Precise Spectral Overlap-Based Donor-Acceptor Pair for a Sensitive Traffic Light-Typed Bimodal Multiplexed Lateral Flow Immunoassay.

Bimodal-type multiplexed immunoassays with complementary mode-based correlation analysis are gaining increasing attention for enhancing the practicability of the lateral flow immunoassay (LFIA). Nonetheless, the restriction in visually indistinguishable multitargets induced by a single fluorescent color and difficulty in single acceptor ineffectual fluorescence quenching due to the various spectra of multiple different donors impede the further execution of colorimetric-fluorescence bimodal-type multiplexed LFIAs. Herein, the precise spectral overlap-based donor-acceptor pair construction strategy is proposed by regulating the size of the nanocore, coating it with an appropriate nanoshell, and selecting a suitable fluorescence donor with distinct colors. By in situ coating Prussian blue nanoparticles (PBNPs) on AuNPs with a tunable size and absorption spectrum, the resultant APNPs demonstrate efficient fluorescence quenching ability, higher colloidal stability, remarkable colorimetric intensity, and an enhanced antibody coupling efficiency, all of which facilitate highly sensitive bimodal-type LFIA analysis. Following integration with competitive-type immunoreaction, this precise spectral overlap-supported spatial separation traffic light-typed colorimetric-fluorescence dual-response assay (coined as the STCFD assay) with the limits of detection of 0.013 and 0.152 ng mL-1 for ractopamine and clenbuterol, respectively, was proposed. This work illustrates the superiority of the rational design of a precise spectral overlap-based donor-acceptor pair, hinting at the enormous potential of the STCFD assay in the point-of-care field.

Carba PBP: a novel penicillin-binding protein-based lateral flow assay for rapid phenotypic detection of carbapenemase-producing Enterobacterales.

Rapid phenotypic detection assays, including Carba NP and its variants, are widely applied for clinical diagnosis of carbapenemase-producing Enterobacterales (CPE). However, these tests are based on the acidification of the pH indicator during carbapenem hydrolysis, which limits test sensitivity and speed, especially for the detection of CPE producing low-activity carbapenem (e.g., OXA-48 variants). Herein, we developed a novel rapid and sensitive CPE detection method (Carba PBP) that could measure substrate (meropenem) consumption based on penicillin-binding protein (PBP). Meropenem-specific PBP was used to develop a competitive lateral flow assay (LFA) for meropenem identification. For the detection of carbapenemase activity, meropenem concentration was optimized using a checkerboard assay. The performance of Carba PBP was evaluated and compared with that of Carba NP using a panel of 94 clinical strains characterized by whole-genome sequencing and carbapenem susceptibility test. The limit of detection of PBP-based LFA for meropenem identification was 7 ng mL-1. Using 10 ng mL-1 meropenem as the substrate, Carba PBP and Carba NP could detect 10 ng mL-1 carbapenemase within 25 min and 1,280 ng mL-1 CPE in 2 h, respectively. The sensitivity and specificity were 100% (75/75) and 100% (19/19) for Carba PBP and 85.3% (64/75) and 100% (19/19) for Carba NP, respectively. When compared with Carba NP, Carba PBP showed superior performance in detecting all the tested CPE strains (including OXA-48-like variants) within 25 min and presented two orders of magnitude higher analytical sensitivity, demonstrating potential for clinical diagnosis of CPE. IMPORTANCE This study successfully achieved the goal of carbapenemase activity detection with both high sensitivity and convenience, offering a convenient lateral flow assay for clinical diagnosis of carbapenemase-producing Enterobacterales.

A comprehensive review on the detection of Staphylococcus aureus enterotoxins in food samples.

