Signal Probe Research Articles

A dual-mode biosensor based on CdIn2S4 hollow microsphere combined with Au@CuO/Cu2O nanozyme for sensitive detection of Sa-16S rDNA

A dual-mode biosensor used CdIn2S4 hollow microspheres as electrochemiluminescence (ECL) and photoelectrochemistry (PEC) dual signal probes combined with Au@CuO/Cu2O nano-enzyme catalysis was fabricated for sensitive detection of Sa-16S rDNA. Firstly, CdIn2S4 microspheres displayed excellent ECL and PEC signals, then the target Sa-16S rDNA introduced a large number of Au@CuO/Cu2O nanoparticles to the electrode via Exo-III amplification strategy. Au@CuO/Cu2O is a highly efficient peroxidase mimicase, and can effectively promote H2O2 to produce ·OH, which further oxidized 4-chloro-1-naphthol (4-CN) to produce a large amount of insoluble precipitate on the electrode surface, then significantly reduced the PEC and ECL signals of CdIn2S4 for target detection. This study opens up a new multifunctional photoelectric microspheres and a flexible biosensor by using CdIn2S4 and nanozymes, showing a new channel for the detection of DNA molecules and providing valuable insights for the development of PEC biosensing technologies based on nanozymes.

Point-of-care testing of Pseudomonas aeruginosa using PCN-222(Pt) prepared by nanoconfinement-guided protocol to catalyze gas generation reaction

BackgroundPathogenic bacteria are keeping threatening global public health since they can cause many infectious diseases. The traditional microorganism identification and molecular diagnostic techniques are insufficiently sensitive, time-consuming, or expensive. Thus it is of great interest to establish pressure signal-based sensing platforms for point-of-care testing of pathogenic bacteria to achieve timely diagnosis of infectious diseases. Rational design and synthesis of nano-sized probes with high peroxidase-mimicking activity have been a long-term cherished goal for improving the sensitivity of pressure signal-based sensing methods. ResultsGuided by nanoconfinement effect, PCN-222(Pt) was prepared by confining Pt clusters within the channels of a zirconium porphyrin MOFs material termed as PCN-222. In comparison to regular platinum nanoparticles, palladium@platinum core-shell nanodendrites, and platinum-coated gold nanoparticles, the prepared PCN-222(Pt) displayed superior peroxidase-mimicking activity with outstanding efficiency for catalyzing the decay of H2O2 to produce O2. Thus it was used as a pressure signal probe to establish a sensitive method on a hydrogel pellets platform for analyzing Pseudomonas aeruginosa (P. aeruginosa), for which polymyxin B and a phage termed as JZ1 were used as recognition agents for the target pathogen. P. aeruginosa was quantified with a handheld pressure meter within a broad range of 2.2 × 102–2.2 × 107 cfu mL−1. This method was used to quantify P. aeruginosa in various biological and food samples with acceptable accuracy and reliability. SignificanceThe proposed nanoconfinement-guided protocol provides a novel approach for rational design and preparation of nano-sized probes with high peroxidase-mimicking activity for catalyzing gas-generation reaction. Thus this study opens an avenue for establishment of sensitive pressure signal-based sensing methods for pathogenic bacteria, which shows broad application prospects in medical diagnosis of infectious diseases.

Study on the photo/electrochemical bi-functional properties of a coupling interface of Ru[dcbpy]32+-AMT/Au by SECM imaging-based joint analytical method

A photo/electrochemical coupling interface of Ru[dcbpy]32+-AMT/Au (AMT; 5-Amino-1,3,4-thiadiazole-2-thiol) was fabricated using a dehydration condensation sulfhydrating method. For the interface functional properties, a combined dual-signal recording (CDSR) method was applied to characterize the response characteristics, and a scanning electrochemical microscopy-electrochemiluminescence (SECM-ECL) imaging was developed to assess the interface distribution uniformity. The interface biosensing compatibility was validated by constructing a simple DNA sensor. The research results show that the interaction between the two functional parameters follows a synergistic effect mechanism in the coupling conditions and an interference effect mechanism in the detection condition. Under optimized conditions, the saturation dual-signal response values are 156.0 and 86.8 μA, respectively. The statistics and imaging comparison analysis validate good interface distribution uniformity and stability performance. The DNA sensor's dual-signal detection limits to the signal probe (SP) are ∼30 fM and 0.3 pM with linear ranges of 100.0 fM ∼ 1.0 nM and 1.0 pM ∼ 10.0 nM, respectively. The fabricated interface exhibits an effective bi-functional response performance compatible with biosensing. The proposed imaging method has a high technical fit for studying photo/electrochemical coupling interfaces and can also provide a reference for other similar coupling interface analyses.

