Spiked Food Samples Research Articles

Probe-based dual-chip digital loop-mediated isothermal amplification for the simultaneous detection of Staphylococcus aureus and Salmonella enteritidis in livestock and aquatic products

Staphylococcus aureus and Salmonella are common pathogens causing foodborne diseases, posing a serious threat to food safety. Accurate detection of foodborne pathogens is particularly critical. This study developed a probe-based dual-chip digital loop-mediated isothermal amplification (cdLAMP) technique that enables the simultaneous detection of Staphylococcus aureus and Salmonella in food samples. The chip contains 20,000 wells, each with a micro-reaction unit volume of approximately 1 nL. The dual-detection is achieved through the dual-color fluorescence channel equipped on the imaging analyzer. Compared with qPCR, the cdLAMP demonstrates superior sensitivity. In the detection of pure cultures and spiked food samples, the detection limit of two foodborne pathogens is 2 CFU/mL. In the detection of field samples, it is capable of detecting single colonies of both pathogens. The dynamic detection range spans 5 logs. In conclusion, the probe-based cdLAMP technique emerges as a user-friendly tool for detecting foodborne pathogens, providing a powerful platform for food safety testing.

3‐Hydroxy‐2‐naphthohydrazide: A Commercially Available Compound for Fluorescence Sensing of Ortho‐Vanillin and Vanillin

ABSTRACTVanillin and ortho‐vanillin are the most important flavoring additives used in the food industry at a large scale. Herein, the aggregation‐induced emission (AIE) behavior of commercially available 3‐hydroxy‐2‐naphthohydrazide (3HN) was explored and applied for the detection of vanillin and ortho‐vanillin. The weakly fluorescent 3HN in DMSO showed fluorescence enhancement at 500 nm with the increase in HEPES or PBS buffer (pH 7.4) fractions in DMSO. The 3HN in DMSO containing 30% HEPES buffer is used as Probe 1 for the selective detection of ortho‐vanillin. Probe 1 showed a new fluorescence emission at 415 nm for ortho‐vanillin without altering the probe emission at 500 nm. With high specificity, Probe 1 can detect ortho‐vanillin down to 0.3 μM. In contrast, 3HN in DMSO containing 20% PBS buffer is used as Probe 2 for the selective turn‐off detection of vanillin. The green fluorescence emission of Probe 2 at 500 nm is selectively quenched by vanillin with a detection limit of 0.8 μM. Finally, the analytical novelty of the developed probes was examined by quantifying ortho‐vanillin and vanillin in spiked food samples with good recovery percentages.

Development of an ultrasensitive electrochemical aptasensor based on aptamer/rGO/SPGE for the detection of Botulinum neurotoxin A (BoTN/A) in food samples

Consumption of Botulinum neurotoxin A (BoTN/A) contaminated foods has increased the public health issues which necessitates the development of rapid and simple diagnostic tools for their sensitive detection. Electrochemical aptasensors can replace existing biosensors and traditional methods of BoTN/A detection in foods. These aptasensors are simple, quick response, economic, precise, sensitive, accurate and reproducible. In the present study, an electrochemical aptasensor was constructed by immobilizing BoTN/A specific aptamer and reduced graphene oxide (rGO) onto screen printed gold electrode (SPGE) for the detection of BoTN/A in spiked food samples. The specificity of this aptasensor was achieved by conjugating BoTN/A specific aptamer on rGO/SPGE. Test sample containing BoTN/A form aptamer-BoTN/A complex onto SPGE which was directly proportional to BoTN/A concentration. Formation of aptamer-BoTN/A complex reduced the surface of working SPGE for redox reactions. Thus decreased the current peaks that was taken as measuring signal of BoTN/A in test food sample. BoTN/A aptasensor showed optimum response at pH 6.5 and 30 °C temperature. The responsetime of BoTN/A/aptamer/rGO/SPGE was 6 s. In optimum conditions aptamer/rGO/SPGE BoTN/A aptasensor exhibited wide linearity ranges from 1-100 pM and 1 pM limit of detection (LOD). The analytical recoveries of aptamer/rGO/SPGE BoTN/A aptasensor at 5 pM and 10 pM BoTN/A were 98.5 % and 99.8 % respectively. The proposed aptasensor showed unique sensitivity, reproducibility and accuracy. Moreover, aptamer/rGO/SPGE aptasensor was used for the detection of BoTN/A in five different types of food samples.

Salmonella Detection in Food Using a HEK-hTLR5 Reporter Cell-Based Sensor.

