Spiked Food Samples Research Articles

Polyvalent aptamer scaffold coordinating light-responsive oxidase-like nanozyme for sensitive detection of zearalenone

An efficient aptasensor was developed for the colorimetric determination of zearalenone (ZEN) based on polyvalent aptamer scaffold and light-responsive oxidase-like nanozyme. The sensitivity and efficiency of the development method were significantly improved owing to rich aptamers and signal labels (3, 4-dihydroxybenzoic acid, PCA) packed in the scaffold. The scaffold integrated functions of target recognition, surface immobilization and signal transduction. The photoresponsive nanoenzyme of TiO2-PCA was formed by PCA coordinated with Ti (IV) on the surface of TiO2. TiO2-PCA catalyzed dissolved oxygen rather than H2O2 to generate colorimetric signal by stimulating the chromogenic substrate, which made the assay greener and safer. The detection limit of colorimetric mode was 0.0087 ng/mL and the satisfactory recoveries 92.00 %−111.00 % were achieved in spiked food samples. This strategy opens new horizons for sensitive detection of small molecule hazards and promises to be a powerful tool for safeguarding food safety.

An Extremely Highly Sensitive ELISA in pg mL-1 Level Based on a Newly Produced Monoclonal Antibody for the Detection of Ochratoxin A in Food Samples.

In this study, an extremely highly sensitive enzyme-linked immunosorbent assay (ELISA) based on a newly produced monoclonal antibody (mAb) for the detection of ochratoxin A (OTA) in food samples was developed. OTA-Bovine serum albumin (BSA) conjugate was prepared and used as the immunogen for the production of the mAb. Among four hybridoma clones (8B10, 5C2, 9B7, and 5E11), the antibody from 8B10 displayed the highest affinity recognition for OTA. Based on the mAb (8B10), the IC50 and LOD of the ELISA for OTA were 34.8 pg mL-1 and 1.5 pg mL-1, respectively, which was 1.53~147 times lower than those in published ELISAs, indicating the ultra-sensitivity of our assay. There was no cross-reactivity of the mAb with the other four mycotoxins (AFB1, ZEN, DON, and T-2). Due to the high similarity in molecular structures among OTA, ochratoxin B (OTB), and ochratoxin C (OTC), the CR values of the mAb with OTB and OTC were 96.67% and 22.02%, respectively. Taking this advantage, the ELISA may be able to evaluate total ochratoxin levels in food samples. The recoveries of the ELISA for OTA in spiked samples (corn, wheat, and feed) were 96.5-110.8%, 89.5-94.4%, and 91.8-113.3%; and the RSDs were 5.2-13.6%, 8.2-13.0%, and 7.7-13.7% (n = 3), respectively. The spiked food samples (corn) were measured by ELISA and HPLC-FLD simultaneously. A good correlation between ELISA (x) and HPLC-FLD (y) with the linear regression equation of y = 0.918x - 0.034 (R2 = 0.985, n = 5) was obtained. These results demonstrated that the newly produced mAb-based ELISA was a feasible and ultra-sensitive analytical method for the detection of OTA in food samples.

Development of a Multiplex Polymerase Chain Reaction (PCR) Assay for the Potential Detection of Insect Contaminants in Food

Molecular methods can potentially be used to detect insect contaminants of food products. In this study, we used three sets of group-specific primers, two of them targeting the amplification of two regions of the insect’s mitochondrial cytochrome c oxidase subunit I (COI-Fa and COI-Fb) and the other targeting a region of the nuclear protein-coding wingless (wg) gene. Using singleplex and multiplex polymerase chain reaction (PCR), we evaluated the three sets of primers using genomic DNA (gDNA) from 48 insect species including food storage insect pests and known vectors of foodborne pathogens. Seven plant-based food matrices were also evaluated for exclusivity testing. Additionally, we spiked fragments from five insect species in a selected food matrix (whole wheat flour). Singleplex and multiplex PCR amplified single specific bands (401–449 bp), corresponding to the wg gene, from insect species belonging to families Blattidae and Formicidae, and in Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae). The COI-Fa primers amplified specific bands (171–188 bp) in all Dipteran species and the COI-Fb primers amplified a specific band (∼140 bp) in DNA from Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and P. interpunctella. However, the presence of specific bands in most Coleopterans was not consistent. No amplicon bands were observed in any of the food matrixes tested and the expected pattern of amplicon bands was seen in multiplex reactions using gDNA from spiked food samples. Our multiplex PCR assay targeted specific groups of insects that commonly contaminate foods without amplifying bands from the food matrixes tested; thus, molecular methods may be suitable for detecting insects or their fragments in foods.

