Search

Point-of-care testing (POCT) of pathogens is important for avoiding food poisoning. Here, dual-functional manganese dioxide nanoclusters (MnO 2 NCs) were elaboratively used as the fluidic driver and signal amplifier for exploring a new power-free biosensor for POCT of Salmonella. First, H 2 O 2 in three chambers of a microfluidic chip was finger driven simultaneously to dissolve MnO 2 NCs, resulting in the production of O 2 to respectively push preloaded immune magnetic nanobeads (IMNBs), bacterial sample and immune MnO 2 NCs (IMONCs) into a sinusoidal convergence-divergence micromixer. After they were efficiently mixed and incubated in a serpentine channel, IMNB-bacteria-IMONC conjugates were obtained and magnetically separated in a multifunctional chamber. Then, two washing solution were successively driven to rinse these conjugates. Finally, colorless H 2 O 2 -TMB substrate was driven to the multifunctional chamber and catalyzed by the IMONCs on the conjugates into blue catalysate, which was analyzed by developed smartphone APP to determinate bacteria amount. The biosensor enabled quantitative detection of 63 CFU/mL Salmonella within 30 min. The complete bacteria detection procedure was achieved on a single microfluidic chip without any peripheral equipment, and it has great potential for POCT of bacteria. [Display omitted] • Dual-functional MnO 2 nanoclusters were elaborately used as fluidic driver and signal amplifier. • The whole bacterial detection procedure was implemented free-of-power in a microfluidic chip. • The sinusoidal convergence-divergence micromixer was verified with good mixing effect. • Smartphone App was self-developed to accurately measure color change of catalysate. • This microfluidic biosensor was able to detect Salmonella as low as 63 CFU/mL in 30 min. [ABSTRACT FROM AUTHOR]

Nucleic acid amplification is crucial for disease diagnosis, especially lethal infectious diseases such as COVID-19. Compared with PCR, isothermal amplification methods are advantageous for point-of-care testing (POCT). However, complicated primer design limits their application in detecting some short targets or sequences with abnormal GC content. Herein, we developed a novel linear displacement isothermal amplification (LDIA) method using two pairs of conventional primers and Bacillus stearothermophilus (Bst) DNA polymerase, and reactions could be accelerated by adding an extra primer. Pseudorabies virus gE (high GC content) and Salmonella fimW (low GC content) genes were used to evaluate the LDIA assay. Using strand displacement (SD) probes, a LDIA-SD method was developed to realize probe-based specific detection. Additionally, we incorporated a nucleic acid-free extraction step and a pocket-sized device to realize POCT applications of the LDIA-SD method. The LDIA-SD method has advantages including facile primer design, high sensitivity and specificity, and applicability for POCT, especially for amplification of complex sequences and detection of infectious diseases. • A novel linear displacement isothermal amplification (LDIA) method was developed by using conventional primers. • Using strand displacement (SD) probes, an LDIA-SD method was established to realize probcleic acid-free extraction step and a pocket-sized device were used to realize its POCT applicate-based specific detection. • A nucleic acid-free extraction step and a pocket-sized device were used to realize its POCT applications. [ABSTRACT FROM AUTHOR]

• A new immunoassay using AI model was developed to rapidly detect candidiasis. • The YOLOv5 model was boosted by coordinate attention mechanism to detect pathogens quantitatively. • Transfer learning and multistage training strategy were used to train the model. • This proposed approach enabled the detection of Candida albicans as low as 3.5×102 CFU/mL in 45 min with an accuracy of 92.7%. Rapid detection of pathogens is of great significance to prevent the outbreak of poultry diseases. In this study, a new immunoassay based on coordinate attention boosted YOLOv5 model and quantum dot labeled fluorescence biosensing was developed to rapidly detect a common fungal infectious poultry disease, candidiasis. The target pathogen, Candida albicans , were specifically labeled by the immune quantum dots to form the fluorescent pathogen. Their fluorescent images were collected using a fluorescence microscope. The YOLOv5 model was boosted by coordinate attention mechanism for identifying the fluorescent pathogen in these images to obtain the quantitative results. With the help of transfer learning and multistage training, the intelligent model was successfully trained and applied. This proposed approach enabled the detection of Candida albicans as low as 3.5 × 102 CFU/mL in 45 min with an accuracy of 92.7 %, which was significantly higher than 87.2 % of YOLOv5 and 81.6 % of Faster RCNN. The new approach was featured with shorter detection time, lower cost and simpler operation, and showed its potential to provide a more efficient solution for pathogen screening. [ABSTRACT FROM AUTHOR]

Early finding of pathogens is significant to avoid foodborne diseases. Here, a novel lab-in-centrifugal-tube colorimetric biosensor was reported for Salmonella typhimurium detection using immune nickel nanowires (NNWs) to form capture nets for specific bacterial separation, gold@platinum nanozymes (GPNs) to mark target bacteria for effective signal amplification, and a smartphone App to analyze color change for quantitative bacterial determination. A 3D-printed cylindrical magnetic separator with air pressure self-regulating structure and NNW capture nets was elaboratively constructed and assembled inside the disposable centrifuge tube to simply perform the bacterial separation, label, wash, coloration and detection. Under optimal conditions, Salmonella typhimurium could be quantitatively detected in 2 h with a low detection limit of 21 CFU/mL. The recovery of target bacteria in spiked pork samples ranged from 87.0% to 97.6% with the averaged recovery of 93.9%. This biosensor was Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free and Deliverable to end-users (ASSURED), and had shown the potential for point-of-care testing of foodborne pathogens to ensure food safety. [ABSTRACT FROM AUTHOR]

A novel colorimetric biosensor was explored for fast, sensitive, and on-site detection of Salmonella on a microfluidic chip employing immune gold@platinum nanoparticles (Au@Pt NPs) for specific bacterial labeling, a finger-driven mixer with two serial air chambers for efficient immunoreaction and a nuclear track membrane as specific-size microfilter for effective bacterial isolation from excessive immune Au@Pt NPs. First, the bacterial sample and immune Au@Pt NPs were pipetted into the mixing chamber and mixed sufficiently through repeated press-release actions on the small air chamber which could precisely control the air volume, leading to the formation of bacteria-immune Au@Pt NP conjugates. Then, the small and large air chambers were pressed simultaneously to push all the solution in the mixing chamber to flow through the microfilter for trap of the formed larger-size conjugates on the membrane and removal of the unbound smaller-size immune Au@Pt NPs. After the H 2 O 2 -TMB substrate was pipetted into the microfilter and catalyzed by the conjugates, ImageJ was used to analyze the color change for bacterial determination. This simple biosensor enabled Salmonella detection as low as 168 CFU/mL in 25 min. [ABSTRACT FROM AUTHOR]

