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An interferometric nanobiosensor for the specific and label-free detection of the pollutant Irgarol 1051 directly in seawater has been settled. Due to the low molecular weight of Irgarol pollutant and its expected low concentration in seawater, the sensor is based on a competitive inhibition immunoassay. Parameters as surface biofunctionalization, concentration of the selective antibody and regeneration conditions have been carefully evaluated. The optimized immunosensor shows a limit of detection of only 3 ng/L, well below the 16 ng/L set by the EU as the maximum allowable concentration in seawater. It can properly operate during 30 assay-regeneration cycles using the same sensor biosurface and with a time-to-result of only 20 min for each cycle. Moreover, the interferometric nanosensor is able to directly detect low concentrations of Irgarol 1051 in seawater without requiring sample pre-treatments and without showing any background signal due to sea matrix effect., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The field of environmental monitoring has experienced a substantial progress in the last years but still the on-site control of contaminants is an elusive problem. In addition, the growing number of pollutant sources is accompanied by an increasing need of having efficient early warning systems. Several years ago biosensor devices emerged as promising environmental monitoring tools, but their level of miniaturization and their fully operation outside the laboratory prevented their use on-site. In the last period, nanophotonic biosensors based on evanescent sensing have emerged as an outstanding choice for portable point-of-care diagnosis thanks to their capability, among others, of miniaturization, multiplexing, label-free detection and integration in lab-on-chip platforms. This review covers the most relevant nanophotonic biosensors which have been proposed (including interferometric waveguides, grating-couplers, microcavity resonators, photonic crystals and localized surface plasmon resonance sensors) and their recent application for environmental surveillance., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This paper reports the development of a novel strategy for the easy immobilization of low molecular weight haptens to microarray platforms by coating with modified lipase molecules. The chimers consist of a dextran network covalently coupled to bacterial thermoalkalophilic lipase (BTL2). The relative high surface hydrophobicity of lipase allows easy immobilization of the conjugates onto glass planar waveguides previously modified with 1,1,1,3,3,3-hexamethyldisilazane, via nonspecific hydrophobic interactions, while the dextran layer provides a three-dimensional network that can be easily modified with different functional groups for further hapten immobilization on the glass substrate. The conjugates have been applied to the development of microarray biosensors for the simultaneous detection of three water pollutants namely, atrazine (ATR), a triazine pesticide, enrofloxacin (ENRO), a fluoroquinolone antimicrobial, and the hepatotoxin microcystin LR (MCLR). In an alternative approach, the chimeric hapten-dextran-BTL2 constructs were synthesized, purified and further immobilized on the hydrophobic transducer surface through their hydrophobic faces (Janus character). Detection of the three model targets was based in a competitive immunoassay format. A combination of detection and tracer antibodies was optimized to avoid significant cross-reactivity. Evanescent wave excitation was used to excite the fluorescent immunocomplexes formed on the planar waveguide and the identity of the target analyte was encoded by its location in the detection platform. The developed microarray allows the simultaneous detection of the target pollutants with IC 50 values, of 4.4 ± 0.7, 75 ± 9, 18 ± 4 ng L −1 for ATR, ENRO and MCLR, respectively and relative standard deviations (RSDs) lower than 15%. Waveguide functionalization using the dextran-BTL2 chimers is rapid, simple and allows the development of highly sensitive microarrays that can be easily applied to the multiplexed detection of pollutants in environmental samples. [ABSTRACT FROM AUTHOR]