A CRISPR/Cas12a-based fluorescence aptasensor for the rapid and sensitive detection of ampicillin

This study introduces CRISPR/Cas-based aptasensor for the highly sensitive and specific detection of the antibiotic, ampicillin. Ampicillin (AMPI) is a commonly used antibiotic for treating pathogenic bacteria and is additionally added to livestock feed in agriculture. This study can enable early detection of antibiotic residues, prevent their accumulation in the environment, and ensure compliance with food safety regulations. Herein, the aptasensor was developed with the CRISPR/Cas system by utilizing three different ampicillin-specific aptamers, each conjugated with a biotin at the 5′-end. The ssDNA activator was bound to the aptamers through complementary base pairings. The attraction of the aptamers to the ampicillin target released the bound ssDNA, causing the activation of the CRISPR/Cas system. The DNA reporter probe, labelled with Cy3 and a quencher, turns on the fluorescence signal when cleaved by the activated Cas12a through trans-cleavage measured using a fluorescence spectrophotometer at 590 nm. The fluorescence signal was linearly proportional to the ampicillin target concentration with a 0.01 nM limit of detection and a read-out time of 30 min. This aptasensor showed high sensitivity towards ampicillin even in the presence of other antibiotics. The method was also successfully implemented for ampicillin detection in spiked food samples.

On-line preconcentration and determination of sulfadiazine in food samples using surface molecularly imprinted polymer coating by capillary electrophoresis

In this study, on-line preconcentration and selective determination of the trace sulfadiazine (SDZ) existing in milk and hen egg white samples were realized by the capillary electrophoresis using molecularly imprinted polymer (MIP) coated capillary. The capillary coated with MIP was firstly prepared through the surface imprinted techniques, using SDZ as template molecule and dopamine as function monomer and crosslinker, and then amine-terminated poly(2-methyl-2-oxazoline) (PMOXA-NH2) was introduced onto polydopamine layer to reduce the non-specific adsorption. Successful preparation of SDZ-MIP-PMOXA coating was verified by zeta potential, as well as water contact angle. The SDZ-MIP-PMOXA coated capillary performed well on-line preconcentration of SDZ and the obtained peak area of SDZ was 46 times higher than that one obtained in bare capillary using the same procedure. Then the proposed on-line preconcentration method was fully validated and displayed good linear behavior in the concentration from 5.0 to 100.0 ng/mL, with the limit of detection was low to 1.5 ng/mL; and this method presented excellent accuracy and robustness. The prepared SDZ-MIP-PMOXA coated capillary also showed high selectivity with the imprinting factor of 5.85 and good repeatability during five consecutive runs with the relative standard deviation value of peak area was 1.6%. At last, the application of the prepared SDZ-MIP-PMOXA coated capillary in the detection of SDZ in spiked food samples was investigated, and good recoveries of 98.7–109.3% were obtained.

A SERS-based lateral flow immunochromatographic assay using Raman reporter mediated-gap AuNR@Au nanoparticles as the substrate for the detection of enrofloxacin in food samples

A lateral flow immunochromatographic assay (LFIA) based on surface-enhanced Raman scattering (SERS) for sensitive and specific detection of antibiotic enrofloxacin (ENR) in food samples was developed. 1,4-benzenedithiol (BDT) was selected as the Raman reporter, and the BDT mediated-gap AuNR@Au nanoparticles (NPs) were synthesized, characterized and used as the substrate in SERS-LFIA due to the existence of the anisotropic gold nanorods (AuNRs) and the nano-gap with the high SERS enhancement. AuNRs were prepared, then covered by monolayer BDT. Under reduction condition and in presence of HAuCl4, the reduced gold was deposited and grown on AuNRs to form AuNRBDT@Au NPs. As the two thiol groups on para-positions in BDT were respectively linked to AuNR (core) and Au (shell), the gap size inside the NPs was uniform. The immunoprobe (e.g. AuNRBDT@Au-Ab) was obtained by immobilizing Ab against ENR on the surface of AuNRBDT@Au NPs. The performance of SERS-LFIA was similar to that in colloidal gold based-LFIA, and the entire assay time was within 15 min. After LFIA procedures, the specific SERS intensity of BDT at 1560 cm−1 on the test line was measured for the quantitative detection of ENR. The IC50 and limit of detection (LOD) of the LFIA for ENR were 59 pg mL−1 and 0.12 pg mL−1 (e.g. 71 pg g−1 and 0.14 pg g−1 in real sample), respectively. There was no cross-reactivity (CR) of the LFIA with other five antibiotics. The recoveries of ENR from spiked food samples were in range of 89.2%–102.4% with the relative standard deviation (RSD) of 1.70%–6.38%. It was proven that the proposed method was able to simply and rapidly detect ENR in food samples with high sensitivity, specificity, accuracy and precision. The platform can be also an alternative platform for the detection of other target analytes using corresponding Abs.