Staphylococcal enterotoxins (SEs), the major virulence factors of Staphylococcus aureus, cause a wide range of food poisoning and seriously threaten human health by infiltrating the food supply chain at different phases of manufacture, processes, distribution, and market. The significant prevalence of Staphylococcus aureus calls for efficient, fast, and sensitive methods for the early detection of SEs. Here, we provide a comprehensive review of the hazards of SEs in contaminated food, the characteristic and worldwide regulations of SEs, and various detection methods for SEs with extensive comparison and discussion of benefits and drawbacks, mainly including biological detection, genetic detection, and mass spectrometry detection and biosensors. We highlight the biosensors for the screening purpose of SEs, which are classified according to different recognition elements such as antibodies, aptamers, molecularly imprinted polymers, T-cell receptors, and transducers such as optical, electrochemical, and piezoelectric biosensors. We analyzed challenges of biosensors for the monitoring of SEs and conclude the trends for the development of novel biosensors should pay attention to improve samples pretreatment efficiency, employ innovative nanomaterials, and develop portable instruments. This review provides new information and insightful commentary, important to the development and innovation of further detection methods for SEs in food samples.

A Proof-of-Concept Sandwich Enzyme-Linked Immunoassay Development for Small Molecules.

A sandwich immunoassay theoretically exhibits higher sensitivity and specificity compared to a competitive counterpart; however, it is extremely difficult to obtain a pair of antibodies that can bind to a small molecule simultaneously, which is always thought to be a single epitope. In the present study, abamectin (ABM) was selected to prove the effect of hapten design and antibody recognition properties on the development of a sandwich immunoassay for small molecules. First, the epitopes of ABM were roughly located, and epitope distances were determined. Then, two haptens were designed by introducing spacer arms at the C4″-OH and C5-OH of ABM, respectively, aiming to provide the longest epitope distances. A total of seven rabbit polyclonal antibodies (pAbs) and 21 mouse monoclonal antibodies (mAbs) with various recognition properties were obtained. Extensive combinatorial associations of antibody pairs for simultaneously binding to ABM were performed, and only two mAb-mAb pairs were observed to achieve a sandwich immunoassay for ABM with a total success rate of 0.27%. The best mAb pair for sandwich immunoassay was confirmed by surface plasmon resonance, used to develop a sandwich immunoassay, and then evaluated by cross-reactivities and molecular docking with structurally similar analogues and abamectin. Altogether, the study provided a theoretical foundation as well as practical experience and demonstrated the importance of careful hapten design and extensive antibody screening to successfully establish the sandwich immunoassay for small molecules.

How Exactly Do AIEgens Target Bacteria? Leveraging the Targeting Mechanism to Design Sensitive Fluorescent Immunosensors.

Aggregation-induced emission luminogens (AIEgens) are promising candidates for bacterial imaging and detection because they can "Light-Up" pathogenic bacteria without complicated labeling or washing steps. However, there have been few in-depth analyses of the intrinsic mechanism underlying their utility as fluorescence probes for targeting bacteria. Therefore, using large-scale molecular dynamics simulations, we investigated the mechanism of their bacterial "Light-Up" behavior with N,N-diphenyl-4-(7-(pyridin-4-yl)benzo[c][1,2,5]thiadiazol-4-yl) aniline functionalized with 1-bromoethane (TBP-1). We propose that the triphenylamine motif of TBP-1, rather than the positively charged pyridine group, first contacts the cell membrane. After TBP-1 completely inserts into the cell membrane, the hydrophobic triphenylamine motif localizes in the hydrophobic core of the cell membrane, restricting the molecular variation of TBP-1, which induces the fluorescent "turn-on" and bacterial "Light-Up." On this basis, we established a heterogeneous lateral flow immunoassay (LFIA) for the detection of foodborne pathogens. The LFIA system showed improved sensitivity with a limit of detection as low as 103 CFU mL-1 and strong specificity. Our protocol opened an effective shortcut to the design of more efficient AIEgens and novel AIEgens-based immunoassays.

Light-induced circadian rhythm disorder leads to microvascular dysfunction via up-regulating NETs.

