Efficient CdIn2S4/MgIn2S4 heterojunction for ultrasensitive detection of lung cancer marker neuron-specific enolase.

In this work, a photoelectrochemical (PEC) immunosensor was constructed for the ultrasensitive detection of lung cancer marker neuron-specific enolase (NSE) based on a microflower-like heterojunction of cadmium indium sulfide and magnesium indium sulfide (CdIn2S4/MgIn2S4, CMIS) as photoactive material. Specifically, the well-matched energy level structure and narrow energy level gradients between CdIn2S4 and MgIn2S4 could accelerate the separation of electron-hole (e--h+) pairs in the CMIS heterojunction to enhance the photocurrent of CMIS, which was increased 5.5 and 80 times compared with that of single CdIn2S4 and MgIn2S4, respectively. Meanwhile, using CMIS as photoactive material, increasing the biocompatibility by dropping Pt NPs on the surface of CMIS to immobilize the antibody through Pt-N bond. Fe3O4-Ab2, acting as the quencher, competitively consumes electron donors and absorbs light, leading to photocurrent quenching. With the increasing of quencher, the photocurrent decreased. Hence, the developed "signal-off" PEC immunosensor realized the trace detection of NSE within the range from 1.0 fg/mL to 10 ng/mL with a low detection limit of 0.34 fg/mL. This strategy provided a new perspective for establishing ternary metal sulfide heterojunction to construct PEC immunosensor for sensitive detection of disease biomarkers.

High-performance assaying cardiac troponin I using Bi-doped tin-based heterojunction in photoelectrochemical biosensing with the quencher of yolk-shell nanostructure.

Cardiac troponin I (cTnI), a protein regulating myocardial contraction, stands the premier biomarker for diagnosing acute myocardial infarction and stratifying heart disease risk. Photoelectrochemical (PEC) biosensing combines traditional PEC analysis with high bioconjugation specificity, rendering a prospective avenue for disease biomarker analysis. However, the performance of sensors often falls short due to inadequate photoelectric materials. Hence, designing heterojunctions with proper band alignment, effective transport and separation of photogenerated carriers is highly expected for PEC sensors. Meanwhile, doping as a synergistic strategy to tune the energy band edges and improve carrier transport in heterojunctions, can also enhance the sensing performance. In this work, bismuth-doped tin oxide and tin disulfide heterojunction (Bi-SnOS) was prepared via a simple one-step hydrothermal method and utilized as a highly sensitive platform. Integrating copper sulfide-coated nano-gold (Au@CuS), a yolk-shell shaped nanocomposites, as the double quenching probe, an excellent PEC biosensor was fabricated to assay cTnI via sandwich immunorecognition. Under optimal conditions, the proposed biosensor displayed a high-performance for cTnI in the range from 0.1 pg/mL to 5.0 ng/mL with a low detection limit (44.7 fg/mL, 3σ). The strong photocurrent response, high stability and suitable selectivity point out that the synergistic effect between heterojunction and doping provides a promising prospect for the design of new PEC materials.

Dual-Ligand Ruthenium Coordination Polymer-Derived Self-Enhanced Electrochemiluminescent Emitters for Sensitive Detection of Procalcitonin.

Ru-based electrochemiluminescence (ECL) coordination polymers are widely employed for bioanalysis and medical diagnosis. However, commonly used Ru-based coordination polymers face the limitation of low efficiency due to the long distance between the ECL reagent and the coreactant dispersed in detecting solution. Herein, we report a dual-ligand self-enhanced ECL coordination polymer, composed of tris(4,4'-dicarboxylic acid-2,2'-bipyridyl) ruthenium(II) dichloride (Ru(dcbpy)32+) as ECL reactant ligand and ethylenediamine (EDA) as corresponding coreactant ligand into Zn2+ metal node, termed Zn-Ru-EDA. Zn-Ru-EDA shows excellent ECL performance which is attributed to the effective intramolecular electron transport between the two ligands. Furthermore, the dual-ligand polymer allows an anodic low excitation potential (+1.09 V) luminescence. The shift in the energy level of the highest occupied molecular orbital (HOMO) upward after the synthesis of the Zn-Ru-EDA has resulted in a reduced excitation potential. The low excitation potential reduced biomolecular damage and the destruction of the modified electrodes. The ECL biosensor has been constructed using Zn-Ru-EDA with high ECL efficiency for the ultrasensitive detection of a bacterial infection and sepsis biomarker, procalcitonin (PCT), in the range from 1.00 × 10-6 to 1.00 × 10 ng·mL-1 with outstanding selectivity, and the detection limit was as low as 0.47 fg·mL-1. Collectively, the dual-ligand-based self-enhanced polymer may provide an ideal strategy for high ECL efficiency improvement as well as designing new self-enhanced multiple-ligand-based coordination in sensitive biomolecular detection for early disease diagnostics.

