Point-of-Care Detection of β-Lactamase in Milk with a Universal Fluorogenic Probe

The illegal addition of beta-lactamase (Bla) in milk to disguise beta-lactam antibiotics has been a serious issue in the milk industry worldwide. Herein, we report a method for point of-care detection of Bla based on a probe, Tokyo Green-tethered beta-lactam (CDG-1), as a common substrate of various Blas (Bla A, B...) which can enzymatically convert CDG-1 (low fluorescence) to Tokyo Green (high fluorescence). This approach allows rapid screening of a broad spectrum of Blas in real milk samples within 15 min without any pretreatment. Combined with the immuno-magnetic separation, we achieved sensitive and quantitative detection of Bla (10(-5) U/mL), which provides a universal platform for screening and determining Blas in complex samples with high efficiency and accuracy.