Ternary BiOI/Bi2S3/Au Nanosheet Arrays as a Photoelectrochemical Signal Converter for the Detection of Cardiac Troponin I.

Nanosheet arrays with stable signal output have become promising photoactive materials for photoelectrochemical (PEC) immunosensors. However, an essential concern is the facile recombination of carriers in one-component nanoarrays, which cannot be readily prevented, ultimately resulting in weak photocurrent signals. In this study, an immunosensor using gold nanoparticle-anchored BiOI/Bi2S3 nanosheet arrays (BiOI/Bi2S3/Au) as a signal converter was fabricated for sensitive detection of cardiac troponin I (cTnI). The ternary nanosheet arrays were prepared by a simple method in which Bi2S3 was well-coated on the BiOI surface by in situ growth, whereas the addition of Au further improved the photoelectric conversion efficiency and could link more antibodies. The three-dimensional (3D) ordered sheet-like network array structure and BiOI/Bi2S3/Au ternary nanosheet arrays showed stable and high photoelectric signal output and no significant difference in signals across different batches under visible light excitation. The fabricated immunosensor has a sensitive response to the target detection marker cTnI in a wide linear range of 500 fg/mL to 50 ng/mL, and the detection limit was 32 fg/mL, demonstrating good stability and selectivity. This work not only shows the great application potential of ternary heterojunction arrays in the field of PEC immunosensors but also provides a useful exploration for improving the stability of immunosensors.

Design of a Double-Photoelectrode Sensing System with a Metal-Organic Framework-Based Antenna-like Strategy for Highly Sensitive Detection of PD-L1.

Currently, the construction of heterojunctions as a method to enhance photoelectrochemical (PEC) activity has shown prospective applications in the analytical field. Restricted by carrier separation at the interface, developing a heterojunction sensing platform with high sensitivity remains challenging. Here, a double-photoelectrode PEC sensing platform was fabricated based on an antenna-like strategy by integrating MIL-68(In)-NH2, a p-type metal-organic framework (MOF) photocatalyst, as a photocathode with the type-II heterojunction of CdSe/MgIn2S4 as a photoanode synchronously. According to the ligand-to-metal charge transition (LMCT), the photo-generated carriers of MIL-68(In)-NH2 transferred from the organic ligand to the metal cluster, which provides an efficient antenna-like transfer path for the charge at the heterojunction interface. In addition, the sufficient Fermi energy difference between the double photoelectrode provides the continuous internal driving force required for rapid carrier separation at the anode detection interface, significantly improving the photoelectric conversion efficiency. Hence, compared with the traditional heterojunction single electrode, the photocurrent response of the double-photoelectrode PEC sensing platform developed using the antenna-like strategy is 2.5 times stronger. Based on this strategy, we constructed a PEC biosensor for the detection of programed death-ligand 1 (PD-L1). The elaborated PD-L1 biosensor exhibited sensitive and precise detection capability with a detection range of 1 × 10-5 to 1 × 103 ng/mL and a lower detection limit of 3.26 × 10-6 ng/mL and demonstrated the feasibility of serum sample detection, providing a novel and viable approach for the unmet clinical need of PD-L1 quantification. More importantly, the charge separation mechanism at the heterojunction interface proposed in this study provides new creative inspiration for designing sensors with high-sensitivity PEC performance.

Magnetic-controlled capsule endoscopy performance in aging patients.