The development of a rapid, sensitive, specific method for detecting foodborne pathogens is paramount for supplying safe food to enhance public health safety. Despite the significant improvement in pathogen detection methods, key issues are still associated with rapid methods, such as distinguishing living cells from dead, the pathogenic potential or health risk of the analyte at the time of consumption, the detection limit, and the sample-to-result. Mammalian cell-based assays analyze pathogens' interaction with host cells and are responsive only to live pathogens or active toxins. In this study, a human embryonic kidney (HEK293) cell line expressing Toll-Like Receptor 5 (TLR-5) and chromogenic reporter system (HEK dual hTLR5) was used for the detection of viable Salmonella in a 96-well tissue culture plate. This cell line responds to low concentrations of TLR5 agonist flagellin. Stimulation of TLR5 ligand activates nuclear factor-kB (NF-κB)-linked alkaline phosphatase (AP-1) signaling cascade inducing the production of secreted embryonic alkaline phosphatase (SEAP). With the addition of a ρ-nitrophenyl phosphate as a substrate, a colored end product representing a positive signal is quantified. The assay's specificity was validated with the top 20 Salmonella enterica serovars and 19 non-Salmonella spp. The performance of the assay was also validated with spiked food samples. The total detection time (sample-to-result), including shortened pre-enrichment (4 h) and selective enrichment (4 h) steps with artificially inoculated outbreak-implicated food samples (chicken, peanut kernel, peanut butter, black pepper, mayonnaise, and peach), was 15 h when inoculated at 1-100 CFU/25 g sample. These results show the potential of HEK-DualTM hTLR5 cell-based functional biosensors for the rapid screening of Salmonella.

Computational simulation-assisted template selection of magnetic MOFs molecularly imprinted materials applying the adsorption and detection of multiple fluoroquinolones

This study utilized computational simulation and surface molecular imprinting technology to develop a magnetic metal-organic framework molecularly imprinted polymer (Fe3O4@ZIF-8@SMIP) capable of selectively recognizing and detecting multiple fluoroquinolones (FQs). The Fe3O4@ZIF-8@SMIP material was synthesized using the “common” template-ofloxacin, identified by computational simulation, demonstrating notable adsorption capacity (88.61–212.93 mg g−1) and rapid mass-transfer features (equilibration time: 2–3 min) for all tested FQs, consistent with Langmuir adsorption model. Subsequently, this material was employed as a magnetic solid-phase-extraction adsorbent for adsorption and detection of multiple FQs by combining with high performance liquid chromatography. The developed method exhibited good linearity for various FQs within the concentration range of 0.1–500 μg L−1, with low limit of detection (0.0605–0.1529 μg L−1) and limit of quantitation (0.2017–0.5097 μg L−1). Satisfactory recoveries (88.38–103.44%) were obtained when applied to spiked food samples, demonstrating the substantial potential of this Fe3O4@ZIF-8@SMIP material for rapid enrichment and identification for multiple FQs residues.

Detection of Tetracycline with a CRISPR/Cas12a Aptasensor Using a Highly Efficient Fluorescent Polystyrene Microsphere Reporter System.

CRISPR-based diagnostics use the CRISPR-Cas system trans-cleavage activity to identify specific target sequences. When activated, this activity cleaves surrounding reporter molecules, producing a detectable signal. This technique has great specificity, sensitivity, and rapid detection, making it an important molecular diagnostic tool for medical and infectious disease applications. Despite its potential, the present CRISPR/Cas system has challenges with its single-stranded DNA reporters, characterized by low stability and limited sensitivity, restricting effective application in complex biological settings. In this work, we investigate the trans-cleavage activity of CRISPR/Cas12a on substrates utilizing fluorescent polystyrene microspheres to detect tetracycline. This innovative discovery led to the development of microsphere probes addressing the stability and sensitivity issues associated with CRISPR/Cas biosensing. By attaching the ssDNA reporter to polystyrene microspheres, we discovered that the Cas12a system exhibits robust and sensitive trans-cleavage activity. Further work revealed that the trans-cleavage activity of Cas12a on the microsphere surface is significantly dependent on the concentration of the ssDNA reporters. Building on these intriguing discoveries, we developed microsphere-based fluorescent probes for CRISPR/Cas aptasensors, which showed stability and sensitivity in tetracycline biosensing. We demonstrated a highly sensitive detection of tetracycline with a detection limit of 0.1 μM. Finally, the practical use of a microsphere-based CRISPR/Cas aptasensor in spiked food samples was proven successful. These findings highlighted the remarkable potential of microsphere-based CRISPR/Cas aptasensors for biological research and medical diagnosis.

