Signal Labels Research Articles

Ultrasensitive detection of patulin based on a Ag+-driven one-step dual signal amplification

Due to improper storage, the presence of patulin in fruits poses a threat to food safety. Herein, a one-step dual amplification strategy-based electrochemical aptasensor was proposed for patulin detection. Silver-palladium nanoparticles (AgPdNPs) with a hollow and branched structure were used as a supporting material for thionine to provide numerous attachment sites. AuNFs/g-C3N4 was employed as an electrode modification material, which has been demonstrated to facilitate electron transport and improve signal label loading capacity. Ag+ ions were released in the presence of patulin, activating the Ag+-DNAzyme on the electrode surface. The formed Ag+-DNAzymes further cyclically cleaved the substrate DNA, and the released sequences were used as a new trigger to mediate the secondary recirculation. This one-step dual amplification strategy enabled double target recycling without additional procedures. The signal cascade amplification through dual target recycling, was thus available for trace detection of patulin. Under the optimal conditions, the electrochemical aptasensor achieved a satisfactory linear range from 5.0 × 10-6 μg L-1 to 50 μg L-1 with a detection limit of 0.92 fg·mL-1 for the determination of patulin. In addition, the aptasensor exhibited favorable selectivity, reproducibility, repeatability and long-term stability, and thus can be employed for patulin detection in apple juice samples, providing excellent choice for the detection of trace patulin.

Handheld device for on-site sensitive detection of genetically modified crop based on supramolecular fluorescence material

Herein, a handheld device for on-site detection of genetically modified crop was developed. To meet the requirement of highly sensitive detection, single-wavelength light emitting diode was used as excitation light source, silicon photodiode with a dark current of pA level was adopted for photoelectric conversion, and phase-sensitive signal acquisition and amplification were carried out to improve the signal-to-noise ratio. Specially, micron-scale supramolecular fluorescence material was proposed for the first time as the signal label of sandwich immunoassay, which is a luminescent molecule aggregate. It could bring much greater increment in fluorescence intensity by increasing the number of luminescent molecules and accelerating the internal energy recombination, resulting in an excellent detection sensitivity. Under optimal experimental conditions, genetically modified protein PAT/bar as a template could be detected in the range of 0.01 ~ 10,000 ng/mL, with a limit of quantification10 pg/mL. Selectivity, stability, precision and accuracy were all satisfied. And, real GM rice sample could be successfully detected, implying that this high-sensitivity on-site detection platform has broad application prospects in food inspection.

Zirconium-Based Metal–Organic Framework and Ti3C2Tx Nanosheet-Based Faraday Cage-Type Electrochemical Aptasensor for Escherichia coli Detection

A Faraday-cage-type electrochemical aptasensor based on two-dimensional (2D) nanomaterials was developed for the sensitive detection of Escherichia coli O157:H7. In this electrochemical aptasensor, 2D titanium carbide (Ti3C2Tx) MXene was used for electrode modification. 2D Ti3C2Tx could immobilize aptamers via chelation between titanium and phosphate groups and provide a large electroactive surface for signal transduction. Another 2D zirconium ferrocene-based metal–organic framework (Zr-Fc MOF) combined with gold nanoparticles (AuNPs) and 4-mercaptophenylboronic acid (4-MPBA) (Zr-Fc MOF/AuNPs/4-MPBA) was used as an electrochemical signal label, in which Fc was a signal molecule and AuNPs could improve the electroactivity and combine with 4-MPBA via Au–S bonds. 4-MPBA could bind with E. coli O157:H7 via covalent bonding between boronic acid and the cis-diol of lipopolysaccharides on bacteria cell walls. So, the signal labels could immobilize on the electrode to form a Faraday-cage-type structure owing to the large surface area of Zr-Fc MOF. In this structure, electrons flowed directly between the electrode and ferrocene, and the electrochemical signal could be amplified. When the application of 2D nanomaterials and the Faraday-cage strategy were combined, E. coli O157:H7 was sensitively detected with a detection limit of 3 CFU·mL–1. The aptasensor was applied for milk sample detection. This aptasensor has practical application potential because of its properties of satisfactory sensitivity, specificity, and stability.

