Self-Assembly Multivalent Fluorescence-Nanobody Coupled Multifunctional Nanomaterial with Colorimetric Fluorescence and Photothermal to Enhance Immunochromatographic Assay

Multi-mode probe based on dual colorimetric and photothermal later flow immunoassay for the ultrasensitive determination of benzo[a]pyrene in vegetable oils

Lateral flow immunoassays (LFIA) have been acknowledged as the promising on-site screening method for food survey. Monoclonal antibodies against benzo[a]pyrene (BaP) conjugated with enzyme-mimetic probes, a multi mode LIFA strips were systemically constructed and evaluated. The PBNPs@mAbs based LFIA could conduct triple measurement in 14 min. This assay had good limit of detections (LODs of 0.057, 0.035, and 0.106 μg kg-1), ultra calibration ranges (0.23-500, 0.076-56, 0.69-167 μg kg-1), and the recoveries ranging from 86 % to 105 % with the precision less than 12 %. Compared with the reported methods, the LODs were 175-, 285- and 94- folds enhanced, and dynamic linear ranges were greatly expanded. Finally, this novel PBNPs@mAbs LFIA assay with simplicity, rapidity, and sensitivity was successfully utilized for the determination of BaP in vegetable oils, which could be used as a superior enzyme-mimetic on-site analytic platform in food safety.

Genetic engineering-powered dual-mode lateral flow immunosensor for colorimetric and fluorescent detection of ochratoxin A in pepper

Ochratoxin A (OTA) poses significant risks to both environment and human health, necessitating the development of rapid and sensitive detection methods. Lateral flow immunosensors (LFIs) typically use monoclonal antibodies and artificial antigens for mycotoxin detection; however, the preparation of these components is time-intensive, laborious, costly, and environmentally harmful. Herein, we developed an innovative genetic engineering-powered colorimetric/fluorescent dual-mode LFI (CM/FL-dLFI) using nanobodies and the mimotope peptide (MP) of OTA. Initially, a heptameric bifunctional fusion (sfGFP-C4bpα-Y4) containing the superfolder green fluorescent protein, the C4-binding protein α-chain, and the MP Y4 was constructed. The fusion was subsequently labeled on gold nanoflowers (AuNFs) to create the AuNFs@sfGFP-C4bpα-Y4 probe, which can be captured by the nanobody heptamer (Nb-C4bpα) and provides colorimetric/fluorescent signals. The optimized CM/FL-dLFI achieved a colorimetric limit of detection (LOD) of 0.01 ng/mL and a fluorescent LOD of 0.05 ng/mL. It exhibited high selectivity for OTA, good recovery rates of 82.85-102.81 % with relative standard deviations not exceeding 14 %, and excellent long-term stability. Moreover, it showed strong correlation with high-performance liquid chromatography in the analysis of 11 real pepper samples. Therefore, this study highlights the promising application potential of nanobodies and MPs in developing an economical and eco-friendly LFI for OTA detection in pepper.

From traditional to modern: Nanotechnology-driven innovation in mycotoxin sensing for Chinese herbal medicines

Mycotoxin contamination in Chinese herbal medicines (CHMs) is a pressing concern that jeopardizes their quality and safety, despite their widespread therapeutic use. Conventional detection methods are often limited by complexity, cost, and sensitivity, particularly in resource-limited settings. This gap in effective and efficient mycotoxin detection necessitates a comprehensive review that explores innovative solutions to enhance the safety and efficacy of CHMs. Advancements in nanomaterials and related advanced sensing techniques have emerged as a beacon of hope. Therefore, this review aims to fill the knowledge gap by providing a comprehensive overview of the latest developments in mycotoxin detection in CHMs, spotlighting the transformative role of nanomaterials and advanced sensing techniques. This review stands out for its in-depth exploration of functional nanomaterials across dimensions and their innovative applications in mycotoxin detection. Its innovation stems from a holistic approach that not only surveys current technologies but also charts a forward-looking path, emphasizing novel nanomaterial development, refined pretreatment, and advanced biosensing for on-site detection. It delves into the integration of nanomaterials with advanced sensing technologies, discussing the advantages and limitations of these approaches. A significant innovation of this review lies in the nuanced integration of nanomaterials with machine learning and artificial intelligence, revealing untapped potential for accuracy enhancement. Through this synthesis of knowledge, we hope to inspire further research and development in this critical area, ensuring the continued safe use of CHMs in traditional medicine practices.