Screening of pathogenic bacteria is an essential measure for ensuring food safety. A fast, sensitive and automatic platform for Salmonella determination was presented employing continuous-flow magnetic isolation, enzymatic impedance amplification and smartphone data analysis. First, magnetic nanoparticles coupling with polyclonal antibody, polystyrene spheres coupling with monoclonal antibody and glucose oxidase, and bacterial sample were simultaneously immitted into reaction chamber, and actively mixed for formation of MNP- Salmonella -PS complexes in the microfluidic chip. After the MNP- Salmonella -PS complexes were continuous-flow caught in separation channel using the enhanced magnetic field and successively washed for removing redundant immune PSs and remanent ions, glucose with high impedance was then pumped and catalyzed into hydrogen peroxide and gluconic acid. Finally, impedance change of catalysate was dynamically measured with the on-chip PCB electrode and analyzed by the self-developed smartphone to quantify target bacteria. The microfluidic platform was able to quantitatively detect Salmonella from 1.3 × 102 to 1.3 × 106 CFU/mL in 1.5 h with a detection limit of 53 CFU/mL. The recovery of Salmonella in spiked chicken meats ranged from 88.2% to 112.0%, verifying its good practical applicability. This platform is featured with fast detection, high sensitivity and simple operation, and promising for in-field Salmonella screening. • An active stirring mixer in microfluidic chip was elaborately developed for efficient mixing. • The on-chip PCB electrode was proved for dynamic and accurate measurement of impedance. • Glucose-glucose oxidase-gluconic acid system was employed for effectively signal amplification. • This biosensor integrated whole detection procedures onto a chip to achieve automatic operations. • Salmonella typhimurium was detected to be as few as 53 CFU/mL within 1.5 h. [ABSTRACT FROM AUTHOR]

In-field screening of pathogenic bacteria is important for preventing food poisoning. Here, a portable pipette-adapted biosensor using magnetic grid separation and nanocatalyst signal amplification was elaboratively developed for rapid detection of Salmonella typhimurium. A common pipette was innovatively adapted with multiple functions to complete the whole bacterial detection procedure, including mixing, separation, catalysis, washing, detection, analysis and display. The target bacteria were effectively captured by the immune magnetic nanobeads and labeled with immune gold@platinum nanocatalysts through pipette-blowing mixing to form the nanobeads-bacteria-nanocatalyst complexes, which were separated against the magnetic grid separation tip under the magnetic field. The pressure change resulting from oxygen production due to mimicking catalysis of hydrogen peroxide by these nanocatalysts on the complexes was quantified through measuring the moving duration of the conductive liquid in the pipette for bacteria determination. Under optimal conditions, this biosensor could detect target bacteria in 90 min with low detection limit of 180 CFU/mL. This pipette-adapted biosensor is affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free and deliverable to end-users (ASSURED), and has the potential for in-field testing of foodborne pathogens to ensure food safety, especially in resource-constrained areas. [ABSTRACT FROM AUTHOR]

An hourglass-mimicking biosensor was developed to detect target bacteria in 15 mL centrifugal tube using immune magnetic nanobeads to isolate the target from large-volume sample, gold@platinum nanozymes to label the target for amplification of biological signals, and a microplate reader/colorimetric card for determination of the target. First, a centrifugal tube with an iron ball framework was first coaxially assembled in the center of a Halbach ring magnet. After immune magnetic nanobeads, gold@platinum nanozymes and bacterial sample were mixed by repeated bottom-up of the tube using a stepper motor, nanobead-bacteria-nanozyme complexes were formed. Then, colorless H 2 O 2 -TMB was catalyzed by the nanozymes to produce blue TMBox. The color change was finally analyzed using the microplate reader or colorimetric card to determine bacterial concentration. This hourglass-mimicking biosensor could separate ∼95% targets from 10 mL bacteria sample and detect targets from 1.6 × 101 to 1.6 × 106 CFU/mL in 1.0 h with low detection limit of 16 CFU/mL. [ABSTRACT FROM AUTHOR]

Pathogen screening is an important measure for ensuring food safety. A colorimetric biosensor was presented for Salmonella determination employing staggered magnetic bead chains for continuous-flow bacteria isolation, MnO 2 nanozymes for effective signal amplification, and smartphone for accurate catalysate analysis. First, immune magnetic beads were distributed under the staggered magnetic field to form higher magnetic bead chains to occupy more cross-section of separation channel. Then, target bacteria were injected and captured onto magnetic bead chains, followed by labeling with the immune MnO 2 nanozymes to form bead-bacteria-nanozyme complexes. Finally, H 2 O 2 -TMB substrate was catalyzed by MnO 2 nanozymes on these complexes, and color change was monitored and analyzed through smartphone to quantify target bacteria. The sensor enabled Salmonella detection as few as 60 CFU/mL in 2 h. • The staggered magnetic field could enhance the occupation of MB chains in the channel. • The MnO 2 nanoflowers were used to greatly amplify the biological signal. • The smartphone App was developed for accurate analysis of color saturation. • This biosensor could detect Salmonella as low as 60 CFU/mL within 2 h. [ABSTRACT FROM AUTHOR]

