Rapid Detection of Food Allergens by Microfluidics ELISA-Based Optical Sensor

Abstract

The risks associated with the presence of hidden allergens in food have increased the need for rapid, sensitive, and reliable methods for tracing food allergens in commodities. Conventional enzyme immunosorbent assay (ELISA) has usually been performed in a centralized lab, requiring considerable time and sample/reagent consumption and expensive detection instruments. In this study, a microfluidic ELISA platform combined with a custom-designed optical sensor was developed for the quantitative analysis of the proteins wheat gluten and Ara h 1. The developed microfluidic ELISA biosensor reduced the total assay time from hours (up to 3.5 h) to 15-20 min and decreased sample/reagent consumption to 5-10 μL, compared to a few hundred microliters in commercial ELISA kits, with superior sensitivity. The quantitative capability of the presented biosensor is a distinctive advantage over the commercially available rapid methods such as lateral flow devices (LFD) and dipstick tests. The developed microfluidic biosensor demonstrates the potential for sensitive and less-expensive on-site determination for rapidly detecting food allergens in a complex sample system.

Keywords: Ara h 1; food allergen; gluten; microfluidics; optical sensor.

Figure 1

Schematic of the Microfluidic ELISA chip layout (not to scale) (A) and Principle of the on-chip absorption detection with the miniaturized optical sensor device (B). The diameters of the sensing and waste wells are 2.5 mm and 6 mm, respectively. The width of the main channel and the branch channels are 200 μm and 100 μm, respectively. All other wells are 0.75 mm in diameter to fit the loading syringe tip.

Figure 2

Photo-detector biosensor output of optical absorption detection upon gluten standard solution of 25 ng/mL (A) and 50 ng/mL; (B) by two different antibody immobilization strategies, passive adsorption (PA) and covalent immobilization (CI). Optimization of the blocking step by using blocking buffer of 1% (w/v) and 5% (w/v) BSA in PBS for gluten standard solution of 50 ng/mL; (C) Experiments were conducted without coating antibodies on the microchannels. The higher concentration of the blocking buffer improved the blocking efficiency.

Figure 3

Time-dependent response of the developed optical microfluidic biosensor upon sensing the gluten standard solution (A) and Ara h 1 standard solution (B); Linear standard curves of gluten (C) and Ara h 1 (D).