Multifunctional metal-organic frameworks-mediated colorimetric/photothermal immunosensor for highly sensitivity detection of dibutyl phthalate

Dibutyl phthalate (DBP), a priority pollutant among phthalic acid esters (PAEs) exhibits significant reproductive and respiratory toxicity. In this study, a multifunctional metal-organic frameworks-mediated colorimetric/photothermal immunosensor was established for the quantitative detection of DBP. Firstly, a highly sensitive and specific monoclonal antibody (mAb), designated 3A5, was prepared with a sensitivity IC50 value of 16.29 ng/mL. Secondly, a metal-organic framework material (ZrO₂@C) was synthesized via a two-step pyrolysis process of UiO-66. Subsequently, a multifunctional immunoprobe was prepared for the detection of DBP. Using ZrO₂@C-based colorimetric and photothermal dual-signal immunosensor ensured the accuracy of the detection results, as the multiple of these signals effectively guaranteed the reliability of the results. The limit of detection (LOD) for the dual signal was 0.766 ng/mL (colorimetric signal) and 0.465 ng/mL (photothermal signal). In conclusion, this work presented a novel and feasible approach for the development of multifunctional nanomaterials for the fabrication of immunosensors.

Multimodal triple-mode probe with colorimetric-fluorescence-SERS (CFSERS) for sensitive and quantitative detection of C-reactive protein in clinical diagnostics

Chronic inflammation remains a major global health concern, necessitating the development of advanced tools for continuous, precise monitoring. This study introduces a novel, clinically impactful triple-mode probe that integrates colorimetric, fluorescence, and surface-enhanced Raman scattering (SERS) signals, offering unparalleled multimodal detection capabilities. The probe's design leverages europium chelate-doped polystyrene nanoparticles (ECNPs), ensuring minimal signal cross-interference through a long Stokes shift. A key innovation is the development of a multimodal mapping algorithm that seamlessly integrates these optical signals, providing a sensitive and robust platform for biomarker detection with broad dynamic ranges. The probe's clinical relevance is demonstrated by its application in lateral flow assays (LFAs) for detecting C-reactive protein (CRP) levels, achieving a detection limit of 6.31 ng/mL and dynamic ranges from 23.13 to 2000 ng/mL, significantly outperforming single-mode detection methods. In clinical validation using urine samples from 31 patients, the triple-mode LFA showed excellent correlation (0.9377) and agreement (93.55 %) with gold standard enzyme-linked immunosorbent assay (ELISA) results. This demonstrates that the proposed multimodal platform offers a highly sensitive, cost-effective, and versatile tool for monitoring inflammation and other disease biomarkers, with substantial potential for clinical applications in diagnostics and disease management.

Determination of parathion by time-resolved fluorescence immunochromatographic assay based on nanobody: Aiming at improving strip sensitivity

The label probe plays a crucial role in enhancing the sensitivity of immunochromatographic assay. Time-resolved fluorescent microspheres (TRFMs) have provided accurate and reliable results for fast and immediate detection. In this study, parathion was used as a model molecule in the time-resolved fluorescence immunochromatographic assay (TRFICA) strip establishment using recognition element of anti-parathion nanobody (VHH9). Under the optimal conditions, this TRFICA demonstrated good analytical performance for the detection of parathion with a cut-off value of 30 ng/mL and the limit of detection (LOD) of 0.016 ng/mL. Meanwhile, the sensitivity of the nanobody-based TRFICA was 10-fold and 480-fold higher than that of the VHH9 based colloidal gold ICA (CGICA) and commercial mAb-ICA. Moreover, this method exhibited good recoveries for the detection of cabbage, cucumber, and orange samples with no obvious cross-reactions with the other analogs observed and showed strong correlation with UPLC-MS/MS results in spiked samples. In summary, the proposed method is feasible, rapid, and could serve as a highly sensitive platform to meet practical samples detection for parathion.

Defective UIO66 metal-organic framework nanoparticles assisted by cascade isothermal amplification technology for the detection of aflatoxin B1

Aflatoxin B1 (AFB1) exhibits significant toxicity and pose a serious threat to food safety, environmental hygiene, and public health even in trace amounts. Hence, the development of a rapid, accurate, and sensitive detection technology has become a pivotal aspect of ensuring control standards. In this study, we introduce the UIO66 and two defective dichloroacetic acid@UIO66 (DCA@UIO66, DU) metal-organic framework nanoparticles, named DU1 and DU2, characterized by different defect levels. It is noteworthy that DU1 exhibits superior DNA sensing capability compared to UIO66 and DU2. With a fluorescence quenching efficiency of 92.66 % and a recovery efficiency of 1256.75 %, DU1 demonstrates the substantial potential in the detection field. Furthermore, we employ cascade isothermal amplification to assist DU1-mediated fluorescence sensors in detecting AFB1. AFB1 is efficiently identified through an aptamer competition process facilitated by magnetic nanoparticles, which initiates the exponential amplification triggered rolling circle amplification reaction, and converts trace amounts of toxin signal into a large number of long single-stranded DNA molecules. Upon recognition of the amplification product by the fluorescent probe on DU1, a more stable double-stranded DNA is formed and leaves the surface of DU1, leading to a significant change in fluorescence intensity. This method exhibits acceptable sensitivity, with a detection limit of 0.09 pg mL-1 and a wide detection range spanning from 0.2 pg mL-1 to 20 pg mL-1. Additionally, this assay exhibits satisfactory specificity and high accuracy in practical sample applications. Our proposed method offers a solid theoretical framework and technical backing, thereby facilitating the establishment of a new generation of mycotoxin detection standards.

