Lab-On-A-Chip For Analysis And Diagnostics: Application To Multiplexed Detection Of Antibiotics In Milk

The concern for “food safety” surely emerged very early in human history, contributing to the establishment of certain rules and customs. In today’s technologically developed countries, food safety is subject to strict laws that regulate the presence of undesired substances in food. In particular, in the milk industry, levels of residues of veterinary medicinal products, of which antibiotics represent a significant part, are regulated by European Council (EC) Regulation no. 2377/90. More precisely, a series of four antibiotic families are found to be of particular interest due to their routine use for treatment in bacterial infection and/or prophylactic purposes: fluoroquinolones, sulfonamides, β-lactams, and tetracyclines. Their excessive use in dairy diet in recent decades gave rise to stronger bacterial resistance, which consequently represents a serious problem in the efficiency of classic antibacterial treatment in humans [1]. In this context, there is a considerable need for developing sensing devices able to detect a series of antibiotic families simultaneously. A few dipstick format tests [1] commercially available that are cheap, fast, and reliable currently offer an interesting alternative to expensive conventional chromatographic techniques. However, those systems are not fully automated and are unable to detect more than two antibiotic families per single test. The present work reports the development of a lab-on-a-chip (LOC) test system for multiplexed detection of four antibiotic families in raw milk. A fabricated microfluidic cartridge is prefilled with the solutions necessary for immunoassays, and the whole detection sequence is operated automatically by external pump-and-valve combinations. The immunoassay principle is based on a competitive assay format, and the resulting refractive index changes at the sensor surface are probed using the wavelength interrogated optical sensing (WIOS) method. The multiplexed sensing system that was consequently developed was adapted for the simultaneous detection of sulfonamides, fluoroquinolones, β-lactams, and tetracyclines. The whole test procedure is fast (less than 10 min), easy to handle (automated actuation), and cost-effective due to the use of novel photosensitive materials in a “one-step” fabrication process.