Rapid detection of antibiotic resistance genes (ARGs) of food microorganisms is critical for preventing the spread of ARGs via the food chain. In this study, slipchip-based immunomagnetic separation (IMS) combined with loop-mediated isothermal amplification (LAMP) was developed for rapid, specific, sensitive and multi-sample detection of Bacillus cereus with tetracycline resistance gene tetL in pasteurized milk. First, the magnetic nanoparticles coated with anti- B. cereus polyclonal antibodies were mixed with samples in the magnetic capture chamber of the slipchip, and the capture efficiency of Bacillus cereus (105 CFU/mL) can reach 80% after incubation for 1h. Then, the captured bacteria were boiled in the lysis chamber using a heating block and the extracted DNA was added into the LAMP reaction as templates. Finally, real-time fluorescent LAMP detection for tetL gene of Bacillus cereus was performed at 65 °C for 50 min. Under optimal conditions, the IMS-LAMP could detect 11.6 CFU/mL of Bacillus cereus with tetL gene in pure culture. Furthermore, the limit of detection of Bacillus cereus with tetL gene in pasteurized milk was 21.5 CFU/mL by the slipchip-based IMS-LAMP within 2 h. Therefore, this method is potentially useful for the rapid detection of Bacillus cereus with tetracycline resistance gene tetL in pasteurized milk and could be extended for other resistance genes. • This method could detect 21.5 CFU/mL of B. cereus with tetL in pasteurized milk. • The IMBs could capture more than 80% B. cereus in 1 h. • Real-time fluorescent LAMP enabled specific detection for tetL of B. cereus. • The slipchip made the method easier, quicker and allowed multi-sample detection. • The detection process could be completed within 2 h. [ABSTRACT FROM AUTHOR]

In this study, a power-free biosensor was presented to detect Salmonella typhimurium on a microfluidic chip using a slide multivalve for channel selection and a disposable syringe for fluidic transfer. First, bacterial sample with immunomagnetic nanoparticles (IMNPs) and glucose oxidase (GOx) modified immune polystyrene nanoparticles (IPNPs), washing buffer, glucose, and peroxide test strip (PTS) were preloaded in their respective chambers at the periphery of chip. After the slide multivalve was selected to connect sample chamber with common separation chamber, which was connected with a syringe, the mixture of Salmonella , IMNPs and IPNPs was back and forth moved through 3D Tesla-structure micromixer using the syringe, resulting in the formation of IMNP- Salmonella -IPNP complexes, which were captured in the separation chamber using a magnet. Then, two washing chambers were selectively connected respectively to remove sample background and excessive IPNPs, and glucose chamber was connected, allowing the GOx to catalyze glucose to produce hydrogen peroxide in the separation chamber. Finally, PTS chamber was connected and the catalysate was transferred from the separation chamber to the PTS chamber, leading to the color change of PTS, followed by using smartphone App to collect and analyze the image of PTS for bacterial determination. The simple biosensor enabled simple detection of Salmonella as few as 130 CFU/mL within 60 min and is promising for practical applications in the resource-limited regions due to its low cost, simple operation, and small size. [ABSTRACT FROM AUTHOR]

Early screening for food pathogens, specifically Escherichia coli O157:H7 in ready-to-eat food remains a central challenge, hyperspectral imaging (HSI) has the potential to acquire both image and spectral information of the target and is simple enough to serve as an effective auxiliary technology in food monitoring. Herein, a visual method was developed based on spectral angle mapping (SAM) and dark-field microscopy for rapid detection and quantification of Escherichia coli. First, immunomagnetic nanoparticle (MNP-probe) and gold nanoparticle (AuNP-probe) probes were prepared to form a sandwich complex for efficient concentration of the target bacteria. The complexes were then dropped directly on a glass slide for colony counting with hyperspectral dark field microscopy. The AuNP-probe bound to the complex was counted and SAM was used to evaluate the spectra and HSI image data to distinguish the target pixel from the background. The linear detection range of the method was estimated to be in the range between 6.1 × 101 and 6.1 × 106 CFU/mL in the milk sample, and the detection limit (LOD) of this method was estimated to be ~61 CFU/mL. The average recovery of organisms in the milk sample was 106.0%, indicating that this method can be utilized to detect Escherichia coli in food samples and serve as an effective method to monitor pathogens in a complex sample. • Colorimetric quantification based on spectral angle mapping (SAM) and hyperspectral dark-field imaging. • Detection of Escherichia coli as low as 61 CFU/mL within ~80 min. • Excellent recovery of organisms. • High specificity of detection was also demonstrated. [ABSTRACT FROM AUTHOR]

Foodborne probiotics substantially impact human health. Thus, there is an urgent need for real-time and in situ detection of targeted probiotics. In this paper, a novel nanopopcorn fluorescent probe based on DNA-mediated Au@Ag@silica was designed and shown to display plasma resonance characteristics that generated more hot spots. This led to >18-fold greater fluorescence of indocyanine green dye with strong emission in the near-infrared (NIR-I and NIR-II) regions. Moreover, the new fluorescent probe exhibited high stability and low biotoxicity, having a strong linear relationship (R2 = 0.9615) with Lactobacillus Plantarum concentration over the range of 105−109 cfu/mL; it enabled in vivo tracing of exogenous probiotics. Compared with the traditional inductively coupled mass spectrometry (ICP-MS), the results are consistent (Correlation coefficient = 0.994), but the analysis time is much reduced by 89.6%. It is remarkable that the probe enabled real-time and in situ monitoring of target probiotic behavior in a simple, robust, and effective manner. [ABSTRACT FROM AUTHOR]

Rapid and sensitive screening of pathogens is a key to prevent the outbreak of foodborne illnesses. Herein, a new colorimetric immunoassay was proposed based on the release of Ag+ ions from AgNPs and the inhibition of PtNPs, and its supporting microfluidic platform was developed to automatically perform the whole bacterial detection procedure using Raspberry Pi and smartphone App. First, the immune AgNPs and magnetic nanobeads (MNBs) were used to conjugate with Salmonella typhimurium. Then, H 2 O 2 was used to etch the AgNPs for release Ag+ ions. Finally, the colorimetric signal was greatly diminished because of the specific and efficient inhibition of Ag+ toward the peroxidase-like activity of the PtNPs. This colorimetric immunoassay showed a good specificity and an ultralow detection limit of 16.8 CFU/mL, which was about 3 orders of magnitude improvement compared with conventional ELISA, and the averaged recovery for the spiked chicken samples was 95.6%. The combination of this immunoassay with this microfluidic platform might be promising for rapid and sensitive screening of foodborne pathogens to ensure food safety. [Display omitted] • A colorimetric immunoassay was proposed by releasing Ag + ions from AgNPs to inhibit PtNPs for bacterial detection. • A new microfluidic platform was developed to automatically perform the whole bacterial detection procedure. • This platform could detect Salmonella typhimurium as low as 16.8 CFU/mL in 1 h. [ABSTRACT FROM AUTHOR]