Genetically engineered integrated aflatoxin B1 and deoxynivalenol bispecific nanobody as surrogate antigens for constructed time-resolved immunoassay dual detection methods

There is a phenomenon of combined contamination of fungal toxins, of which aflatoxin B1 (AFB1) is the most toxic, and deoxynivalenol (DON) contamination is common. The use of antigens for double or multiple testing of mycotoxins is easy to cause environmental pollution, and surrogate antigens have become necessary. The small molecule and susceptibility to genetic modification of nanobodies can be used to develop alternative antigens for mycotoxins. In this study, using the nanobody gene sequences of the heavy chain recognition regions of anti-aflatoxin and deoxynivalenol monoclonal antibodies, recombinant plasmids were successfully constructed by one-step cloning, and low-temperature-induced bispecific nanobodies against AFB1-DON were obtained, which can be used as alternative antigens to reduce the pollution of the environment from mycotoxin detection. Enzyme-linked immunosorbent assay validated the bispecific nanobody, and the semi-inhibitory concentration (IC50) of the bispecific nanobody were 0.47 μg/L and 149 μg/L for AFB1 and DON, respectively. Finally, a time-resolved fluorescent dual-detection test strip was constructed by this bispecific nanobody as a surrogate antigen for AFB1 and DON, which was capable of detecting AFB1 and DON at the same time, and the limits of detection (LOD) for the two toxins were 0.0254 μg/L and 21.4 μg/L, respectively. This method has satisfactory sensitivity and does not require antigen, which reduces the toxicity of using antigen.

Nanobody-Based Immunoassays for the Detection of Food Hazards-A Review

Food safety remains a significant global challenge that affects human health. Various hazards, including microbiological and chemical threats, can compromise food safety throughout the supply chain. To address food safety issues and ensure public health, it is necessary to adopt rapid, accurate, and highly specific detection methods. Immunoassays are considered to be an effective method for the detection of highly sensitive biochemical indicators and provide an efficient platform for the identification of food hazards. In immunoassays, antibodies function as the primary recognition elements. Nanobodies have significant potential as valuable biomolecules in diagnostic applications. Their distinctive physicochemical and structural characteristics make them excellent candidates for the development of reliable diagnostic assays, and as promising alternatives to monoclonal and polyclonal antibodies. Herein, we summarize a comprehensive overview of the status and prospects of nanobody-based immunoassays in ensuring food safety. First, we begin with a historical perspective on the development of nanobodies and their unique characteristics. Subsequently, we explore the definitions and boundaries of immunoassays and immunosensors, before discussing the potential applications of nanobody-based immunoassays in food safety testing that have emerged over the past five years, and follow the different immunoassays, highlighting their advantages over traditional detection methods. Finally, the directions and challenges of nanobody-based immunoassays in food safety are discussed. Due to their remarkable sensitivity, specificity and versatility, nanobody-based immunoassays hold great promise in revolutionizing food safety testing and ensuring public health and well-being.

Phase engineered amorphous-crystalline MIL-101(CuFe)@AuNPs with enhanced photothermal activity for sensitive immunochromatographic bimodal detection of streptomycin

Phase engineering-assisted tuning of the plasma resonance properties of multifunctional nanocomposites provides an excellent opportunity to improve analytical performance. It is anticipated to break the dominating bottleneck of insufficient signal brightness in identifying imperceptible variation of the target concentration and further enhance the sensitive immunochromatographic assays (ICAs) analysis. Herein, by simply assembling isolated gold nanoparticles (AuNPs) on the surface of MIL-101(CuFe) (named MCF) with a tunable size and crystal phase, we synthesized amorphous-crystalline MCF@AuNPs nanocomposites as immuno signal tracers. For the first time, we utilized phase transformation to assist in realizing the effective regulation of the plasma resonance properties of MCF@AuNPs. It exhibits extraordinary colorimetric intensity, photothermal conversion efficiency (59.1%), stability, and dispersion, all of which facilitate the construction of sensitive and accurate bimodal complementary ICA. With a proof-of-concept for streptomycin, the MCF@AuNPs-ICA showed the limit of detection (LOD) at 0.14 ng mL-1 with remarkable university in different samples. This work demonstrates the importance of the rational design of phase-transformation-assisted tuning plasma resonance properties to improve analytical performance with terrific potential for point-of-care (POC) diagnostic applications.