Circadian rhythm is a physical, mental, and behavioral pattern over the course of 24-hour cycle, and its disturbance is associated with increased risk of cardiovascular diseases. Microvascular dysfunction serves as an important cause of cardiovascular disease, but the relationship between rhythm disturbances and microcirculation remains elusive. Herein, we constructed the mice model of circadian rhythm disturbance and investigated the alterations of microvascular conditions. It was revealed that coronary microcirculatory function and cardiac diastolic function were significantly reduced, along with endothelium-dependent diastolic function of microvessels remarkably impaired in the rhythm-disordered group of mice compared to the control group. Notably, rhythm disturbance led to a significant upregulation of neutrophil extracellular traps (NETs) levels in mice, which cause endothelial dysfunction by inhibiting microvascular endothelial cell activity and migration capacity as well as inducing apoptosis. Additionally, intraperitoneal injection of Cl-amidine suppressed the production of NETs, which further improved coronary microcirculatory function and endothelium-dependent diastolic function. In conclusion, this study demonstrated that circadian rhythm disorders could induce the development of coronary microvascular dysfunction (CMD) through the up-regulation of NETs, providing a potential therapeutic direction for the treatment of CMD.

High efficient electrochemical biosensor based on exonuclease-â ¢-assisted dual-recycling amplification for ultrasensitive detection of kanamycin.

A target-triggered and exonuclease-Ⅲ-assisted strand displacement, dual-recycling amplification reaction-based biosensor was developed for the rapid, ultrasensitive and accurate detection of kanamycin. The robust profiling platform was constructed using high conductive MXene/VS2 for the electrode surface modification and high active CeCu2O4 bimetallic nanoparticles as nanozyme to improve the sensitivity as well as the catalytic signal amplification of the biosensor. Using the dual supplementary recycling of primer DNA and hairpin DNA, the electrochemical platform could accurately detect kanamycin to as low as 0.6 pM from the range of 5 pM to 5 µM. By profiling five other antibiotics, this platform exhibited high specificity, enhanced repeatability and reproducibility. Based on these intrinsic characteristics and by utilizing milk and water samples, the as-designed biosensor offers a remarkable strategy for antibiotic detection due to its favorable analytical accuracy and reliability, thereby demonstrating potential application prospect for various antibiotic biosensing in food quality control, water contamination detection and biological safety analysis.

Effects of Microplastics on the Transport of Soil Dissolved Organic Matter in the Loess Plateau of China.

Microplastics (MPs) pollution and dissolved organic matter (DOM) affect soil quality and functions. However, the effect of MPs on DOM and underlying mechanisms have not been clarified, which poses a challenge to maintaining soil health. Under environmentally relevant conditions, we evaluated the major role of polypropylene particles at four micron-level sizes (20, 200, and 500 µm and mixed) in regulating changes in soil DOM content. We found that an increase in soil aeration by medium and high-intensity (>0.5%) MPs may reduce NH4+ leaching by accelerating soil nitrification. However, MPs have a positive effect on soil nutrient retention through the adsorption of PO43- (13.30-34.46%) and NH4+ (9.03-19.65%) and their leached dissolved organic carbon (MP-leached dissolved organic carbon, MP-DOC), thereby maintaining the dynamic balance of soil nutrients. The regulating ion (Ca2+) is also an important competitor in the MP-DOM adsorption system, and changes in its intensity are dynamically involved in the adsorption process. These findings can help predict the response of soil processes, especially nutrient cycling, to persistent anthropogenic stressors, improve risk management policies on MPs, and facilitate the protection of soil health and function, especially in future agricultural contexts.

Production of monoclonal antibody against tylosin and tilmicosin with homogeneous cross-reactivity and its application in lateral flow immunoassay.

