Mechanism and enhancement of the surface stress caused by a small-molecule antigen and antibody binding.

Generation of microcantilever bending from biochemical interactions can have wide applications, ranging from high-throughput molecular detection to bioactuation. However, the origin of the biochemically induced surface stress causing the bending is a subject of much scientific debate and interest. Unlike a compressive surface stress caused by biomacromolecule antigen and antibody binding, here we show that a small molecule antigen and antibody binding on the surface gives rise to a tensile stress. We propose that the tensile stress is induced by antibody conformational change which manifests itself as Fab arm motion that exposes the C1q binding site of the antibody due to antigen binding. A microcantilever immunosensor was developed for the detection of Chlorimuron-ethyl (CE). We found that antibodies with oriented immobilization induce a greater resultant surface stress than those with random immobilization. The length of linker between the surface and the antibody plays an important role on the stress transmission. The shorter the length, the greater the surface stress. These mechanism and principles will underpin the design of devices and coatings to significantly lower the small molecule detection limit and may also have an impact on our understanding of antigen and antibody binding.

Palladium@gold bimetallic nanostructures as peroxidase mimic for development of sensitive fluoroimmunoassay.

In this paper, gold nanoparticles coated with palladium dots (Pd@Au) bimetallic nanostructures have been reported to have a peroxidase like activity which is not found in their monometallic counterparts. Based on this finding, we have developed an immunoassay in which antibody-modified Pd@Au nanostructure catalyzes the dimerization of a fluorogenic substrate for peroxidase, 3-(4-dihydroxy phenyl) propionic acid (HPPA), to generate high fluorescence signal. Specific antibodies against bensulfuron-methyl were generated by using a well characterized bensulfuron-protein conjugate as an immunogen, and the assay was performed in a competitive immunoassay format where Pd@Au nanostructure was bound to secondary antibody to show the peroxidase like activity. The developed immunoassay exhibited an excellent sensitivity showing a dynamic response range from 0.001 to 100 ng mL(-1) for herbicide bensulfuron-methyl with a detection limit of 0.01 ng mL(-1) (n=3). The newly synthesized bimetallic nanostructure shows the advantages of low cost, easy synthesis and tunable catalytic activity, making it a promising substitution of enzyme peroxidase in different applications.

Development of a class-specific ELISA for sulfonylurea herbicides (sulfuron screen).

The development of a direct competitive ELISA for the detection of a broad range of sulfonylurea herbicides (SUs) is described. Polyclonal antibodies were generated in rabbits using three different immunizing haptens. Antiserum with the broadest specificity was obtained with a mesosulfuronbenzylamine derivative which was coupled via a succinic acid spacer to keyhole limpet hemocyanine. A heterologous enzyme tracer which did not contain the succinic acid bridge was prepared using activated horseradish peroxidase. The direct competitive ELISA was optimized and applied for spiked tap and surface water samples. From 30 SUs, 8 compounds showed a molar cross-reactivity (CR) higher than 100% (this value was set for the hapten) and 11 compounds CRs between 10% and 100%. The ELISA can detect 16 SUs at a concentration of 0.1 microg/L or lower. Different surface and tap water samples were spiked with chlorimuron ethyl, metsulfuron methyl, or primisulfuron methyl at concentrations of 100, 200, or 500 ng/L and subsequently analyzed by both ELISA and HPLC-UV. Correlation analysis revealed good agreement between both methods (r2 = 0.983/0.948/0.982; n = 21 for each analyte). Using ELISA, no sample pretreatment other than filtration was necessary.

Development of an immunoassay for the residues of the herbicide bensulfuron-methyl.