Considering processing concerns regarding emerging food safety incidents and large-scale food testing, efficient and straightforward screening tools are urgently needed. The requirements for this technology include effective sample pretreatment, sensitive assay, and sample-to-answer solution that enable the detection of trace amounts of contaminants in complex food matrices. Here, we developed a chemiluminescence- and optical fiber-based fully automated immunosensing (COFFAI) system that conducts chemical contaminant food screening in a truly "sample-to-result" manner. Instead of utilizing laborious benchtop sample purification techniques followed by a time-consuming manual ELISA procedure, the user simply injects the sample of interest, and the whole procedure is automatically processed. We demonstrated that the utility of our COFFAI system can be used to detect trace amounts of chemical contamination in various milk samples within approximately 75 min. This method showed an ultrahigh sensitivity with a quinolone detection limit in the 0.022–0.065 µg/L range for skim milk, whole milk, and raw milk samples. The integration of pretreatment and assay into one automated system is an effective method for food testing. We believe that this platform provides a general method for efficient contaminant screening in foodstuffs. [Display omitted] • We designed a fully automated system that enables "sample-to-result" contaminant screening. • A novel immunoaffinity-based sample pretreatment method that does not require the use of an organic solvent was designed. • An optical fiber and charge-coupled device sensor was used for highly sensitive quantification. [ABSTRACT FROM AUTHOR]

A lab-on-a-tube biosensor was established to rapidly, sensitively and automatically detect foodborne bacteria through a rotatable Halbach magnet to form and rotate magnetic nanobead (MNB) chains for specific isolation of target bacteria, gold@platinum nanocatalysts (Au@PtNCs) to label target bacteria for efficient amplification of detection signal and Raspberry Pi App to collect and analyze the image of catalysate. First, the glass tube was successively preloaded with the mixture of MNBs, sample and Au@PtNCs, the washing buffer (skim milk) and the substrate (hydrogen peroxide-3,30,5,50-tetramethylbenzidine), and they were separated by air gaps. After the tube was placed on the biosensor, the MNB chains were stably formed and continuously rotated using the Halbach magnet and the mixture was moved back and forth using a programmable peristaltic pump, thus making the formation of MNB-bacteria-Au@PtNCs complexes. After the washing buffer was moved to wash the complexes, the substrate was then moved to resuspend the complexes, resulting in the catalytic reaction that changed the color of the substrate. Finally, the catalysate was moved to the designated area, the image of which was analyzed by the Raspberry Pi App to quantitatively determine the concentration of bacteria in the samples. This biosensor was able to detect Salmonella in spiked chicken samples in 1 h with lower detection limit of 8 CFU/50 μL and a recovery from 88.96% to 99.74%. This biosensor based on a single tube is very promising to automatically detect foodborne bacteria due to its low cost, high integration and simple operation. [Display omitted] • The MNB chains were successfully formed and rotated by rotating the Halbach magnet. • The rotated MNB chains were able to effectively capture and label the target bacteria. • Mixing, separation, catalysis and detection were automatically performed in the tube. • This biosensor was able to detect Salmonella as low as 8 CFU/sample within 1 h. [ABSTRACT FROM AUTHOR]

The morphology of nanomaterials plays a critical role in their physicochemical properties, and a precise modulation of the morphology is vitally important. As a promising capping agent, DNA has been used for directing the transition of metal nanoparticle seeds into different morphologies with enhanced properties, which has received extensive attention in biosensing. This paper reviews the research on DNA-mediated growth of noble metal nanomaterials for biosensing applications. We present the formation mechanism, which mainly includes DNA binding to metal nanoparticles, metal ion reduction, and regrowth on nanoparticle seeds. We then systematically summarize various metal nanomaterials with different morphologies mediated by physisorbed and thiolated DNA, and introduce the stability, recognition, surface-enhanced Raman scattering, surface plasmon resonance, catalytic, and biocompatibility properties of these nanomaterials and their biosensing applications. This review provides a ground for further research on the DNA-mediated growth of nanomaterials and their application to biosensing and beyond. • The morphology of metal nanomaterial plays a critical role in biosensing applications. • The growth of metal nanomaterials can be mediated via absorption or covalent binding. • DNA-mediated nanomaterials have versatile properties and biosensing applications. • The challenges and prospects focus on material innovations, DNA, and analytes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pristine and ultrahigh-load metal-organic frameworks on inert glass fibers. • Hybrid membranes to collect organic hazardous substances in unconventional environs. • Presented ultrahigh-adsorption abilities to substances that included dyes and antibiotics. • Extraordinary robustness to high temperature, organic solvent, extreme alkaline solution. • Suitable for difficult environments, satisfactory recycling, and long-term operation abilities. Exploring new membrane matrices with demanding functions but inert surficial properties to prepare hybrid membranes is challenging. Inspired by biomineralization, we proposed a strategy to grow pristine and ultrahigh-load metal-organic frameworks (MOFs) on inert glass fibers (GF) to prepare GF@MOFs (ZIF-8) hybrid membranes to efficiently collect organic hazardous substance in conventional and unconventional solutions. Comparing with the poor coverage of the MOFs using the conventional method, this new method induced an ultra-high load of MOFs, and even interesting intergrown-particle-, sheet-flower-, and grain-like shapes. The GF@ZIFs exhibited adsorbability of malachite green up to 3964.8 mg g−1, whereas that of the reported analogues only reached 1667 mg g−1. The hybrid membranes also exhibited adsorption capability of 192.2 mg g−1 to tetracycline. More importantly, having benefited from the introduction of robust GF matrices, the robustness of the GF@ZIFs was significantly enhanced: synergetic effect derived from the GF and MOFs could be observed. Furthermore, all three types of GF@ZIFs presented well-maintained performance in 70-°C hot water, chloroform, and pH 14 NaOH solution, which are generally nonadoptive to conventional hybrid membranes. The GF@ZIF membranes were further developed as a filter device for rapid collection of over 95% malachite green (50 mg L−1, 10 mL) in 1 h. The proposed method could create a new direction for exploring new types of matrices to fabricate hybrid materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • First report on long-term monitoring of biohythane process via UMFC biosensor. • UMFCs dynamically reflected the COD of effluent from biohythane process. • Microbial evolution in MFC and bioreactor revealed various metabolic associations. • Drastic shift of microbial community in MFC with the effect of biohythane reactors. • Microbial network analysis suggested in-situ sensors had a more stable community. Microbial stability and evolution are a critical aspect for biosensors, especially in detecting dynamic and emerging anaerobic biohythane production. In this study, two upflow air–cathode chamber microbial fuel cells (UMFCs) were developed for in situ monitoring of the biohydrogen and biomethane reactors under a COD range of 1000–6000 mg/L and 150–1000 mg/L, respectively. Illumina MiSeq sequencing evidenced the dramatic shift of dominant microbial communities in UMFCs from hydrolytic and acidification bacteria (Clostridiaceae_1, Ruminococcaceae, Peptostreptococcaceae) to acetate-oxidizing bacteria (Synergistaceae, Dysgonomonadaceae , Spirochaetaceae). In addition, exoelectroactive bacteria evaluated from Enterobacteriaceae and Burkholderiaceae to Desulfovibrionaceae and Propionibacteriaceae. Especially, Hydrogenotrophic methanogens (Methanobacteriaceae) were abundant at 93.41% in UMFC (for monitoring hydrogen reactor), which was speculated to be a major metabolic pathway for methane production. Principal component analysis revealed a similarity in microbial structure between UMFCs and methane bioreactors. Microbial network analysis suggested a more stable community structure of UMFCs with 205 days' operation. [ABSTRACT FROM AUTHOR]