To avoid false negative results due to the low cross-reactivity rate (CR) in rapid immunoassay, a group-specific antibody with homogeneous CR toward target compounds is needed for accuracy. In this study, tylosin (TYL) and tilmicosin (TM) were selected as model molecules. Firstly, two-dimensional similarity, electrostatic potential energy, spatial conformation and charge distribution of the haptens TYL-CMO, TYL-6-ACA, TYL-4-APA, TYL-CHO and DES-CMO and target compounds of TYL and TM were obtained using Gaussian 09W and Discovery Studio. The optimal hapten was DES-CMO because it is the most similar to TYL and TM. Subsequently, the mAb 14D5 cell line was obtained with IC50 values of 1.59 and 1.72 ng/mL for TYL and TM, respectively, and a CR of 92.44%. Finally, amorphous carbon nanoparticles (ACNPs) were conjugated with mAb 14D5 to develop an accurate lateral flow immunoassay (LFA) for detection of TYL and TM by the reflectance value under natural light. The recoveries of TYL and TM ranged from 77.18 to 112.04% with coefficient of variation < 13.43%. The cut-off value in milk samples was 8 ng/mL, and the limits of detection were 11.44, 15.96, 22.29 and 25.53 µg/kg for chicken muscle, bovine muscle, porcine muscle and porcine liver samples, respectively, and the results being consistent with HPLC-UV. The results suggest that the developed LFA is accurate and potentially useful for on-site screening of TYL and TM in milk and animal tissue samples.

Similarity measurements of B cell receptor repertoire in baseline mice showed spectrum convergence of IgM.

BACKGROUND: The B cell receptor (BCR) repertoire is highly diverse among individuals. Poor similarity of the spectrum among inbred baseline mice may limit the ability to discriminate true signals from those involving specific experimental factors. The repertoire similarity of the baseline status lacks intensive measurements. RESULTS: We measured the repertoire similarity of IgH in blood and spleen samples from untreated BALB/c and C57BL/6J mice to investigate the baseline status of the two inbred strains. The antibody pool was stratified by the isotype of IgA, IgG and IgM. Between individuals, the results showed better convergence of CDR3 and clonal lineage profiles in IgM than in IgA and IgG, and better robustness of somatic mutation networks in IgM than in IgA and IgG. It also showed that the CDR3 clonotypes and clonal lineages shared better in the spleen samples than in the blood samples. The animal batch differences were detected in CDR3 evenness, mutated clonotype proportions, and maximal network degrees. A cut-off of 95% identity in the CDR3 nucleotide sequences was suitable for clonal lineage establishment. CONCLUSIONS: Our findings reveal a natural landscape of BCR repertoire similarities between baseline mice and provide a solid reference for designing studies of mouse BCR repertoires.

Minimum Distance Between Two Epitopes in Sandwich Immunoassays for Small Molecules.

The pursuit of the limit between dimensionalities is a scientific goal with high applicability. Sandwich immunoassay, usually based on two antibodies binding two epitopes, is one of the most popular mainstay tools in both academic and industrial fields. Herein, we determined and evaluated the minimum distance of two epitopes in sandwich immunoassays for small molecules. Briefly, nine model analytes comprising two hapten epitopes, that is, melamine (MEL) and p-nitroaniline (NIA), were designed by increasing the linear chain linkers brick by brick. Two groups of monoclonal antibodies (mAbs) were produced with different recognition properties toward MEL and NIA using 12 new haptens with different spacer arms. The results indicated that two epitopes of the analyte with a distance of only 2.4 Å could be simultaneously bound by two mAbs, which is the known limit of epitope distance in sandwich immunoassays thus far. We further found that an epitope distance of below 8.8 Å for the analyte generally induces noticeable steric hindrance of antibodies, preventing a sandwich immunoassay with high probability. These observations were investigated and evaluated by molecular docking, molecular dynamics, and surface plasmon resonance and using model and real analytes. Altogether, we determined the minimum distance of two epitopes and explored the molecular mechanism of the antibody-analyte-antibody ternary complex in sandwich immunoassays, providing a theoretical basis for hapten design, antibody discovery and development, and sandwich immunoassay establishment for small molecules.

Self-Assembling Antibody Network Simplified Competitive Multiplex Lateral Flow Immunoassay for Point-of-Care Tests.