Simultaneous Detection of Micro-RNAs by a Disposable Biosensor via the Click Chemistry Connection Strategy.

Simultaneous detection of multiple breast cancer-associated miRNAs significantly raises the accuracy and reliability of early diagnosis. In this work, disposable carbon fiber paper serves as the biosensing interface, linking DNA probes via click chemistry to efficiently capture targets and signals efficiently. DNA probes have multiple recognition domains that trigger a cascade reaction through the helper probes and targets, resulting in two signals output. The signals are centrally encapsulated in the pore of the MIL-88(Fe)-NH2. The signal carriers are directed by signal probes to the recognition domains that correspond to the DNA probes. The biosensor is selective and stable, and it can quantify miRNA-21 and miRNA-155 simultaneously with detection limits of 0.64 and 0.54 fmol/L, respectively. Furthermore, it demonstrates satisfactory performance in tests conducted with normal human serum and cell lysate. Overall, this method makes a satisfactory exploration to realize an inexpensive and sensitive biosensor for multiple biomarkers.

Paper-based immunosensor integrated with bioinspired Cu-polydopamine nanozyme for voltammetric detection of CA-15-3 tumor marker

This manuscript describes the fabrication and characterization of a highly conductive paper-based nanoplatform for immobliztion of anti-CA 15-3 antibodies. For this purpose, cellulosic filter paper (FP) was first coated with Cu nanosponges (CuNSs) through ion beam sputtering deposition (IBSD) method and then covered with Cu-doped polydopamine nanospheres (Cu-PDA). Polydopamine doped with copper exhibited laccase (multi-copper oxidase)-mimicking properties. Bioinspired by the structure of the active site and the electron transfer mechanism of laccase, Cu-PDA nanozyme catalyzed the oxidation of hydroquinone (HQ) signal probe. In this design, CA-15-3, a prognostic biomarker in the breast cancer, was chosen as a model target. To the best of our knowledge, this is the only paper on the design of an electrochemical biosensor based on dense and uniform CuNSs produced by IBSD. More importantly, Cu-PDA is biocompatible and biodegradable, which makes it a potential competitor in the point-of-care (POC) biosensing applications. Thus, this paper-based sensing strategy can be used in designing cost-effective flexible chips consisting of electrodes printed on paper for in-situ and real-time monitoring biomarkers under clinical conditions. In addition to these outstanding features, the LOD (1.3 mU mL 1) and LOQ (4.3 mU mL 1) of the Ab/HQ/Cu-PDA/CuNSs/FP-based immunosensor was significantly lower than the clinically relevant cut-off level (30 U mL 1). In the practical applications, one of the key superiorities of this immuosensor is the wide DLR (5 mU mL 1–280 U mL 1) which covers the ultimate value of healthy and patient individuals.

CRISPR/Cas12a-mediated DNA-AgNC label-free logical gate for multiple microRNAs' assay.

CRISPR/Cas system has been widely applied in the assay of disease-related nucleic acids. However, it is still challenging to use CRISPR/Cas system to detect multiple nucleic acids at the same time. Herein, we combined the preponderance of DNA logic circuit, label-free, and CRISPR/Cas technology to construct a label-free "AND" logical gate for multiple microRNAs detectionwith high specificity and sensitivity. With the simultaneous input of miRNA-155 and miRNA-141, the logic gate starts, and the activation chain of Cas12a is destroyed; thus, the activity is inhibited and the fluorescence of the signal probe ssDNA-AgNCs is turned on. The detection limit of this method for simultaneous quantitative detection of double target is 84 fmol/L (S/N = 3). In this "AND" logic gate, it is only necessary for the design of a simple DNA hairpin probe, which is inexpensive and easy, and sincethis method involves only one signal output, the data processing is very simple. What is more important, in this strategy two types of microRNAs can be monitored simultaneously by only using CRISPR/Cas12a and a type of crRNA, which offers a new design concept for the exploitation of single CRISPR/Cas system for multiple nucleic acid assays.

