Molecularly imprinted polymer films for reflectometric interference spectroscopic sensors

Reflectometric interference spectroscopic measurements were performed on molecularly imprinted polymer (MIP) films with the herbicide atrazine as the template molecule. A conventional imprinting protocol was used relying on non-covalent interactions between the functional monomers and the template. The MIPs were deposited on glass transducers by two different methods: spin-coating followed by in situ polymerization of thin films of monomers containing a sacrificial polymeric porogen, and autoassembly of MIP nanoparticles with the aid of an associative linear polymer. Reproducible results were obtained upon measurements of atrazine solutions in toluene with both films. Atrazine concentrations as low as 1.7 pprn could be detected with the autoassembled particle film. No or very little analyte adsorption was observed onto non-imprinted control films made by spin-coating and by particle assembly, respectively. We believe that these MIP layers in combination with the general reflectrometric transduction scheme could be a versatile sensing tool for the detection of environmentally important and other analytes. (c) 2007 Elsevier B.V. All rights reserved

Simultaneous multi-analyte determination of estrone, isoproturon and atrazine in natural waters by the RIver ANAlyser (RIANA), an optical immunosensor

8 pages, 5 figures, 2 tables.-- PMID: 14709380 [PubMed].-- Available online Sep 10, 2003.In most medical and environmental applications of biosensors, only single analytes are determined. However, the monitoring of several analytes is obviously preferable in order to gather more information about the sample under analysis. In line with this, different technologies are being developed to obtain multi-analyte sensors.In this paper, an analytical method for the simultaneous determination of three different contaminants—atrazine, isoproturon, and estrone—in natural waters by using an optical immunosensor prototype, the so-called “RIver ANAlyser” (RIANA), is described. RIANA is based on a rapid solid-phase fluoroimmunoassay that takes place at an optical transducer chip. The transducer surface is chemically modified with three analytes derivatives placed in different discrete locations. The sensor surface can be regenerated thus allowing the performance of several measurements with the same transducer. Each test cycle, including one regeneration step, is accomplished in 15 min. Detection limits achieved were 0.155, 0.046, and 0.084 μg/l, for atrazine, isoproturon, and estrone, respectively. Satisfactory repetition, with relative standard deviations between 1.06 and 6.98%, was obtained. Excluding a minor non-specifical binding of the isoproturon antibodies, no cross-reactivity effects were observed. Matrix effects were significant only in the case of wastewater samples. Biosensor measurements were validated using conventional liquid chromatography-mass spectrometry. The results obtained with both techniques were in good agreement.This work has been supported by the Commission of the European Community (Projects RIANA ENV4-CT95-0066, AWACSS EVK1-CT-2000-00045).Peer reviewe

Structural basis of GM1 ganglioside recognition by simian virus 40

Simian virus 40 (SV40) has been a paradigm for understanding attachment and entry of nonenveloped viruses, viral DNA replication, and virus assembly, as well as for endocytosis pathways associated with caveolin and cholesterol. We find by glycan array screening that SV40 recognizes its ganglioside receptor GM1 with a quite narrow specificity, but isothermal titration calorimetry shows that individual binding sites have a relatively low affinity, with a millimolar dissociation constant. The high-resolution crystal structure of recombinantly produced SV40 capsid protein, VP1, in complex with the carbohydrate portion of GM1, reveals that the receptor is bound in a shallow solvent-exposed groove at the outer surface of the capsid. Through a complex network of interactions, VP1 recognizes a conformation of GM1 that is the dominant one in solution. Analysis of contacts provides a structural basis for the observed specificity and suggests binding mechanisms for additional physiologically relevant GM1 variants. Comparison with murine Polyomavirus (Polyoma) receptor complexes reveals that SV40 uses a different mechanism of sialic acid binding, which has implications for receptor binding of human polyomaviruses. The SV40–GM1 complex reveals a parallel to cholera toxin, which uses a similar cell entry pathway and binds GM1 in the same conformation

Sensitivity enhancement of transducers for total internal reflection fluorescence

We have developed, modeled and optimized optical transducers for total internal reflection fluorescence (TIRF). The transducers are part of a compact and rugged immuno-analytical instrument designed for simultaneous detection of up to six analytes in aquatic samples (e.g. atrazine and 2,4-D). Binding inhibition assays, using Cy5.5 labeled antibodies to detect the target analytes, have been carried out. Calibration curves with mid-points of tests below 1 µg/1 and detection limits below 0.1 µg/1 have been achieved. As transducer either ion exchanged integrated optical channel waveguides or planar multimode slab waveguides have been employed. The transducer performance was significantly enhanced by incorporating thin high index films at the waveguide surface and by applying high refractive index solutions in the superstrate. Peak signal enhancement factors of more than ten have been observed and an increase in signal to noise ratio by a factor of more than four have been achieved. Strong polarization dependent effects on the enhancement by high index films have been found both theoretically and experimentally

Integrated optical fluorescence multisensor for water pollution

A 32-analyte integrated optical multisensor for organic pollutants has been realised and tested. The sensor exploits fluorescence immunoassay in the evanescent field of channel waveguides to enable rapid, simultaneous and high-sensitivity fluorescence detection of up to 32 pollutants in water. The chemical modification used to render the surface specific to analytes allows automatic regeneration for immediate reuse. The system has been demonstrated for the key pollutant estrone and a detection limit below 1 ng/L has been achieved