under optimum conditions, the proposed immunosensor shows a wide detection range from 100 fg mL -1 to 50 ng mL -1 with a low detection limit of 0.03 pg mL -1 , featuring favorable selectivity, repeatability and stability. This proposed immunosensor is expected to be a powerful tool for realizing quantitative detection of PSA and other biomarkers in actural sample analysis., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this work, by using amorphous bimetallic sulfides of CoSnS x Pd as signal amplifier and magnetic material of Fe 3 O 4 @PPyAu as the substrate, we fabricated an electrochemical immunoassay for Nterminal prohormone of brain natriuretic peptide (NTpro BNP). CoSnS x was used as the signal amplifier of the immunosensor for the first time, which was synthesized by fast stoichiometric co-precipitation method. The binary sulfide was identified as an amorphous structure and performed apparent electrochemical behavior. The excellent performance of signal marker was induced by the synergistic effect between SnS 2 and cobalt, as well as the loaded Pd nanoparticles (NPs). Both CoSnS x and Pd NPs presented excellent electrocatalytic activity toward H 2 O 2 oxidation. Moreover, the magnetic nanocomposite of Fe 3 O 4 @PPyAu was firmly immobilized on the magnetic glassy carbon electrode (MGCE) by the magnetic force. The magnetic substrate not only performed good electron conductivity, but also improved the stability of the fabricated electrochemical immunosensor. The developed immunosensor for the NTpro BNP detection exhibited a wide linear response (0.1 pg/mL to 50 ng/mL), and low detection limit of 31.5 fg/mL. In addition, the immunosensor held an excellent analysis capability and broad fascinating application for the detection of other biomarkers in medical diagnosis and treatment., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This work reported curcumin quenched electrochemiluminescence (ECL) behavior of luminol with H 2 O 2 as coreactant. To achieve excellent ECL signal, luminol was anchored on Au functionalized MoS 2 /Bi 2 S 3 nanorods (Luminol-Au@MoS 2 /Bi 2 S 3 ), which not only exhibited super catalysis for H 2 O 2 decomposition to enhance the ECL intensity of luminol/H 2 O 2 system, but also offered a satisfying substrate material for grafting more Au nanoparticles via Au-S binding which was used to adsorb luminol and primary antibodies. As an antioxidant, the hydrophobicity of curcumin limited its bioavailability. Herein, curcumin was conjugated with ZnO nanomaterials (ZnO-CR) to increase its dispersity in water which can make it more bioavailable. Moreover, the possible quenching mechanism between luminol/H 2 O 2 system and ZnO-CR was ascribed to the consumption of superoxide radical (O 2 •- ) and energy transfer. The consumption amount of O 2 •- was calculated to be 1.2092 μM/mL through superoxide anion free radical detection kit. Besides, polydopamine was self-polymerized on the surface of ZnO-CR (PDA@ZnO-CR) to anchor secondary antibodies. In optimum parameter, the ECL immunosensor exhibited excellent performance for amyloid-β(Aβ) proteins detection with a wide detection range from 0.05 pg mL -1 to 10 ng mL -1 and a low detection limit of 21 fg mL -1 (S/N = 3)., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A novel label-free electrochemiluminescent (ECL) immunosensor based upon luminol functionalized platinum nanoparticles loaded on graphene sheets (Lu-Pt@GS) as sensing platform was fabricated for highly sensitive and selective determination of prostate specific antigen (PSA). In this work, for the first time luminol was employed as both ECL luminescence reagent and reductants to in-situ reduce H 2 PtCl 6 forming Pt NPs on surface of GS. A great deal of luminol could be attached onto the surface of Pt NPs within the reduction process, which can generate strong ECL emission. Pt NPs not only could enhance ECL signals of luminol but supply active sites for the immobilization of PSA antibodies with micro friendly environment. For preventing the consecutive reaction among luminol and H 2 O 2 , single-step cycle pulse was adopted, resulting in stable and strong ECL signals. Under optimized experimental conditions, the proposed ECL immunosensor acquired a wide linear range of 1 pg/mL to 10 ng/mL with a relatively low detection limit of 0.3 pg/mL for PSA. Furthermore, due to high sensitivity, simplicity and cost-effectiveness, the designed immunosensor provides a new method for detecting other important biomarkers in clinical analysis., (Copyright © 2018 Elsevier Inc. All rights reserved.)