Isolation and characterization of two phages against emetic Bacillus cereus and their potential applications

AbstractBacillus cereus is a common foodborne pathogen capable of producing cereulide and enterotoxin. Consumption of food contaminated with cereulide can even result in fatality. Bacteriophages are increasingly being utilized as biocontrol agents to combat specific pathogens in a variety of food products. However, there are currently no lytic phages available to target cereulide‐producing B. cereus. This study aims to isolate and characterize two novel phages, DC1 and DC2, and assess their potential for use in food substrates. These two phages possessed the widest host range among the reported lytic phages that target B. cereus. The whole genome analysis demonstrated that DC1 and DC2 belonged to the Tsarbombavirus genus of the Bastillevirinae subfamily, which is part of the Herelleviridae family. The one‐step growth curve analysis revealed that DC1 had a latent period of 30 min and a burst size of approximately 39 PFU (plaque‐forming units) per cell. On the other hand, DC2 exhibited a shorter latent period of 15 min and a larger burst size of 124 PFU per cell. Both phages had a burst period of 30 min. Furthermore, DC1 and DC2 displayed excellent stability within a wide range of pH levels and temperatures. After undergoing a brief phage‐soaking treatment, DC1 and DC2 effectively reduced the bacterial count in spiked food samples. Additionally, they inhibited the formation of biofilms and degraded already‐formed biofilms. Collectively, DC1 and DC2 exhibit great potential as biocontrol agents for the prevention and control of B. cereus contamination in foods.

Molecularly imprinted sensors for the determination of anthocyanins in food products

A novel molecularly imprinted electrochemical sensor was developed for the sensitive and selective determination of anthocyanins in athletic food products. The sensor was fabricated by incorporating a conductive composite of graphene oxide and gold nanoparticles as the transducer material, which was modified with a silylation agent to enhance compatibility with the molecularly imprinted polymer. The MIP was synthesized using functional monomers that can interact with anthocyanins through hydrogen bonding and π-π interactions. The MIP sensor exhibited a linear response range from 1 nM to 10 μM for cyanidin-3-O-glucoside, with a detection limit of 0.3 nM. The sensor demonstrated high selectivity towards the target anthocyanin, with selectivity coefficients ranging from 7.2 to 48.6 over various interfering compounds. The MIP sensor was successfully applied to the determination of anthocyanin content in commercial athletic food products, with relative errors ranging from -2.1 % to 1.3 % compared to the reference HPLC method. The recoveries of anthocyanins from spiked food samples ranged from 96.4 % to 102.8 %.

Carbon dots and covalent organic frameworks based FRET immunosensor for sensitive detection of Escherichia coli O157:H7

The combination of carbon dots (CDs) with covalent organic frameworks (COFs) was used to design an innovative sensor based on fluorescence resonance energy transfer (FRET) for the detection of Escherichia coli O157:H7 (E. coli O157:H7) in food samples. Carbon dots were used as fluorescence donors, covalent organic frameworks as fluorescence acceptors. The antibody (Ab) specific to E. coli O157:H7 was used to form a CD-Ab-COF immunosensor by linking CDs and COFs. The antibody was specifically bound with E. coli O157:H7, which caused the connection between CDs and COFs to be interrupted, and the carbon dots exhibited fluorescence restoration. The sensor exhibited a linear detection range spanning from 0 to 106 CFU/mL, with the limit of detection (LOD) of 7 CFU/mL. The analytical performance of the developed immunosensor was evaluated using spiked food samples with different concentrations of E. coli O157:H7, validating the capability of assessing risks in food testing.

Smartphone-assisted carbon dots fluorescent sensing platform for visual detection of Thiophanate-methyl in fruits and vegetables

Trimesic acid and o-phenylenediamine (OPD) were employed as precursors to synthesize yellow-green fluorescent carbon dots (Y-G-CDs) by solvothermal synthesis for the sensitive detection of Thiophanate-methyl (TM) in real agricultural products. The Y-G-CDs probe could specifically recognize the TM primarily through π-π stacking. Moreover, the fluorescence quenching of the probe was ultimately dominated by the PET effect, based on the interaction between the abundant carboxyl groups on the surface of the Y-G-CDs and the amino group of TM. A strong linear relationship between the fluorescence quenching of the probe and TM concentration in the range of 0–10 µmol/L was observed and the limit of detection (LOD) was calculated to be 50.7 nmol/L. Compared to the interference pesticides, the Y-G-CDs probe demonstrated exceptional selectivity toward TM, with satisfactory recoveries of 96.3 % − 104.2 % in spiked food samples. The Y-G-CDs probe enables simple pretreatment, cost-effective, and on-site detection of TM in fruits and vegetables with visual detection of the TM employing a smartphone-assisted sensing platform.