Dual-sensitized heterojunction Ag2S/ZnS/NiS composites with entire visible-light region absorption for ultrasensitive photoelectrochemical detection of tobramycin.

In this study, an ultrasensitive photoelectrochemical (PEC) aptasensor based on dual-sensitized heterojunction Ag2S/ZnS/NiS composites as a signal probe was proposed for the detection of tobramycin (TOB) by combining a cascaded quadratic signal amplification strategy. Specifically, compared to the limited visible light-harvesting capability of single sensitized composites, Ag2S/ZnS/NiS composites with p-n and n-n heterojunction could greatly improve the light energy utilization to tremendously strengthen the optical absorption in the entire visible-light region. Moreover, dual-sensitized heterojunction could effectively hinder the rapid recombination of photoelectrons and holes (carriers) to obtain a good photocurrent for improving the sensitivity of the aptasensor. Furthermore, a cascaded quadratic signal amplification strategy was applied to convert trace target TOB into plentiful gold nanoclusters (Au NCs) labelled double-stranded DNA for the construction of PEC aptasensor, with a broad linear detection range from 0.01 to 100 ng mL-1 and a low detection limit of 3.38 pg mL-1. Importantly, this study provided a versatile and sensitive PEC biosensing platform for TOB analysis, and demonstrated its successful application for TOB detection in milk samples. This protocol provides a novel dual-sensitized heterojunction composites to develop a highly efficient and harmfulless PEC aptasensor, which is expected to be used in food safety, environmental monitoring and other areas.

Ultrasensitive MicroRNA Photoelectric Assay Based on a Mimosa-like CdS-NiS/Au Schottky Junction.

Seeking and constructing superior photoactive materials have the potential to improve the performance of photoelectrochemical (PEC) biosensors. In this work, we proposed a novel mimosa-like ternary inorganic composite with a significantly enhanced light-harvesting ability and photogenerated carrier separation rate. This ternary photoactive material was obtained via electrodeposition of gold nanoparticles (Au) on the surface of transition metal sulfide composite of CdS and NiS (CdS-NiS/Au). The experimental results showed that the high initial photocurrent was acquired on CdS-NiS/Au (68-fold higher than that of individual CdS) with the synergistic effect of p-n heterojunction, Schottky junction, and the eminent optical properties of gold nanoparticles. Meanwhile, using silver nanoclusters prepared by link DNA protection as an effective quencher, integrating the duplex-specific nuclease-assisted rolling circle amplification strategy, a "Signal ON" PEC biosensor was fabricated for the detection of microRNA 21 (miRNA 21). With the release of the quencher, the recovered photocurrent is able to achieve determination of miRNA 21 within the range from 10 aM to 1 pM with a detection limit down to 4.6 aM (3σ). Importantly, this work not only provides a superb idea for designing ternary inorganic heteromaterials with exceptional photoactive ability but also allows the detection of other biomarkers by selecting appropriate recognition units.

Novel electrochemiluminescence luminophore based on flower-like binuclear coordination polymer for high-sensitivity detection of tetracycline in food products.