A fluorescence and SERS dual-mode biosensor for quantification and imaging of Mucin1 in living cells

Mucin1 (MUC1) is a cell surface transmembrane protein overexpressed in multiple types of tumor cells, which is generally considered as a tumor-associated biomarker. Thus, quantifying and imaging of MUC1 in tumor cells is of great significance for the diagnosis and biological therapy of tumors. Herein, a fluorescence (FL) and surface-enhanced Raman scattering (SERS) dual-mode biosensor was developed for sensitive detection and imaging of MUC1 in living cells. The FL-SERS biosensor was based on self-assembled satellite structures mediated by the competition of MUC1 and complementary DNA modified on Au nanostars (AuNS-cDNA-PEG) with aptamer modified on quantum dots (QD-PDDA-Apt). This biosensor achieved dual-mode quantification and imaging of MUC1 by quenching the FL signal of QD and significantly enhancing the SERS signal of PDDA through the metal FL quenching effect and hotspot effect of AuNS, respectively. The dual-mode biosensor exhibited high sensitivity to MUC1, with a detection limit of 1.19 fg/mL under FL mode and 1.16 fg/mL under SERS mode. Moreover, this biosensor displayed good selectivity, nice biological stability and low cytotoxicity. Importantly, this biosensor possessed an excellent MUC1 dual-mode imaging capability with high specificity in different tumor cells, providing a new idea for clinical diagnosis of tumors.

Development of a nanobody-horseradish peroxidase fusion-based competitive ELISA to rapidly and sensitively detect Enrofloxacin residues in animal-derived foods

The ability to reliably detect enrofloxacin in animal-derived food products has important health implications. In the present study, a nanobody-horseradish peroxidase fusion specific for ENR was generated to enable a sensitive and rapid competitive ELISA suitable for detecting enrofloxacin in samples of milk and animal tissue. An enrofloxacin hapten generated via the glutaraldehyde method was initially used to immunize an adult Bactrian camel as a means of constructing a phage library. Enrofloxacin-specific nanobodies were then selected through three rounds of biopanning, and HRP-fused versions of these nanobodies were then expressed. Lastly, these nanobodies were used to develop a sensitive cELISA for enrofloxacin detection in milk and animal tissues, with the resultant assay exhibiting an IC50 of 37.41 ng/mL and a linear detection range (IC20-IC80) of 10.89 to 244.34 ng/mL. The limit of detection for this cELISA was 6.48 ng/mL, with 4.66 % cross-reactivity with ciprofloxacin, and recovery rates that ranged from84.99 % to 107.72 % together with an RSD below 10.70 %.

Supramolecular Coassembly Activated Dual-Excitation Fluorescent Sensing Platform for Precise Detection of Aflatoxin B1

The development of a sensory signal amplification approach is very crucial for rapid and precise detection of aflatoxin B1 (AFB1). However, such approaches remain scarce due to the weak interactions between AFB1 and the sensing probes. Herein, the first example of a dual-excitation fluorescent platform for antibody-free AFB1 detection is reported, which is assembled by an ordered π-π stack of cationic perylene derivative (PTHA) and tris(2,2'-bipyridine)ruthenium(II) [Ru(bpy3)2+]. Taking advantage of stepwise assembly and multiple binding sites of the nanoprobe, its ability for capturing AFB1 is significantly improved driven by multiple noncovalent interactions. Interestingly, dual-excitation fluorescent sensing mode with signal superposition and self-calibration is activated in the supramolecular coassembly process. Under excitation of 365 nm and 440 nm, the platform exhibits specific recognition toward AFB1 and the limit of detection is determined to be 0.12 ng mL-1. Notably, the dual-excitation platform demonstrates exceptional sensitivity enhancements of 106-fold, revealing that the self-calibrated reference improves the sensitivity and accuracy of analytical method significantly. The applications of our platform not only crack the problem of precise AFB1 detection via supramolecular coassembly strategy but also provide a universal sensitization strategy for ultrasensitive analysis in complex environments.

Rapid transformation of nanobodies affinity based on AlphaFold2's high-accuracy predictions and interaction analysis for enrofloxacin detection in coastal fish

High-affinity antibodies are crucial in biosensors, disease diagnostics, therapeutic drug development, and immunological analysis, making the enhancement of antibody affinity a key research focus within the field. Computer-aided design is recognized as a time-saving and labor-efficient method for nanobodies in vitro affinity maturation. Compared to experimental mutagenesis techniques, it is advantageous due to the elimination of the need for laborious library construction and screening processes. However, these approaches are constrained by structural prediction since inaccuracy in structure could readily result in maturation failures. Herein, a novel nanobodies modification method for in vitro affinity maturation, utilizing the high accuracy prediction of AlphaFold2, was employed to rapidly transform a low affinity nanobody against enrofloxacin (ENR) into one with high affinity. The molecular docking results revealed a 1.5- to 2.5-fold increase in the number of noncovalent interactions of modified nanobodies, accompanied by a reduction in binding free energy ranging from 14.1 to 62.6%. The evaluation results from ELISA and BLI indicated that the affinity of the modified nanobodies had been enhanced by 6.2-91.6 times compared to the template nanobody. Furthermore, the modified nanobodies were employed for the detection of ENR-spiked coastal fish samples. In summary, this research proposed a nanobodies modification method from a new perspective, endowing its great application potential in biosensors, food safety, and environmental monitoring.