A new ratiometric molecularly imprinted electrochemical sensor for the detection of Sunset Yellow based on gold nanoparticles

Since a high dosage or excessive intake of Sunset Yellow (SY) may pose a threat to human health, it is in great demand to construct an effective method to detect and control SY. Based on the molecularly imprinted polymers (MIPs) and dual-signal output mode, a ratiometric molecularly imprinted electrochemical sensor (RMIECs) was developed for sensitive detection of SY. AuNPs not only provided a large specific surface area to enhance the electron transfer rate but also served as a reference signal (S1), together with SY signal (S2), to produce dual signals. For a proof-of-application study, RMIECs was applied to detect SY with a wide linear range from 10 nM to 100 μM and a low detection limit (LOD) of 1.60 nM (S/N = 3, n = 3). Besides, the method was applied in spiked food samples with recoveries of 94.0 ∼ 97.0 % as well as relative errors of 5.4 ∼ 8.3 %, revealing its promising potential in detection of SY.

Highly selective monoclonal antibody-based fluorescence immunochromatographic assay for the detection of fenpropathrin in vegetable and fruit samples

Fenpropathrin (FPT) is a typical pyrethroid pesticide that can cause chronic toxicity to humans. Herein, an anti-FPT monoclonal antibody (mAb) was elicited via a novel hapten synthesized by introducing a carboxyl-containing spacer arm in the cyclopropane moiety of FPT. Characterized by enzyme-linked immunosorbent assay (ELISA), the mAb exhibited high affinity and selectivity to FPT with a half-maximal inhibitory concentration of 31.05 μg/L and negligible cross-reactivities with analogs of pyrethroids. Based on the mAb, a fluorescence immunochromatographic assay (FICA) for FPT detection was firstly developed. The detection limit of the FICA is 0.012 mg/kg which is much lower than the maximum residue limit of FPT for food samples. The average recoveries of FPT from spiked food samples by the FICA were 85.0–105.0%, and the obtained results were in good agreement with those of gas chromatography-tandem mass spectrometry. Overall, this work provided a reliable tool suitable for the detection of FPT residue for large-scale samples in a rapid and cost-effective manner.

Online solid-phase extraction based on size-controllable spherical covalent organic framework for efficient determination of polybrominated diphenyl ethers in foods

An analytical method of microspheric brominated covalent organic framework (Br-COF)-online solid-phase extraction integrated with high-performance liquid chromatography (online SPE-HPLC) was proposed for efficiently enriching six polybrominated diphenyl ethers (PBDEs) in foods. The Br-COF microspheres were facilely prepared with uniformity and dispersion by a size-controllable synthesis at the room temperature. Attributed to multiple interactions of the halogen bonding, Van der Waals forces, hydrophobic interaction along with size-matching effect, Br-COF performed satisfactory extraction capacity for PBDEs compared with commercial adsorbents. Five primary influencing factors were optimized, including loading solvent, loading flow rate, elution solvent, elution flow rate and elution volume. Under the optimal parameters, the implement displayed excellent linear ranges (0.5–500 ng mL−1) and low detection limits (0.01–0.05 ng mL−1). The relative recoveries in six spiked food samples ranged from 87.8 to 119.7 % with relative standard deviations below 10 %. This research estabished a promising platform for quantitatively determining trace PBDEs in complex foods.