Multiplex lateral flow immunoassay (mLFIA) has attracted great attention due to the increasing need for rapid detection of multiple analytes. However, it has a number of disadvantages with regard to accuracy and interference because of difficulties in simplifying the process of preparing nanomaterial-based probes. In this work, inspired by protein self-assembly, for the first time, a facile natural antibody network (NAN)-based mLFIA for multiple chloramphenicol (CAP) and streptomycin (STR) determination was designed. The NAN structure was constructed by introducing a second antibody (Ab2) as a scaffold to noncovalently combine with various monoclonal antibodies (mAbs), thus permitting each mAb to act as an independent functional unit to maintain bioactivity. Furthermore, the NAN was colored by simple one-step staining using coomassie brilliant blue R-250 (CBBR) to form a chromogenic probe, eliminating the need for complex nanomaterials to improve reproducibility and precision. Under optimal conditions, a satisfactory detection performance (the visual limit of detection (v-LOD) of 3 ng mL-1 for CAP and 20 ng mL-1 for STR) was obtained for whole milk analysis, which met the basic requirement of detection and had good specificity, reproducibility (relative standard deviation (RSD) < 15%), and robustness. In addition, the precision of the detection results was improved usefully since the test procedure was simplified. Overall, the developed system enables fast, simple, and reliable point-of-care assays of multiple analytes.

Enzyme-Loaded Hemin/G-Quadruplex-Modified ZIF-90 Metal-Organic Framework Nanoparticles: Bioreactor Nanozymes for the Cascaded Oxidation of N-hydroxy-l-arginine and Sensing Applications.

Biocatalytic cascades are challenging to operate in homogeneous solution, where diffusional mass transport hinders efficient communication between the reactive components. There is great interest in developing devices to perform such transformations in confined environments, which increase the efficiency of the cascaded process by generating high local concentrations of the reactive species. Herein, a bioreactor-nanozyme assembly is introduced for the cascaded aerobic oxidation of N-hydroxy-l-arginine (NOHA) to citrulline in the presence of glucose. The reaction mimics a key step in the nitric oxide synthase oxidation of l-arginine in nature. The system consists of glucose oxidase (GOx)-loaded hemin/G-quadruplex (hemin/G4)-modified ZIF-90 metal-organic framework nanoparticles. The aerobic oxidation of glucose by GOx yields H2 O2 that fuels the hemin/G4-catalyzed oxidation of NOHA into citrulline. The process driven by the bioreactor-nanozyme system is ≈sixfold enhanced compared to the homogeneous mixture of the biocatalysts, due to its operation in the confined environment of the nanoparticles. Extension to a three-step cascade is then demonstrated using a bioreactor composed of ß-galactosidase/GOx-loaded hemin/G4-modified ZIF-90 nanoparticles activating the cascaded oxidation of NOHA to citrulline, in the presence of lactose. Moreover, the bioreactor-nanozyme hybrid is applied as a functional optical sensor of glucose, using fluorescence or chemiluminescence as readout signals.

A rare monoclonal antibody discovery based on indirect competitive screening of a single hapten-specific rabbit antibody secreting cell.

A rare antibody that is able to tolerate physio-chemical factors is preferred and highly demanded in diagnosis and therapy. Rabbit monoclonal antibodies (RmAbs) are distinguished owing to their high affinity and stability. However, the efficiency and availability of traditional methods for RmAb discovery are limited, particularly for small molecules. Here, we present an indirect competitive screening method in nanowells, named CSMN, for single rabbit antibody-secreting cells (ASCs) selection with 20.6 h and propose an efficient platform for RmAb production against small molecules within 5.8 days for the first time. Chloramphenicol (CAP) as an antibacterial agent poses a great threat to public health. We applied CSMN to select CAP-specific ASCs and produced one high-affinity RmAb, surprisingly showed extremely halophilic properties with an IC50 of 0.08 ng mL-1 in the saturated salt solution, which has not yet been seen for other antibodies. The molecular dynamic simulation showed that the negatively charged surface improved the stability of the RmAb structure with additional disulfide bonds compared with mouse antibodies. Moreover, the reduced solvent accessible surface area of the binding pocket increased the interactions of RmAb with CAP in a saturated salt solution. Furthermore, RmAb was used to develop an immunoassay for the detection of CAP in real biological samples with simple pretreatment, shorter assay time, and higher sensitivity. The results demonstrated that the practical and efficient CSMN is suitable for rare RmAb discovery against small molecules.

