Dual-Enhanced Novel Fluorescence Quencher with Internal Hollow Structure and External Polydopamine Layer for Sensitive Detection of Chlortetracycline in Milk

Chlortetracycline (CTC), a broad-spectrum veterinary antibiotic, poses serious risks to human health through bioaccumulation due to excessive use. To address the critical need for CTC monitoring, we developed a fluorescence quenching lateral flow immunoassay (FQ-LFIA) employing black bimetallic hollow nanoparticles (BBHNPs) as quencher. BBHNPs were engineered with a unique dual-advantage architecture: an internal hollow structure for enhanced light capture capability and an external polydopamine layer for higher spectral overlap with fluorophores. This design resulted in exceptional photophysical characteristics, including a remarkable molar extinction coefficient (2.18×10 12 L mol -1 cm -1 ) and an unprecedented fluorescence quenching constant (5.20×10 13 L mol -1 ). BBHNP-based FQ-LFIA achieved a limit of detection (LOD) of 0.32 ng mL -1 , representing a 6.91-fold improvement over conventional gold nanoparticle-based lateral flow immunoassay (LFIA). Validation studies in spiked milk samples showed excellent recovery rates (87.73-118.09%) with high precision (coefficient of variation < 10.36%). Method comparison with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis confirmed the reliability of BBHNP-FQ-LFIA for real-world applications.