Development of immunochromatographic and homogeneous assay based on quantum dot-functionalized polystyrene nanoprobes for the qualitative and quantitative screening of respiratory viruses

Accurately differentiating respiratory diseases caused by viruses is challenging because of the similarity in their early or clinical symptoms. Moreover, different infection sources require different treatments. However, the current diagnostic methods have limited differentiating efficiency and sensitivity. We developed a dual-system immunosensor with a bilayer fluorescent label as a signal amplifier for the on-site, sensitive, and accurate identification of multiple respiratory viruses (RVs). The nanomaterial, comprising a polystyrene (PS) nanosphere core encapsulated by two layers of CdSe@ZnS-COOH quantum dots (QDs), outperforms the conventional color and fluorescent labels in RV detection. The dual-system detection platform, comprising a PS@DQD-based lateral flow immunoassay (LFIA) and a PS@DQD-based homogeneous sensor, enables qualitative and quantitative screening of multiple respiratory viruses within 10 and 30 min, respectively, depending on the specific detection requirements for different application scenarios. This remarkable method provides 51.2 to 1000 times sensitivity improvement over commercial antigen detection kits and greater than 12.5 to 100 times improvement over QD-based immunosensors. Furthermore, we comprehensively evaluated the specificity, reproducibility, and stability of the integrated dual-system detection platform, demonstrating its reliability. Remarkably, the respiratory viral testing was validated using biological samples, thus illustrating its promise and convenience in the detection of respiratory viruses.

Bifunctional nanobody facilitates a colorimetric and fluorescent dual-mode immunoassay of Staphylococcal enterotoxin A

Immunoassay is a diagnostic tool based on the specific binding of antibodies and antigens with widespread applications. Nonetheless, several research obstacles, like poor specific antibodies, the poisonous reagents and unstable results, still remain challenges. Herein, we innovatively reported a colorimetric and fluorescent dual-mode immunoassay based on the bifunctional nanobody for SEA detection. Benefiting from the advantages of nanobodies, the bifunctional protein with both recognition and catalysis was built to identify and catalyze with efficiency to generate the first colorimetric signal. Meanwhile, the introduction of quinine as the natural source of the second fluorescent signal greatly improved the stability and safety of detection. In addition, the proposed method was successfully applied to detecting SEA in food samples with high accuracy and stability. This study integrated the bifunctional nanobody with eco-friendly fluorescent product to provide a specific and green platform for the detection of foodborne toxins.

Bioinspired Core-shell nanospheres integrated in multi-signal immunochromatographic sensor for high throughput sensitive detection of Bongkrekic acid in food

Nowadays, notable progress has been achieved in detecting foodborne toxins by employing nanoenzyme-based lateral flow immunoassay (NLFIA) sensors in point-of-care testing (POCT). It continues to be a major challenge to maximize the enzyme-like performance of nanozymes for educe any potential uncertainties in catalytic process. In this study, we employed a facile and efficient self-assembly approach to fabricate nucleoid-shell structured biomimetic nanospheres CuS@Au-Pt (CAP), which demonstrates enhanced brightness of the colorimetric signal, excellent affinity, and excellent peroxidase activity. The integration of CAP with a competitive-assay NLFIA platform enabled sensitive immunochromatographic detection of bongkrekic acid (BA), with LOD as low as 0.66 ng/mL. After signal amplification through enzyme-like reaction, the detection range was extended around 1-fold. Additionally, CAP-NLFIA effectively detected BA with a recovery rate of 80.96-119.36% for real samples. The study proposes using CAP as a signal reporter in a dual-readout LFIA, which can establish a high throughput sensitive detection platform.

Biosensing strategies using recombinant luminescent proteins and their use for food and environmental analysis

Progress in synthetic biology and nanotechnology plays at present a major role in the fabrication of sophisticated and miniaturized analytical devices that provide the means to tackle the need for new tools and methods for environmental and food safety. Significant research efforts have led to biosensing experiments experiencing a remarkable growth with the development and application of recombinant luminescent proteins (RLPs) being at the core of this boost. Integrating RLPs into biosensors has resulted in highly versatile detection platforms. These platforms include luminescent enzyme-linked immunosorbent assays (ELISAs), bioluminescence resonance energy transfer (BRET)-based sensors, and genetically encoded luminescent biosensors. Increased signal-to-noise ratios, rapid response times, and the ability to monitor dynamic biological processes in live cells are advantages inherent to the approaches mentioned above. Furthermore, novel fusion proteins and optimized expression systems to improve their stability, brightness, and spectral properties have enhanced the performance and pertinence of luminescent biosensors in diverse fields. This review highlights recent progress in RLP-based biosensing, showcasing their implementation for monitoring different contaminants commonly found in food and environmental samples. Future perspectives and potential challenges in these two areas of interest are also addressed, providing a comprehensive overview of the current state and a forecast of the biosensing strategies using recombinant luminescent proteins to come.

