Multiplex environmental pollutant analysis using an array biosensor coated with chimeric hapten-dextran-lipase constructs

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 IC50 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.