Determination of Aflatoxins B1 and B2 in Powdered Milk Using Modified Liquid Chromatography Method

Abstract: Background & Aims: In this study, using a liquid-liquid microextraction method for pre-concentration trace amounts of aflatoxins, the amount of Aflatoxins B1 and B2 in powdered milk was determined. Determination of aflatoxins was done by using high-performance liquid chromatography coupled with fluorescent detector. Method: Samples were extracted by immunoaffinity column (IAC) clean-up, and their eluents were used as dispersants of the subsequent DLLME, for further enrichment of aflatoxins. Various parameters (the type of elution solvent, the type and volume of extraction solvent and disperser solvent, extraction time and centrifugation time) that affect the efficiency of two steps were optimized. Results: Under the optimum conditions, the calibrations for B1 and B2 were found to be linear in the range of 0.03¬¬¬-5.0 and 0.006-1.0 ng ml-1 with 0.98 and 0.99 coefficient of estimation (R2), respectively. Conclusion: The results showed that dispersive liquid–liquid microextraction combined with HPLC is a selective, simple, sensitive and effective analytical method for the pre-concentration and determination of ultra trace amounts of aflatoxins. The method is suggested for pre-concentration and determination of B1 and B2 aflatoxins in milk powder. Keywords: Aflatoxins, High pressure liquid chromatography (HPLC), Immunoaffinity cleanup, Powdered Milk, DLLM

Label-free impedimetric biosensor for Salmonella Typhimurium detection based on poly [pyrrole-co-3-carboxyl-pyrrole] copolymer supported aptamer

The Gram-negative bacterium, Salmonella Typhimurium (S. Typhimurium) is a food borne pathogen responsible for numerous hospitalisations and deaths all over the world. Conventional detection methods for pathogens are time consuming and labour-intensive. Hence, there is considerable interest in faster and simpler detection methods. Polypyrrole-based polymers, due to their intrinsic chemical and electrical properties, have been demonstrated to be valuable candidates for the fabrication of chemo/biosensors and functional surfaces. Similarly aptamers have been shown to be good alternatives to antibodies in the development of affinity biosensors. In this study, we report on the combination of Poly [pyrrole-co-3-carboxyl-pyrrole] copolymer and aptamer for the development of a label-less electrochemical biosensor suitable for the detection of S. Typhimurium. Impedimetric measurements were facilitated by the effect of the aptamer/target interaction on the intrinsic conjugation of the poly [pyrrole-co-3-carboxyl-pyrrole] copolymer and subsequently on its electrical properties. The aptasensor detected S. Typhimurium in the concentration range 10(2)-10(8) CFU mL(-1) with high selectivity over other model pathogens and with a limit of quantification (LOQ) of 100 CFU mL(-1) and a limit of detection (LOD) of 3 CFU mL(-1). The suitability of the aptasensor for real sample detection was demonstrated via recovery studies performed in spiked apple juice samples. We envisage this to be a viable approach for the inexpensive and rapid detection of pathogens in food, and possibly in other environmental samples. (C) 2016 Elsevier B.V. All rights reserved.Funding Agencies|Ministry of Science Research and Technology of Iran; Research Council of Ferdowsi University of Mashhad [3/29828]; Linkoping University, Vetenskapsradet [D0675001]; Swedish Research Council [VR-2014-3079]</p

Micropatterned Coumarin Polyester Thin Films Direct Neurite Orientation

Guidance and migration of cells in the nervous system is imperative for proper development, maturation, and regeneration. In the peripheral nervous system (PNS), it is challenging for axons to bridge critical-sized injury defects to achieve repair and the central nervous system (CNS) has a very limited ability to regenerate after injury because of its innate injury response. The photoreactivity of the coumarin polyester used in this study enables efficient micropatterning using a custom digital micromirror device (DMD) and has been previously shown to be biodegradable, making these thin films ideal for cell guidance substrates with potential for future in vivo applications. With DMD, we fabricated coumarin polyester thin films into 10 × 20 μm and 15 × 50 μm micropatterns with depths ranging from 15 to 20 nm to enhance nervous system cell alignment. Adult primary neurons, oligodendrocytes, and astrocytes were isolated from rat brain tissue and seeded onto the polymer surfaces. After 24 h, cell type and neurite alignment were analyzed using phase contrast and fluorescence imaging. There was a significant difference (<i>p</i> < 0.0001) in cell process distribution for both emergence angle (from the body of the cell) and orientation angle (at the tip of the growth cone) confirming alignment on patterned surfaces compared to control substrates (unpatterned polymer and glass surfaces). The expected frequency distribution for parallel alignment (≤15°) is 14% and the two micropatterned groups ranged from 42 to 49% alignment for emergence and orientation angle measurements, where the control groups range from 12 to 22% for parallel alignment. Despite depths being 15 to 20 nm, cell processes could sense these topographical changes and preferred to align to certain features of the micropatterns like the plateau/channel interface. As a result this initial study in utilizing these new DMD micropatterned coumarin polyester thin films has proven beneficial as an axon guidance platform for future nervous system regenerative strategies