Simple fluorochromic detection of chromium with ascorbic acid functionalized luminescent Bio-MOF-1.

The bioaccumulation of various heavy metals in the environment and agriculture is posing serious hazards to human health. Hexavalent chromium is one of the most encountered heavy metal pollutants. The routine monitoring of Cr(VI) via simple methods assumes great analytical significance in sectors like environmental safety, food quality, etc. This study reports a novel biocompatible and luminescent metal-organic framework (ascorbic acid functionalized Bio-MOF-1) based "Turn-on" nanoprobe for rapid and sensitive optical detection of Cr(VI). Bio-MOF-1 has been synthesized, functionalized with ascorbic acid (AA), and then comprehensively characterized for its key material properties. The presence of Cr(VI) results in the photoluminescence recovery of Bio-MOF-1/AA. Using the above approach, Cr(VI) is detected over a wide concentration range of 0.02 to 20 ng mL-1, with the limit of detection being 0.01 ng mL-1. The nanoprobe is capable of detecting Cr(VI) in real water as well as in some spiked food samples. Hence, the ascorbic acid functionalized Bio-MOF-1 nanoprobe is established as a potential on-field detection tool for Cr(VI).

Selective extraction and quantitative analysis of pyrroloquinoline quinone from food.

Pyrroloquinoline quinone (PQQ) is a bioactive compound that has attracted significant attention due to its potential health benefits. In this study, we developed a new magnetic molecularly imprinted nanoparticle (MMIN) for the selective extraction and determination of PQQ from food samples. The MMIN was synthesized using a surface molecular imprinting technique with PQQ as the template molecule, Fe3O4 nanoparticles as the magnetic core, and methacrylic acid as the functional monomer. The MMIN exhibited high selectivity and affinity towards PQQ, allowing for efficient extraction and preconcentration of PQQ from complex food matrices. The extracted PQQ was then quantified using HPLC-DAD. The developed method showed good linearity (R2 = 0.9985) and low limits of detection (0.03 μg L-1). The accuracy and precision of the method were evaluated by analyzing spiked food samples, with average recoveries close to 89.8%. The MMIN also demonstrated good reusability, with negligible decrease in extraction efficiency after five cycles of use. Overall, the developed MMIN-based method provides a reliable and efficient approach for the analysis of PQQ in food samples.

A biphasic accelerated strand exchange amplification strategy for culture-independent and rapid detection of Salmonella enterica in food samples.

Salmonella enterica is a common foodborne pathogen that can cause food poisoning in humans. The organism also infects and causes disease in animals. Rapid and sensitive detection of S. enterica is essential to prevent the spread of this pathogen. Traditional technologies for the extraction and detection of this pathogen from complex food matrices are cumbersome and time-consuming. In this study, we introduced a novel strategy of biphasic assay integrated with an accelerated strand exchange amplification (ASEA) method for efficient detection of S. enterica without culture or other extraction procedures. Food samples are rapidly dried, resulting in a physical fluidic network inside the dried food matrix, which allows polymerases and primers to access the target DNA and initiate ASEA. The dried food matrix is defined as the solid phase, while amplification products are enriched in the supernatant (liquid phase) and generate fluorescence signals. The analytical performances demonstrated that this strategy was able to specifically identify S. enterica and did not show any cross-reaction with other common foodborne pathogens. For artificially spiked food samples, the strategy can detect 5.0 × 101 CFU mL-1S. enterica in milk, 1.0 × 102 CFU g-1 in duck, scallop or lettuce, and 1.0 × 103 CFU g-1 in either oyster or cucumber samples without pre-enrichment of the target pathogen. We further validated the strategy using 82 real food samples, and this strategy showed 92% sensitivity. The entire detection process can be finished, sample-to-answer, within 50 min, dramatically decreasing the detection time. Therefore, we believe that the proposed method enables rapid and sensitive detection of S. enterica and holds great promise for the food safety industry.

