Multiplexed detection of food contaminants with a portable reader based on all-in-one monolithic photonic chips

Abstract

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.