Magnetic microbead enzyme-linked immunoassay based on phage encoded protein RBP 41-mediated for rapid and sensitive detection of Salmonella in food matrices

Rapid and sensitive quantitative detection methods are required to monitor and detect Salmonella throughout the food supply chain and early prevention of foodborne disease outbreaks. In this study, a magnetic microbead enzyme-linked immunoassay (MELISA) based on phage receptor binding protein was developed for rapid enrichment and detection of Salmonella in complex food matrices. RBP 41 from phage T102 acted as a species-specific recognition element for Salmonella by exploiting its strong binding capacity to Salmonella surface receptors. RBP 41-MBs were prepared by coupling recombinant RBP 41 with MBs and used to separate and enrich Salmonella cells from spiked food samples. The captured complexes were further integrated with ELISA procedures by HRP-labeled anti-Salmonella antibody for rapid and accurate detection of Salmonella. The whole method took <1.5 h and the detection limit was 10 CFU/mL. Therefore, MELISA was successfully developed for the detection of Salmonella in various spiked food samples (skim milk, lettuce, and chicken breast). The ELISA reaction process of this method was carried out on magnetic beads. It simplified the process of the traditional ELISA method and reduces the reaction time. This study expanded the use of phage-associated proteins and demonstrated the promising prospects for practical applications in the detection of foodborne pathogens.

The Simultaneous Determination of Chlorpyrifos-Ethyl and -Methyl with a New Format of Fluorescence-Based Immunochromatographic Assay.

The improper and excessive use in agriculture of chlorpyrifos-methyl (CPSM) and chlorpyrifos-ethyl (CPSE) may affect the health of human beings. Herein, a fluorescence-based immunochromatographic assay (FICA) was developed for the simultaneous determination of CPSM and CPSE. A monoclonal antibody (mAb) with equal recognition of CPSM and CPSE was generated by the careful designing of haptens and screening of hybridoma cells. Instead of labeling fluorescence with mAb, the probe was labeled with goat-anti-mouse IgG (GAM-IgG) and pre-incubated with mAb in the sample. The complex could compete with CPS by coating antigen in the test line. The new format of FICA used goat-anti-rabbit IgG (GAR-IgG) conjugated with rabbit IgG labeled with fluorescence microspheres as an independent quality control line (C line). The novel strategy significantly reduced nonspecific reactions and increased assay sensitivity. Under the optimal conditions, the proposed FICA showed a linear range of 0.015-64 mg/L and limit of detection (LOD) of 0.015 mg/L for both CPSE and CPSM. The average recoveries of CPS from spiked food samples by FICA were 82.0-110.0%. The accuracy was similar to the gas chromatography-tandem mass spectrometry (GC-MS/MS) results. The developed FICA was an ideal on-site tool for rapid screening of CPS residues in foods.

A HCR based multivalent aptamer amplifier for ultrasensitive detection of Salmonella

Aptamer holds great promise as an alternative recognition element for foodborne pathogens detection because of its superior structural features. However, its application is still limited by the diminished affinity in food samples and the sophisticated signal amplifications. Herein, we fabricate a hybridization chain reaction (HCR) based multivalent aptamer (multi-Apt) as an effective signal amplifier for the sensitive detection of Salmonella. The aptamer was assembled on the HCR product to construct a DNA programmable multi-Apt, which displayed a 33-fold enhancement binding affinity and a much faster reaction kinetics than that of a monovalent aptamer (mono-Apt). Furthermore, the HCR scaffold was exploited as the signal carrier via the abundant DNA hairpins. Due to the synergism of the high affinity of multi-Apt and the scaffold-based signal amplification, the proposed HCR based multi-Apt amplifier could detect Salmonella as low as 7 cfu mL−1 with a broad detection range of 10 to 107 cfu mL−1. Besides, it also exhibited excellent specificity against target bacteria and performed well on the detection of spiked food samples, indicating the promise in practical detection of Salmonella.

Identification of Leuconostoc species based on novel marker genes identified using real-time PCR via computational pangenome analysis.

Leuconostoc species are important microorganisms in food fermentation but also cause food spoilage. Although these species are commercially important, their taxonomy is still based on inaccurate identification methods. Here, we used computational pangenome analysis to develop a real-time PCR-based method for identifying and differentiating the 12 major Leuconostoc species found in food. Analysis of pan and core-genome phylogenies showed clustering of strains into 12 distinct groups according to the species. Pangenome analysis of 130 Leuconostoc genomes from these 12 species enabled the identification of each species-specific gene. In silico testing of the species-specific genes against 143 publicly available Leuconostoc and 100 other lactic acid bacterial genomes showed that all the assays had 100% inclusivity/exclusivity. We also verified the specificity for each primer pair targeting each specific gene using 23 target and 124 non-target strains and found high specificity (100%). The sensitivity of the real-time PCR method was 102 colony forming units (CFUs)/ml in pure culture and spiked food samples. All standard curves showed good linear correlations, with an R2 value of ≥0.996, suggesting that screened targets have good specificity and strong anti-interference ability from food sample matrices and non-target strains. The real-time PCR method can be potentially used to determine the taxonomic status and identify the Leuconostoc species in foods.