In this study, we firstly propose a novel smartphone-assisted visualization SNP genotyping method termed competitive activation cross amplification (CACA). The mutation detection strategy depends on the ingenious design of both a start primer and a verification probe with ribonucleotide insertion through competitive combination and perfect matching with the target DNA, Meanwhile, the RNase H2 enzyme was utilized to specifically cleave ribonucleotide insertion and achieve extremely specific dual verification. Simultaneously, the results allow both colorimetric and fluorescence product dual-mode visualization by using self-designed 3D-printed dual function cassette. We validated this novel CACA by analyzing the Salmonella Pullorum rfbS gene at the 237th site, successfully solve the current bottleneck of specific identification and visual detection of this pathogen. The concentration detection limits of the plasmid and genomic DNA were 1500 copies/μL and 3.98 pg/μL, respectively, and as low as the presence of 0.1% mutant-type can be distinguished from 99.9% wild-type. Combined with a powerful hand-warmer, which can provide heating more than 60 °C for 20 h to realize power-free, dual function cassette and smartphone quantitation, our novel CACA platform firstly realizes user-friendly, cost-effective, portable, rapid, and accurate POC detection of SNP. [Display omitted] • A novel visual SNP genotyping method named competitive activation cross amplification. • Dual visual signal include colorimetric and fluorescent product for SNP detection. • 3D-printed dual function cassette and self-designed smartphone app quantitation. • Power-free strategy suitable for POCT in remote areas. • The first solution for visual rapid detection of Salmonella Pullorum on site. [ABSTRACT FROM AUTHOR]

Rapid screening of pathogenic bacteria contaminated foods is crucial to prevent food poisoning. However, available methods for bacterial detection are still not ready for in-field screening because culture is time-consuming; PCR requires complex DNA extraction and ELISA lacks sensitivity. In this study, a microfluidic biosensor was developed for rapid, sensitive and automatic detection of Salmonella using metal-organic framework (MOF) NH 2 -MIL-101(Fe) with mimic peroxidase activity to amplify biological signal and Raspberry Pi with self-developed App to analyze color image. First, the target bacteria were separated and concentrated with the immune magnetic nanobeads (MNBs), and labeled with the immune MOFs to form MNB- Salmonella -MOF complexes. Then, the complexes were used to catalyze colorless o-phenylenediamine and H 2 O 2 to produce yellow 2,3-diaminophenazine (DAP). Finally, the image of the catalysate was collected under the narrow-band blue light and analyzed using the Raspberry Pi App to determine the bacterial concentration. The experimental results showed that this biosensor was able to detect Salmonella Typhimurium from 1.5 × 101 to 1.5 × 107 CFU/mL in 1 h with the lower detection limit of 14 CFU/mL. The mean recovery for Salmonella in spiked chicken meats was ~112%. This biosensor integrating mixing, separation, labelling and detection onto a single microfluidic chip has demonstrated the merits of automatic operation, fast reaction, less reagent and small size, and is promising for in-field detection of foodborne bacteria. • An active vibrating mixer was demonstrated with efficient and continuous-flow mixing. • The improved image processing under blue light was verified with higher sensitivity. • Mixing, separation, catalysis and detection were integrated for automatic operation. • This low-cost biosensor could detect Salmonella as low as 14 CFU/mL within 1 h. [ABSTRACT FROM AUTHOR]

An impedance biosensor using rotary magnetic separation and cascade reaction was developed for rapid and ultrasensitive detection of Salmonella typhimurium. First, magnetic nanoparticles (MNPs) modified with anti- Salmonella monoclonal antibodies were injected into a capillary at the presence of a rotary high gradient magnetic field, which was rotated by a stepper motor. Then, a bacterial sample was injected into the capillary and the target bacteria were continuous-flow captured onto the MNPs. After organic-inorganic hybrid nanoflowers were prepared using manganese dioxide (MnO 2), glucose oxidase (GOx) and anti- Salmonella polyclonal antibodies (pAbs), they were injected to label the bacteria, resulting in the formation of MNP-bacteria-nanoflower sandwich complexes. Finally, glucose (low conductivity) was injected and oxidized by GOx on the complexes to produce H 2 O 2 (low conductivity) and gluconic acid (high conductivity), leading to impedance decrease. Besides, the produced H 2 O 2 triggered a cascade reduction of MnO 2 into Mn2+, leading to further impedance decrease. The impedance changes were measured using an interdigitated microelectrode and used to determine the concentration of target bacteria. This biosensor was able to detect Salmonella ranging from 101 to 106 CFU/mL in 2 h with a low detection limit of 101 CFU/mL and a mean recovery of 100.1% for the spiked chicken samples. • Rotatory magnetic separation was used to separate bacteria for first time. • Two cascade reaction was used to amplify impedance signal. • The method was able to detect Salmonella as low as 101 CFU/mL in 2 h. • The mean recovery for the spiked chicken meat samples was 100.1%. [ABSTRACT FROM AUTHOR]

