Microfluidic chemistry assisted synthesis of cobalt quantum dot embedded nitrogen doped carbon with oxidase-like properties toward ascorbic acid detection.

Ascorbic acid (AA) is a powerful antioxidant in food safety and disease treatment. It is of great significance to develop a low-cost, high-stability, and easy-to-operate colorimetric method for quantitative detection of AA in food or human body. Although various nanozymes have been developed for the colorimetric detection of AA, the size regulation of the catalytic center of nanozymes remains a challenge. In this work, we propose a combined strategy of flow chemistry synthesis and pyrolysis to realize the controllable adjustment of the catalytic center size of nanozymes. Zinc-cobalt zeolitic imidazole frameworks (ZnCo-ZIFs) with different sizes are synthesized by flow chemistry. Nitrogen-doped carbon materials with different Co catalytic centers (80 nm-10 nm) are then obtained by pyrolysis of ZnCo-ZIFs precursors. Among them, cobalt quantum dot embedded nitrogen-doped carbon (Co QDs/N-C) exhibits excellent oxidase activity, with Vmax and Km of 4.19 × 10-7 M s-1 and 0.12 mM. Therefore, a simple, low-cost, and stable colorimetric method for the detection of AA is established with a good linear relationship (3-500 µM) and low detection limit (0.40 µM). This work has certain guiding significance for the size regulation of catalytic center of nanozyme, and the detection method has broad application prospects in biochemical sensing field.

Smartphone-coupled three-layered paper-based microfluidic chips demonstrating stereoscopic capillary-driven fluid transport towards colorimetric detection of pesticides.

The existence of pesticide residues in the hydrosphere, biosphere, and anthroposphere can cause acute or chronic diseases and deteriorate the environment. Therefore, efficient detection of pesticide residues is of great significance to prevent food poisoning, control food pollution, and protect human lives by recognizing their distribution and concentration. Herein, a novel smartphone-coupled three-layered paper-based microfluidic chip is proposed as a facile platform to detect the pesticides. The stereoscopic capillary-driven fluid transport is enabled by the three-layered microfluidic chip configuration. The detection mechanism is based on the enzyme inhibition reaction and the chromatic reaction. The detection results are obtained by a smartphone and figured out by colorimetric quantitative analysis. Taking advantages of the above merits, we demonstrate the utilization of this smartphone-coupled three-layered paper-based microfluidic chip for the effective analysis of typical pesticides (profenofo and methomyl). The linear ranges of profenofo and methomyl are 0.27-2.1 µmol L-1 and 0.14-1.85 µmol L-1, respectively. The corresponding limits of detection in the chips are 55 nM and 34 nM, respectively. The paper-based chips are also highly cost-effective with a total cost of 0.082 ¥ per piece. It can be anticipated that this technique will open new avenues for the mass fabrication of paper-based microfluidic chips and provide state-of-the-art methods in the field of analytical chemistry.

Identification of pyruvate kinase 2 as a possible crab allergen and analysis of allergenic proteins in crabs consumed in Taiwan.

In Taiwan, crab is one of the main causes for food allergy. Several proteins are recognized as crustacean allergens, and tropomyosin is known to be the major one. However, sensitization patterns of Taiwanese patients to crustacean allergens remain unclear. Therefore, we analyzed the specific-IgE binding ability of crucifix crab (Charybdis feriatus) allergens by western blot using patients' sera. In particular, we found a 56 kDa protein in crucifix crab reacted with specific-IgEs in patients' sera, and we further identified the protein as a novel crab allergen pyruvate kinase 2. Additionally, little is known about tropomyosin contents in crabs consumed in Taiwan. Thus, we also quantified the levels of tropomyosin by using enzyme-linked immunosorbent assay (ELISA) among raw and cooked crab species. Our results showed tropomyosin levels varied depending on crab species. In summary, these findings improve the understanding of crustacean allergens and contribute to the clinical diagnosis of crustacean allergies.

Identification of pyruvate kinase as a novel allergen in whiteleg shrimp (Litopenaeus vannamei) by specific-IgE present in patients with shrimp allergy.

Food allergy is one of the most important health issues worldwide. In Taiwan, current literature suggests shrimps and crabs are the most common causes of food allergy, and are frequently associated with acute allergic reactions such as urticaria, atopic dermatitis, and asthma. However, knowledge regarding the shrimp allergens remains limited. Thus, there is an urgent need to establish comprehensive information for elucidating underlying triggers for food allergy. In this study, whiteleg shrimp (Litopenaeus vannamei) was used to evaluate the IgE-binding properties of various shrimp proteins to 7 allergic patients' sera by western blot. A 63 kDa protein was found in raw and cooked shrimp bound to specific-IgEs in 7 and 4 patients' sera, respectively. This protein was further identified as pyruvate kinase based on the proteomic mass spectrometry. This study identifies an important shrimp allergen unique to Taiwan and further testing and prevention measures might be implemented in the allergen analysis.