In this study, we propose a SnO 2 /CdCO 3 /CdS-based label-free photoelectrochemical (PEC) immunosensor for the sensitive quantification of amyloid β-protein (Aβ) which plays a critical role in the early diagnosis of Alzheimer's disease. Under specific pH conditions, SnO 2 /CdCO 3 /CdS was first designed and successfully synthesized with simple one-pot method. The synthesis of SnO 2 /CdCO 3 /CdS circumvents the trouble of traditional composite materials to be gradually compounded, saving a lot of time and energy. The synthesis mechanism of SnO 2 /CdCO 3 /CdS nanocomposite was also deeply explored. Moreover, thanks to the matched energy levels of its three components, SnO 2 /CdCO 3 /CdS nanocomposite exhibited enhanced photocurrent intensity, which is dozens of times bigger than any of its components, thus making it an excellent photoactive matrix for PEC immunosensor. Under optimal conditions, the as-constructed PEC immunosensor manifested a broad linear range (0.1 pg mL -1 to 100 ng mL -1 ) with a low detection limit (LOD, 0.05 pg mL -1 , S/N = 3). High selectivity, coupled with good stability, allowed the developed PEC immunosensor to be applied in the clinical detection of Aβ or other biomarkers in human serum., (Copyright © 2018. Published by Elsevier B.V.)

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 (Ab 1 ) via Au-NH 2 bond and enhance the electron transport of PTCA-GO. CuS was used as a novel co-reaction accelerator in PTCA-K 2 S 2 O 8 system to label secondary antibodies (Ab 2 ), which can react with the coreactant (K 2 S 2 O 8 ) to produce more SO 4 •- . SiO 2 nanospheres with large specific surface area were used to load a mass of CuS and Au NPs, which can directly combine with Ab 2 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., (Copyright © 2018 Elsevier B.V. All rights reserved.)

An ultrasensitive label-free photoelectrochemical (PEC) immunosensor with high visible-light activity was developed for quantitative detection of amyloid β-protein (Aβ) by cross-linking anti-Aβ antibody onto the Ag 2 S sensitized SnO 2 /SnS 2 nanocomposites. Specifically, SnO 2 with flower-like porous nanostructure was innovatively applied in PEC immunosensor as a basal material. It could form a heterostructure with SnS 2 , which brought about the sensitization of SnO 2 and enhanced the separation of photogenerated electrons and holes. Moreover, Ag 2 S was in-situ growth on the surface of SnO 2 /SnS 2 , which further enhanced the photocurrent response significantly. Therefore, SnO 2 /SnS 2 /Ag 2 S could form stepwise band-edge structure, which benefited the light harvesting and provided a good foundation for sensor construction and detection. Under optimal conditions, the PEC immunosensor was used to detect the content of Aβ and exhibited a wide linear concentration range from 0.5 pg mL -1 to 100 ng mL -1 , with low limit of detection (0.17 pg mL -1 ) and limit of quantification (0.56 pg mL -1 ). Additionally, the designed PEC immunosensor exhibited good reproducibility, specificity, and stability which may find potential applications in the biosensor, biomedicine, clinical diagnosis, photocatalysis and other related fields., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A new, photoelectrochemical immunosensor was proposed on the basis of the La-CdS/3D ZnIn 2 S 4 /Au@ZnO sensitization structure for detection of aminoterminal pro-brain natriuretic peptides (NT-proBNP). The Au@ZnO-modified electrode was first assembled with 3D ZnIn 2 S 4 , and then further deposited with lanthanum doped cadmium sulfide (La-CdS) via successive ionic layer adsorption and reaction strategy. The Au@ZnO has excellent photoelectric activity and electrical conductivity. The ZnIn 2 S 4 with 3D architectures not only exhibit high photocurrent intensity under visible-light irradiation but also have large surface for the La-CdS deposition. Meanwhile, the La-CdS doped structure could depress the charge recombination, which effectively promotes separation of the generated electron-hole (e - /h + ) pairs and consequently enhances the photocurrent conversion efficiency. The polydopamine (PDA) was used not only as a cross-linker reagent for the immobilization of the anti-NT-proBNP but also as an electron donor for promoting the photo-generated e - /h + separation of the semiconductors. Under optimal conditions, the well-designed photoelectrochemical immunoassay exhibited