CeO2 nanozyme mediated RPA/CRISPR-Cas12a dual-mode biosensor for detection of invA gene in Salmonella

This study reports a novel biosensing system that leverages recombinase polymerase amplification (RPA) in conjunction with clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a technology, integrated with a nanozyme (NZ) based on cerium dioxide (CeO2). With the integration of CeO2 NZ, a dual-mode detection platform could be developed for Salmonella detection using fluorometric and colourimetric assays. The CRISPR/Cas12a system, when activated in the presence of target DNA, could cleave the FAM-labelled probe to lead to a fluorometric response. Also, when the CeO2 NZ was introduced in the presence of H2O2, a colourimetric response was generated, directly proportional to the concentration of target DNA present. We hypothesise that adding highly reactive H2O2 within the post-CRISPR/Cas12a reaction system allows for increased release of hydroxyl free radicals within the mixture. Thus, the double recognition through NZ and the CRISPR/Cas12a system provided enhanced selectivity and sensitivity to the method. The proposed biosensor could successfully detect Salmonella at concentrations as low as 0.88 pg/μL and 1.28 pg/μL for fluorometric and colourimetric responses, respectively. Furthermore, the developed biosensor could be applied in real sample analysis of raw food samples (chicken, egg, and beef) to give a good recovery in the spiked food samples with varying concentrations of cultured bacterial DNA.

Development of Filtering Electrospray Ionization-Ion Trap Mass Spectrometry Technique for the Rapid Detection of Antibiotic Residues in Food

This article reports on the development of an atmospheric pressure filtering electrospray ionization (FESI) source – composed of a syringe, a filter, and the ESI source – for the determination of furazolidone, amoxicillin, nitrofurantoin, and nitrofural, common antibiotics. Spiked food samples were also analyzed; the analytes were placed in the filter head, and the flow rate of the extraction solution from the syringe pump was adjusted. Using a mixture of oleic acid and antibiotics, hydrophilic and hydrophobic filters were compared, demonstrating the advantage of FESI in reducing the background and noise for the mixture. The device simplifies not only the experimental procedure but also the sample pretreatment process. Additionally, the limits of detection of the antibiotics were determined to be 1 mg L−1 for furazolidone, amoxicillin, and nitrofurantoin and 2 mg L−1 for nitrofural. The linear regression coefficients (R 2) of the antibiotic standard solutions were all ≥0.99. Furthermore, the spiked recovery rates of pork, chicken, and egg samples ranged from 73.3% to 107.5%, with relative standard deviations (RSDs) from 1.1% to 15.6%. This study uncovers the potential capabilities of ion trap mass spectrometry (ITMS) for the on-site detection of antibiotics and offers a new method for ensuring food safety.

Design and fabrication of a competitive lateral flow assay using gold nanoparticle as capture probe for the rapid and on-site detection of penicillin antibiotic in food samples

Lateral flow assays (LFAs) are among the utmost cost-efficient, paper-based point-of-care (POC) diagnostic devices. Herein, we have reported the fabrication of a competitive LFA for on-site detection of penicillin. Various parameters such as Ab concentration for conjugation, Pen-BSA conjugate concentration, pore size of membrane, and blocking buffer were standardised for the fabrication of LFA. Different concentrations of penicillin (1 pM-1 mM) were added to the sample pad to observe the color intensity. The visual detection limit (LOD) achieved from the LFA was 10 nM for Penicillin that correlated with the LOD calculated from the ‘ColorGrab’ colorimeter application. Additionally, LFA showed insignificant cross reactivity with other β-lactam antibiotics and were also validated with spiked food samples such as milk, meat and egg. Hence, the fabricated LFA can be successfully utilised for the POC detection of penicillin in food samples on large scale.

Magnetic and N–doped nanofibrous carbon microsphere with hierarchical porosity as a nanozyme for on-site and visual detection of glucose