BACKGROUND: The increasing elderly population and wide use of magnetic capsule endoscopy (MCE) have led to more attention to elderly patients. AIM: The aim of this study was to assess the performance (including transit time, cleanliness score, positive findings and safety) of MCE in aging patients (≥ 60 years), especially patients over 80 years old. METHODS: Consecutive patients of ≥ 60 years undergoing MCE at our center from August 2017 to August 2022 were classified into the oldest (≥ 80 years) and the older (60-79 years) groups. Esophageal transit time (ETT), gastric examination time (GET), small bowel transit time (SITT), and the quality of gastric preparation were compared. Information on examination indications, subjective discomforts, adverse events, and MCE outcomes were compared. RESULTS: Of 293 enrolled patients, 128 patients were in the oldest group and 165 patients were in the older group. ETT and GET were longer in the oldest group, whereas SITT was slightly longer in the oldest patients. Visualization scores were significantly lower in the body and antrum in the oldest patients. The total visualization score was lower in the older group compared with the oldest group; however, the difference was not significant. Cleanliness scores at the fundus and antrum and total cleanliness scores were lower in the oldest patients compared with the older patients. Positive findings and ulcers and erosions in the small intestine were more common in the oldest group. One patient had nausea during the gastric examination. Capsule retention in the cecum occurred in one case. CONCLUSION: MCE was feasible and safe for aging patients. ETT and GET were markedly longer and gastric cleanliness and visualization were worse, while overall small intestine-positive findings were higher in the oldest patients compared with the older patients.

A ZnIn2S4/Ag2CO3 Z-scheme heterostructure-based photoelectrochemical biosensor for neuron-specific enolase.

An efficient photo-to-electrical signal is pivotal to photoelectrochemical (PEC) biosensors. In our work, a novel PEC biosensor was fabricated for the detection of neuron-specific enolase (NSE) based on a ZnIn2S4/Ag2CO3 Z-scheme heterostructure. Due to the overlapping band potentials of the ZnIn2S4 and Ag2CO3, the formed Z-scheme heterostructure can promote the charge separation and photoelectric conversion efficiency. And the concomitant Ag nanoparticles in Ag2CO3 provided multiple functions to enhance the PEC response of the Z-scheme heterostructure. It acts not only as a bridge for the transfer of carriers between ZnIn2S4 and Ag2CO3, promoting the constructed Z-scheme heterostructure, but also as electron mediators to accelerate the transfer of photogenerated carriers and improve the capture of visible light of the Z-scheme heterostructure by surface plasmon resonance (SPR). Compared with single Ag2CO3 and ZnIn2S4, the photocurrent of the designed Z-scheme heterostructure increased more than 20 and 60 times respectively. The fabricated PEC biosensor based on a ZnIn2S4/Ag2CO3 Z-scheme heterostructure exhibits sensitive detection to NSE, and presents a linear range of 50 fg·mL-1 ~ 200 ng·mL-1 with a limit of detection of 4.86 fg·mL-1. The proposed PEC biosensor provides a potential approach for clinical diagnosis.

Sandwich-type electrochemical immunosensor based on CuFe2O4-Pd for cardiac troponin I detection.

A sandwich-type electrochemical immunosensor was designed by highly efficient catalytic cycle amplification strategy of CuFe2O4-Pd for sensitive detection of cardiac troponin I. CuFe2O4 with coupled variable valence metal elements exhibited favorable catalytic performance through bidirectional cycling of Fe2+/Fe3+ and Cu+/Cu2+ redox pairs. More importantly, Cu+ acted as the intermediate product of the catalytic reaction, promoted the regeneration of Fe2+ and ensured the continuous recycling occurrence of the double redox pairs, and significantly amplified the current signal response. Pd nanoparticles (Pd NPs) loaded on the surface of amino-functionalized CuFe2O4 (CuFe2O4-NH2) served as electrochemical mediators to capture labeled antibodies (Ab2), and also as co-catalysts of CuFe2O4 to further enhance the catalytic efficiency, thus improving the sensitivity of the electrochemical immunosensor. Under the optimal experimental conditions, the linear range was 0.001 ~ 100 ng/mL, and the detection limit was 1.91 fg/mL. The electrochemical immunosensor has excellent analytical performance, giving a new impetus for the sensitive detection of cTnI.

Mixed-Ligand-Regulated Self-Enhanced Luminous Eu-MOF as an ECL Signal Probe for an Oriented Antibody-Decorated Biosensing Platform.

