Multichannel Biolayer Interferometry to Probe the Binding of Microbial Extracellular Polymeric Substances to Sulfamethoxazole

Microbial extracellular polymeric substances (EPS) can bind to sulfonamides, influencing the removal of antibiotics in biological wastewater treatment systems. However, information about the binding kinetics and affinities of EPS for sulfonamides remains unavailable due to the lack of an effective approach. In this study, biolayer interferometry (BLI), a multichannel sensing technique, is first established to probe the binding of the antibiotic sulfamethoxazole (SMX) to microbial EPS. The influence of environmental conditions, such as pH, ionic strength, and temperature, on this binding interaction is investigated. The results indicate that multichannel BLI can rapidly and accurately determine the association/dissociation rate constants and binding affinities of the binding interactions between EPS and SMX. The high reproducibility of the sensorgrams demonstrates the reliability of the BLI approach. Via comparison of the obtained parameters, the binding interactions between EPS and SMX are significantly improved under acidic conditions compared to those under neutral or alkaline conditions. A higher ionic strength and a lower temperature yield stronger binding between EPS and SMX. BLI analysis allows multichannel operations concurrently, substantially reducing the testing time. The BLI approach developed in this study provides a powerful tool for probing the binding interactions between complex environmental samples.