Pen direct writing of multiplex-LFIA for detection of thiamphenicol and tylosin in milk

Therapeutic and misuse of veterinary drugs, such as antibiotics, can increase the potential risk of residue contamination in animal-derived food products. For milk, these residual antibiotics can have an impact on efficiency in dairy processing factories, as well as economic loss, and can also cause side effects on consumer health. Lateral flow immunoassays (LFIAs) are gaining popularity for their ease of use, low cost and their fulfilment to the REASSURED (real-time connection/monitoring, easy sampling, affordable, specific, user-friendly, rapid/robust, equipment free, deliverable to end user) criteria. At the same time, direct writing of functional materials has been recently used for facile applications on point-of-care test (POCT) fabrication. Herein, a novel multiplex-LFIA has been developed for the simultaneous detection of two antibiotics in milk: thiamphenicol and tylosin. In contrast to the traditional automated dispensers, a direct pen writing method was used to deposit control and test lines. The response of each antibiotic was tested, as well as the selectivity of the test during cross-testing. For both antibiotics, the test was successful in distinguishing between safe and unsafe milk samples, according to the maximum residue limits (MRLs) set for both antibiotics. The visual LOD obtained was 100 ppb for the two antibiotics, and the IC₅₀ was lower than the set maximum residue limits (MRLs).