Search

A silicon-based miniaturized sensor chip combined with an advanced microfluidic module for the simultaneous, label-free immunochemical determination of four allergens, bovine milk protein, peanut protein, soy protein, and gliadin, is presented. The sensor chip consists of an array of 10 broad-band Mach–Zehnder interferometers (BB-MZIs) monolithically integrated on silicon, along with their respective broad-band light sources. The BB-MZIs were biofunctionalized with the targeted allergens and their responses during immunoreaction were monitored by multiplexing their transmission spectra through an external miniaturized spectrometer. The assay is performed by running mixtures of calibrators or samples with the antibodies against the four allergens followed by an antispecies specific antibodies solution. Employing a fluidic module of nearly one-dimensional geometry, that provided for uniform delivery of the reagents, CV values <6% were achieved for the responses of the 10 BB-MZIs, allowing for reliable multianalyte determinations. The analysis is completed in 6.5 min, and the detection limits were 0.04 μg/mL for bovine k-casein, 1.0 μg/mL for peanut protein, 0.80 μg/mL for soy protein, and 0.10 μg/mL for gliadin. The assays were accurate (recoveries 88–118%) and repeatable (intra- and interassay CVs <7% for all four allergens). Finally, the sensor was evaluated by analyzing samples from a cleaning in place system (CIP) of a dairy industry and the results obtained were in good agreement with those received by the respective ELISAs. The analytical characteristics of the sensor combined with the short analysis time and the small chip size make the proposed system an ideal tool for on-site multianalyte determinations.

Polymer with pendant methacryloyl group was synthesized by the substitution reaction of poly(2-hydroxyethyl methacrylate) [poly(HEMA)] with methacryloyl chloride. This photocurable polymer was characterized using 1H-NMR and bromine titration, and the results were reasonably well consistent. The photocrosslinking of this modified poly(HEMA) was carried out by the addition of a low molecular weight sensitizer without adding functional monomer and crosslinker. These precursors showed a high photosensitivity. Polymers with a degree of substitution as low as 2 mol-% methacryloyl group could be efficiently crosslinked within few seconds of UV exposure to give water insoluble transparent hydrogel membranes. By irradiation of a film of the photocurable polymer precursor containing lacatate oxidase (LOD), a rather unstable enzyme, the enzyme was gently immobilized by physical entrapment.