To meet the growing concerns about food safety, sensors for tetracycline antibiotics have been urgently needed. Herein, we synthesized a series of binuclear coordination polymers (Tb-Zn-CPs) based on lanthanide and transition metal ions by solvothermal method using [1,1':4',1''-terphenyl]-3,3'',5,5''-tetracarboxylic acid, Tb(NO3)3 and Zn(NO3)2. The morphologies and electrochemiluminescence (ECL) performances of Tb-Zn-CPs varied with different molar ratios of terbium and zinc ions (Tb:Zn). The flower-like Tb-Zn-CP (9:3) possessed the highest ECL intensity due to the ligand antenna effect and the sensitization of Zn2+. An ECL sensor for the detection of tetracycline (TC) was constructed utilizing Tb-Zn-CP (9:3) as a novel ECL luminophore and potassium persulfate as a coreactant. The proposed sensor achieved sensitive detection of TC in the range of 5.0 fmol·L-1 to 3.0 mmol·L-1 with a low limit of detection (1.6 fmol·L-1). It also was applied for TC detection in dairy products with good recovery rates.

Schottky-functionalized Z-scheme heterojunction: Improved photoelectric conversion efficiency and immunosensing.

Designing photovoltaic materials with good photoelectric activity is the crucial to boost the sensitivity of photoelectrochemical (PEC) biosensors. To meet this concern, a Schottky-functionalized direct Z-scheme heterojunction photovoltaic material was proposed by electrodeposition of gold nanoparticles on two kinds of bismuth oxyhalide composites surface (bismuth oxybromide and bismuth oxyiodide with different but matched band gaps) (depAu/BiOI/BiOBr). Specifically, synergistic effect was achieved through the direct Z-scheme heterojunction formed by BiOBr and BiOI as well as the gold Schottky junction, resulting in the enhanced light harvest and photoelectric conversion efficiency. Meanwhile, combined with sandwich immunotechnology, a "signal-off" PEC biosensor was fabricated for highly sensitive detection of carcinoembryonic antigen (CEA). In which, using depAu/BiOI/BiOBr modified glassy carbon electrodes both as the photoactive sensing interface and capture antibody loading matrix, polyethyleneimine copper complex encapsulated gold nanoclusters labeled detection antibody (Ab2-Au@PEI-Cu) as the quencher, the photocurrent decreased with the increasing target CEA introduced by sandwich immune reaction. The proposed smart PEC immunoassay platform exhibited a wide detection range (1.0 fg/mL-2.0 ng/mL) and a detection limit as low as 0.11 fg/mL with favorable selectivity and stability. In addition, this PEC sensing strategy can be easily extended for other tumor marker analysis, which offers a new perspective of using multiple bismuth oxyhalide as photoactive materials for early diseases diagnosis.

Highly Sensitive Photoelectrochemical Immunosensor Based on Organic Multielectron Donor Nanocomposite as Signal Probe.

Organic photoelectric materials with conjugated electron-rich structures and good biocompatibilities have broad application prospects in biosensors. Herein, we report a promising organic photoelectric multielectron donor nanocomposite for highly sensitive PEC immunoassays. Specifically, the organic multielectron donor nanocomposite (DA-ZnTCPP-g-C3N4) was prepared from dopamine (DA, polyphenol hydroxyl structure substance), zinc tetracarboxylate porphyrin (ZnTCPP, large p-π conjugated heterocyclic compound), and two-dimensional graphene-like nitrogen carbide (g-C3N4) via an amidation reaction. With a multielectron donor structure and photoelectricity, this nanocomposite can achieve sensitization by self-structure without the addition of an electron donor in the test solution. It was utilized to label the carcinoembryonic detection antibody as a immuno-probe (Ab2-DA-ZnTCPP-g-C3N4). Meanwhile, the glassy carbon electrode electrodeposited with gold nanoparticles anchoring the capture antibody was used as a PEC immunomatrix (Ab1/DpAu/GCE). The enhanced PEC current, "signal on", was confirmed by the immunosensor via sandwich immunorecognition of a carcinoembryonic antigen (CEA). Under optimal conditions, the as-prepared sensing platform displayed high sensitivity for CEA with a dynamic linear response range from 10 fg·mL-1 to 1 mg·mL-1 and a lower detection limit of 3.6 fg·mL-1. This organic nanocomposite showed good sensitivity and stability in an immunosensing system with a low background. This strategy affords a promising approach for biological applications of organic photoelectric materials.

Cluster-Dominated Electrochemiluminescence of Tertiary Amines in Polyethyleneimine Nanoparticles: Mechanism Insights and Sensing Application.