Chemical and electrochemical conversion of magnetic nanoparticles to Prussian blue for label-free and refreshment-enhanced electrochemical biosensing of enrofloxacin

Magnetic biosensor takes advantage of rapid and facile magnetic separation/collection of targets, however, generally relies on additional signal labels to generate signal in a tedious and high-cost way. Here, we proposed a chemical and electrochemical conversion (C-ECC) method to develop a label-free electrochemical magnetic biosensor to detect antibiotics enrofloxacin (ENR). The C-ECC method integrates the chemical decomposition of magnetic beads (MBs) to release ironic ions and the simultaneous electrochemical deposition of Prussian blue (PB) analogs through the reaction of ironic ions and co-existing K4Fe(CN)6. Unlike conventional method that relies on the physical magnetic property of MBs, the C-ECC method fully exploited the chemical/electrochemical properties of MBs to produce electrochemically active PB to generate signal, thus endowing MBs with dual roles in both sample treatment and signal generation. The incorporation of chemical and electrochemical conversion produced more PB with higher electroactivity when compared with sole chemical or electrochemical conversion. Moreover, an interesting electrochemical refreshment (ER) was designed to remove insulative species on the electrode surface to improve electroactivity of electrode and benefit amperometric detection significantly. Under optimized conditions, the C-ECC-based biosensor presented limit of detection (LOD) of 4.17 pg mL−1 for ENR, which is lower than most analogs, as well as satisfactory specificity. The biosensor also performed well in fish and chicken meat samples, with LODs lower than maximum residue limits of national standards. The C-ECC method may create a new way to design magnetic sensors and contribute to rapid, facile and sensitive detection in agriculture/food, clinic diagnosis and environmental monitoring.

Electrochemical aptasensor based on Ce3NbO7/CeO2@Au hollow nanospheres by using Nb.BbvCI-triggered and bipedal DNA walker amplification strategy for zearalenone detection

Herein, an electrochemical aptasensor combining Nb.BbvCI-triggered bipedal DNA walking strategy was constructed for ultrasensitive assay of zearalenone (ZEN). The aptasensor used Ce3NbO7/CeO2 @Au hollow nanospheres as electrode modification material and PdNi@MnO2/MB as the signal label. Importantly, the Ce3NbO7/CeO2 synthesized by hydrothermal method were combined with Au nanoparticles and applied to the electrode surface. The as-prepared Ce3NbO7/CeO2 @Au possessed a large surface area, excellent electrical conductivity, stability and more binding sites. PdNi@MnO2 with high specific surface area and porosity combined with molecule methylene blue (MB) was introduced into electrodes as the signal label. The proposed aptasensor utilized the advantages of specific recognition of aptamers and target molecules to release bipedal DNA walker (w-DNA), and then the w-DNA was triggered by Nb.BbvCI and entered the cycle to release more signal probes. The feasibility of this strategy was recorded by the differential pulse voltammetry (DPV) method. Under the optimized conditions, the electrochemical aptasensor exhibited a wide linear dynamic range from 1 × 10−4 to 1 × 103 ng mL−1 with a low detection limit of 4.57 × 10–6 ng mL−1. Moreover, the aptasensor had high selectivity, good stability, excellent repeatability and provided an effective method for the trace detection of ZEN in real samples.

Fluorescent Immunoassay with a Copper Polymer as the Signal Label for Catalytic Oxidation of O-Phenylenediamine.