Label free flexible electrochemical DNA biosensor for selective detection of Shigella flexneri in real food samples

An effective tool for early-stage selective detection of the foodborne bacterial pathogen Shigella flexneri (S. flexneri) is essential for diagnosing infectious diseases and controlling outbreaks. Here, a label-free electrochemical DNA biosensor for monitoring S. flexneri is developed. To fabricate the biosensor, detection probe (capture probe) is immobilized on the surface of poly melamine (P-Mel) and poly glutamic acid (PGA), and disuccinimidyl suberate (DSS) functionalized flexible indium tin oxide (ITO) electrode. Anthraquinone-2-sulfonic acid monohydrate sodium salt (AQMS) is used as a signal indicator for the detection of S. flexneri. The proposed DNA biosensor exhibits a wide dynamic range with concentration of the targets ranging from 1 × 10−6 to 1 × 10−21 molL−1 with a limit of detection (LOD) of 7.4 × 10−22 molL−1 in the complementary linear target of S. flexneri, and a detection range of 8 × 1010–80 cells/ml with a LOD of 10 cells/ml in real S. flexneri sample. The proposed flexible biosensor provides high specificity for the detection of S. flexneri compared to other target signals such as discrete base mismatches and different bacterial species. The developed biosensor displayed excellent recoveries in detecting S. flexneri in spiked food samples. Therefore, the proposed biosensor can serve as a model methodology for the detection of other pathogens in a broad span of industries.

Screening of specific aptamers against chlorpromazine and construction of novel ratiometric fluorescent aptasensor based on metal-organic framework

Chlorpromazine is a phenothiazine representative drug that can be used to anesthetize and calm animals. However, chlorpromazine excess may lead to residual persistence in edible tissues, which is potentially harmful to human health and animal production. In this work, high affinity and specificity aptamers against chlorpromazine were screened out based on Capture-SELEX. After ten rounds of screening, the candidate aptamers were obtained. The optimal aptamer of CHL-3 was obtained by isothermal titration calorimetry (ITC) and SYBR Green I (SGI) fluorescence-competition methods. The Kd value of CHL-3 was 69.8 ± 9.81 nM. Subsequently, the Uio-66-NH2 material was prepared, filled with rhodamine 6G (Rho 6G) dye into the pore, and sealed with CHL-3, and fluorescence probes were obtained. The ratiometric fluorescence detection method was established to detect the concentration of chlorpromazine. A linear relationship was obtained in a range of 1–100 nM, with a lower detection limit of 0.67 nM. Meanwhile, a good recovery was shown in spiked food samples, such as eggs and milk. These results indicate that the constructed ratiometric fluorescence strategy can be successfully applied in food detection.

Facile Synthesis of N, S-Doped Carbon Quantum Dots from Food Waste as Fluorescent Probe for Sensitive Detection of Thiamphenicol and Its Analogues in Real Food Samples along with an Application in Bioimaging.

Herein, N, S co-doped carbon quantum dots (N, S-CDs) with high absolute quantitative yield (Abs-QY) of 50.2% were produced by hydrothermal treatment of food residue crayfish shells. A new detection method of thiamphenicol (TAP) and its analogues was established by discovering the obvious fluorescence response between TAP and N, S-CDs, which achieved a wide linear range of 20–300 μg·L−1 with a detection limit (LOD) of 11.12 μg·L−1. This novel probe exhibited strong sensitivity and shows rapid response in complex food matrices (overall detection time is less than 45 min) mainly induced by static quenching. Spiked food sample recovery ranged from 97.3 to 99.34%. Further, the cell experiments of N, S-CDs were conducted, and the cell viability remained 91.76% under high concentration of N, S-CDs due to the environmentally friendly materials. The low cytotoxicity and good cytocompatibility make these N, S-CDs compatible for cell bioimaging and intracellular detection of TAP.

Carbon dots@Cu metal-organic frameworks hybrids for ratiometric fluorescent determination of pesticide thiophanate-methyl.

