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[Display omitted] • Ten MZIs, optical sources, spectral analyzers, and photodiode arrays on a single chip. • Portable reader based on all-in-one monolithic photonic chips. • Multiplexed determination of 3 allergens in industry rinsing water samples in 10 min. • Dual mycotoxins determination in beer samples within 15 min. Silicon chips that monolithically integrate ten Mach-Zehnder interferometers (MZIs), their respective broad-band optical sources, and spectral analyzers, as well as photodiode arrays that record the spectrally-resolved output signals of the ten MZIs, are exploited for the multiplexed immunochemical determination of allergens and mycotoxins. The monolithically integrated light sources emit light in the visible/infrared spectrum (530–950 nm), and thus the detection based on broad-band Mach-Zehnder interferometry provided information about changes in the refractive index on the transducer surface due to binding reactions across the entire spectrum, surpassing the limitations of traditional monochromatic interferometry. The assays were run using a portable automated reader incorporating the chip fluidic and electronic interfacing, a micropump for continuous fluid delivery, and control electronics combined with a software for real-time signal monitoring. The photonic chips and portable reader were applied for allergen detection in dairy industry rinsing waters and mycotoxin detection in beer samples. All analytes were determined through competitive immunoassays. For the multiplexed detection of three allergens (bovine κ-casein, peanut protein, and gliadin), the respective proteins were immobilized onto the sensing windows of different MZIs on a single chip. For the detection of mycotoxins (fumonisin B1 and deoxynivalenol), the respective mycotoxin-protein conjugates were employed. In all cases, the reaction with mixtures of calibrators/samples and analyte-specific antibodies was followed by a reaction with appropriate secondary antibodies to enhance the signal and reduce the assay duration. The allergen assays were completed in 10 min with detection limits of 0.01, 0.25, and 0.05 μg/mL for κ-casein, peanut protein, and gliadin, respectively. The mycotoxin assays took 15 min with detection limits of 2.0 and 10 ng/mL for fumonisin B1 and deoxynivalenol, respectively, in beer samples. The results demonstrate the potential of the developed solution for the rapid and sensitive on-site multiplexed detection of targeted analytes. [ABSTRACT FROM AUTHOR]

An optical biosensor for label-free detection of ochratoxin A (OTA) in beer samples is presented. The biosensor consists of an array of ten Mach-Zehnder interferometers (MZIs) monolithically integrated along with their respective broad-band silicon light sources on the same Si chip (37 mm 2 ). The chip was transformed to biosensor by functionalizing the MZIs sensing arms with an OTA-ovalbumin conjugate. OTA determination was performed by pumping over the chip mixtures of calibrators or samples with anti-OTA antibody following a competitive immunoassay format. An external miniaturized spectrometer was employed to continuously record the transmission spectra of each interferometer. Spectral shifts obtained due to immunoreaction were transformed to phase shifts through Discrete Fourier Transform. The assay had a detection limit of 2.0 ng/ml and a dynamic range 4.0–100 ng/ml in beer samples, recoveries ranging from 90.6 to 116%, and intra- and inter-assay coefficients of variation of 9% and 14%, respectively. The results obtained with the sensor using OTA-spiked beer samples spiked were in good agreement with those obtained by an ELISA developed using the same antibody. The good analytical performance of the biosensor and the small size of the proposed chip provide for the development of a portable instrument for point-of-need determinations. [ABSTRACT FROM AUTHOR]

A dual-analyte assay for the simultaneous determination of C-reactive protein (CRP) and D-dimer in human blood plasma based on a white light interference spectroscopy sensing platform is presented. Measurement is accomplished in real-time by scanning the sensing surface, on which distinct antibody areas have been created, with a reflection probe used both for illumination of the surface and collection of the reflected interference spectrum. The composition of the transducer, the sensing surface chemical activation and biofunctionalization procedures were optimized with respect to signal magnitude and repeatability. The assay format involved direct detection of CRP whereas for D-dimer a two-site immunoassay employing a biotinylated reporter antibody and reaction with streptavidin was selected. The assays were sensitive with detection limits of 25 ng/mL for both analytes, precise with intra- and inter-assay CV values ranging from 3.6% to 7.7%, and from 4.8% to 9.5%, respectively, for both assays, and accurate with recovery values ranging from 88.5% to 108% for both analytes. Moreover, the values determined for the two analytes in 35 human plasma samples were in excellent agreement with those received for the same samples by standard diagnostic laboratory instrumentation employing commercial kits. The excellent agreement of the results supported the validity of the proposed system for clinical application for the detection of multiple analytes since it was demonstrated that up to seven antibody areas can be created on the sensing surface and successfully interrogated with the developed optical set-up. [ABSTRACT FROM AUTHOR]