This work suggested that Cu2+ ion coordinated by the peptide with a histidine (His or H) residue in the first position from the free N-terminal reveals oxidase-mimicking activity. A biotinylated polymer was prepared by modifying His residues on the side chain amino groups of lysine residues (denoted as KH) to chelate multiple Cu2+ ions. The resulting biotin-poly-(KH-Cu)20 polymer with multiple catalytic sites was employed as the signal label for immunoassay. Prostate specific antigen (PSA) was determined as the model target. The captured biotin-poly-(KH-Cu)20 polymer could catalyze the oxidation of o-phenylenediamine (OPD) to produce fluorescent 2,3-diaminophenazine (OPDox). The signal was proportional to PSA concentration from 0.01 to 2 ng/mL, and the detection limit was found to be eight pg/mL. The high sensitivity of the method enabled the assays of PSA in real serum samples. The work should be valuable for the design of novel biosensors for clinical diagnosis.

Photoelectrochemical immunosensor for the sensitive detection of neuron-specific enolase based on the effect of Z-scheme WO3/NiCo2O4 nanoarrays p-n heterojunction

In this study, a signal-on type PEC immunosensor was constructed to detect neuron-specific enolase (NSE) via Z-scheme WO3/NiCo2O4 p-n heterojunction with cactus-like structure used as photoactive materials and MnxCd1-xS⊃Au NPs (MCS⊃Au NPs) as signal labels. Firstly, Z-scheme WO3/NiCo2O4 heterojunction could accelerate the separation efficiency of carriers and well-matched photoactive materials may promote charge migration, which resulted in WO3/NiCo2O4 generating strong and stable current. In addition, Z-scheme WO3/NiCo2O4 heterojunction directly grown on the surface of FTO via hydrothermal method facilitated the preparation of PEC immunosensor with outstanding stability. Secondly, an efficient signal amplification strategy was proposed by MnxCd1-xS⊃Au NPs incubating with signal antibody (Ab2). On the one hand, the well-matched energy levels of MnxCd1-xS with WO3/NiCo2O4 boosted the photo-generated electrons transferred to the electrode; on the other hand, the LSPR effect of Au may convert thermion to photocurrent to achieve signal amplification. Based on the above strategies, a PEC immunosensor with outstanding reproducibility and stability was obtained for sensitive detection of NSE. Under the optimum experimental conditions, current response range of the constructed signal amplification PEC sensor to NSE was 0.1 pg/mL ∼50 ng/mL and the detection limit was 0.07 pg/mL (S/N = 3). After the application tests in the detection of actual samples, the feasibility of the prepared PEC immunosensor with excellent selectivity, high sensitivity and satisfactory reproducibility was verified and the satisfactory results were obtained.

Reliable UAV Monitoring System Using Deep Learning Approaches

In recent years, unmanned aerial vehicles (UAV) or drones have become ubiquitous in our daily lives, bringing great convenience to our lives and playing a pivotal role in future wireless networks and the Internet of things. One of the major problems associated with the UAV is the heterogeneous nature of such deployments; this heterogeneity poses many challenges, particularly in the areas of security and privacy. The key to solving these problems is to accurately identify and authenticate drones. In this article, a reliable UAV identify framework based on radio frequency fingerprint is proposed. First, we established a wireless signal label architecture and systematically collected, analyzed, and recorded the radio frequency signals of different UAVs in different flight modes and different distances in the telemetry link, and established UAV signal datasets. Then, the intelligent algorithm and anti-UAV system are designed by using the collected dataset, and the feasibility of the developed dataset for detecting and identifying UAVs is verified by using machine learning and deep learning. The simulation results show that under the condition of Gaussian white noise, the method based on deep learning achieves high reliability, and when the SNR is not less than 5dB, the model achieves more than 95% of the monitoring and recognition accuracy. Finally, we discussed the possible applications of the dataset in the future.

CuO Nanozymes as Multifunctional Signal Labels for Efficiently Quenching the Photocurrent of ZnO/Au/AgSbS2 Hybrids and Initiating a Strong Fluorescent Signal in a Dual-Mode Microfluidic Sensing Platform.