a low detection limit of 0.32 pg mL -1 and a wide linear range from 0.8 pg mL -1 to 45 ng mL -1 for target NT-proBNP detection. Meanwhile, it also presented good reproducibility, specificity, and stability and might open a new promising strategy for the detection of other important tumor markers., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A sandwich-type photoelectrochemical (PEC) immunosensor for detecting N-terminal pro-brain natriuretic peptide (NT-proBNP) was constructed on the basis of SnO 2 /SnS 2 /mpg-C 3 N 4 nanocomposites and PbS/SiO 2 , with the former as a photoactive matrix and the latter as an efficient quencher. SnO 2 /SnS 2 /mpg-C 3 N 4 was synthesized via in situ growth of SnO 2 and SnS 2 on mesoporous graphene like C 3 N 4 nanocomposites (mpg-C 3 N 4 ). Specifically, SnO 2 /SnS 2 /mpg-C 3 N 4 exhibited intense PEC signal responses, which are tens of times stronger than its each single component. Because of its superior performance, SnO 2 /SnS 2 /mpg-C 3 N 4 was applied as a photoactive matrix and signal indicator for fabricating PEC immunosensor. Interestingly, the excellent PEC signals from SnO 2 /SnS 2 /mpg-C 3 N 4 could be reduced severely with the addition of PbS/SiO 2 . Hence, the secondary antibody bioconjugates (PbS/SiO 2 -Ab 2 ) were prepared as an efficient quencher. The mechanism of the quench reaction was further discussed in detail. On the basis of the interaction between the matrix and the quencher, the NT-proBNP immunosensor was fabricated and a wide linear range of 0.1 pg·mL -1 to 50 ng·mL -1 was obtained with a low detection limit of 0.05 pg·mL -1 . Additionally, the PEC immunosensor manifested good stability, reproducibility, and selectivity, which could underlie robust platforms for detecting multitudinous biomarkers or other targets of interest.

A novel electrochemiluminescence (ECL) signal-off strategy based on CuS in situ grown on reduced graphene oxide (CuS-rGO) quenching luminol/H 2 O 2 system was firstly proposed. Luminol was grafted on the surface of Au@Fe 3 O 4 -Cu 3 (PO 4 ) 2 nanoflowers (Luminol-Au@Fe 3 O 4 -Cu 3 (PO 4 ) 2 ) which exhibited excellent catalytic effect towards the reduction of H 2 O 2 to enhance the ECL intensity of luminol. Cu 3 (PO 4 ) 2 nanoflowers showed large surface area which can immobilize more Fe 3 O 4 and Au nanoparticles. The quenching mechanism of CuS-rGO was due to ECL resonance energy transfer (RET). The spectral overlap between fluorescence spectrum of Luminol-Au@Fe 3 O 4 -Cu 3 (PO 4 ) 2 and UV-vis absorption spectrum of CuS-rGO revealed that resonance energy transfer was possible. Au nanoparticles were immobilized on the surface of CuS-rGO to capture secondary antibodies. After a sandwich-type immunoreaction, a remarkable decrease of ECL signal was observed. Under the optimal conditions, the immunosensor showed excellent performance for N-terminal pro-brain natriuretic peptide (NT-proBNP) detection with a wide detection range from 0.5 pg mL -1 to 20 ng mL -1 and a low detection limit of 0.12 pg mL -1 (S/N = 3). The prepared NT-proBNP immunosensor displayed high sensitivity, excellent stability and good specificity., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this study, a sensitive sandwich-type electrochemical immunosensor was fabricated for the detection of alpha fetoprotein (AFP) based on Co 3 O 4 @MnO 2 -thionine (Co 3 O 4 @MnO 2 -Th) and the screen printing technique. Meanwhile, the pseudo enzyme-linked immunosorbent assay (pseudo-ELISA) method was applied in fabricating the immunosensor. Screen-printed carbon electrode (SPCE) was applied for achieving the detection of AFP. Simultaneously, the amino functionalized Co 3 O 4 @MnO 2 -Th was employed as secondary label and could greatly improve the electrochemical response signal, which was beneficial for detecting AFP. Differential pulse voltammetry (DPV) was applied for the detection of AFP and electrochemical impedance spectroscopy (EIS) confirmed the successful fabrication of the immunosensor. Under optimal conditions, the immunosensor exhibited a linear response toward AFP in the range of 0.001-100 ng/mL, with a low detection limit of 0.33 pg/mL. Simultaneously, the proposed immunosensor displayed acceptable selectivity, excellent stability and well reproducibility. Furthermore, this proposed strategy may open up new ideas and find many potential applications in the detection of other tumor