Time-resolved fluorescence/visual dual-readout nanobiosensors for the detection of aflatoxin B1, benzo(α)pyrene and capsaicin in edible oils using a miniaturized paper analytical device

Edible oil safety impacts food safety and consumer health. The typical pollutants-aflatoxin B1 (AFB1) and benzo(α)pyrene (BaP), and kitchen waste oil-are significant hazards in edible oil consumption. Herein, we developed a dual-readout lateral flow immunoassay (tdLFIA) for the multi-quantitative detection of AFB1, BaP and capsaicin (CAP). A novel monoclonal antibody against BaP was developed with a sensitivity of 1.92 ng/mL. Subsequently, gold nanoparticles and Eu3+ labelled fluorescent nanospheres were synthesized as colorimetric and fluorescent sensors. A rapid synchronous pretreatment method based on immunomagnetic beads(IMAB)combined with a molecularly imprinted solid phase extraction (MISPE) was developed. The tdLFIA enabled a rapid response of 7 min for AFB1, BaP and CAP detection, with quantitative limits of detection of 0.003, 0.6, and 0.01 ng/mL, respectively. The proposed strategy indicated reliability and has been applied in real samples, providing useful products for evaluating edible oil quality and safety.

Janus plasmonic-aggregation induced emission nanobeads as high-performance colorimetric-fluorescent probe of immunochromatographic assay for the ultrasensitive detection of staphylococcal enterotoxin B in milk

Herein, a colorimetric-fluorescent hybrid bifunctional nanobead with Janus structure (J-cf-HBN) was synthesized via one-pot microemulsification. Oleylamine-coated AuNPs and aggregation-induced emission luminogens (AIEgens) were suggested as building blocks to obtain high-performance colorimetric-fluorescent signals. The as-prepared J-cf-HBNs were used as a signal amplification probe to construct an immunochromatographic assay (J-cf-HBNs-ICA) platform for the ultrasensitive detection of staphylococcal enterotoxin B (SEB) in milk samples. Owing to the rational spatial distribution of AuNPs and AIEgens, the J-cf-HBNs present a highly retained photoluminescence and enhanced colorimetric signals. Combined with a pair of highly affinitive anti-SEB antibodies, the J-cf-HBN-ICA platform enabled the fast naked-eye visualization and fluorescent quantitative detection of SEB in various milk matrices. Given the advantages of the dual-mode high-performance J-cf-HBNs, the proposed strip achieved a high sensitivity for SEB qualitative determination with a visual limit of detection (LOD) of 1.56 ng mL-1 and exhibited ultrasensitivity for SEB quantitative detection with a LOD of 0.09 ng mL-1, which is 139-fold lower than that of ELISA using same antibodies. In conclusion, this work provides new insights into the construction of multimode immunochromatographic methods for food safety detection in the field.

Overview of the Design and Application of Dual-Signal Immunoassays

Immunoassays have been widely used for the determination of various analytes in the fields of disease diagnosis, food safety, and environmental monitoring. Dual-signal immunoassays are now advanced and integrated detection technologies with excellent self-correction and self-validation capabilities. In this work, we summarize the recent advances in the development of optical and electrochemical dual-signal immunoassays, including colorimetric, fluorescence, surface-enhanced Raman spectroscopy (SERS), electrochemical, electrochemiluminescence, and photoelectrochemical methods. This review particularly emphasizes the working principle of diverse dual-signal immunoassays and the utilization of dual-functional molecules and nanomaterials. It also outlines the challenges and prospects of future research on dual-signal immunoassays.

Decentralized food safety and authentication on cellulose paper-based analytical platform: A review

Food safety and authenticity analysis play a pivotal role in guaranteeing food quality, safeguarding public health, and upholding consumer trust. In recent years, significant social progress has presented fresh challenges in the realm of food analysis, underscoring the imperative requirement to devise innovative and expedient approaches for conducting on-site assessments. Consequently, cellulose paper-based devices (PADs) have come into the spotlight due to their characteristics of microchannels and inherent capillary action. This review summarizes the recent advances in cellulose PADs in various food products, comprising various fabrication strategies, detection methods such as mass spectrometry and multi-mode detection, sampling and processing considerations, as well as applications in screening food safety factors and assessing food authenticity developed in the past 3 years. According to the above studies, cellulose PADs face challenges such as limited sample processing, inadequate multiplexing capabilities, and the requirement for workflow integration, while emerging innovations, comprising the use of simplified sample pretreatment techniques, the integration of advanced nanomaterials, and advanced instruments such as portable mass spectrometer and the innovation of multimodal detection methods, offer potential solutions and are highlighted as promising directions. This review underscores the significant potential of cellulose PADs in facilitating decentralized, cost-effective, and simplified testing methodologies to maintain food safety standards. With the progression of interdisciplinary research, cellulose PADs are expected to become essential platforms for on-site food safety and authentication analysis, thereby significantly enhancing global food safety for consumers.