Designing and screening highly efficient and cost-effective luminophores have always been a challenge to develop sensitive electrochemiluminescence (ECL) biosensors. Herein, polyethyleneimine nanoparticles (PEI NPs), a kind of nonconjugated polymer (NCP) NPs with tertiary amine clusters, were developed as an ECL luminophore. Specifically, PEI NPs were synthesized by a one-step hydrothermal method using PEI and formaldehyde. The properties of PEI NPs were investigated in detail using photochemical and electrochemical techniques. The results showed cluster-dominated luminescence of tertiary amines in PEI NPs via "through-space conjugation". This non-negligible ECL performance (at 631 nm) was also verified by the initiated reduction-oxidation process. With persulfate as a coreactant, PEI NPs acted as both the luminophore and coreaction accelerator to enhance the ECL intensity remarkably, which was eightfold higher than that of isolated PEI. Moreover, choosing dopamine as the model target, a highly sensitive "signal off" ternary ECL sensor was constructed utilizing PEI NPs as the luminophore. Dopamine could be oxidized to benzoquinone at the sensing interface, quenching the signal via ECL energy transfer. Free from any signal amplification, the proposed sensor achieved a low detection limit (4.3 nM) for target monitoring with good selectivity and stability. This strategy not only provides a unique perspective for designing novel efficient and facile ECL luminophores of tertiary amines but also broadens the biological application of NCP NPs.

Self-enhanced photoelectrochemical sensor based on a Schottky heterostructure organic electron donor matrix.

A self-enhanced photoelectrochemical copper ions sensor was constructed using an organic electron donor matrix with a Schottky heterostructure prepared from dopamine and single walled carbon nanohorns. The determination of Cu2+ with no additional electron donor solution, with high sensitivity and low background, provides new inspiration for the development of photoelectric sensing.

Construction of self-enhanced photoelectrochemical platform for L-cysteine detection via electron donor-acceptor type coumarin 545 aggregates.

Self-enhanced electron donor-acceptor type coumarin 545 aggregates prepared via an anionic surfactant-assisted reprecipitation method provide an underlying approach for the photoelectrochemical detection of L-cysteine, which can be employed in aqueous solution without the addition of electron donors.

Novel optoelectronic metal organic framework material perylene tetracarboxylate magnesium: preparation and biosensing.

The pursuit for improving photoelectrochemical (PEC) performances of organic materials remains an urgent need. Here, we have proposed an envision of the preparation the metal-organic frameworks (MOFs) with arenes to realize high photo-to-current conversion efficiency and excellent PEC performances. Magnesium 3,4,9,10-perylene tetracarboxylic acid metal-organic frameworks (Mg-PTCA MOFs) were synthesized for the first time. The uniformly distributed and regular-shaped Mg-PTCA MOFs showed a much more stable and higher photocurrent than the single PTCA and its derivatives, which confirmed our hypothesis. A regenerated-biosensor was designed for microRNA analysis based on Mg-PTCA MOFs as a novel photoelectric material, target-triggered three-dimensional DNA Scaffold (3D-Sca) as an efficient signal amplifier, and gold nanoclusters (Au NCs) as quencher. The elaborately designed biosensor achieved ultrasensitive detection for miRNA 21 with a dynamic range from 10 aM to 10 pM and a detection limit of 2.8 aM. This biosensor showed good analytical performance in the extracts of different cancer cells, indicating the possibility for early diagnosis, timely staging assessment, and accurate prognostic judgment for diseases. The recommendable performances of Mg-PTCA MOFs highlight the significance of organic MOFs in PEC sensing.

Ultrasensitive dual-quenching electrochemiluminescence immunosensor for prostate specific antigen detection based on graphitic carbon nitride quantum dots as an emitter.

