A broad-spectrum sensing strategy for the tetracycline family of antibiotics based on an ovalbumin-stabilized gold nanocluster and its application in a pump-free microfluidic sensing platform.

With increasing concerns related to the abuse of antibiotics in livestock production worldwide, simple and rapid screening methods for monitoring antibiotics in animal-derived foods are highly desirable. In this study, we propose a facile synthesis strategy for gold nanoclusters (AuNCs) exhibiting remarkable optical properties by employing ovalbumin (OVA) as the template. The OVA-stabilized AuNCs (AuNCs@OVA) manifest intriguing multicolour fluorescence and a gradually declining fluorescence intensity at 650 nm with an increasing concentration of tetracycline family antibiotics (TCs) including tetracycline, chlorotetracycline, oxytetracycline, and doxycycline, which are a widely used class of antibiotics for treating infections in food-producing animals. This performance makes AuNCs@OVA particularly attractive as a broad-spectrum detector for TCs sensing, and we demonstrate that this simple sensing procedure can be realized in real time by directly mixing the target sample and AuNCs@OVA components. Based on this sensing strategy, a microfluidic lab-on-a-chip platform was constructed for the ultrarapid detection of TCs within 30 s. The detection limit was determined to be 0.09 μg/mL in chicken muscle extract, with the recovery ranging from 86.20% to 93.57% in spiked samples. This work provides not only a broad-spectrum sensing strategy for TCs but also a pump-free microfluidic chip with the advantages of being portable, ultrarapid, and low cost, offering a viable alternative for on-the-spot ultrarapid screening of TCs.