The self-luminescence behavior of lanthanide MOFs (Ln-MOFs) due to the unique antenna effect is considered to be a promising electrochemiluminescence (ECL) emission for biosensors. It is more challenging for Ln-MOFs on account of the difficulty to stimulate Ln ions with the desired energy-transfer efficiency to produce stronger ECL emissions at a low potential. Here, guided by a second ligand-assisted energy-transfer strategy, we present an efficient self-enhanced luminescence mixed-ligand Eu-MOF as an ECL signal probe for an oriented antibody-decorated biosensing platform with a low detection limit and a broad detection range. Diamino terephthalic acid (NH2-H2BDC) and 1,10-phenanthroline (Phen) were selected as the first and second ligands, respectively, to form highly conjugated structures, as well as suppress the nonradiative energy transfer. Impressively, Phen precisely adjusts the energy gap between the triplet ligand and the excited state of Eu3+, realizing the self-enhancement of ECL efficiency of the Eu-MOF. The mixed ligand adjusted the molar ratio to obtain the stable and strong ECL signal at a lowered triggering potential (0.83 V). In addition, FeCo@CNT features densely active FeCo sites along with a rich hierarchy conductive carbon nanotube (CNT) network, which is efficiently a co-reaction accelerator to produce more TPA•+ radicals to accelerate the reduction process of the Eu-MOF for achieving the ECL emission amplification. FeCo@CNT with heptapeptide HWRGWVC (HWR) constructed a matrix biosensing interface that allowed the fragment antigen-binding (Fab) regions to target specific antigens and enhance the incubation efficiency. The present study has gone some way toward designing a self-enhanced luminous Eu-MOF, thus giving new fresh impetus to develop high-performance ECL emitters for biological analysis.

Sandwich-type electrochemical immunosensor based on nitrogen-doped porous carbon and nanoporous trimetallic nanozyme (PdAgCu) for determination of prostate specific antigen.

A sandwich-type electrochemical immunosensor was designed for the ultrasensitive detection of prostate-specific antigen (PSA), using Au nanoparticles (Au NPs) modified nitrogen-doped porous carbon (NPC) as sensor platform and trimetallic PdAgCu mesoporous nanospheres (PdAgCu MNSs) as enzyme-mimicking labels. NPC was prepared by a facile one-step pyrolysis strategy of biomimetic phylloid zeolite imidazole framework (ZIF-L) nanosheets. Through this strategy, the graphitization of the microcrystalline structure enhanced the electrical conductivity, while its enlarged specific surface area and abundant pore volume can enrich H2O2 to improve the catalytic efficiency. Moreover, Au NPs were used to modify NPC without cross-linking agents to further optimize electron transport while capturing primary antibodies, improving stability and sensitivity of the immunosensor. PdAgCu MNSs with uniform size, cylindrical open mesoporous channels, and continuous crystal frame structure were self-assembling synthesized by electrostatic adsorption and ascorbic acid (AA) co-reduction with amphiphilic dioctadecyldimethylammonium chloride (DODAC) as surfactant-cum-micelle, whose unique structure maximizes the use of polyatoms to expose catalytic sites, exhibiting good biocompatibility and electrocatalytic ability. Under the optimal conditions, the immunosensor showed superior sensitivity, a wide dynamic detection range (10 fg mL-1 ~ 100 ng mL-1) and a low limit of detection (LOD, 3.29 fg mL-1). This work provides a convenient strategy for the clinical detection of PSA.

Simultaneous electrochemical determination of two hepatitis B antigens using graphene-SnO2 hybridized with sea urchin-like bimetallic nanoparticles.