Screening of pathogenic bacteria in foods is an effective way to prevent foodborne diseases. In this study, an impedance biosensor was developed for rapid and sensitive detection of Salmonella typhimurium using multiple magnetic nanobead (MNB) nets in a ring channel for continuous-flow separation of target bacteria from 10 mL of sample, manganese dioxide nanoflowers (MnO 2 NFs) for efficient amplification of biological signal, and an interdigitated microelectrode for sensitive measurement of impedance change. First, the MNBs modified with capture antibodies were vortically injected from outer periphery of this ring channel to form multiple ring MNB nets at specific locations with high gradient magnetic fields. Then, the bacterial sample was continuous-flow injected, resulting in specific capture of target bacteria onto the nets, and the MnO 2 NFs modified with detection antibodies were injected to form MNB-bacteria-MnO 2 NF complexes. After the complexes were washed with deionized water to remove excessive nanoflowers and residual ions, H 2 O 2 with poor conductivity was injected to reduce MnO 2 NFs to conductive Mn2+ at neutral medium, leading to impedance decrease. Finally, impedance change was measured using the microelectrode for quantitative determination of Salmonella. This biosensor was able to separate ~60% of Salmonella from 10 mL of bacterial sample and detect Salmonella with a linear range of 3.0 × 101 to 3.0 × 106 CFU/mL in 1.5 h with lower detection limit of 19 CFU/mL. This biosensor might be further improved with higher sensitivity using a larger volume (100 mL or more) for routine screening of foodborne bacteria without bacterial pre-culture. • Magnetic nanobead nets were formed to separate Salmonella from large-volume sample. • MnO 2 nanoflowers were first used to amplify impedance signal for bacteria detection. • This impedance biosensor could detect Salmonella as low as 19 CFU/mL in 1.5 h. • The mean recovery of Salmonella in spiked chicken samples was 101.8%. • This biosensor might be promising for bacterial routine screening without pre-enrichment. [ABSTRACT FROM AUTHOR]

• Pt@MnO 2 nanoflowers were synthesized for dual mimic enzymatic catalysis of H 2 O 2. • Piezoresistor was combined with smartphone to real-time monitor pressure change. • This pressure biosensor was able to detect Salmonella as low as 13 CFU/mL in 1.5 h. • The mean recovery of Salmonella in the spiked chicken samples was 96.8%96.8 %. Salmonella is the leading factor for microbial food poisoning. In this study, a facile pressure biosensor was developed for rapid and sensitive detection of Salmonella using magnetic nanobeads (MNBs) to separate target bacteria, platinum nanoparticle loaded manganese dioxide nanoflowers (Pt@MnO 2 NFs) to amplify detection signal, and a thin-film piezoresistor based pressure detector to monitor pressure change. First, the capture antibodies (CAbs) modified MNBs were used to specifically separate Salmonella from sample to form MNB-CAb- Salmonella complexes (magnetic bacteria). Then, the detection antibodies (DAbs) modified Pt@MnO 2 NFs were used for labelling magnetic bacteria to form MNB-CAb- Salmonella -DAb-Pt@MnO 2 NF complexes (nanoflower bacteria). After nanoflower bacteria were resuspended with H 2 O 2 in a sealed centrifuge tube, H 2 O 2 was catalyzed by Pt@MnO 2 NFs to produce O 2 , resulting in the increase on pressure. Finally, the pressure increase was real-timely monitored by piezoresistor based pressure detector and transferred to smartphone App via Bluetooth for analysis and determination of Salmonella. This biosensor could quantitatively detect Salmonella from 1.5 × 101 to 1.5 × 105 CFU/mL in 1.5 h with low detection limit of 13 CFU/mL. The Pt@MnO 2 NFs with high loading capacity of platinum nanoparticles were demonstrated as dual mimic enzymatic catalyst of H 2 O 2 to greatly enhance the sensitivity. More importantly, it is the first time to combine a thin-film piezoresistor with a smartphone App for realtime monitoring of the pressure change resulting from the mimic enzymatic catalysis of H 2 O 2 into O 2 by the Pt@MnO 2 NFs on the target bacteria to determine pathogenic bacteria in food samples. [ABSTRACT FROM AUTHOR]

• Novel SERS tags with cracked octahedral shape and small protrusion shape were fabricated. • The SERS tags have strong Raman signal and bio-recognition specificity. • Sensitive and simultaneous detection of E. coli O157:H7 and S. typhimurium were achieved. • Limit of detection of E. coli O157:H7 and S. typhimurium were lower than 10 cfu/mL. • This study provides a promising method for simultaneous detection of various pathogens. A biosensor based on novel SERS tags, consisting of gold nanorods (GNRs) complexed with oligonucleotide aptamers and the Raman reporters, was developed for the sensitive and simultaneous detection of different food pathogens. The aptamers not only act as bio-recognition molecules, but along with the Raman reporters, induce the GNRs to grow to specific shapes, which in turn enhance the Raman signal and facilitate sensitive detection. Signal interference during the simultaneous detection of pathogens is avoided, due to the stable anchored aptamers and embedded Raman reporters. We combined the novel SERS tags with antibody-modified magnetic nanoparticles to create a biosensor capable of simultaneous detection of Escherichia coli O157:H7 and Salmonella typhimurium with good linear response (101 to 106 cfu/mL), high detection sensitivity (<8 cfu/mL) and recovery rate (95.26–107.88%) in spiked food samples. This strategy achieves the goal of sensitive and simultaneous quantitative detection of pathogens. [ABSTRACT FROM AUTHOR]