Emerging Nano/Microporous Architectures for Food Hazards: New Strategies for Precise Inspection and New Principles for Controllable Regulation

The big progress of materials science along with chemical engineering and biotechnology has significantly promoted interdisciplinary development, achieving advanced analytical methodologies, improved inspection performance, as well as promising regulation principles for food safety. The very recent progress on nano/microporous architectures for agri-food science, including new strategies for precise inspection and new principles for controllable regulation of food hazards, are summarized and discussed. Major attention is paid to the newly emerged porous architectures with their derivative nano/microstructures contributing to food safety through their instinctive advantages including special material surface, extraordinary porous structure, ease-of-modification, and excellent diversity and variability. This review clearly and logically displays the research road maps and development trends for current food safety issues and give suggestive directions for future outlook as well as the bottleneck problems to be solved, not only smart inspection and analysis but also elimination and control of ever-emerging food hazards.

"Three-in-One" Plasmonic Au@PtOs Nanocluster Driven Lateral Flow Assay for Multimodal Cancer Exosome Biosensing

Exploiting the multiple properties of nanozymes for the multimode lateral flow assay (LFA) is urgently required to improve the accuracy and versatility. Herein, we developed a novel plasmonic Au nanostar@PtOs nanocluster (Au@PtOs) as a multimode signal tag for LFA detection. Based on the PtOs bimetallic nanocluster doping strategy, Au@PtOs can indicate both excellent SERS enhancement and nanozyme catalytic activity. Meanwhile, Au@PtOs displays a better photothermal effect than that of Au nanostars. Therefore, catalytic colorimetric/SERS/temperature three-mode signals can be read out based on the Au@PtOs nanocomposite. The Au@PtOs was combined with LFA and applied for breast cancer exosome detection. The detection limit for the colorimetric/SERS/temperature mode was 2.6 × 103/4.1 × 101/4.6 × 102 exosomes/μL, respectively, which was much superior to the common Au nanoparticles LFA (∼105 exosomes/μL). Moreover, based on the fingerprint molecular recognition ability of the SERS mode, exosome phenotypes derived from different breast cancer cell lines can be discriminated easily. Based on the convenient visual colorimetric mode and sensitive SERS/temperature quantitative modes, Au@PtOs driven LFA can satisfy the requirements of accurate and flexible multimodal sensing in different application scenarios.

Nanobodies-based colloidal gold immunochromatographic assay for specific detection of parathion

Parathion is one of organophosphorus pesticide, which has been prohibited in agricultural products due to its high toxicity to human beings. However, there are still abuse cases for profit in agricultural production. Hence, we established nanobodies-based colloidal gold immunochromatographic assay (GICA) in which nanobodies (Nbs) as an excellent recognition element, greatly improving the stability and sensitivity of ICA. Under the optimal conditions, the developed Nbs-based GICA showed a cut-off value of 50 ng/mL for visual judgment and a half-inhibitory concentration (IC50) of 2.39 ng/mL for quantitative detection. The limit of detection (LOD) was as low as 0.15 ng/mL which was significantly 50-fold higher sensitivity than the commercial mAb-ICA. Additionally, this method exhibited good recoveries for the detection of cabbage, cucumber, and orange samples and excellent correlation with the UPLC-MS/MS method. The results showed that this method developed in this work based on nanobody can be used in practical detection of parathion in foods and nanobody is novel prospective antibody resource for immunoassays of chemical contaminants.

Nanobody and CuS Nanoflower-Au-Based Lateral Flow Immunoassay Strip to Enhance the Detection of Aflatoxin B1

In the realm of analysis, the lateral flow immunoassay (LFIA) is frequently utilized due to its capability to be fast and immediate. However, the biggest challenge of the LFIA is its low detection sensitivity and tolerance to matrix interference, making it impossible to enable accurate, qualitative analyses. In this study, we developed a new LFIA with higher affinity and sensitivity, based on a nanobody (G8-DIG) and CuS nanoflowers-Au (CuS NFs-Au), for the detection of aflatoxin B1 (AFB1) in maize. We synthesized the immunoprobe G8-DIG@CuS NFs-Au, stimulated the in situ development of Au nanoparticles (Au NPs) on Cu NFs by electrical displacement, and obtained Cu NFs-Au for fixing the G8-DIG. G8-DIG@CuS NFs-Au probe-based LFIAs may, in ideal circumstances, use a strip chromatography reader to accomplish sensitive quantitative detection and qualitative visualization. AFB1 has a detection range of 2.82-89.56 µg/L and a detection limit of 0.87 µg/L. When compared with an LFIA based on CuS NFs, this sensitivity is increased by 2.76 times. The practical application of this method in corn flour demonstrated a recovery rate of 81.7% to 117%. Therefore, CuS NFs-Au show great potential for detecting analytes.