Early monitoring of prostate-specific antigen (PSA) is crucial in diagnosis and proactive treatment of prostate disease. Herein, a dual-quenching ternary ECL immunosensor was designed for PSA detection based on graphitic carbon nitride quantum dots (g-CNQDs, as an emitter), potassium persulfate (K2S2O8, as a coreactant), and silver nanoparticles doped multilayer Ti3C2 MXene hybrids (Ag@TCM, as a coreaction accelerator). First, Ag@TCM was immobilized on the surface of a glassy carbon electrode, then g-CNQDs was further adsorbed on Ag@TCM to acquire a higher initial ECL signal at a potential window from - 1.3 to 0.0 V (vs. Ag/AgCl). Ag@TCM not only acted as the coreaction accelerator, but also as a matrix to load enormous g-CNQDs and prostate-specific capture antibody via Ag-N bond. Meanwhile, prostate-specific detection antibody was marked by gold nanoparticles modified manganese dioxide as a dual-quenching probe (Ab2- Au@MnO2). When Ab2-Au@MnO2 was introduced into the ternary ECL system via sandwiched immuno-reaction, the high-sensitive detection of PSA was achieved by the dual-quenching effect, caused by the resonant energy transfer from g-CNQDs (energy donor) to Au@MnO2 (energy acceptor). As a result, this ECL immunosensor showed a good dynamic concentration range from 10 fg·mL-1 to 100 ng·mL-1 with a detection limit of 6.9 fg·mL-1 for PSA detection. The dual-quenching ECL strategy presented high stability and good specificity to open up a new pathway for ultrasensitive immunoassay.

Novel Enhanced Lanthanide Electrochemiluminescence Luminophores: Ce3+-Doped TbPO4 Facile Synthesis and Detection for Mucin1.

Despite the upsurging interest in electrochemiluminescence (ECL) of lanthanides, the research in this field is still in its infancy due to the low intensity. In this work, a series of Ce3+-doped terbium orthophosphates (TbPO4:Ce) in different proportions have been synthesized through the co-precipitation method at room temperature. Meanwhile, through the investigation of morphologies and ECL properties of these TbPO4:Ce, it is concluded that the ECL intensity reaches the maximum when the molar ratio of Tb/Ce is 9:1 and the material is nanorod-shaped. The ECL intensity of TbPO4:Ce is significantly improved by doping with Ce3+ due to the dual sensitization strategy of the antenna effect from PO43- to Tb3+ and the energy transfer from Ce3+ to Tb3+. Interestingly, doping with Ce3+ can not only adjust morphology of TbPO4:Ce but also improve the ECL intensity. In addition, to verify the application of TbPO4:Ce, two single mucin1 (MUC1) aptamers are linked together to form a dual MUC1 aptamer chain. Then, a simple and sensitive ECL biosensor is constructed for the detection of MUC1, which can recognize the double amount of MUC1 and quench the ECL signal. As expected, the proposed biosensor shows good stability and acceptable selectivity and achieves sensitive detection of MUC1 with a dynamic range from 1 fg·mL-1 to 10 ng·mL-1 and a limit of detection of 0.5 fg·mL-1. This work may pave a new avenue for the study of direct ECL emission of lanthanides and prove to be ideal for the research of new ECL luminophores in electrochemical analysis.

Gold Nanoparticles Photosensitization towards 3,4,9,10-Perylenetetracarboxylic Dianhydride Integrated with a Dual-Particle Three-Dimensional DNA Roller: A General "ON-OFF-ON" Photoelectric Plasmon-Enhanced Biosensor.

A high initial signal for the sensitive detection of analytes is critical in photoelectrochemical (PEC) biosensing systems. As a semiconductor, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) possesses an appropriate optical band gap of 2.5 eV and inherently intense and stable PEC response. When gold nanoparticles (Au NPs) are electrodeposited on the surface of PTCDA to form a Schottky junction (Au NPs/PTCDA), a surprising and satisfactory PEC performance is unfolded before our eyes. Considering the outstanding PEC behaviors of Au NPs/PTCDA and the great quenching effect of gold nanoclusters (Au NCs), the "ON-OFF-ON" PEC sensing platform has been developed for microRNA 1246 (miRNA 1246) detection combined with the cascaded quadratic amplification strategy of the polymerization/nicking reaction and dual-particle 3D DNA roller. The higher initial PEC signals of the system can be acquired by regulating the deposition time for 35 s (-0.2 V), which is derived from the synergetic effect of localized surface plasmon resonance of Au NPs and the formation of a Schottky junction. The dual-particle 3D DNA roller has been designed to guarantee wide walking space, remarkable operation performances, and inhibition of derailment. The proposed biosensor shows a dynamic range from 10 aM to 1 pM at a low detection limit of 3.1 aM and exhibits good analytical behaviors while analyzing miRNA 1246 in healthy human serum samples. This work not only expands the application of organic photoelectric materials in bioanalysis but also provides potential possibility of detecting other biomarkers by choosing appropriate target units.