The hepatitis B virus (HBV) can cause chronic hepatitis and hepatocellular carcinoma. Hepatitis B surface antigen (HBs-Ag) and Hepatitis B e-antigen (HBe-Ag) are key markers for the diagnosis of HBV. In this study, electrodeposited gold was used as a sensing platform. Three-dimensional (3D) SnO2-loaded graphene sheets functionalized by Thionine (Thi) and ferrocene (Fc) and hybridized by sea urchin-like bimetallic nanoparticles (GS-SnO2-BMNPs) were used as redox probes for labeling antibodies to fabricate sandwich-type immunosensors for the simultaneous determination of HBs-Ag and HBe-Ag. The bimetallic nanoparticles, gold hybrid platinum nanoparticles (Au@Pt) and L-cysteine-connected gold-silver nanoparticles (Ag-cys-Au), have large electroactive surface areas. They were prepared by an efficient and economical method. Additionally, the sea urchin morphology accelerates spatial utilization, thus increasing the number of combination sites. Therefore, the immune probe can load a mass of signal source molecules (Thi and Fc). Furthermore, GS-SnO2-BMNPs (GS-SnO2-Au@Pt and GS-SnO2-Ag-cys-Au) with excellent electrical conductivity and bimetallic synergy can enhance the square wave voltammetry (SWV) signal. SWV was used to record the electrochemical signal by scanning the potential from - 0.6 to 0.6 V (vs. SCE). The signal peaks resulted from the reduction reaction of Thi and Fc, and two signal peaks were completely separate. The peak position and current intensity reflect the identity and level of the corresponding antigens. Therefore, the simultaneous detection of two viral biomarkers was achieved by the proposed immunosensor. The fabricated immunosensor showed a linear concentration range for HBs-Ag (0.01-100 ng·mL-1) and HBe-Ag (0.01-100 ng·mL-1), with detection limits for HBs-Ag and HBe-Ag of  4.67 pg·mL-1 and 4.68 pg·mL-1, respectively.  The RSD of HBs-Ag ranged between 2.0 and 4.4%and the recovery was in the range 98.7 to 99.4%. For  HBe-Ag the RSD  was between 2.6 and 3.3% andrecoveries  in the range 99.2 to 100.5% were obtained.

A photoelectrochemical immunosensor based on CdS/CdTe-cosensitized SnO2 as a platform for the ultrasensitive detection of amyloid ß-protein.

An ultrasensitive label-free photoelectrochemical (PEC) immunosensor was developed to detect amyloid ß-protein (Aß) 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 Aß antibody to further construct the immunosensor. Under optimal conditions, the as-constructed PEC immunosensor was used to detect Aß 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 Aß or other biomarkers.

A voltammetric immunoassay for the carcinoembryonic antigen using a self-assembled magnetic nanocomposite.

The authors describe a voltammetric immunoassay for the carcinoembryonic antigen (CEA). It is based on the use of a self-assembled magnetic nanocomposite as multifunctional signal amplification platform. The core of the nanocomposite consists of Fe3O4 microspheres, and the shell of zirconium hexacyanoferrate loaded with gold nanoparticles (AuNPs@ZrHCF@Fe3O4). The material was synthesized by an electrostatic self-assembly process which is caused by the strong interaction between cyano groups and AuNPs. The surface of the Fe3O4 microspheres was functionalized with amino groups to facilitate the immobilization of ZrHCF which acts as an electron mediator. The nanocomposite was placed on a glassy carbon electrode which then displays noteworthy electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2). The AuNPs serve as a support for the immobilization of antibodies by the interaction between AuNPs and amino groups on antibodies to construct a covalent Au-N bond. This facilitates electron transfer on the electrode surface using H2O2 as the electrochemical probe. Square wave voltammetry (measured typically at +0.2 V vs. SCE) was carried out to record the electrochemical behavior. Under the optimal conditions, a response is linear in the 0.5 pg·mL-1 to 50 ng·mL-1 CEA concentration range, and the detection limit is as low as 0.15 pg·mL-1 (S/N = 3). The method is selective, highly stable and acceptably reproducible. Graphical abstract A self-assembly magnetic nanocomposite for voltammetric immunoassay of CEA. GCE glassy carbon electrode; Au NPs gold nanoparticles; ZrHCF zirconium hexacyanoferrate; CEA carcinoembryonic antigen; Anti-CEA CEA antibody; BSA bovine serum albumin; SWV square wave voltammetry. A high sensitive voltammetric immunoassay method has been used for detecting CEA, It is based on a self-assembled magnetic nanocomposite (Au NPs@ZrHCF@Fe3O4) as multifunctional signal amplification platform.

Upregulation of ASAP3 contributes to colorectal carcinogenesis and indicates poor survival outcome.