Aversatile MOF as an electrochemical/fluorescence/colorimetric signal probe for the tri-modal detection of MMP-9 secretion in the extracellular matrix to identify the efficacy of chemotherapeutic drugs

BackgroundMMP-9 plays a crucial role in regulating the degradation of proteins within the extracellular matrix (ECM). This process closely correlates with the occurrence, development, invasion, and metastasis of various tumors, each exhibiting diverse levels of MMP-9 expression. However, the accuracy of detection results using the single-mode method is compromised due to the coexistence of multiple biologically active substances in the ECM. ResultsTherefore, in this study, a tri-modal detection system is proposed to obtain more accurate information by cross-verifying the results. Herein, we developed a tri-modal assay using the ZIF-8@Au NPs@S QDs composite as a multifunctional signal probe, decorated with DNA for the specific capture of MMP9. Notably, the probe demonstrated high conductivity, fluorescence response and mimicked enzyme catalytic activity. The capture segments of hybrid DNA specifically bind to MMP9 in the presence of MMP9, causing the signal probe to effortlessly detach the sensor interface onto the sample solution. Consequently, the sensor current performance is weakened, with the colorimetric and fluorescent signals becoming stronger with increasing MMP9 concentration. Notably, the detection range of the tri-modal sensor platform spans over 10 orders of magnitude, verifying notable observations of MMP-9 secretion in four tumor cell lines with chemotherapeutic drugs. Furthermore, the reliability of the detection results can be enhanced by employing pairwise comparative analysis. SignificanceThis paper presents an effective strategy for detecting MMP9, which can be utilized for both the assessment of MMP-9 in cell lines and for analyzing the activity and mechanisms involved in various tumors.

Disposable amperometric biotool for peanut detection in processed foods by targeting a chloroplast DNA marker

This work reports the development and application of a disposable amperometric sensor built on magnetic microcarriers coupled to an Express PCR strategy to amplify a specific DNA fragment of the chloroplast trnH-psbA. The procedure involves the selective capture of a 68-mer synthetic target DNA (or unmodified PCR products) through sandwich hybridization with RNA capture probe-modified streptavidin MBs and RNA signaling probes, labeled using antibodies specific to the heteroduplexes and secondary antibodies tagged with horseradish peroxidase. Amperometric measurements were performed on screen-printed electrodes using the H2O2/hydroquinone system. Achieving a LOD of 3 pM for the synthetic target, it was possible to detect 2.5 pg of peanut DNA and around 10 mg kg−1 of peanut in binary mixtures (defatted peanut flours prepared in spelt wheat). However, the detectability decreased between 10 and 1000 times in processed samples depending on the treatment. The Express PCR-bioplatform was applied to the detection of peanut traces in foodstuff.

Ligand regulation strategy enhanced anodic electrochemiluminescence of copper nanoclusters for enrofloxacin trace determination

Copper nanoclusters (Cu NCs) have emerged as promising nano-emitters. However, their limited luminescence stability and emission intensity restrict their application in electrochemiluminescence (ECL). Herein, a ligand regulation strategy was developed to enhance the anodic ECL of Cu NCs. Specifically, we utilized ovalbumin (OVA), a naturally occurring protein, as a stabilizing ligand for the Cu NCs and introduced terbium ions into the ligand. This approach optimizes ECL performance by enhancing electron transfer efficiency and suppressing non-radiative relaxation. Additionally, we used the enhanced ECL nano-emitter as a signal probe and combined it with split aptamers to develop an analytical platform. This platform is designed for the detection of enrofloxacin (ENR) in food samples. The sensing platform incorporated a self-designed ENR test cell combined with 3D printing, ITO sputtering and screen-printing technologies, which greatly improved the reproducibility of the test results. Our study highlights the potential of this innovative detection method in the realm of food detection.

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.

Label-free electrochemical aptasensor for ultrasensitive lead ion detection based on flower-like AuNPs@MoS2 and core-shell Pt@Pd bimetallic nanoparticles.

