Color-selective labyrinth-like quantum dot nanobeads enable point-of-care dual assay of Mycotoxins

Establishment of an immunoassay for detection of nonylphenols in surfactant oilfield chemicals based on computer-aided design

Nonylphenols (NPs) are confirmed endocrine disruptors that are banned in many countries due to correlations with human cancers. NPs pollution in surfactant oilfield chemicals (OFCs) has become an important environmental safety issue. It is significant to establish a simple, accurate and low-cost method for detection of NPs in OFCs. In this research, computer-aided molecular design technology was utilized to design NPs haptens. High affinity monoclonal antibodies against NPs were obtained using a matrix effect-enhanced screening method, with an IC50 value of 183.01 ng/mL. A colloidal gold immunochromatography assay (ICA) for detection of NPs enabled rapid on-site detection of large volumes of OFCs. Under optimal conditions, the limit of detection was 0.72-1.82 mg/kg, with a detection range of 4.49-191.28 mg/kg. The recovery was 84 %-104 %, with coefficients of variation < 13 %. As confirmed by high-performance liquid chromatography of natural positive OFCs samples, the proposed colloidal gold ICA demonstrated accuracy and reliability, with potential for fast and economical on field test.

A sensitive intelligent point-of-care test method for tert-butylhydroquinone in edible oil via a test strip with a smartphone

Tert-butylhydroquinone (TBHQ) is easily overused or illegally added to edible oil and attracts a growing concern because of its cytotoxic, liver-damaging, and carcinogenic effects. Thus, a sensitive and intelligent point-of-care testing (iPOCT) method is developed to fulfill the on-site monitoring. This iPOCT method depended on a fluorescent immunochromatographic assay within 15 min. Under optimization, the limit of quantification (LOQ) was calculated as 0.03 μg mL-1. The iPOCT method provided a low limit of detection (LOD) of 0.02 μg mL-1, a wide linear range of 0.03-100 μg mL-1, and great selectivity. Recoveries by the spiking experiments ranged from 97.4% to 103.5% with relative standard deviations (RSDs) of 2.4%-4.9% in soybean, peanut, rapeseed, and corn oil samples. The results showed that the iPOCT method is highly consistent with the high-performance liquid chromatography (HPLC) method.

Solvent directed morphogenesis of a peptidic-benzimidazolium dipodal receptor: ratiometric detection and catalytic degradation of ochratoxin A

Ochratoxin A (OTA) is the most abundant and harmful toxin found in agriculture and processed food. The environment and human health are both harmed by this mycotoxin. As a result, in various scenarios, selective detection and biodegradation of ochratoxin A are essential. The current study reveals the morphogenesis of a peptidic-benzimidazolium dipodal receptor (SS4) and its application as a catalytic and sensing unit for the detection and degradation of OTA in an aqueous medium. Initially, a facile and scalable method was executed to synthesize SS4, and solvent-directed morphogenesis were examined under SEM analysis. Consequently, molecular recognition properties of self-assembled architectures were explored using UV-visible absorption, fluorescence spectroscopy, and atomic force microscopy (AFM). The designed probe showed a ratiometric response for OTA and served as a catalytic unit for the degradation of OTA at a short interval of 25 min. The biodegradation pathway for OTA was accomplished using LC-MS analysis. Furthermore, the reliability of the developed method was checked by determining the spiked concentrations of the OTA in cereals and wine samples. The results obtained are in good agreement with the % recovery and RSD values. The present work provides a robust, selective, and sensitive method of detection and degradation for OTA.

QD-based fluorescent nanosensors: Production methods, optoelectronic properties, and recent food applications

