Brian Pedersen

A quantitative enzyme-linked immunoassay for the detection of 2,6-dichlorobenzamide (BAM), a degradation product of the herbicide dichlobenil.

2,6-Dichlorobenzamide (BAM) is the dominant degradation product in soil of the widely used herbicide dichlobenil. To detect BAM in water, a highly sensitive and specific enzyme-linked immunosorbent assay (ELISA) was developed. As an alternative to conventional coating of ELISA plates, the assay is based on direct covalent immobilisation. We achieved a surface which requires a short time for the immobilisation of ligand, is stable under dry storage, and which permits assays with a low CV. The performance of the assay was demonstrated by an inter-well CV that was generally less than 6%, a detection limit (DL(15)) of 0.02 microg/l and an IC(50) of 0.19 microg/l. Cross-reactivity was measured against nine analytes with structural homology to BAM. The highest degree of cross-reactivity (10.8%) was seen with 2,6-dichlorothiobenzamide (Chlorthiamid). Considering an EU-limit of 0.1 microg/l as the permissible maximum for the presence of pesticides in drinking water, this ELISA-procedure is suitable for large-scale screening of water samples suspected of being contaminated with BAM.

Characterization of monoclonal antibodies raised against different structures belonging to the s-triazine group of herbicides

Monoclonal antibodies were raised against seven haptens, representing different structures of the s-triazine group of herbicides. Two side groups on the s-triazine ring were used to couple reactive s-triazine-haptens to immunogenic carrier molecules. For each hapten, one monoclonal antibody was selected for further analysis based on its affinity for the homologous s-triazine. The selected monoclonal antibodies were characterized with respect to their reactivity to the seven immunogens in a direct ELISA assay and cross-reactivity to nine free s-triazines (atrazine, hydroxyatrazine, simazine, hydroxysimazine, terbutylazine, deisopropylatrazine, deethylatrazine, deethylterbutylazine and cyanazine) in competitive assays. The pattern of reactivities illustrates the varying antigenic dominance of the different side groups of the s-triazine ring as well as the potential of monoclonal antibodies for use in screening drinking water, etc. for the presence of s-triazine herbicides.

Tetramethyl Fluoro Formamidinium Hexafluorophoshate – An Improved Synthesis and Some New Uses.

Abstract A non-phosgene, cheap synthesis of Tetramethyl Fluoro Formamidinium Hexafluorophosphate (TFFH) has been developed, and TFFH has been shown to be an useful reagent for preparation of isothiocyanates and hydrazides.

New technology for regiospecific covalent coupling of polysaccharide antigens in ELISA for serological detection.

In this study we demonstrate a new UV irradiation technique for covalent coupling of bacterial polysaccharides derived from lipopolysaccharides to microtiter plates and the use of such plates in an enzyme linked immunosorbent assay (ELISA). Lipopolysaccharides were cleaved by mild acid hydrolysis into the lipid A part and the polysaccharide part. The polysaccharide was conjugated regiospecifically to a photochemically active compound, anthraquinone, resulting in a polysaccharide-anthraquinone conjugate. Anthraquinones forms active radicals when exposed to soft UV irradiation (350 nm) permitting the formation of stable covalent bonds to polymers e.g. microtiter plates. By this technique the polysaccharides are bound through the anthraquinone part of the polysaccharide-anthraquinone conjugates to the microtiter plates. This minimizes denaturation of O-antigen epitopes during binding to the microtiter plates and avoids cross-reactivity due to conserved domains in the lipid A. Furthermore, the covalent binding of the polysaccharide antigens are compatible with harsh assay conditions, such as extensive washing procedures and buffers with high salt concentrations with no risk of antigen leakage. Here we describe the use of this technique for the immobilization of lipopolysaccharide derived polysaccharides from Salmonella Typhimurium and Salmonella Choleraesuis lipopolysaccharides, representing the O-antigens 1, 4, 5, 6, 7, and 12. The functional polysaccharide surface gave similar ELISA results to plates coated passively with the corresponding unmodified lipopolysaccharide antigens. The plates were highly reproducible, showed very low inter- and intra-plate variation and were stable at room temperature for more than 8 months.

In vitro assessment of lidocaine release from aqueous and oil solutions and from preformed and in situ formed aqueous and oil suspensions. Parenteral depots for intra-articular administration.

In vitro drug release rates from aqueous and oil solutions as well as preformed and in situ formed aqueous and oil suspensions intended for intra-articular delivery have been investigated using the rotating dialysis cell model. Using lidocaine as a model drug substance the release kinetics from aqueous and oil suspensions have been compared and the sustained release properties from such suspensions formed in situ has been evaluated. The appearance of lidocaine in the acceptor phase after instillation of preformed and in situ formed aqueous and oil suspensions into the small aqueous donor compartment applied to zero-order kinetics as long sufficient amounts of solid lidocaine remained in the donor cell. The obtained data indicate that oil solutions and oil suspensions of lidocaine possess prolonged release properties equal to or better than those of aqueous counterparts. Also the release properties of preformed aqueous and oil suspensions are identical to such suspension types formed in situ. The present in vitro model appears useful in quality control and formulation development in the field of parenteral depots.

Physicochemical characteristics and in vitro release from oil-based vehicles of peptidomimetics: parenteral depots for intra-articular administration

Results: Basic physicochemical properties including their apparent solubility in aqueous buffer and vegetable oils of a series of 11 peptidomimetics varying with respect to chain length and degree of N-methylation were estimated. It was observed that the compounds in contact with water transformed into sticky, slowly dissolving semisolid materials. Based on these observations, the in vitro release behavior of selected peptide derivatives from oil solutions and in situ formed precipitates was investigated using a validated in vitro release model. Conclusion: The results of this investigation suggest that both types of oil-based drug delivery systems might constitute alternative sustained release formulation principles of such amorphous peptide derivatives for the intra-articular route of administration.