A signal-amplified platform was designed to construct a label-free electrochemical aptasensor for lead ions (Pb2+) assay. First, flower-like molybdenum disulfide-supported AuNPs (AuNPs@MoS2) nanocomposites were synthesized and used as substrates for modifying the electrode. The AuNPs@MoS2 material possessed large surface area and superior biocompatibility, which was beneficial to improve the loading amount of the complementary DNA (cDNA) and amplified the response signal. Importantly, the prepared core-shell Pt@Pd bimetallic nanoparticles (Pt@PdNPs) were used to conjugate with redox marker thionine (Thi) and aptamer (Apt) for further signal amplification; the obtained signal probes (Thi-Pt@PdNPs-Apt) were connected by the cDNA assembled on the electrode through DNA hybridization. Differential pulse voltammetry was performed to monitor the signal of Thi. After incubating of aptasensor with Pb2+, the specific recognition of Pb2+ and Apt resulted in the dissociation of aptamer-cDNA complex, thereby the Thi-Pt@PdNPs-Apt separated from the electrode surface and decreased current response was obtained. The prepared electrochemical sensor exhibited linear response to Pb2+ in the range 5.0 × 10-4-100 nM and a detection limit of 1.0 × 10-4nM was achieved. The sensor was applied to the determination ofPb2+ in actual sample with high sensitivity and accuracy, demonstrating potential applications in heavy metal monitoring.

Metal‐organic frameworks‐assisted electrochemical sensing toward magnesium in medicinal and edible homologous for pharmacological evaluation.

AbstractGiven the importance of Magnesium (Mg) assay for efficacy evaluation of medicinal and edible homologous (MEH), an electrochemical sensor is designed by exploiting the cooperative properties of metal–organic frameworks (MOFs) and gold nanoparticles (AuNPs). To be specific, the constructed bimetallic MOFs ((FeZr)MOF) are designed by using Zr(IV) and Fe(III) clusters as metal sources, which provide a large platform for AuNPs attachment to design signal probes. Benefitting from the catalytic properties of (FeZr)MOF toward hydroxylamine, electrochemical signal is attained for Mg2+ analysis with the detection limit to be 3 μM (corresponding to 0.072 μg g−1). Relying on DNAzymes as recognition elements, good anti‐jamming is achieved for Mg2+ analysis against the coexisting ions in Puerarin, Chinese wolfberry, hawthorn and dangshen. With the superiority of rapid response, acceptable sensitivity and specificity, the electrochemical sensor provides a useful pattern for assessing the pharmacological effects of MEH substances, pointing to reasonable selection and combination of multiple health function dietary therapy formulas.

G protein-specific mechanisms in the serotonin 5-HT2A receptor regulate psychosis-related effects and memory deficits

G protein-coupled receptors (GPCRs) are sophisticated signaling machines able to simultaneously elicit multiple intracellular signaling pathways upon activation. Complete (in)activation of all pathways can be counterproductive for specific therapeutic applications. This is the case for the serotonin 2 A receptor (5-HT2AR), a prominent target for the treatment of schizophrenia. In this study, we elucidate the complex 5-HT2AR coupling signature in response to different signaling probes, and its physiological consequences by combining computational modeling, in vitro and in vivo experiments with human postmortem brain studies. We show how chemical modification of the endogenous agonist serotonin dramatically impacts the G protein coupling profile of the 5-HT2AR and the associated behavioral responses. Importantly, among these responses, we demonstrate that memory deficits are regulated by Gαq protein activation, whereas psychosis-related behavior is modulated through Gαi1 stimulation. These findings emphasize the complexity of GPCR pharmacology and physiology and open the path to designing improved therapeutics for the treatment of stchizophrenia.

A versatile photoelectrochemical biosensor based on in-situ grown 2D COFs film for sensitive detection of Hg2+ and aflatoxin B1

Herein, a highly stable and low-toxic photoelectrochemical (PEC) biosensor was constructed based on two-dimensional covalent organic frameworks (COFs) film composed of tris(4-aminophenyl)amine and 1,4-phthalaldehyde connected through imine bonds (TA-P COFs) was grown in situ on the electrode surface under mild conditions for detecting mercury ion (Hg2+) and aflatoxin B1 (AFB1). Impressively, the TA-P COF film adhered to the electrode surface through in-situ growth not only accelerated the charge transfer between the interfaces, but also improved the stability of the biosensor, further improving the accuracy of detection. Accordingly, when the cyclic amplification process was triggered in the presence Hg2+ to generate a large amount of output DNA, the signal probe with abundant quencher porous carbon hollow spheres s (PCHS) was modified on the electrode surface through the output DNA for the signal “OFF” detection of Hg2+. Meanwhile, due to the specific binding of the target to the aptamer, the released hairpin DNA 2 (H2) signal probe was modified on the electrode surface through base complementary pairing to achieve the signal “ON” detection of AFB1. The suggested multifunction biosensor achieved sensitive detection of Hg2+ in the range of 10 fM–100 nM and AFB1 in the range of 10 fg mL−1–10 ng mL−1, which showed great practical application potential in both environmental and food analysis.