"Cave Effect" Induces Self-Assembled Bimetallic Hollow Structure for Three-in-One Lateral Flow Immunoassay

Bimetallic hollow structures have attracted much attention due to their unique properties, but they still face the problems of nonuniform alloys and excessive etching leading to structural collapse. Here, uniform bimetallic hollow nanospheres are constructed by pore engineering and then highly loaded with hemin (Hemin@MOF). Interestingly, in the presence of polydopamine (PDA), the competitive coordination between anionic polymer (γ-PGA) and dimethylimidazole does not lead to the collapse of the external framework but self-assembly into a hollow structure. By constructing the Hemin@MOF immune platform and using E. coli O157:H7 as the detection object, we find that the visual detection limits can reach 10, 3, and 3 CFU/mL in colorimetric, photothermal, and catalytic modes, which is 4 orders of magnitude lower than the traditional gold standard. This study provides a new idea for the morphological modification of the metal-organic skeleton and multifunctional immunochromatography detection.

Fluorescent and Colorimetric Dual-Readout Immunochromatographic Assay for the Detection of Phenamacril Residues in Agricultural Products

The fungicide phenamacril has been employed to manage Fusarium and mycotoxins in crops, leading to persistent residues in the environment and plants. Detecting phenamacril is pivotal for ensuring environmental and food safety. In this study, haptens and artificial antigens were synthesized to produce antiphenamacril monoclonal antibodies (mAbs). Additionally, gold nanoparticles coated with a polydopamine shell were synthesized and conjugated with mAbs, inducing fluorescence quenching in quantum dots. Moreover, a dual-readout immunochromatographic assay that combines the positive signal from fluorescence with the negative signal from colorimetry was developed to enable sensitive and precise detection of phenamacril within 10 min, achieving detection limits of 5 ng/mL. The method's reliability was affirmed by using spiked wheat flour samples, achieving a limit of quantitation of 0.05 mg/kg. This analytical platform demonstrates high sensitivity, outstanding accuracy, and robust tolerance to matrix effects, making it suitable for the rapid, onsite, quantitative screening of phenamacril residues.

Fortified Dual-Spectral Overlap with Enhanced Colorimetric/Fluorescence Dual-Response Immunochromatography for On-Site Bimodal-Type Gentamicin Monitoring

Immunochromatography (ICA) remains untapped toward enhanced sensitivity and applicability for fulfilling the nuts and bolts of on-site food safety surveillance. Herein, we report a fortified dual-spectral overlap with enhanced colorimetric/fluorescence dual-response ICA for on-site bimodal-type gentamicin (Gen) monitoring by employing polydopamine (PDA)-coated AuNPs (APDA) simultaneously serving as a colorimetric reporter and a fluorescence quencher. Availing of the enhanced colorimetric response that originated from the PDA layer, the resultant APDA exhibits less required antibody and immunoprobes in a single immunoassay, which facilitates improved antibody utilization efficiency and immuno-recognition in APDA-ICA. Further integrated with the advantageous features of fortified excitation and emission dual-spectral overlap for the Arg/ATT-AuNCs, this APDA-ICA with a "turn on/off" pattern achieves the visual limits of detection of 1.0 and 0.5 ng mL-1 for colorimetric and fluorescence patterns (25- and 50-fold lower than standard AuNPs-ICA). Moreover, the excellent self-calibration and satisfactory recovery of 79.03-118.04% were shown in the on-site visual colorimetric-fluorescence analysis for Gen in real environmental media (including real river water, an urban aquaculture water body, an aquatic product, and an animal byproduct). This work provides the feasibility of exploiting fortified dual-spectral overlap with an enhanced colorimetric/fluorescence dual response for safeguarding food safety and public health.

Development of an Open Droplet Microchannel-Based Magnetosensor for Immunofluorometric Assay of Trimethoprim in Chicken and Pork Samples with a Wide Linear Range

Trimethoprim (TMP), functioning as a synergistic antibacterial agent, is utilized in diagnosing and treating diseases affecting livestock and poultry. Human consumption of the medication indirectly may lead to its drug accumulation in the body and increase drug resistance due to its prolonged metabolic duration in livestock and poultry, presenting significant health hazards. Most reported immunoassay techniques, such as ELISA and immunochromatographic assay (ICA), find it challenging to achieve the dual advantages of high sensitivity, simplicity of operation, and a wide detection range. Consequently, an open droplet microchannel-based magnetosensor for immunofluorometric assay (OMM-IFA) of trimethoprim was created, featuring a gel imager to provide a signal output derived from the highly specific antibody (Ab) targeting trimethoprim. The method exhibited high sensitivity in chicken and pork samples, with LODs of 0.300 and 0.017 ng/mL, respectively, and a wide linear range, covering trimethoprim's total maximum residue limits (MRLs). Additionally, the spiked recoveries in chicken and pork specimens varied between 81.6% and 107.9%, maintaining an acceptable variation coefficient below 15%, aligning well with the findings from the ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) technique. The developed method achieved a much wider linear range of about 5 orders of magnitude of 10-2-103 levels with grayscale signals as the output signal, which exhibited high sensitivity, excellent applicability and simple operability based on magnetic automation.