A press-actuated slidable microfluidic colorimetric biosensor was designed for rapid, sensitive and multi-channel detection of Salmonella. The nickel mesh sheet (NMS) modified with capture antibodies was employed for capturing target bacteria, and metal organic frameworks decorated with palladium (Pd) and platinum (Pt) nanoparticles (MIL-88@Pd/Pt NPs) modified with detection antibodies were used for amplifying colorimetric signals. The capture efficiency of the immune NMS reached 83 %, and the detection limit of this colorimetric biosensor was 35 CFU/mL in 20 min. The average recoveries for Salmonella in spiked chicken meats ranged from 92.2 % to 102.5 % with a variation from 3.7 % to 7.2 %. The press-actuated slidable microfluidic chip was elaboratively developed with multiple functions, including mixing, separation, washing, catalysis and detection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Bioaerosol infections containing pathogenic viruses and bacteria have resulted in significant economic losses and posed a serious threat to public health, as evidenced by outbreaks of coronavirus disease and avian influenza. Consequently, the sampling and screening of bioaerosols are crucial for the prevention of bioaerosol-borne diseases. In this study, an ultrasensitive biosensor based on zeolitic imidazolate framework-8-melamine foam (ZIF-8-MF) was innovatively developed for the specific capture and in situ detection of bioaerosols. The bacterial bioaerosols were collected by a wet cyclone into phosphate-buffered saline (PBS) buffer at a high collection rate, achieving a satisfactory collection efficiency of ∼80% within 10 min. The target bacteria collected in the PBS buffer were specifically captured and effectively concentrated using immune ZIF-8-MF. The gold@platinum nanozymes (GPNs) were employed to specifically label the captured target bacteria and efficiently amplify the biological signal. And the resulting colorimetric signal was analyzed via a self-developed smartphone application (App). This biosensor demonstrated the capability to detect bioaerosols containing Salmonella typhimurium in the range of 1.6 × 10 2 -1.6 × 10 5 CFU/m 3 within 1.5 h, with a detection limit as low as 100 CFU/m 3 . Compared with other bioaerosol detection methods, the biosensor offered advantages such as high collection rate, specific capture, efficient concentration, and in situ detection, positioning it as a highly promising and practical tool for the monitoring of bioaerosols containing diverse pathogenic bacteria.

Low levels of human norovirus (HuNoV) in food and environment present challenges for nucleic acid detection. This study reported an evaporation-enhanced hydrogel digital reverse transcription loop-mediated isothermal amplification (HD RT-LAMP) with interfacial enzymatic reaction for sensitive HuNoV quantification in food and water. By drying samples on a chamber array chip, HuNoV particles were enriched in situ. The interfacial amplification of nucleic acid at the hydrogel-chip interface was triggered after coating HD RT-LAMP system. Nanoconfined spaces in hydrogels provided a simple and rapid "digital format" to quantify single virus within 15 min. Through in situ evaporation for enrichment, the sensitivity level was increased by 20 times. The universality of the sensitivity-enhanced assay was also verified using other bacteria and virus. Furthermore, a deep learning model and smartphone app were developed for automatic amplicon analysis. Multiple actual samples, including 3 lake waters, strawberry, tap water and drinking water, were in situ enriched and detected for norovirus quantification using the chamber arrays. Therefore, the sensitivity-enhanced HD RT-LAMP is an efficient assay for testing biological hazards in food safety monitoring and environmental surveillance., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier B.V. All rights reserved.)

The serious combination of abundant electrons/holes in bulk primarily hinders the efficiency in the photocatalytic reaction. It is crucial to control the spatial charge dynamics through delicately designing the crystal configuration of photocatalyst. In this work, a modified tungsten trioxide nanosheet colloid (M-WO 3 ) was synthesized by an ion exchange method. Compared to pristine WO 3 (P-WO 3 ), the crystal lattice vibration frequency of M-WO 3 increases from 2.8 meV to 4.3 meV, which effectively prohibits electron-phonon coupling and powerfully accelerates the separation and transfer of photoinduced charge carriers. Irradiated by visible-light, M-WO 3 shows much higher photocatalytic bacterial inactivation performance than P-WO 3 . In addition, this regulation method increases the surface charges of the WO 3 colloid to improve its stability, which endows this colloid photocatalyst with broad prospects in practical photocatalytic antibacterial applications. This work offers guidance to construct efficiently separated photoinduced electron/hole pairs of the colloid photocatalyst by designing its crystal structure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Pathogen testing is effective to prevent food poisoning. Here, an electrochemical biosensor was explored for Salmonella detection by combining magnetic grid based bacterial separation with enzymatic catalysis based signal amplification on a PCB interdigitated electrode in a microfluidic chip. First, immune magnetic nanobeads, target bacteria, and immune polystyrene microspheres decorated with glucose oxidase were sufficiently mixed to form nanobead-bacteria-microsphere sandwich conjugates. Then, these conjugates were injected into the chip to form conjugate chains right over the electrode under an iron grid enhanced magnetic field. After non-conductive glucose was injected and catalyzed by glucose oxidase on the conjugate chains, conductive glucose acid and non-conductive hydrogen peroxide were continuously produced and rapidly diffused from the conjugate chains to the electrode. Finally, the impedance change was real-timely monitored and used to determine the bacterial amount. This sensor enabled detection of 50 CFU/mL Salmonella typhimurium in 1 h., Competing Interests: The authors declare no competing interests., (© 2023 The Authors.)

Tumor necrosis factor-alpha (TNF-α) neutralization has become increasingly important in the treatment of inflammatory bowel diseases (IBD). A series of monoclonal antibodies were approved in the clinic for anti-TNF-α therapy. However, a comprehensive assessment of TNF-α levels throughout the colon, which facilitates the diagnosis of IBD and predicts anti-TNF-α efficacy, remains challenging. Here, we radiolabeled infliximab with long-lived radionuclides 89 Zr for immuno-positron emission tomography (PET) imaging of TNF-α in vivo . The increased TNF-α level was detected in the inflammatory colon of the dextran sodium sulfate-induced colitis mice. The immuno-PET imaging of 89 Zr-desferrioxamine-infliximab reveals a high uptake (7.1 ± 0.3%ID/g) in the inflammatory colon, which is significantly higher than in the healthy control and blocked groups. The colon-to-muscle ratio reached more than 10 and was maintained at a high level for 10 h after injection. The ex vivo biodistribution study also verified the superior uptake in the inflammatory colon. This study provides an in vivo immune-PET approach to molecular imaging of the pro-inflammatory cytokine TNF-α. It is promising in diagnosing and predicting efficacy in both IBD and other autoimmune diseases.

