Rapid preparation of molecularly imprinted polymers by custom-made microwave heating for analysis of atrazine in water.

The rapid preparation of an atrazine-imprinted polymer in a cost-effective custom-made microwave reactor was demonstrated. The polymerization reaction was accelerated by microwave heating, and the preparation time was greatly shortened (to 1 h). The resulting polymer was successfully applied as solid-phase extraction adsorbent for the selective extraction and preconcentration of atrazine in environmental water samples. The binding capacity of the polymer was 1.11 mg/g polymer. The polymer provided selectivity with higher recovery of atrazine than of other interfering related contaminants. The proposed method had good limits of detection and quantitation at 0.20 and 0.60 ng/mL, respectively. The recoveries were from 83 to 89% at two spiking levels, with relative standard deviations less than 5%. This method was successfully applied to determine the atrazine levels in environmental water samples.

Alpha-glucosidase inhibitory activity of ethanol extract, fractions and purified compounds from the wood of Albizia myriophylla.

Albizia myriophylla Benth. is a medicinal herb which is used as a traditional remedy for various ailments including diabetes in Thailand. In our continued investigation of the biological activity of A. myriophylla, the ethanol extract, fractions and the isolated compounds from the wood of this plant were evaluated for in vitro α-glucosidase inhibition using spectrophotometric method. The plant ethanol extract and its different fractions possessed α-glucosidase inhibitory activity in a concentration-dependent manner. Dichloromethane fraction of the wood ethanol extract exhibited the highest percent inhibition against α-glucosidase (69.30%) among all fractions. Subsequent α-glucosidase inhibition assay proved that indenoic acid (1), 8-methoxy-7, 3',4'-trihydroxyflavone (2) and 3,4,7,3'-tetrahydroxyflavan (3) were partially rational for antidiabetic effect of this plant species. Among these compounds, 3 (IC50 98.59 µg/mL) exhibited potent inhibition of α-glucosidase, compared with a positive control acarbose (IC50 125 µg/mL). The inhibitory effect towards α-glucosidase of compounds 1-3 was reported herein for the first time.

Development of a rubber elongation factor, surface-imprinted polymer-quartz crystal microbalance sensor, for quantitative determination of Hev b1 rubber latex allergens present in natural rubber latex products.

Molecularly imprinted polymers (MIPs) for screening to detect rubber latex allergens (Hev b1) in natural rubber based products were designed as artificial recognition polymeric materials coated onto a quartz crystal microbalance (QCM). The polymers were prepared using a stamp imprinting procedure after mixing optimum amounts of methacrylic acid-vinylpyrrolidone-dihydroxyethylene bisacrylamide and Hev b1 latex allergen proteins, obtained from rubber gloves. QCM measurements showed that the resulting polymer layers after removal of the proteins used in their preparation could incorporate structures and features down to nanometer scale of protein templates into the imprinted polymer much better than a non-specific control polymer under controlled sensor conditions and an optimized polymerization process. This selective polymer but not the non-selective polymer clearly distinguished between the latex allergen Hev b1 and proteins such as lysozyme, ovalbumin and bovine serum albumin, with a selectivity factor of from 2 to 4, and the response of the rubber elongation factors by an astonishing factor of 12. The imprinted cavities recognized specific binding sites and could distinguish among related hevein latex allergenic proteins isolated from fresh natural rubber latex; Hev b1, Hev b2, and Hev b3 with a selectivity factor of from 4 to 6. The different QCM measurements obtained presumably reflected slightly different conformations and affinities to the MIP binding sites. The sensor layers selectively adsorbed Hev b1 within minutes in amounts ranging from 10 to 1500 µg L⁻¹ and with a detection limit of 1 µg L⁻¹. This work has demonstrated that this new sensor provides a fast and reliable response to natural rubber latex protein, even after being extracted from the matrix of rubber gloves.

Interdigitated capacitive biosensor based on molecularly imprinted polymer for rapid detection of Hev b1 latex allergen.

Allergen protein detection was performed by a surface imprinted layer combined with an interdigitated capacitance (IDC) transducer that allowed label-free measurements. The immobilized imprinted polymers are the probes that bind to rubber allergen proteins extracted from products such as rubber gloves. Copolymers made from methacrylic acid-vinylpyrrolidone-dihydroxyethylene-bisacrylamide (MAA-NVP-DHEBA) are soluble in aqueous solution and eliminate the denaturation of protein. When deposited as a coating onto an IDC microelectrode transduction system, such materials lead to sensors that produce capacitance responses that are clearly dependent on the concentration of the latex protein (10-900 ng ml(-1)) in pH 7.4 buffer. The biosensor can detect Hev b1 within minutes and with a detection limit of 10 ng ml(-1). Different but related hevein allergenic proteins isolated from natural rubber latex from the rubber tree (Hev b1, Hev b2, and Hev b3) were distinguished by the imprinted material, depending on the dimension and conformation of these proteins with a selectivity factor of 4. They recognized Hevea latex proteins better than non-Hev b proteins, such as lysozyme, ovalbumin, and bovine serum albumin, by a factor of 2. Moreover, the sensor exhibited good operational stability of up to 180 days when used continuously at room temperature.