NH2-MIL-125(Ti)/Reduced Graphene Oxide Enhanced Electrochemical Detection of Fenitrothion in Agricultural Products.

The abuse of organophosphate pesticides causes serious threats to human health, which threatens approximately 3 million people and leads to more than 2000 deaths each year. Therefore, it is necessary to determine the residue of fenitrothion (FT) in environmental and food samples. Herein, we developed a non-enzymatic electrochemical sensor with differential pulse voltammetry signal output to determine FT in model solutions and spiked samples. Delicately, the sensor was designed based on the fabrication of hydrothermally synthesized titanium-based metal-organic frameworks (MOFs) material (NH2-MIL-125(Ti))/reduced graphene oxide (RGO) (NH2-MIL-125(Ti)/RGO) nanocomposites for better target enrichment and electron transfer. The peak response of differential pulse voltammetry for FT under optimized conditions was linear in the range of 0.072-18 µM with the logarithm of concentrations, and the detection limit was 0.0338 µM. The fabricated sensor also demonstrated high stability and reproducibility. Moreover, it exhibited excellent sensing performances for FT in spiked agricultural products. The convenient fabrication method of NH2-MIL-125(Ti)/RGO opens up a new approach for the rational design of non-enzymatic detection methods for pesticides.

An electrochemical immunosensor based on prussian blue@zeolitic imidazolate framework-8 nanocomposites probe for the detection of deoxynivalenol in grain products.

The presence of deoxynivalenol (DON) in grains poses a threat to human health, which is critical for sensitive detection of DON. In this electrochemical immunosensor, zeolitic imidazolate framework-8 (ZIF-8) loaded with Prussian blue (PB) nanoparticles was coated by polydopamine (PDA) as a redox probe. The high porosity of ZIF-8, the unique electrochemical activity of PB and the outstanding electrical conductivity of PDA improved the sensitivity of the immunosensor. Under the optimized conditions, the peak current in differential pulse voltammetry displayed a good linear relationship over DON concentrations in a range of 0.1-5000 pg mL-1 with a detection limit of 0.0186 pg mL-1. In addition, the immunosensor also had good selectivity and stability. Good recoveries of 85.67 to 118.00 % have been achieved for the detection of DON in spiked grain products. This new strategy exhibits great potential for simple and rapid detection of DON in grain and feed products.

Colorimetric ELISA based on urease catalysis curcumin as a ratiometric indicator for the sensitive determination of aflatoxin B1 in grain products.

There is an urgent need to measure aflatoxin B1 (AFB1) in food to prevent contaminated food consumption. In this work, a novel colorimetric enzyme-linked immunosorbent assay (ELISA) was developed for the detection of AFB1 using curcumin as a colorimetric indicator. An indirect competitive enzyme-label immunoassay was developed using urease and rabbit anti-mouse immunoglobulin G labeled with gold nanoparticles as the signal-transduction tag. Urease catalyzed the hydrolysis of urea to produce ammonia, which increased the pH of the solution. The phenolic hydroxyl group of curcumin ionized into phenolic oxygen anions under alkaline conditions, which strengthened the synergistic effect of electron supply and absorption in curcumin. As a result, the color of curcumin changed from yellow to reddish-brown, producing a visible color change. Under optimal conditions, AFB1 could be qualitatively determined with the naked eye, and quantitatively assessed by measuring the ratio of absorbance at wavelengths of 550 and 428 nm. The change in the ratio of absorbance Δ550/Δ428 decreased linearly in a range of 0.01-5 ng mL-1, and the limit of detection was 67 pg mL-1. Therefore, the selectivity and reliability of this proposed method were well validated. This method was also successfully used for the quantitation of AFB1 in spiked rice flour and wheat flour samples. This approach may broaden the application field of colorimetric ELISA for aflatoxin, providing a promising platform for the rapid screening of aflatoxin in food.

Well-aligned cellulose nanofiber-reinforced polyvinyl alcohol composite film: Mechanical and optical properties.

Uniaxially aligned cellulose nanofibers (CNFs), which are fabricated by electrospinning of cellulose acetate derived from bamboo cellulose (B-CA) followed by deacetylation, were used as reinforcements to make optically transparent composite films. We examined the effects of B-CA concentration and electrospinning parameters (e.g. spinning distance, and collection speed) on fiber morphology and orientation, which act on mechanical-to-optical properties of the CNFs-reinforced composites. Consequently, the resultant composite film exhibits high visible-light transmittance even with high fiber content, as well as improved mechanical properties. The understanding obtained from this study may facilitate the development of novel nanofibrous materials for various optical uses.

Novel development and characterisation of dietary fibre from yellow soybean hulls.

Dietary fibres (DFs) from yellow soybean hulls (Glycine max) were developed by mimicking pH in the human digestive system. Using both traditional AOAC991.43 and newly developed AOAC2011.25 methods, DFs were quantified, and their physicochemical properties were characterised by determining colour, particle size, water absorption and solubility capacity. Viscoelastic properties of the fibres with whole wheat flours were evaluated using dynamic rheological measurements. The results showed that colour of lightness (L value) was significantly improved (p<0.05). The levels of soluble, insoluble, and total dietary fibres determined by 2011.25 were 2.6±0.7%, 85.9±0.4%, and 88.5±0.8% (as is), respectively. There was an approximately 50% increase of total dietary fibre in the treatment, which reached 98.6±0.8% (dry basis). The results clearly indicated that acid-base hydrolysis and autoclaving processes in yellow soybean hulls could significantly boost total dietary fibre content, which has potential application in snacks.