The function and clinical implication of ArfGAP with SH3 domain, ankyrin repeat, and PH domain 3 (ASAP3) in colorectal cancer (CRC) remains undefined. In the present study, we showed that the expression level of ASAP3 was dramatically increased in CRC and its upregulation was associated with American Joint Committee on Cancer stage (P < 0.001) and poor prognosis (P = 0.0022). The combination of stage and ASAP3 expression improved the prediction of survival in CRC patients. Suppression of ASAP3 inhibited cell proliferation by inducing G1 phase arrest without influencing apoptosis. ASAP3 promoted growth of colon tumors in mice with colitis, and accelerated cell invasion and migration in vitro. Increased ASAP3 was associated with activation of the nuclear factor-κB (NF-κB) canonical pathway in CRC. Upregulation of ASAP3 increased the phosphorylation and nuclear translocation of the p65 NF-κB subunit. Mechanistically, ASAP3 interacts with NF-κB essential modulator (NEMO) and could reduce the polyubiquitinylation of NEMO. Overall, ASAP3 might regulate NF-κB via binding to NEMO. ASAP3 acts as an oncogene in colonic cancer and could be a potential biomarker of colon carcinogenesis.

Electrochemiluminescence assay of Cu2+ by using one-step electrodeposition synthesized CdS/ZnS quantum dots.

A sensitive and selective method was proposed to detect Cu2+ based on the electrochemiluminescence quenching of CdS/ZnS quantum dots (QDs). Herein, CdS/ZnS QDs were one-step electrodeposited directly on a gold electrode from an electrolyte (containing Cd(NO3)2, Zn(NO3)2, EDTA and Na2S2O3) by cycling the potential from 0 to -1.8 V. The prepared CdS/ZnS QDs exhibited excellent solubility and strong and stable cathodic ECL activity. Meanwhile, Nafion was used to immobilize CdS/ZnS QDs. The quenching effect of Cu2+ on the cathodic ECL of CdS/ZnS QDs was found to be selective and concentration dependent. The linear range for Cu2+ detection was from 2.5 nM to 200 nM with a detection limit of 0.95 nM. Furthermore, the designed method for the detection of Cu2+ can provide a reference for the detection of other heavy metal ions.

An ultrasensitive electrochemical immunosensor for the detection of prostate-specific antigen based on conductivity nanocomposite with halloysite nanotubes.

A sensitive label-free amperometric electrochemical immunosensor for detection of prostate-specific antigen (PSA) was proposed in this work. The nanocomposite of halloysite nanotubes with polypyrrole shell and palladium nanoparticles (HNTs@PPy-Pd) was used as a novel signal label. The HNTs with adequate hydroxyl groups are economically available raw materials. PPy, as an electrically conducting polymer material, can be absorbed to the surface of HNTs by in situ oxidative polymerization of the pyrrole monomer and form a shell on the HNTs. The shell of PPy could not only improve the conductivity of the nanocomposite but also absorb large amounts of Pd nanoparticles (NPs). The Pd NPs with high electrocatalytic activity toward the reduction of H2O2 and the HNTs@PPy-Pd nanocomposite as the analytical signal label could improve the sensitivity of the immunosensor. Under optimal conditions, the immunosensor showed a low detection limit (0.03 pg/mL) and a wide linear range (0.0001 to 25 ng/mL) of PSA. Moreover, its merits such as good selectivity, acceptable reproducibility, and stability indicate that the fabricated immunosensor has a promising application potential in clinical diagnosis. Graphical Abstract A new label-free amperometric electrochemical immunosensor based on HNTs@PPy-Pd nanocomposite for quantitative detection of PSA.

A sensitive electrochemical immunosensor based on high-efficiency catalytic cycle amplification strategy for detection of cardiac troponin I.