BackgroundOn-site and rapid detection of glucose level in foods is important for monitoring and control glucose intake. MethodsMagnetic and N–doped nanofibrous carbon microspheres (Fe@NCMs) with hierarchical porosity were designed as a novel nanozyme (Fe@NCMzyme), and the catalytic mechanism was investigated via the density functional theory (DFT) calculation. Therefore, Fe@NCMzyme sensor and point-of-care testing (POCT) platform were developed for glucose detection in food samples. Significant findingsFe@NCMzyme showed 3D porous structure, a larger surface area, and N–doped carbon material properties, resulting in an enhanced peroxidase (POD)–like activity. In Fe@NCMzyme, Fe3O4 nanoparticles (FeNPs) act as catalytic centers and N–doped carbon nanofibers could be used as substrate binding sites. DFT results revealed that Fe–induced Fenton–like reaction was the main catalytic mechanism. The low detection limit and linear range of Fe@NCMzyme sensor was 0.247 μM and 1–900 μM, respectively. The excellent recovery ration in spiked food samples was 85.0 %–110.0 %. The applicability of Fe@NCMzyme sensor for glucose detection was verified by the commercial Glucometer. Furthermore, Fe@NCMzyme POCT platform was established and a linear detection range (10–900 μM) was obtained with low detection limit (3.125 μM). Importantly, Fe@NCMzyme POCT platform was realized visual, on–site, and rapid detection of glucose in food samples.

Development of rapid on-site detection of Salmonella Enteritidis, S. Typhimurium, and S. Thompson in food samples using an ultrafast PCR system

The conventional Salmonella serotyping methods are labor intensive and time-consuming; therefore, rapid identification method is needed to detect outbreaks early and prevent their spread. In this study, we developed for the first time a detection method for the rapid and accurate on-site serotyping of Salmonella enterica subsp. enterica serovar Enteritidis, Thompson, and Typhimurium, all of which have epidemiological importance worldwide. This method, which is based on specific marker genes, was constructed with portable equipment and a simple DNA extraction step. For the specific detection of the three serovars, genetic markers obtained via a bioinformatics analysis were selected and showed high specificity for 97 strains. The ultrafast polymerase chain reaction (PCR) showed high linearity (≥0.997) in both pure culture and a spiked food sample, with a detection specificity of 102 colony forming unit (CFU)/ml; these results are consistent with real-time PCR. Moreover, ultrafast PCR was further improved for developing direct ultrafast PCR method for field detection, the entire procedure of which could be completed within 25 min. The test results of an artificially contaminated food sample showed that the three serovars could be detected using the direct ultrafast PCR with a very short (3 h) enrichment step when inoculated at 1 CFU/g. This method exhibited various advantages, such as its ultrafast and labor-saving characteristics, which can be applied to the diagnosis of Salmonella serovar in the field.

A fluorescence sensing array based on photonic crystals and RAA for sensitive and high-throughput detection of Salmonella in foods

Salmonella can cause serious foodborne diseases, which is a major concern for global public health. The sensitive and fast analysis of Salmonella is of importance for food safety. Herein, we developed a fluorescence sensing array based on photonic crystals (PCs) and recombinase-aided amplification (RAA) for high-throughput and high-sensitive analysis of Salmonella in foods. In this assay, RAA was employed for powerful amplification of the target DNA of Salmonella, and the generated dsDNA amplicon was embedded with nucleic acid dye SYBR Green I (SGI), emitting fluorescence. Furthermore, the fluorescence signal was physically enhanced by PCs array; meanwhile, the high-throughput and sensitive detection was realized by microplate reader. Because of the isothermal reaction and lyophilized regent of RAA, the proposed array possessed gentle operation and stable amplification performance. Besides, a small volume of loading samples with 2 μL was required on the PCs array for powerful fluorescence enhancement. Due to the synergistic signal amplification effect of RAA and photonic crystals, a low limit of detection (LOD) of 10 CFU/mL was achieved. Besides, the proposed array exhibited excellent performance with 100% accuracy in 20 spiked food samples. Therefore, the proposed method with the advantages of sensitivity and high throughput showed great application potential.

A bifunctional core–shell gold@Prussian blue nanozyme enabling dual-readout microfluidic immunoassay of food allergic protein

Food allergy has posed a great threat for public health due to its rising prevalence worldwide, and thus sensitive and reliable food allergen monitoring methods is of great significance. In this study, we prepared a bifunctional core–shell gold@Prussian blue nanoparticles (Au@PBNP) nanozyme, which not only could serve as an alternative to natural peroxidase for colorimetric immunoassay, but also act as a unique Raman label in Raman-silent region (1800–2800 cm−1) for SERS analysis. By combining microfluidic device, smartphone, and portable Raman spectrometer, a new smartphone/SERS dual-readout microfluidic immunoassay platform was established for portable detection of food allergic protein (i.e., alpha-lactalbumin (α-LA)). The established method for detection of α-LA showed a LOD of 0.011 ng/mL in a liner range of 0.2–600 ng/mL. Furthermore, this method was also challenged in spiked food samples with good average recoveries, showing a great potential in practical applications.