On-Site Food Toxin Detection System Using a Gb3-Immobilized Microchip and a Portable Fluorescence Sensing System

Shiga toxin (Stx) is one of the most potent bacterial toxins known to cause serious gastrointestinal disease in humans. However, the high costs in terms of time, equipment, and operators hinder their further application in timely diagnosis. In this work, we provide a method of coating globotriaosylceramide (Gb₃), an Stx receptor, on a glass chip to detect food toxins in real time and a portable fluorescence detection system that can diagnose Stx after loading the chip. The total size of the system with an organic light-emitting diode (OLED) display is about 8.8 × 6.2 × 15 cm³ and its weight is about 375.5 g with a lithium-ion battery. The novel solvent-assisted lipid bilayer method was utilized to coat a bilayer of receptors on the glass substrate instead of placing a bi-lipid membrane and inserting receptors into the membrane, thereby increasing the fluorescence intensity within the chip and being detected by the system. The optimal conditions for coating receptors were verified and the flow rate of 3 μL/min and flow time of 10 min for the process of solvent exchange showed relatively good efficiency. The limit of detection was 250 pg/mL of Stx1B and the system successfully detected Stx in the lettuce eluate sample. The stability of the chip remained highly reliable within 3 days of storage, but after 14 days, the chip lost most of its detection ability due to delamination of the coated receptor bilayer.