Rapid screening of foodborne pathogens is key to preventing food poisoning. In this study, a slidable centrifugal disc was developed for automatic and multi-channel detection of Salmonella typhimurium using Flinders Technology Associates (FTA) cards for nucleic acid extraction and recombinase aided amplification (RAA) for nucleic acid detection. The slidable FTA switching and centrifugal fluidic control were elaborately combined to achieve fully automatic operations, including centrifugation of the bacterial sample to obtain the concentrated bacteria, heating and drying of the FTA card to extract the nucleic acids, washing of the FTA card to remove the impurities, and RAA detection of the extracted DNA to determine the concentration. Under the optimal conditions, this slidable centrifugal disc was able to detect 10 CFU mL -1 in a spiked chicken meat supernatant in 1 h with an average recovery of 101.8% and an average standard deviation of 6.5%. This disc has been demonstrated as an alternative for sample-in-result-out detection of Salmonella and has shown potential for simultaneous detection of multiple bacteria.

In-field screening of foodborne pathogens plays an important role in ensuring food safety. Thus, a microfluidic biosensor was developed for rapid and sensitive detection of Salmonella using manganese dioxide nanoflowers (MnO 2 NFs) for amplifying the biological signal, a microfluidic chip with a convergence-divergence spiral micromixer for performing automatic operations, and a smartphone app with a saturation calculation algorithm for processing the image. First, immune magnetic nanoparticles (MNPs), the sample, and immune MnO 2 NFs were fully mixed and sufficiently incubated in the spiral micromixer to form MNP-bacteria-MnO 2 sandwich complexes, which were magnetically captured in a separation chamber in the microfluidic chip. Then, a 3,3',5,5'-tetramethylbenzidine (TMB) substrate was injected and catalyzed by a MnO 2 NF nanomimetic enzyme on the complexes, resulting in the production of yellow catalysate. Finally, the catalysate was transferred into a detection chamber and its image was measured and processed using the smartphone app to determine the number of bacteria. This biosensor was able to detect Salmonella from 4.4 × 10 1 to 4.4 × 10 6 CFU/mL in 45 min with a detection limit of 44 CFU/mL, and has the potential to provide a promising platform for on-site detection of foodborne bacteria.

Screening of foodborne pathogens is an effective way to prevent microbial food poisoning. A microfluidic biosensor was developed for rapid and sensitive detection of Salmonella Typhimurium using quantum dots (QDs) as fluorescent probes for sensor readout and manganese dioxide nanoflowers (MnO 2 NFs) and as QDs nanocarriers for signal amplification. Prior to testing, amino-modified MnO 2 nanoflowers (MnO 2 -NH 2 NFs) were conjugated with carboxyl-modified QDs through EDC/NHSS method to form MnO 2 -QD NFs, and MnO 2 -QD NFs were functionalized with polyclonal antibodies (pAbs) to form MnO 2 -QD-pAb NFs. First, the mixture of target Salmonella Typhimurium cells and magnetic nanoparticles (MNPs) modified with monoclonal antibodies (mAbs) was injected with MnO 2 -QD-pAb NFs into a microfluidic chip to form MNP-bacteria-QD-MnO 2 complexes. Then, glutathione (GSH) was injected to dissolve MnO 2 on the complexes into Mn 2+ , resulting in the release of QDs. Finally, fluorescent intensity of the released QDs was measured using the fluorescent detector to determine the amount of Salmonella . A linear relationship between fluorescent intensity and bacterial concentration from 1.0 × 10 2 to 1.0 × 10 7 CFU/mL was found with a low detection limit of 43 CFU/mL and mean recovery of 99.7% for Salmonella in spiked chicken meats, indicating the feasibility of this biosensor for practical applications., Competing Interests: The authors declare no conflict of interest.

Screening of pathogenic bacteria is a key to avoid food poisoning. The major drawbacks of existing assays for foodborne bacteria detection include long time for culture, complex DNA extraction for the polymerase chain reaction (PCR), and low sensitivity for enzyme-linked immunosorbent assay (ELISA), greatly limiting their practical applications. Here, we developed a sensitive optical biosensor based on porous gold@platinum nanocatalysts (Au@PtNCs) and a passive three-dimensional (3D) micromixer for fast detection of Salmonella typhimurium . The target Salmonella cells were first separated using immunomagnetic nanoparticles and the passive 3D micromixer. Then, immune Au@PtNCs were labeled onto the target cells as signal output to catalyze hydrogen peroxide-3,3',5,5'-tetramethylbenzidine. Finally, the absorbance was measured at 652 nm to calculate the bacterial amount. This optical biosensor could detect Salmonella at concentrations from 1.8 × 10 1 to 1.8 × 10 7 CFU/mL in 1 h. Its detection limit was calculated to be 17 CFU/mL. Besides, this passive 3D micromixer could magnetically separate 99% of target bacteria from the sample in 10 min. This biosensor has the potential to be extended to detect other bacteria by changing the antibodies.

Separation and concentration of target bacteria has become essential to sensitive and accurate detection of foodborne bacteria to ensure food safety. In this study, we developed a bacterial separation system for continuous-flow separation and efficient concentration of foodborne bacteria from large volume using a nickel nanowire (NiNW) bridge in the microfluidic chip. The synthesized NiNWs were first modified with the antibodies against the target bacteria and injected into the microfluidic channel to form the NiNW bridge in the presence of the external arc magnetic field. Then, the large volume of bacterial sample was continuous-flow injected to the channel, resulting in specific capture of the target bacteria by the antibodies on the NiNW bridge to form the NiNW-bacteria complexes. Finally, these complexes were flushed out of the channel and concentrated in a lower volume of buffer solution, after the magnetic field was removed. This bacterial separation system was able to separate up to 74% of target bacteria from 10 mL of bacterial sample at low concentrations of ≤10 2 CFU/mL in 3 h, and has the potential to separate other pathogenic bacteria from large volumes of food samples by changing the antibodies., Competing Interests: The authors declare no conflict of interest.