An electron donor-acceptor organic photoactive composite with Schottky heterojunction induced photoelectrochemical immunoassay.

A signal enhancement photoelectrochemical (PEC) immunoassay system induced by the composite (PTCs@Au) of electron donor-acceptor with Schottky heterojunction was designed. Carcinoembryonic antigen (CEA) was selected as a model target. Initially, the capture anibody (Ab1) was linked to gold nanoparticles electrodeposited on glassy carbon electrode and sealed by bovine serum albumin. Meanwhile, the organic semiconductor (PTCs) with the structure of electron donor-acceptor was synthetized from perylene tetracarboxylic dianhydride (acceptor) and dopamine (donor) via amidation reaction. Then PTCs@Au composite with Schottky heterojunction was formed through gold nanoparticles in situ reduction and functionalization with PTCs. Next, the detection antibody was labeled by PTCs@Au composite (Ab2-PTCs@Au) as an immuno-probe. The PTCs@Au was introduced via sandwich immune reaction leading to enhancement PEC signal without additional electron donor nor acceptor for achieving quantitative detection of CEA under external light. The proposed immunoelectrode showed dynamic ranges of 0.5 fg mL-1 to 10 pg mL-1 and 10 pg mL-1 to 1 µg mL-1 with the detection limit of 0.17 fg mL-1. In addition, this PEC strategy with acceptable selectivity and stability can be potentially applied to detect other targets by choosing appropriate target recognition unit.

Functionalized europium-porphyrin coordination polymer: Rational design of high performance electrochemiluminescence emitter for mucin 1 sensing.

The excellent characteristics of porphyrins have inspired widespread interest in electrochemiluminescence (ECL). However, the limited ECL intensity and poor stability of porphyrins in aqueous solution are still severely restricted further biological application. Here, we subtly synthesized a functionalized europium and 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) coordination polymer (Eu-PCP) by a one-step solvothermal method. In sharp contrast to the pristine TCPP, Eu-PCP showed a higher and more stable ECL red-light emission (673 nm) at low potential (-1.1 V, vs Ag/AgCl), which was 7.7-fold higher ECL intensity and 4.6-fold efficiency. In view of the crucial role of mucin 1 (MUC1) in tumor overexpression, it was selected as the target molecule. Combined with exonuclease III (Exo III)-assisted recycling amplification strategy, a ternary ECL biosensor was constructed for the MUC1 detection based on Eu-PCP as a satisfied ECL emitter, gold nanoparticles capped CeO2 (CeO2@Au) as the coreactant accelerator and peroxydisulfate as coreactant. Meanwhile, gold nanoparticles capped MnO2 (MnO2@Au) was used as the quenching probe to achieve a highly sensitive detection of MUC1. The proposed biosensor exhibited a wide linear range from 1 fg mL-1 to 10 ng mL-1 with a low limit of detection (0.32 fg mL-1). By changing the corresponding target recognition DNA, this strategy could be expanded to detect other biomarkers.

Gut microbial metabolite TMAO portends prognosis in acute ischemic stroke.

BACKGROUND: Over the recent years, the role of trimethylamine N-oxide (TMAO) as a gut-derived metabolite mediating cardiovascular disease pathogenesis has been under particularly intense scrutiny. The aim was to explore whether TMAO levels were associated with clinical severity or functional outcome in Chinese patients with ischemic stroke. METHODS: This is a single-center, prospective cohort study from Xiamen, China. We examined the relationship between fasting TMAO and 2 of its nutrient precursors, choline and betaine, vs. 3-month functional outcome and mortality in 351 first-ever patients with acute ischemic stroke. RESULTS: The median value of the plasma level of TMAO was 6.1 µM (IQR, 3.7-9.9 µM), which was higher than in those control cases (4.0; 2.4-5.9 µM). Patients with a poor outcome and nonsurvivors had significantly increased TMAO levels on admission (P < 0.001). Following adjustments for traditional risk factors, increased TMAO concentrations remained predictive of both poor outcome and mortality risks in stroke patients [e.g., quartiles 4 vs 1, odd ratio 5.65 (95% CI, 2.87-13.45), P < 0.001; and 5.84 (95% CI, 3.05-16.12), P < 0.001, respectively]. In multivariate analysis, TMAO was an independent predictor of functional outcome and mortality and improved the prognostic accuracy of the NIHSS to predict functional outcome (combined areas under the curve, 0.82; 95% CI 0.77-0.89, P = 0.003) and mortality (combined areas under the curve, 0.85; 95% CI: 0.80-0.90, P = 0.002). CONCLUSIONS: Fasting plasma concentrations of gut microbial TMAO are higher in patients with ischemic stroke and portend higher poor functional outcome events and mortality.