An electrochemical immunosensor based on the novel high efficiency catalytic cycle amplification strategy for the sensitive detection of cardiac troponin I (cTnI). With its variable valence metal elements and spiny yolk structure, the Cu2O/CuO@CeO2 nanohybrid exhibits high speed charge mobility and exceptional electrochemical performance. Notably, fluorite-like cubic crystal CeO2 shell would undergo redox reaction with Cu2O core, which successfully ensures the continuous recycling occurrence of "fresh" Cu (II)/Cu (I) and Ce (Ⅳ)/Ce (Ⅲ) pairs at the electrode interface. The "fresh" active sites continue to emerge constantly, resulting in a significant increase in the current signal. In light of the electrochemical characterization, the electron transfer pathway and catalytic cycle mechanism among CeO2, Cu2O and CuO were further discussed. The developed electrochemical immunosensor detected cTnI from 100 fg/mL to 100 ng/mL with a LOD of 15.85 fg/mL under optimal conditions. The analysis results indicate that the immunosensor would hold promise for broad application prospects in the biological detection for other biomarkers.

An electrochemiluminescence sensor based on lanthanide bimetallic MOFs with a "cascade sensitization mechanism" for the sensitive detection of CA242.

Lanthanide metal-organic frameworks (Ln-MOFs) broaden the optical sensing applications of lanthanide ions due to the antenna effect between organic ligands and metals. However, the sensitization ability of the ligand to metal ions is limited, and maximizing the sensitization of the electrochemiluminescence behavior of Eu3+ is still a challenge for the application of Ln-MOFs. Therefore, under the guidance of the "cascade sensitization mechanism" based on the antenna effect sensitizing the electrochemiluminescence of bimetallic Ln-MOFs, we proposed Eu/Tb-MOFs with high luminescence intensity as a signal probe. According to the antenna effect, the conjugated structure and high extinction coefficient of the benzene ring of 2-amino terephthalic acid (NH2-BDC) can enhance the ECL luminescence intensity of Eu/Tb-MOFs. Tb3+ can act as an energy bridge between NH2-BDC and Eu3+, buffering the energy gap. The bimetallic sensitization is formed between Tb3+ and Eu3+, which can inhibit the reverse internal flow of energy and ensure the high luminous efficiency of Eu3+. In addition, the nanosphere mixed valence Fe3O4 as a co-reactant accelerator promotes the formation of transient free radical SO4•- through the valence change of Fe2+/Fe3+. The ECL immunosensor constructed by luminophores Eu/Tb-MOFs and nanosphere Fe3O4 provided a new explanation for the ECL self-luminous of Eu/Tb-MOFs.

An ultrasensitive electrochemical immunosensor based on meso-PdN NCs and Au NPs/N-CNTs for quantitative cTnI detection.

Electrochemical immunosensors have gained considerable attention in detecting human disease markers due to their excellent specificity, high sensitivity, and facile operation. Herein, a rational-designed sandwich-type electrochemical immunosensor is constructed for the sensitive detection of cardiac troponin I (cTnI) using nitrogen-doped carbon nanotubes loaded with gold nanoparticles (Au NPs/N-CNTs) as substrate and highly active mesoporous palladium-nitrogen nanocubes (meso-PdN NCs) as secondary antibody markers. Benefitting from its large specific surface area (638.04 m2 g-1) and high nitrogen content, novel polydopamine (PDA)/ halloysite nanotubes (HNTs) hybrid derived one-dimensional (1D) N-CNTs can provide more binding sites for the in-situ growth of Au NPs to connect Ab1. Furthermore, as an ideal substrate material, Au NPs/N-CNTs exhibit finely tuned mesoporous structures and outstanding conductivity, which facilitate the mass and electron transfer during the electrocatalysis process. Besides, highly concave surfaces and crystalline mesopores of meso-PdN NCs expose more surfaces and crevices, providing abundant reactive sites for H2O2 reduction. Remarkably, the as-obtained immunosensor presented a wide linear range (from 10 fg mL-1 to 100 ng mL-1) and an excellent low detection limit (9.85 fg mL-1). This study may offer new insights into the precise fabrication of efficient electrochemical immunosensors for various clinical diagnosis applications.

A photoelectrochemical sensor based on In2S3/AgInS2 in situ Z-type heterojunction with "photo-modulated interface charge" for sensitive detection of Programmed Death-Ligand 1.