markers., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this work, a highly-efficient competitive method-based electrochemiluminescence (ECL) immunosensor was proposed based on {[Ru(bpy) 3 ][Cu 2x Ni 2(1-x) (ox) 3 ]} n (Cu/Ni/Ru) as luminophor to efficiently detect aflatoxins B1 (AFB1). Cu/Ni/Ru exhibited excellent ECL behavior. While polyethyleneimine capped silicon dioxide (PEI@SiO 2 ) could decrease the ECL performance of Cu/Ni/Ru due that PEI could destroy the structure of Cu/Ni/Ru via producing the complex between PEI and metal ions (Cu(II)/Ni(II)), inducing the release of Ru(bpy) 3 2+ . Since Au nanoparticles can directly combine with antibody and antigen, the Cu/Ni/Ru and PEI@SiO 2 was functionalized by Au nanoparticles. The quantitative detection of AFB1 was based on the competitive binding between AFB1-bovine serum albumin labeled Au-PEI@SiO 2 (Au-PEI@SiO 2 -AFB1-BSA) and free AFB1 with antibody-AFB1 which immobilized on Au-Cu/Ni/Ru. The ECL signal increased with augmenting the concentrations of the free AFB1 due to less Au-PEI@SiO 2 -AFB1-BSA combining with antibodies. Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.01ngmL -1 to 100ngmL -1 with a detection limit of 0.0039ngmL -1 (S/N = 3). The proposed immunosensor also provides a promising approach for ultrasensitive detection of other mycotoxins., (Copyright © 2017 Elsevier B.V. All rights reserved.)

An ultrasensitive sandwich-type photoelectrochemical (PEC) immunosensor was constructed for the detection of prostate specific antigen (PSA). In this work, Au-nanoparticle-loaded tungsten oxide (WO 3 -Au) hybrid composites was applied as PEC sensing platform, while Ca ions doped CdSe equipped on the conducting framework of reduced graphene oxide (rGO-Ca:CdSe) nanocomposites were employed as the signal amplification probe. As for WO 3 -Au, massive Au nanoparticles were formed on the surface of WO 3 without any additional reducing agent, providing a novel nanocarriers for anchoring plenty of the primary antibodies due to the large specific surface area and good biocompatibility by chemical bonding between Au nanoparticles and -NH 2 of antibodies. Besides, the incorporation of the rGO and the doping of Ca ions could improve the conductivity and hinder the recombination of electron-hole pairs of CdSe nanoparticles effectively, thereby enhancing the photocurrent conversion efficiency. Based on the sandwich immunoreaction, the primary antibody was immobilized onto WO 3 -Au substrate, after the formed rGO-Ca:CdSe labels were captured onto the electrode surface via the specific antibody-antigen interaction, the photocurrent intensity could be further enhanced due to the sensitization effect. Under the optimal conditions, the proposed PEC immunosensor shows a linear relationship between photocurrent variation and the logarithm of PSA concentration in the wide range of 5pgmL -1 to 50ngmL -1 with a low detection limit of 2.6pgmL -1 (S/N=3). Moreover, it also presented good stability and acceptable specificity, indicating the potential applications in clinical diagnostics., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of alpha fetoprotein (AFP). Multifunctionalized graphene nanocomposites (TB-Au-Fe 3 O 4 -rGO) were applied to modify the electrode to achieve the amplification of electrochemical signal. TB-Au-Fe 3 O 4 -rGO includes the advantages of graphene, ferroferric oxide nanoparticles (Fe 3 O 4 NPs), gold nanoparticles (Au NPs) and toluidine blue (TB). As a kind of redox probe, TB can produce the electrochemical signal. Graphene owns large specific surface area, high electrical conductivity and good adsorption property to load a large number of TB. Fe 3 O 4 NPs have good electrocatalytic performance towards the redox of TB. Au NPs have good biocompatibility to capture the antibodies. Due to the good electrochemical performance of TB-Au-Fe 3 O 4 -rGO, the effective and sensitive detection of AFP was achieved by the designed electrochemical immunosensor. Under optimal conditions, the designed immunosensor exhibited a wide linear range from 1.0 × 10 -5  ng/mL to 10.0 ng/mL with a low detection limit of 2.7 fg/mL for AFP. It also displayed good electrochemical performance including good reproducibility, selectivity and stability, which would provide potential applications in the clinical diagnosis of other tumor markers., Competing Interests: The authors declare no competing financial interests.