A novel dual-mode microfluidic sensing platform based on CuO nanozymes as a photoelectrochemical (PEC)-fluorescent (FL) multifunctional signal label was developed for ultrasensitive neuron specific enolase (NSE) detection. Herein, ZnO/Au/AgSbS2 hybrids, possessing excellent PEC properties, were first exploited as a sensing matrix to provide a stable photocurrent. The controlled synthesis of photoactive ZnO nanoflowers (NFs) was successfully conducted using a microfluidic reactor in the scale of seconds. Furthermore, the photocurrent of ZnO NFs decorated by Au and AgSbS2 nanoparticles significantly improved, owing to the local surface plasma resonance effect of Au and matching band structure between ZnO and AgSbS2. A strategy of catalytic oxidation ascorbic acid (AA) by CuO nanozymes was proposed to quench the PEC signals and initiate FL signals. CuO nanoparticles growing on conductive carbon spheres (CuO@CSs) as secondary antibodies' labels could efficiently catalyze the oxidation of AA to achieve a PEC "signal-off" state. Then, the produced dehydroascorbic acid reacting with o-phenylenediamine opportunely generated a strong FL signal. Importantly, wide linear ranges of 0.0001-150 ng/mL for the PEC technique and 0.001-150 ng/mL for the FL method with a low detection limit of 0.028 and 0.25 pg/mL, respectively, could guarantee the sensitive detection of NSE.

Novel electrochemical PMI marker biosensor based on quantum dot dissolution using a double-label strategy

A novel and facile post-mortem interval (PMI) biosensor was fabricated using a double-label strategy to detect the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) biomarker. A monoclonal anti-GAPDH antibody was immobilized on a surface label containing cadmium selenide quantum dots (CdSe QDs) on a cysteamine graphene oxide (Cys-GO) self-assembled monolayer. Glucose oxidase (GOx) was used as a signal label to conjugate with GAPDH. GAPDH recognition was achieved through the dissolution of the surface-attached CdSe QDs by hydrogen peroxide generated through GAPDH-conjugated GOx-catalyzed β-glucose oxidation. To enhance sensitivity, a competitive interaction was introduced between free and conjugated GAPDH to the active site of the anti-GAPDH antibody. The electrochemical response due to CdSe dissolution decreased proportionally with the concentration of free GAPDH. Differential pulsed voltammetry was conducted to determine the analytical characteristics of the immunosensor, including the limit of detection, linear dynamic range, target selectivity, system stability, and applicability toward the analysis of real samples.

A novel bionic magnetic SERS aptasensor for the ultrasensitive detection of Deoxynivalenol based on “dual antennae” nano-silver

Deoxynivalenol (DON), as a mycotoxin produced by Fusarium, showed great harm to human body, crops and animals, so it is urgent to establish an efficient, sensitive and selective method for the detection of DON. Here, a novel bionic magnetic SERS aptasensor based on “dual antennae” nano-silver was designed. β-CD@AgNPs was modified 4-MBA and the aptamers respectively with chemical bond and host-guest interaction, which was reflected in the “dual antennae” characteristics of identifying target and SERS signal label. In addition, Fe3O4@Au was conjugated with SH- modified complementary DNA to prepare capture probes, enabling fast magnetic separation of the captured target and further enhanced Raman scattering. With the specific recognition and competitive binding of DON and aptamer, the combination of “dual antenna” signal probe and capture probe is significantly reduced, exerting a lower SERS intensity. There was a good linear relationship in the range of 0.0001–100 ng mL−1 between the SERS intensity and the logarithm of DON concentration, and the limit of detection (LOD) was as low as 0.032 pg mL−1. The SERS aptasensor exhibited good selectivity, satisfactory repeatability and expected practicability, presenting a great application prospect in the detection of mycotoxins and biochemical analysis.