Comparative analysis of HBV basic core promoter/pre-core gene mutations and viral quasispecies diversity in HIV/HBV co-infected and HBV mono-infected patients.

Human immunodeficiency virus (HIV)/hepatitis B virus (HBV) co-infection accelerates the progression of HBV-related liver diseases. HBV basic core promoter (BCP)/pre-core (preC) gene mutations may be one of the most important risk factors. In this study, a total of 230 patients were recruited, and 199 patients whose HBV BCP/preC gene were successfully amplified and sequenced, including 99 HIV/HBV co-infected and 100 HBV mono-infected patients. Next-generation sequencing was used for detection of BCP/preC mutations which were then compared in patients with different HBV genotypes and different HBeAg statuses, and 1% and 20% cutoff values were defined to evaluate the mutations. HBV quasispecies diversity was also compared in HIV/HBV co-infected and HBV mono-infected patients. Among the patients infected with HBV genotype C and HBeAg-negative status, the frequency of A1762T/G1764A double mutations was significantly lower in HIV/HBV co-infected patients than in HBV mono-infected patients (53.3% vs. 100.0%, P = 0.008) regardless of the 1% or 20% cutoff value level. However, A1762T/G1764A double mutations did not differ in the other groups (P >0.05). Viral quasispecies diversity was lower in HIV/HBV co-infected patients than in HBV mono-infected patients (P Keywords: human immunodeficiency virus, hepatitis B virus; mutations; viral quasispecies; next-generation sequencing.

Engineering of Organic Solvent-Tolerant Antibody to Sulfonamides by CDR Grafting for Analytical Purposes.

The use of organic solvents to extract chemical contaminants for an immunoassay is mostly inevitable. On this occasion, the intolerance of natural antibodies against organic solvent is detrimental to the performance of immunoassays in terms of sensitivity, assay time, accuracy, and precision. Few studies have focused on improving the low tolerance of natural antibodies to organic solvents for analytical purposes. In this study, we engineered the monoclonal antibody (mAb) 4D11 to sulfonamides through CDR grafting by using one proven highly stable humanized antibody (hAb) 4D5 for the first time. The engineered antibody hAb 4D11 showed significantly improved tolerance abilities to acetonitrile (2% to 20%) and methanol (10% to 20%), and retained the highly affinity and class-specificity to sulfonamides. This study provided a general strategy to improve antibody tolerance to organic solvents and was greatly beneficial to the robust development of immunoassays.

Portable Magnetofluidic Device for Point-of-Need Detection of African Swine Fever.

With a nearly 100% mortality rate, African swine fever (ASF) has devastated the pork industry in many countries. Without a vaccine in sight, mitigation rests on rapid diagnosis and immediately depopulating infected or exposed animals. Unfortunately, current tests require centralized laboratories with well-trained personnel, take days to report the results, and thus do not meet the need for such rapid diagnosis. In response, we developed a portable, sample-to-answer device that allows for ASF detection at the point of need in <30 min. The device employs droplet magnetofluidics to automate DNA purification from blood, tissue, or swab samples and utilizes fast thermal cycling to perform real-time quantitative polymerase chain reaction (qPCR), all within an inexpensive disposable cartridge. We evaluated its diagnostic performance at six farms and slaughter facilities. The device exhibits high diagnostic accuracy with a positive percent agreement of 92.2% and a negative percent agreement of 93.6% compared with a lab-based reference qPCR test.

ELISA-Based Method for Variant-Independent Detection of Total Microcystins and Nodularins via a Multi-immunogen Approach.