A novel and simple fluorescent biosensor has been realized through the fluorescence quenching of graphite carbon nitride (g-C 3 N 4 ) for mercuric ion (Hg 2+ ) detection. In this assay, the g-C 3 N 4 sheets which were functionalized with single-stranded DNA (ssDNA) aptamer showed strong fluorescence emission at 440nm under the excitation of 380nm in the absence of Hg 2+ . When added to the assay solution, Hg 2+ was embedded in the hairpin-shaped double-stranded DNA (dsDNA) due to the formation of the thymine-Hg 2+ -thymine (T-Hg 2+ -T) complex, which made the Hg 2+ close to the surface of g-C 3 N 4 sheet. Therefore, the fluorescence of g-C 3 N 4 was quenched. This sensor has good selectivity with a limit of detection as low as 0.17nM under optimal conditions. The present work demonstrates that the g-C 3 N 4 -based fluorescent sensor has a promising application for detection of metal ions in real samples., (Copyright © 2016 Elsevier B.V. All rights reserved.)

An ultrasensitive photoelectrochemical (PEC) aptasensor based on a novel signal amplification strategy was developed for the quantitative determination of microRNA (miR)-155. CH3NH3PbI3 quantum dots (QDs) functionalized ZnO nanosheets (NSs) were employed as the light harvester. Owing to the synergetic effect between CH3NH3PbI3 QDs and ZnO NSs, ZnO@CH3NH3PbI3 can provide an obviously increasing PEC signal by forming the heterojunction. Due to the larger steric hindrance, the sensitive decrease of the PEC signal can be achieved by the specific recognition between the primers and ssDNA of miR-155. In this sense, this developed aptasensor can achieve a high sensitivity (especially in the presence of the low concentrations of miR-155) and a wide detection range (0.01fmol/L to 20,000pmol/L). Under the optimal conditions, the proposed aptasensor offered an ultrasensitive and specific determination of miR-155 down to 0.005fmol/L. This aptassay method would open up a new promising platform at ultralow levels for early diagnose of different miRNA., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this work, a novel electrochemical aptasensor was developed for sensitive and specific detection of Hg(2+) based on thymine-Hg(2+)-thymine (T-Hg(2+)-T) structure via application of thionine (Th) as indicator signal. For the fabrication of the aptasensor, streptavidin modified magnetic beads (Fe3O4-SA) was firmly immobilized onto the magnetic glassy carbon electrode (MGCE) benefited from its magnetic character. Then biotin labeled T-riched single stranded DNA (Bio-ssDNA) connected with Fe3O4-SA specifically and steadily because of the specific binding capacity between streptavidin and biotin. The stable structure of T-Hg(2+)-T formed in the present of Hg(2+) provided convenience for the intercalation of Th. The detection of Hg(2+) was achieved by recording the differential pulse voltammetry (DPV) signal of Th. Under optimal experimental conditions, the linear range of the fabricated electrochemical aptasensor was 1-200nmol/L, with a detection limit of 0.33nmol/L. Furthermore, the proposed aptasensor may find a potential application for the detection of Hg(2+) in real water sample analysis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this work, an ultrasensitive electrochemical aptasensor for the detection of thrombin was developed based on Au nanoparticles decorated graphene sheet (Au@GS) and CoPd binary nanoparticles (CoPd NPs). A sulfydryl-labeled thrombin capture probe (Apt1) and a biotin-labeled thrombin reporter probe (Apt2) were designed to achieve a sandwich-type strategy. Au@GS was used as a sensing platform for the facile immobilization of Apt1 through Au-S bond, forming a sensing interface for thrombin. The specific recognition of thrombin induced the attachment of Apt2-CoPd NPs to the electrode. The labeled CoPd NPs showed good catalytic properties toward the reduction of H2O2, resulting in an amperometric signal. The amperometric response was correlated to the thrombin concentration in sample solutions. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) confirmed the successful fabrication of the aptasensor. A linear response to thrombin in the range of 0.01-2.00 ng mL(-1) with a low detection limit (5 pg mL(-1)) was achieved. The proposed aptasensor showed good selectivity, good reproducibility and acceptable stability. This proposed strategy may find many potential applications in the detection of other biomolecules., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Carcinoembryonic antigen (CEA) was used as the model, an ultrasensitive label-free photoelectrochemical immunosensor was developed using 2D TiO2 nanosheets and carboxylated graphitic carbon nitride (g-C3N4) as photoactive materials and ascorbic acid as an efficient electron donor. 2D TiO2 nanosheets was sythsized by surfactant self-assembly method and proved to have higher photoelectrochemical signals than TiO2 nanoparticles. Firstly, carboxylated g-C3N4 could be attached to 2D TiO2 nanosheets through the bond formed between carboxyl group of carboxylated g-C3N4 and TiO2. And the photocurrent of g-C3N4/TiO2 drastically enhances compared to carboxylated g-C3N4 and TiO2. Then, antibody of CEA was bonded to TiO2 through the dentate bond formed between carboxyl group of anti-CEA and TiO2, leading to the decrease of the photocurrents. As proven by PEC experiments and electrochemical impedance spectroscopy (EIS) analysis, the fabrication process of the immunosensor is successful. Under the optimal conditions, the intensity decreased linearly with CEA concentration in the range of 0.01~10 ng/mL. The detection limit is 2.1 pg/mL. The work provides an effective method for the detection of tumor markers and can be extended for the application in food safety and environmental monitoring analysis.