Rhodium nanocatalyst-based lateral flow immunoassay for sensitive detection of staphylococcal enterotoxin B

Compared with traditional laboratory-based tests, lateral flow immunoassay (LFA) has been developed as one of the emergent and popularly used rapid detection technology. Due to unique physical and chemical properties, novel nanomaterials have been widely used as the signal label in LFA for the detection of analytes, but these assays merit further development to improve sensitivity. Here, we developed a rhodium (Rh) nanozyme-labeled LFA with high sensitivity for paper-based detection of staphylococcal enterotoxin B (SEB), one of the super-antigens that may cause illness. The synthesis and optimization of Rh nanozymes were illustrated, which show excellent peroxidase-like catalytic activity. Harnessing the catalytic amplification of Rh nanozymes enabled naked-eye detection of SEB as low as 1.2 pg·mL-1 in the whole milk sample, which increases 250 folds compared with the commercial ELISA tests. Additionally, the recoveries rate for spiking dairy samples was determined to be 94.3–124.8% for SEB, which indicated the good accuracy and precision of Rh-based LFA. We believe this Rh based LFA for detecting toxins may open new possibilities for similar immunochromatographic testing methods.

Enzyme-free sandwich-type electrochemical immunosensor based on high catalytic binary PdCu mesoporous metal nanoparticles and conductive black phosphorous nanosheets for ultrasensitive detection of pro-SFTPB in non-small cell lung cancer

Pro-surfactant protein B (pro-SFTPB) has been proven to be a powerful biomarker for the early diagnosis of non-small-cell lung cancer (NSCLC). In this study, a novel enzyme-free electrochemical immunosensor is developed for the ultrasensitive detection of pro-SFTPB using binary PdCu mesoporous metal nanoparticles (MMNs) and few-layer black phosphorous (BP nanosheets). Concretely, PdCu MMNs, as novel essential signal labels, were successfully synthesized, offering excellent outstanding peroxidase-like catalytic activity toward hydrogen peroxide (H2O2). Meanwhile, the combination of BP nanosheets with biocompatible gold nanoparticles (AuNPs) served as the substrate on the electrode. With the aid of binary PdCu MMNs nanozymes and BP nanosheets, the enzyme-free electrochemical immunosensor revealed ultrasensitivity detection of pro-SFTPB ranging from 10 pg/mL to 100 ng/mL with an ultralow limit of detection of 5.3 pg/mL. In addition, the immunosensor enables accurate detection of pro-SFTPB in serum samples. Altogether, the developed electrochemical immunosensor provides an enzyme-free platform for pro-SFTPB detection, providing a new method for the early diagnosis of NSCLC.

Regulated room temperature phosphorescence from zero-dimensional organometallic halide hybrids for anti-counterfeiting and encryption

Organometallic materials with room temperature phosphorescence (RTP) emission are of bright development prospects in optoelectronic application. Herein, we prepared two types of isostructural zero-dimensional metal-organic single crystals with RTP effect named as bis(tetraphenylphosphonium) titanium hexafluoride (Ph4P)2TiF6·2H2O and bis(tetraphenylphosphonium) zirconium hexafluoride (Ph4P)2ZrF6·2H2O. The as-prepared fluoride crystals can simultaneously emit ultraviolet (UV) fluorescence and green phosphorescent emission under 290 nm excitation at room temperature. The RTP could be observed by naked eyes for more than 6 s after removing the excited UV source. By introducing bromide ions into the crystal framework to enhance the heavy-atom effect, the photoluminescence quantum yield of the compounds dramatically boosted to 19.47%. These results provide a facile design strategy for the adjustment of efficient transient and long-lasting RTP. Furthermore, the as-prepared materials were blended in the resins and printed as the anti-counterfeiting signal labels. Therefore, this work does not only reveal the efficient RTP phenomenon in the zero-dimensional metal-organic ionic compounds, but also provide potential candidates for the realization of anti-counterfeiting technology.

Electrogenerated chemiluminescence biosensor for microRNA detection incorporating enzyme-free dual DNA cyclic amplification and Ru(bpy)32+-functionalized metal-organic framework