Optimized detection of Salmonella typhimurium using aptamer lateral flow assay.

Salmonella typhimurium, a pathogenic bacterium with significant implications in medicine and the food industry, poses a substantial threat by causing foodborne illnesses such as typhoid fever. Accurate diagnosis of S. typhimurium is challenging due to its overlap symptoms with various diseases. This underscores the need for a precise and efficient diagnostic approach. In this study, we developed a biosensor using the Taguchi optimization method based on aptamer lateral flow assay (LFA) for the detection of S. typhimurium. Therefore, signal probe and nanobioprobe were designed using anti-Salmonella aptamer, conjugated with gold nanoparticles (GNPs), and used in LFA. The strategy of this test is based on a competitive format between the bacteria immobilized on the membrane and the bacteria present in the tested sample. Moreovere, the optimization of various factors affecting the aptamer LFA, including the concentration of bacteria (immobilized and into the sample) and the concentration of nanobioprop, were performed using the Taguchi test designing method. The data showed that the optimal conditions for the LFA reaction was 108CFU/mL of immobilized bacteria and 1.5μg/μL of nanobioprop concentration. Then, the visual detection limit of S. typhimurium was estimated as 105CFU/mL. The reaction results were obtained within 20min, and there were no significant cross-reactions with other food pathogens. In conclusion, the aptamer-LFA diagnostic method, optimized using the Taguchi approach, emerges as a reliable, straightforward, and accurate tool for the detection of S. typhimurium. Overall, this method can be a portable diagnostic kit for the detection and identification of bacteria.

Exo Ⅲ-assisted amplification signal strategy synergized with Au@Pt NFs/CoSe2 for sensitive detection of enrofloxacin

Overuse of enrofloxacin (ENR) has posed a potential threat to ecosystems and public health, so it is critical to sensitive and accurate determination of ENR residues. In this work, a novel ultra-sensitive and specific electrochemical aptasensor was fabricated based on the cobalt diselenide loaded gold and platinum nanoflowers (Au@Pt NFs/ CoSe2) and Exonuclease III (Exo III)-assisted cycle amplification strategy for the detection of ENR. Au@Pt NFs/ CoSe2 nanosheets as the substrate material, with large surface area, accelerate electron transfer and attach more DNA probes on the electrode substrate, have effectively enhanced the electrochemical performance of the electrode. With the existence of Enrofloxacin (ENR), the aptamer recognizes and binds to ENR, thus the signal probe cDNA was released and immobilized onto the electrode surface to hybridized with methylene blue (MB) labelled DNA (MB-DNA), thereby triggering the Exo III-assisted cycle for further signal amplification. As expected, the prepared aptasensor demonstrated excellent sensitivity and selectivity, with a wide linear range from 5.0 × 10−6 ng/mL to 1.0 × 10−2 ng/mL for ENR, a low detection limit of 1.59 × 10−6 ng/mL. Consequently, this strategy provided a promising avenue for ultrasensitive and accurate detection of ENR in milk samples.

Electrochemical biosensor based on RNA aptamer and ferrocenecarboxylic acid signal probe for C-reactive protein detection

Monitoring health-related biomarkers using fast and facile detection techniques provides key physicochemical information for disease diagnosis or reflects body health status. Among them, electrochemical detection of various bio-macromolecules, e.g., the C-reactive protein (CRP), is of great interest in offering potential diagnosis for acute inflammation caused by infections, heart diseases, etc. Herein, a novel electrochemical aptamer biosensor was constructed from Ti3C2Tx MXene and in-situ reduced Au NPs for thiolated-RNA aptamer immobilization and CRP protein detection using Fc(COOH) as the signal probe. The sensory performances for CRP detection were optimized based on working conditions, including the incubation times and the pH. The large surface area offered by Ti3C2Tx MXene and high electrical conductivity originating from Au NPs endowed the as-fabricated aptamer biosensor with a decent sensitivity for CRP in a wide linear range of 0.05–80.0 ng/mL, good selectivity over interfering substances, and a low detection limit of 0.026 ng/mL. Such aptamer biosensors also detected CRP in serum samples using the spike & recovery method with reasonable recovery rates. The results demonstrated the potential of the as-fabricated electrochemical aptamer biosensor for fast and facile CRP detection in practical applications.