The construction of heterostructure photoelectrodes can enhance the performance of photoelectrochemical (PEC) sensors. However, it is still a critical challenge to achieve efficient transfer of interface carriers. In this paper, we propose a strategy of "photo-modulated interface charge" to design a PEC sensor based on a hollow hexagonal tubular In2S3/AgInS2 in situ Z-type heterojunction for the susceptible detection of Programmed Death-ligand 1 (PD-L1). The hollow structured In2S3/AgInS2 is ingeniously synthesized employing indium-sourced MIL-68 as a sacrificial template and in situ cation exchange technique. This composite material has close contact interfaces due to in situ growth, which facilitates the spontaneous establishment of a robust and stable built-in electric field between the interfaces. Moreover, the inner cavity structure promotes multiple light refractions and scatterings, significantly enhancing light trapping capability. Under the influence of both light irradiation and electric field force, the migration direction of the interfacial charge is reversed, forming a Z-transfer path, which effectively delays the compounding of the electron-hole pairs (e-/h+) and further improves the sensitivity of the sensor. The minimum detection threshold of the PEC sensor is 26.58 fg/mL, and the feasibility of real samples is investigated, providing new insights for early diagnosis and prognostic treatment of diseases.

An enzymatic activity regulation-based clusterzyme sensor array for high-throughput identification of heavy metal ions.

The accurate identification and sensitive quantification of heavy metal ions are of great significance, considering that pose a serious threat to environment and human health. Most array-based sensing platforms, to date, utilize nanozymes as sensing elements, but few studies have explored the application of the peroxidase-like activity of clusterzymes in identification of multiple analytes. Herein, for the first time, we developed a clusterzyme sensor array utilizing gold nanoclusters (AuNCs) as sensing elements for five heavy metal ions identification including Hg2+, Pb2+, Cu2+, Cd2+ and Co2+. The heavy metal ions can differentially regulate the peroxidase-like activity of AuNCs, and that can be converted into colorimetric signals with 3,3',5,5'-tetramethylbenzidine (TMB) as the chromogenic substrate. Subsequently, the generated composite responses can be interpreted by combining pattern recognition algorithms. The developed clusterzyme sensor array can identify five heavy metal ions at concentrations as low as 0.5 µM and their multi-component mixtures. Especially, we demonstrated the successful identification of multiple heavy metal ions in tap water and traditional Chinese medicine, with an accuracy of 100% in blind test. This study provided a simple and effective method for identification and quantification of heavy metal ions, rendering a promising technique for environmental monitoring and drug safety assurance.

Triple signal-enhancing sandwich-type electrochemical immunosensor based on Au@SNHC and PtPdCu/BNC for detection of Cardiac Troponin I.

A novel multiple amplification strategy for electrochemical immunoassay was developed elaborately. The realization of this strategy is based on the high efficiency catalysis of boron nitrogen double-doped carbon loaded trimetallic PtPdCu mulberry-like nanospheres (PtPdCu/BNC) and the satisfactory conductivity of gold nanoparticles modified with sulfur nitrogen co-doped hollow porous carbon (Au@SNHC). Single crystal anisotropic Pt octahedral seeds were synthesized with sodium citrate as shape-directing agent, and then three metals were grown in situ to prepare the trimetallic PtPdCu mulberry nanospheres, which had excellent utilization of atoms and a significant number of catalytic active centers. Boron nitrogen double-doped carbon (BNC) with abundant free electrons and high electron density micro-mesoporous can be used as the supported dispersion material of PtPdCu MBNSs, further catalytically enrich H2O2. Moreover, the etching vulcanization of small ZIF template and the co-doping of sulfur and nitrogen endow sulfur nitrogen co-doped hollow porous carbon (SNHC) with shorter the diffusion distance of charge carrier and lower mass transfer resistance. Under optimal conditions, the developed immunosensor exhibits good sensing performance with a detection limit of 4.27 fg⋅mL-1, and the wide linear dynamic range (10 fg⋅mL-1-100 ng⋅mL-1). This study provides a possible strategy for early diagnosis and postoperative monitoring of AMI.