A dual-emission fluorescent (FL) probe was constructed by coordinating Cu2+ of copper metal-organic frameworks (Cu-MOFs) with - COO- group of carbon dots (CDs) for pesticide thiophanate-methyl (TM) determination. TM was recognized by organic ligands (H2BDC and H2BDC-NH2) of Cu-MOFs via π stacking. Due to the higher affinity of Cu2+ to TM than ligands and CDs, TM chelated with Cu2+ to form TM-Cu complex. Thus coordination of Cu-MOFs was damaged and the ligands were released resulting in the FL intensity increase of Cu-MOFs (F430). And also CDs were released from CDs@Cu-MOFs hybrids and electron transfer from CDs to CuMOFs was inhibited, leading to the FL intensity increase of CDs (F600). The FL intensity ratio (F430/F600) showed a good linear relationship with TM concentrations of 0.0307-0.769μmol L-1 with a limit of detection (LOD) of ~ 3.67nmol L-1. The probe was successfully applied to detect TM in spiked food samples with satisfactory recoveries of 93.1-113%. Additionally, visual detection of TM was achieved according to the fluorescence color variation from blue to carmine, indicating promising application of CDs@Cu-MOFs probe.

An upconversion biosensor based on DNA hybridization and DNA-templated silver nanoclusters for the determination of acrylamide

Acrylamide is widely present in many fried and baked foods, that has been proved as potentially carcinogenic to humans. In this work, a novel biosensor using core-shell upconversion nanoparticles (CSUCNPs) with aptamer as recognized element was designed for the determination of acrylamide. The principle of this work was based on the fluorescence resonance energy transfer (FRET) process from CSUCNPs to silver nanoclusters (AgNCs). Whereas the binding between acrylamide and the aptamer disturbed the DNA structure and inhibited the synthesis of AgNCs, which induced a higher fluorescence intensity. Under the optimal conditions, a low limit of detection (LOD) was calculated as 1.13 nM in the range of 1–105 nM. This biosensor was further applied in the spiked food samples to validate the applicability that recoveries were at the range of 78.52–117.09% with a relative standard deviation of 1.54–10.46%. The approach was compared with the standard HPLC method in great agreement (P ＞ 0.05).

The accurate identification and quantification of six Enterococcus species using quantitative polymerase chain reaction based novel DNA markers

Because of their beneficial effects, some enterococci species are used in probiotics, whereas some species are considered opportunistic pathogens implicated in human infections. High 16S rRNA sequence similarities among Enterococcus can impede their accurate classification. In this study, using pan-genome analysis, we developed an accurate method for the identification and quantification of six major Enterococcus species in different foods. Bioinformatics analysis revealed that some Enterococcus faecium genomes deposited in GenBank were misclassified. Six novel markers (FBPase_2 for Enterococcus durans, EcsB for Enterococcus faecalis, PurR for E. faecium, SDF for Enterococcus hirae, HTH_ARSR for Enterococcus lactis, and wxL for Enterococcus mundtii) were mined based on pan-genome analyses and used for quantitative polymerase chain reaction (qPCR). For all species, the detection limits in pure cultures and spiked food samples were 102 colony-forming units/ml (CFU/ml). This method facilitated the sensitive identification of six species in foods and the presence of nontarget bacteria. Moreover, qPCR efficiency was identified using 140 isolates and showed the same or higher resolution when compared with 16S rRNA sequencing. Our qPCR assay will help identify and quantify Enterococcus species in foods, thereby enabling a better understanding of ecological and safety aspects in food samples.

Carbon dots and graphene oxide based FRET immunosensor for sensitive detection of Helicobacter pylori

We report a novel Fluorescence Resonance Energy Transfer (FRET) immunosensor for sensitive detection of whole cell H. pylori, a causative organism for gastric carcinoma. Highly fluorescent and well-dispersed functionalized carbon dots (FCDs) were synthesized and chemically conjugated with anti-H. pylori antibody to fabricate a fluorescent probe (FCDs-Ab). The fluorescence of FCDs-Ab gets quenched upon interaction with graphene oxide (GO), whereas in presence of H. pylori, the interaction between the FCD-Ab and GO gets interrupted and gradual restoration of fluorescence was observed due to the specific affinity and binding of Ab towards H. pylori. The immunosensor was characterized at each step of fabrication. The assay exhibits a linear detection range of 5-107 cells mL−1 with limit of detection (LOD) of 10 cells mL−1 with high specificity and selectivity to target pathogen. The analytical performance of the developed immunosensor was evaluated with different spiked food samples and the substantial recovery validates its potential for risk assessment in food testing, thus ensuring general safety of public health.