Food quality and safety are crucial public health concerns with global significance. In recent years, a series of fluorescence detection technologies have been widely used in the detection/monitoring of food quality and safety. Due to the advantages of wide detection range, high sensitivity, convenient and fast detection, and strong specificity, quantum dot (QD)-based fluorescent nanosensors have emerged as preferred candidates for food quality and safety analysis. In this comprehensive review, several common types of QD production methods are introduced, including colloidal synthesis, self-assembly, plasma synthesis, viral assembly, electrochemical assembly, and heavy-metal-free synthesis. The optoelectronic properties of QDs are described in detail at the electronic level, and the effect of food matrices on QDs was summarized. Recent advancements in the field of QD-based fluorescent nanosensors for trace level detection and monitoring of volatile components, heavy metal ions, food additives, pesticide residues, veterinary-drug residues, other chemical components, mycotoxins, foodborne pathogens, humidity, and temperature are also thoroughly summarized. Moreover, we discuss the limitations of the QD-based fluorescent nanosensors and present the challenges and future prospects for developing QD-based fluorescent nanosensors. As shown by numerous publications in the field, QD sensors have the advantages of strong anti-interference ability, convenient and quick operation, good linear response, and wide detection range. However, the reported assays are laboratory-focused and have not been industrialized and commercialized. Promising research needs to examine the potential applications of bionanotechnology in QD-based fluorescent nanosensors, and focus on the development of smart packaging films, labeled test strips, and portable kits-based sensors.

Rapid and sensitive point-of-care PTS-CRISPR assay for food safety monitoring of aflatoxin B1

Food safety is crucial for human health, but its effective on-site monitoring remains a challenge. Pregnancy test strip (PTS) is the successful point-of-care testing (POCT) product of the highest market share in the world, with the cost as low as $0.10 per test. Herein, combined with the CRISPR (clustered regularly interspaced short palindromic repeats) system, PTS-CRISPR was for the first time introduced into food safety monitoring, for rapid and sensitive POCT of aflatoxin B1. The low-cost, easy-to-operate PTS-CRISPR is expected to bring security to the grassroots food market.

Dextran-Functionalized Super-nanoparticle Assemblies of Quantum Dots for Enhanced Cellular Immunolabeling and Imaging

Colloidal semiconductor quantum dots (QDs) are a popular material for applications in bioanalysis and imaging. Although individual QDs are bright, some applications benefit from the use of even brighter materials. One approach to achieve higher brightness is to form super-nanoparticle (super-NP) assemblies of many QDs. Here, we present the preparation, characterization, and utility of dextran-functionalized super-NP assemblies of QDs. Amphiphilic dextran was synthesized and used to encapsulate many hydrophobic QDs via a simple emulsion-based method. The resulting super-NP assemblies or "super-QDs" had hydrodynamic diameters of ca. 90-160 nm, were characterized at the ensemble and single-particle levels, had orders-of-magnitude superior brightness compared to individual QDs, and were non-blinking. Additionally, binary mixtures of red, green, and blue (RGB) colors of QDs were used to prepare super-QDs, including colors difficult to obtain from individual QDs (e.g., magenta). Tetrameric antibody complexes (TACs) enabled simple antibody conjugation for selective cellular immunolabeling and imaging with both an epifluorescence microscope and a smartphone-based platform. The technical limitations of the latter platform were overcome by the increased per-particle brightness of the super-QDs, and the super-QDs outperformed individual QDs in both cases. Overall, the super-QDs are a very promising material for bioanalysis and imaging applications where brightness is paramount.

Microelectromechanical Microsystems-Supported Photothermal Immunoassay for Point-of-Care Testing of Aflatoxin B1 in Foodstuff

Accurate identification of acutely toxic and low-fatality mycotoxins on a large scale in a quick and cheap manner is critical for reducing population mortality. Herein, a portable photothermal immunosensing platform supported by a microelectromechanical microsystem (MEMS) without enzyme involvement was reported for point-of-care testing of mycotoxins (in the case of aflatoxin B₁, AFB₁) in food based on the precise satellite structure of Au nanoparticles. The synthesized Au nanoparticles with a well-defined, graded satellite structure exhibited a significantly enhanced photothermal response and were coupled by AFB₁ antibodies to form signal conversion probes by physisorption for further target-promoted competitive responses in microplates. In addition, a coin-sized miniature NIR camera device was constructed for temperature acquisition during target testing based on advanced MEMS fabrication technology to address the limitation of expensive signal acquisition components of current photothermal sensors. The proposed MEMS readout-based microphotothermal test method provides excellent AFB₁ response in the range of 0.5-500 ng g^-1 with detection limits as low as 0.27 ng g^-1. In addition, the main reasons for the efficient photothermal transduction efficiency of Au with different graded structures were analyzed by finite element simulations, providing theoretical guidance for the development of new Au-based photothermal agents. In conclusion, the proposed portable micro-photothermal test system offers great potential for point-of-care diagnostics for residents, which will continue to facilitate immediate food safety identification in resource-limited regions.