To develop a competitive indirect enzyme-linked immunosorbent assay based on polyclonal antibodies for the detection of the sulfonylurea herbicide bensulfuron-methyl, seven structurally related haptens were synthesized. Four of them mimicking the target analyte were conjugated to keyhole limpet hemocyanin by the N-hydroxysuccinimide activated ester method to use as immunogens, and all of them were conjugated to bovine serum albumin to use as plate-coating antigens. Polyclonal antibodies raised in rabbits and the coating antigens were screened and selected for the assay in simple homologous and heterologous ELISA formats. Three sensitive heterologous ELISAs were selected and optimized, showing the average IC(50) values of bensulfuron-methyl as low as 0.17, 0.09, and 0.09 ng/mL, the detection ranges of 0.04-0.60, 0.01-0.60, and 0.04-0.25 ng/mL, and the lowest detection limits of 0.03, 0.002, and 0.03 ng/mL, respectively. The cross-reactivities of other sulfonylurea herbicides and metabolites of bensulfuron-methyl to the antibodies were less than 15% in the two assays. Recoveries from the analyte-fortified water samples in assay I were in the range of 81-125% by simple dilution. The correlation between the ELISA and HPLC was 0.999 (n = 15) with a slope of 1.37 in the analysis of groundwater samples fortified with bensulfuron-methyl. The results obtained strongly indicate that the ELISA can be a highly sensitive and convenient tool for detecting bensulfuron-methyl residues in agricultural and environmental samples.

The roles of receptor abnormalities in the pathogenesis and chronic complications of type 2 diabetes mellitus.

Type 2 diabetes mellitus is a polygenic disorder with complicated biochemical alterations. Numerous investigators have examined the implication of receptor abnormalities in the pathogenesis of the disorder. The authors review the potential roles of some important receptors, such as the insulin receptor, beta 3-adrenergic receptor, leptin receptor and peroxisome proliferator-activated receptor gamma, in the pathogenesis of human type 2 diabetes. They emphasize the significance of effective glycemic control by examining the evidence that strongly suggests the association of chronic complications of type 2 diabetes with abnormalities of receptors for the advanced glycation end products, transforming growth factor-beta and platelet-derived growth factor. The molecular understanding of receptor abnormalities and alterations in postreceptor signalling pathways may not only clarify the pathogenesis of human type 2 diabetes and the development of chronic complications in the disorder but also provide insight into more efficacious drug regimens that target these receptors.

[Hypersensitivity to hypoglycemic sulfonylurea compounds. Are there cross-reactions?]. / Allergies aux sulfonylurées hypoglycémiantes. Les réactions croisées existent-elles?

We describe 5 observations of cutaneous reactions or immediate hypersensitivity with different hypoglycemic sulfonylurea: Quincke's oedema with glibornuride, three urticaria (one was followed by bronchospasm and collapsus) with glibenclamide, one bullous dermatitis with carbutamide. With special regard to cross reactions between sulfonylurea: we observe the tolerance of glipizide after glibenclamide induced urticaria, tolerance of glicalazide after glibornuride induced Quincke's oedema and eruption, tolerance of glibornuride after chlorporpamide induced urticaria and Quincke's oedema. In the literature, cross reactions between 1st generation sulfonylurea are noted, but not cross reactions between 1st and 2nd generation.

[Radioimmuno assay of the sulfonylurea AR-DF 26(author's transl)]. / Radioimmunologische Bestimmung des Sulfonylharnstoffes AR-DF 26

A radioimmunological method was developed for 1-cyclohexyl-3-[p-(beta-4,4-dimethyl-7-methoxy-1,3-(2H,4H)-isoquinolinedion-2-yl)phenethyl]-sulfonylurea (AR-DF 26, gliquidone, Glurenorm) estimations in plasma. The antisera were obtained by immunization of rabbits with AR-DF 26-bovine serum albumin (BSA) conjugate. The estimation is based on the competitive displacement in plasma samples of known amounts of labelled AR-DF 26, bound to a specific antibody by unknown amounts of unlabelled AR-DF 26. Concentrations of as low as 1 ng of AR-DF 26 per sample can be measured by this method. The investigations into the specificity of this reaction have shown that the antiserum is extremely specific for AR-DF 26. There is good reproducibility of the results and no differences could be found by variance analysis between different measurements of the same AR-DF 26 concentration. Since more than 70% of the plasma concentration correspond to unchanged AR-DF 26 for a longer period after application, the results of this AR-DF 26-radioimmuno assay is only minimally altered by its metabolites.