Required routine monitoring of microcystins (MCs) and nodularins (NODs) in water samples, as posed by U.S. EPA Unregulated Contaminant Monitoring Rule 4, demands cost-effective, reliable, and sensitive detection methods. To target as many MC and NOD variants as possible, we developed an indirect competitive enzyme-linked immunosorbent assay (ELISA) with group-specific monoclonal antibodies for variant-independent detection of total MCs and NODs. In this ELISA method, the mice monoclonal antibodies presenting both high affinities and broad-spectrum recognition capabilities against MCs and NODs were self-produced by designing MC hapten-based multi-immunogens to minimize specificity for the particular variant. Their high affinities and variant-independent binding capabilities against MCs and NODs were validated by both wet lab and in silico methods. The developed ELISA method achieved a limit of detection of below 0.3 µg/L for 13 MC/NOD variants, well with the reported best cross-reactivities of 60-127% relative to MC-LR. As a case study, this ELISA method was used to map the variations of intracellular and extracellular total MCs/NODs in the Luoma Lake drinking water source, China, in July, 2020. Its capability to measure total MCs/NODs with high sensitivity and high throughput in a simple and affordable way would truly be a disruptive technology capable of changing our understanding of bloom/toxin dynamics and having obvious implications for monitoring efforts.

Production of highly sensitive monoclonal antibody and development of lateral flow assays for phallotoxin detection in urine.

Phallotoxins, toxic cyclopeptides found in wild poisonous mushrooms, are predominant causes of fatal food poisoning. For the early and rapid diagnosis mushroom toxin poisoning, a highly sensitive and robust monoclonal antibody (mAb) against phallotoxins was produced for the first time. The half-maximum inhibition concentration (IC50) values of the mAb-based indirect competitive ELISAs for phallacidin (PCD) and phalloidin (PHD) detection were 0.31 ng mL-1 and 0.35 ng mL-1, respectively. In response to the demand for rapid screening of the type of poisoning and accurate determination of the severity of poisoning, colloidal gold nanoparticle (GNP) and time-resolved fluorescent nanosphere (TRFN) based lateral flow assays (LFA) were developed. The GNP-LFA has a visual cut-off value of 3.0 ng mL-1 for phallotoxins in human urine sample. The TRFN-LFA provides a quantitative readout signal with detection limit of 0.1 ng mL-1 in human urine sample. In this study, urine samples without pretreatment were used directly for the LFA strip tests, and both two LFAs were able to accomplish analysis within 10 min. The results demonstrated that LFAs based on the newly produced, highly sensitive, and robust mAb were able to be used for both rapid qualitative screening of the type of poisoning and accurate quantitative determination of the severity of poisoning after accidental ingestion by patients of toxic mushrooms.

An ultrasensitive, homogeneous fluorescence quenching immunoassay integrating separation and detection of aflatoxin M1 based on magnetic graphene composites.

A homogeneous fluorescence quenching immunoassay is described for simultaneous separation and detection of aflatoxin M1 (AFM1) in milk. The novel assay relies on monoclonal antibody (mAb) functionalized Fe3O4 decorated reduced-graphene oxide (rGO-Fe3O4-mAb) as both capture probe and energy acceptor, combined with tetramethylrhodamine cadaverine-labeled aflatoxin B1 (AFB1-TRCA) as the energy donor. In the assay, AFB1-TRCA binds to rGO-Fe3O4-mAb in the absence of AFM1, quenching the fluorescence of TRCA by resonance energy transfer. Significantly, the immunoassay integrates sample preparation and detection into a single step, by using magnetic graphene composites to avoid washing and centrifugation steps, and the assay can be completed within 10 min. Under optimized conditions, the visual and quantitative detection limits of the assay for AFM1 were 50 and 3.8 ng L-1, respectively, which were significantly lower than those obtained by fluorescence polarization immunoassay using the same immunoreagents. Owing to its operation and highly sensitivity, the proposed assay provides a powerful tool for the detection of AFM1.