Exo I-based cyclic digestion coupled with synergistic enhancement strategy for integrating dual-mode optical aptasensor platform

The improvement of dual-mode techniques was of particular interest to researchers, which might enhance the detection performance and applicability. Here, a dual-mode optical aptasensor (DO-aptasensor) platform based on exonuclease I (Exo I) cyclic digestion and synergistic enhancement strategy had proposed for zearalenone (ZEN). Following the preparation of dumbbell-shaped signal probe, the Exo I-based cyclic digestion amplification performed, and then the synergistic enhancement effect carried out to achieve the Poly-HRP-based colorimetry and FAM-SGI-based fluorescence. The efficient homogeneous system realized through the magnetic separation, while the signal interference further eliminated by the graphene oxide (GO). The LOD values were as low as 0.067 ng mL−1 for colorimetry mode and 0.009 ng mL−1 for fluorescence mode, which reduced 23-fold and 172-fold than ELASA by same ZEN-Apt. This promising platform gave rise to a dual-mode optical readout, improved sensitivity and positively correlated detection. Meanwhile, the DO-aptasensor also exhibited the acceptable specificity, desirable reliability and excellent practicability. This novel avenue of aptasensor platform hold great potential for dual-mode optical monitoring of other targets, which can further expand the application scope of Exo I-based signal amplification and synergistic enhancement effect.

Multiplex fluorescence quenching immunoassay based on multicolor magnetic quantum dot and dual spectral-overlapped polydopamine nanospheres for ultrasensitive detection of aflatoxin B1, zearalenone, ochratoxin A, and fumonisin B1

Due to the increasing fungal infections and the implementation of strict food safety regulations, the demand for sensitive, rapid, and easy assays for testing co-contaminated mycotoxins in food has grown in recent years. In this study, a multiplex fluorescence quenching immunoassay is developed to simultaneously detect prevalent mycotoxins in cereals, namely aflatoxin B1 (AFB1), zearalenone (ZEN), ochratoxin A (OTA), and fumonisin B1 (FB1). Four spherical nanocomposites with magnetic core and three-layer quantum dot (QD) shell (MagTQD) are fabricated. These nanocomposites exhibit different maximum emission peaks without overlap and interference at the same excitation wavelength. Four MagTQD conjugated with corresponding coating antigens to prepare four fluorescence signal probes with rapid magnetic enrichment ability, respectively. Moreover, polydopamine nanospheres (PDANs) with dual-spectral overlapped fluorescence quenching properties are conjugated with four mycotoxin antibodies to prepare four fluorescence quenching probes, respectively. The established immunoassay has the low detection limit at 1.29 pg mL−1 for AFB1, 0.80 pg mL−1 for ZEN, 1.97 pg mL−1 for OTA, and 13.89 pg mL−1 for FB1, respectively. This developed assay can provide a new approach to realize the efficient detection of multi-mycotoxins in food safety supervision.

Versatile Platinum Nanoparticles-Decorated Phage Nanozyme Integrating Recognition, Bacteriolysis, and Catalysis Capabilities for On-Site Detection of Foodborne Pathogenic Strains Vitality Based on Bioluminescence/Pressure Dual-Mode Bioassay.

Sensitive and on-site discrimination of live and dead foodborne pathogenic strains remains a significant challenge due to the lack of appropriate assay and signal probes. In this work, a versatile platinum nanoparticle-decorated phage nanozyme (P2@PtNPs) that integrated recognition, bacteriolysis, and catalysis was designed to establish the bioluminescence/pressure dual-mode bioassay for on-site determination of the vitality of foodborne pathogenic strains. Benefiting from the bacterial strain-level specificity of phage, the target Salmonella typhimurium (S.T) was specially captured to form sandwich complexes with P2@PtNPs on another phage-modified glass microbead (GM@P1). As the other part of the P2@PtNPs nanozyme, the introduced PtNPs could not only catalyze the decomposition of hydrogen peroxide to generate a significant oxygen pressure signal but also produce hydroxyl radicals around the target bacteria to enhance the bacteriolysis of phage and adenosine triphosphate release. It significantly improved the bioluminescence signal. The two signals corresponded to the total and live target bacteria counts, so the dead target could be easily calculated from the difference between the total and live target bacteria counts. Meanwhile, the vitality of S.T was realized according to the ratio of live and total S.T. Under optimal conditions, the application range of this proposed bioassay for bacterial vitality was 102-107 CFU/mL, with a limit of detections for total and live S.T of 30 CFU/mL and 40 CFU/mL, respectively. This work provides an innovative and versatile nanozyme signal probe for the on-site determination of bacterial vitality for food safety.