Selective Co-Assembly of Water-Soluble Conjugated Polyelectrolyte with Discernable Fluorescence Modulation for Antibiotic Detection

Residual antibiotics threaten ecosystems and public health by fostering antibiotic resistance and water contamination. To address this, PQx-Ph, a water-soluble conjugated polyelectrolyte, is developed as a selective fluorescent probe for antibiotic detection. The sulfonate-functionalized architecture of PQx-Ph facilitates the molecular co-assembly with antibiotics, resulting in fluorescence responses through antibiotic-selective distinct mechanisms, i.e., aggregation-induced emission (AIE) and twisted intramolecular charge transfer (TICT). These antibiotic-selective mechanisms enable 1) fluorescence quenching upon co-assembly with kanamycin (KAN) due to electrostatic binding and 2) fluorescence enhancement upon co-assembly with erythromycin (ERY) through hydrophobic interactions and TICT stabilization. PQx-Ph exhibits remarkable selectivity toward KAN, demonstrating strong binding with minimal interference from various competing substances. PQx-Ph exhibits matrix-dependent sensing performance, achieving nanomolar-level KAN detection (LOD = 0.021 µm) in mild environments containing low levels of natural organic matter (NOM), and maintaining reliable micromolar-level sensitivity (LOD = 0.37–1.44 µm) in environmentally complex matrices such as synthetic urine, tap water, and NOM-rich water samples. Given its excellent water solubility, environmental stability, and structural adaptability, PQx-Ph emerges as a promising candidate for real-time monitoring of antibiotic contamination. Future integration into portable sensing platforms will broaden its applications in environmental and public health monitoring.