Developing enzyme-free biosensors offers promising solutions for more effective antibiotic detection methods, especially for complex matrices and unstable environmental conditions where traditional enzymatic approaches may fail. This paper introduces an innovative dual-channel optical biosensor using chitosan-coated ZnS:Mn nanomaterials for the ultra-sensitive detection of doxycycline hyclate, a commonly used antibiotic from the tetracycline (TET) class. The developed sensors demonstrate remarkable sensitivity, exhibiting a linear working range from 13.1 to 72.2 femtomolar (fM), with an impressive detection limit of just 2.09 fM and a limit of quantification of 6.32 fM. They also exhibit excellent selectivity against a variety of common antibiotics, including ampicillin, penicillin, cephalexin, amoxicillin, TET, as well as non-antibiotic substances like glucose. Furthermore, the sensors maintain high stability over time and perform effectively in complex matrices such as tap water. These features suggest that our novel sensor could significantly improve antibiotic monitoring in clinical and environmental contexts, making a substantial contribution to the global fight against antibiotic resistance.