Determination of ascorbic acid using electrochemiluminescence sensor based on nitrogen and sulfur doping graphene quantum dots with luminol as internal standard.

A novel internal standard electrochemiluminescence (ECL) sensor has been designed for the detection of ascorbic acid (AA). The adopted dual-emission luminophore (NSGQDs-PEI-luminol-Pt) is composed of nitrogen and sulfur double-doped graphene quantum dots (NSGQDs, as the main luminophore), luminol (as the auxiliary luminophore and internal standard), platinum nanoparticles (Pt NPs, as the co-reaction accelerator), and polyetherimide (PEI, as the linker of NSGQDs and luminol). The results suggest obviously enhanced  ECL intensities by the Förster resonance energy transfer (FRET) between luminol (donor) and NSGQDs (acceptor). In this sensing system, the cathodic ECL intensities of NSGQDs (ECL-1, -1.8 V vs. Ag/AgCl) gradually decrease with increasing concentration of AA, while the anodic ECL intensities of luminol (ECL-2, 0.3 V vs. Ag/AgCl) almost remain essentially constant at a potential window from -2.0 to 0.4 V. The natural logarithm of the ratio between ECL-1 and ECL-2 (ln I (ECL-1/ECL-2)) shows a good linear relationship with AA concentration ranging from 10 to 360 nM. The regression equation is ln I (ECL-1/ECL-2) = - 0.0059 cAA + 3.55 (R2 = 0.992) with a limit of detection of 3.3 nM. Such sensor has also been applied for monitoring AA in human serum. The recovery range was 96.5-105.3% and the relative standard deviation was  1.3-3.3%.

Efficient Curing Sacrificial Agent-Induced Dual-Heterojunction Photoelectrochemical System for Highly Sensitive Immunoassay.

A photoelectrochemical (PEC) biosensor is a very efficient and sensitive detection technology for the quick and effective conversion of light to electrical signals. However, the sensitivity and stability of the sensors are still unsatisfactory based on single-phase semiconductors or in the absence of sacrificial agents in the test solution. Herein, we present an efficient curing sacrificial agent-induced dual-heterojunction PEC system, which can detect the prostate-specific antigen (PSA) with high sensitivity. This PEC immune system was initially fabricated using single-walled carbon nanohorns (SWCNHs), p-type MoS2, and n-type Ag2S successively through a Schottky junction and p-n heterojunction on a glassy carbon electrode with electrodeposited gold nanoparticles. Then, the capture antibody (Ab1) was modified and the nonspecific binding sites were sealed off. Meanwhile, the ferrocene (Fc) solidified with hollow nanospheres of zinc ferrite (ZnFe2O4) served as a curing electronic sacrificial agent (Fc-ZnFe2O4). Next, the detection antibody labeled with Fc-ZnFe2O4 (Ab2-Fc-ZnFe2O4) was used as a bio-nanoprobe and captured by PSA and Ab1 via sandwich immunorecognition. Under white light, PEC signal amplification could be driven by the curing electronic sacrificial agent-induced dual-heterojunction to achieve the highly sensitive detection of the target. This proposed system exhibited excellent photocurrent performance within the working range from 1 fg·mL-1 to 100 ng·mL-1 at a low detection limit of 0.44 fg·mL-1 (S/N = 3). The proposed strategy features high sensitivity, selectivity, and stability that provides a new opportunity for the development of biosensors in the PEC field.