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 novel controlled release system-based sandwich-type immunosensor is fabricated to detect squamous cell carcinoma antigen (SCCA). The 1-methyl-1H-benzimidazole functionalized mesoporous SiO2 (MBI-MS) is used to load methylene blue (MB). β-cyclodextrin functionalized gold (CD-Au) is introduced as the gatekeeper for encapsulating MB and capturing the adamantly functional detection antibody (ADA-Ab2). And pH stimulus serves as the trigger system to control the MB release. After the load of MB, the CD-Au blocks the pores of the MBI-MS by the host-guest interaction in the neutral condition. However, when the pH is below 7.0, CD-Au is separated from the surface of MBI-MS owing to the protonation of the aromatic amines. The encapsulated MB is released from the pores of MBI-MS and detected by square wave voltammetry. The controlled release immunosensor shows a relatively wide linear range from 0.001 to 20 ng · mL(-1) with a low detection limit of 0.25 pg · mL(-1). The immunosensor also shows good reproducibility and selectivity, which endows it broad application prospect in clinical research.

An ultrasensitive electrochemical immunosensor for the detection of cluster of differentiation 146 antigen (CD146) based on TiO2 colloidal sphere laden Au/Pd nanoparticles (Au/Pd@TiO2) was developed. In this work, reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) was applied as an electrode modifying material to modify the surface of a glassy carbon electrode (GCE). Au/Pd@TiO2 was used as the secondary-antibody (Ab2) label for the fabrication of the immunosensor. Amperometric response of the immunosensor for electrocatalytic reduction of hydrogen peroxide (H2O2) was recorded. Electrochemical impedance spectroscopy (EIS) proved that fabrication of the immunosensor was successful. The anti-CD146 primary antibody (Ab1) was immobilized on the rGO-TEPA modified GCE by a cross-linking reagent of glutaraldehyde (GA). With Ab1 immobilized onto the rGO-TEPA modified GCE and Ab2 linked with Au/Pd@TiO2, the immunosensor displayed a wide linear range (0.0050-20 ng mL(-1)), a low detection limit (1.6 pg mL(-1)), good reproducibility, good selectivity and acceptable stability. The designed sensing strategy may provide a potential application in the detection of other tumor markers.

A sandwich-type immunosensor was developed for the detection of human tissue polypeptide antigen (hTPA). In this work, a graphene sheet (GS) was synthesized to modify the surface of a glassy carbon electrode (GCE), and Pd-Pt bimetallic nanocrystals were used as secondary-antibody (Ab2) labels for the fabrication of the immunosensor. The amperometric response of the immunosensor for catalyzing hydrogen peroxide (H2O2) was recorded. And electrochemical impedance spectroscopy was used to characterize the fabrication process of the immunosensor. The anti-human tissue polypeptide antigen primary antibody (Ab1) was immobilized onto the GS modified GCE via cross-linking with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide (EDC/NHS). With Ab1 immobilized onto the GS modified GCE and Ab2 linked on Pd-Pt bimetallic nanocrystals, the immunosensor demonstrated a wide linear range (0.0050-15 ng ml(-1)), a low detection limit (1.2 pg ml(-1)), good reproducibility, good selectivity and acceptable stability. This design strategy may provide many potential applications in the detection of other cancer biomarkers.