Herein, a novel electrogenerated chemiluminescence (ECL) biosensor for the determination of microRNA was developed on the basis of enzyme-free dual signal amplification and Ru(bpy)32+-functionalized metal-organic frameworks (Ru@MIL-101(Al)–NH2) as ECL signal labels. MicroRNA-21 (miRNA-21) was used as a model target, which initiated the toehold-mediated strand displacement reaction (TSDR). The first cyclic amplification TSDR converted a small quantify of miRNA-21 to abundant report strands (RS), which then catalyzed the second cyclic amplification catalytic hairpin assembly (CHA). The CHA ran cyclically to produce numerous H1–H2 duplexes with the exposed segment. Finally, the newly exposed segment of H2 could bind with the ECL probe (DNA-Ru@MIL-101(Al)–NH2), leading to an evident ECL signal enhancement. The results showed that the ECL intensity varied linearly with the logarithm of the concentration of miRNA-21 ranging from 0.01 to 10,000 pM. The detection limit was as low as 4 fM because of the signal amplification through TSDR and CHA processes coupling with Ru@MIL-101(Al)–NH2. In addition, this biosensor has been successfully applied to detect miRNA-21 in MCF-7 cells, providing great potential for the related clinical diagnosis.

A rationally designed triple-qualitative and double-quantitative high precision multi-signal readout sensing platform

Single mode sensing is more likely suffers from false positive or negative results than multi-signal readout assay. By using a layer-by-layer modified ITO/Au/BiOI electrode as the matrix and core/shell upconversion nanoparticles (UCNPs) as the signal labels, a triple-qualitative (smartphone based naked-eye readout, photoelectrochemical (PEC) and fluorescence (FL)) and double-quantitative (PEC and FL) multi-signal readout sensing platform was designed for high-precision assay of prostate-specific antigen (PSA), a biomarker for prostate cancer diagnosis. Based on the PSA bio-recognition events, the PEC mode sensing was achieved, while the specific enzymatically active of PSA for 5-Carboxyfluorescein (FAM) labeled helix peptide (CGHSSKLQK-FAM) enabled the FL sensing. Besides, under the excitation of 980 nm near-infrared (NIR) laser, the signal antibody@UCNPs bioconjugates can emit visible light for smartphone based naked-eye readout. Compared with the single-signal method, the accuracy of PSA serodiagnosis was obviously improved. Moreover, the above procedure could be extended to the single-molecule fluorescence counting method, the limit of detection for PSA can reach 0.005 ag/mL (S/N = 3). This work combined the advantages of different techniques, minimized the misdiagnose detection, and provides a rational design idea for multi-signal readout sensing platform.

A novel signal amplification tag to develop rapid and sensitive aptamer-based biosensors

Determination of microRNAs (miRNAs) as valuable blood-borne biomarkers has attracted many scientific attentions. However, analytical methods are still restricted by miRNAs intrinsic characteristics. In this study, for the first time, novel blackberry-like magnetic DNA/FMMA nanospheres were synthesized and mounted on a gold stir-bar as signal amplification probes. To produce this strong electrochemical signal label, double strand DNAs were immobilized on gold coated magnetic nanospheres through a hybridization chain reaction followed by reversible addition-fragmentation chain-transfer polymerization, which brought a great quantity of the electroactive tags (FMMA) on the nanosphere surface. These nanospheres were then fixed on the gold stir-bar as signal probes. The magnetic DNA/FMMA nanosphere probes can be released by substituting with the newly emerging DNA fragments of catalyzed hairpin assembly products. Eventually, these signal probes were magnetically enriched on the electrode surface to produce electrochemical signal and finally, the biosensor was developed to detect miRNA-106a (model target). The suggested aptamer-based biosensor demonstrated considerable selectivity, acceptable storage stability, high specificity, and excellent performance in real sample analysis without any pretreatments. As a result, current study reveals that the developed strategy has a great potential for the early diagnosis of gastric cancer and additionally the clinical monitoring of any miRNA sequences.

An efficient electrochemical immunosensor for Alpha-Fetoprotein detection based on the CoFe prussian blue analog combined PdAg hybrid nanodendrites

A sandwich-type electrochemical immunosensor was developed using PdAg nanodendrites modified CoFe prussian blue analog (PdAg NDs/CoFe PBA) as the signal label for the alpha-fetoprotein (AFP) detection. The novel hollow porous CoFe PBA with KCoFe phase was synthesized via self-template epitaxial growth strategy. Benefiting from the filling of K ions and the hollow porous structure, the electron transfer rate and the mass transfer rate of CoFe PBA were improved, further enhancing the catalytic capacity. In addition, the special dendritic morphology of PdAg NDs can maximize the proportion of catalytic active sites, and stable Pd-N and Ag-N bonds can further fix more immune molecules to increase the sensitivity of electrochemical immunosensors. Under optimized parameters, the fabricated immunosensor demonstrated a wide linear range detection from 100.0 fg mL−1 to 200.0 ng mL−1, and a low detection limit of 18.6 fg mL−1. Simultaneously, the immunosensor with acceptable reproducibility, specificity, stability and exhibited satisfactory performance in human serum analysis. This work provides a new line for the detection of other tumor markers, which means that it has great application potential in immune analysis.

Electrocatalytic excitation and Co-reaction acceleration synergistic amplification signal of hydrazide-conjugated carbon dots for an electrochemiluminescence immunoassay

Biocompatible nitrogen-doped hydrazide-conjugated carbon dots (NHCDs) as an anodic luminophores with low excitation potential were equipped with an efficient multiple signal-amplification strategy for electrochemiluminescence (ECL) trace bioanalysis. To promote the ECL emission of NHCDs-H2O2 system, gold nanoparticles (Au NPs) functionalized tin oxide nanocrystals (Au@SnO2 NCs) were adopted to anchor large amount of NHCDs, the formed NHCDs-Au@SnO2 NCs could conjugate with detection antibody as the signal label. Moreover, 3,4,9,10-perylenetetracarboxylic acid (PTCA) molecules were immobilized on the flower-like microsphere (PTCA@ZnCo2O4/ZnO) nanocomposites to fabricate as an electro-active sensing substrate to incubate the capture antibody, which could efficiently accelerate the generation of reactive oxygen species (OH·/O2·-) through electrocatalytic excitation and co-reaction acceleration. Integrating with the sandwich-type sensing model, an ECL immunosensor was established to detect biomarkers of squamous cell carcinomas named cytokeratin 19 fragments (cyfra21–1). Combining with the synergistic signal-amplification induced by the Au@SnO2 NCs, PTCA, and ZnCo2O4/ZnO nanocomposites, the developed immunosensor performed detection range from 0.09 pg/mL to 100 ng/mL with a detection limit of 34.38 fg/mL. The results showcased the great potential of this sensing strategy for real sample analysis of biomarker with reliable stability, selectivity and repeatability.

Synergetic PtNP@Co3O4 hollow nanopolyhedrals as peroxidase-like nanozymes for the dual-channel homogeneous biosensing of prostate-specific antigen.

In this paper, novel synergetic PtNP@Co3O4 hollow nanopolyhedrals with peroxidase-like activities are designed and prepared, which can be used as electrochemical and colorimetric signal labels for the enzyme-free dual-channel homogeneous sensing of prostate-specific antigen. When prostate-specific antigens are present, the aptamer-modified PtNP@Co3O4 hollow nanopolyhedrals and magnetic beads form sandwich structures, which have excellent peroxidase-like activities, because of the synergetic effect of PtNP@Co3O4 hollow nanopolyhedrals. The sandwich structures can be separated from the mixture by the magnetic effect of the magnetic beads and catalyze the redox reactions between H2O2 and TMB, generating quantitative electrochemical and colorimetric responses in homogeneous solution simultaneously. Under the optimized conditions, the linear range of both electrochemical (0.01 to 10ng/ml) and colorimetric (0.01-15ng/ml) channels can satisfy the demand of prostate-specific antigen detection in clinic (4ng/ml), and the electrochemical and colorimetric channels have a low detection limit of 0.0079ng/ml and 0.01ng/ml respectively without using natural enzymes. The strategy by using synergetic PtNP@Co3O4 hollow nanopolyhedrals as signal probes provides a promising scheme for developing simple, rapid, reliable, and ultrasensitive dual-channel homogeneous biosensors, which has a great potential as a powerful tool in prostate cancer diagnosis.