Ratiometric rapid distinction of two structurally similar fluoroquinolone antibiotics by a Tb/Eu hydrogel

Norfloxacin and ofloxacin are two frequently prescribed second-generation fluoroquinolone antibiotics with an identical 4-quinolone chromophore and hence, are difficult to distinguish by conventional methods (UV or fluorescence). We have designed a Tb³⁺/Eu³⁺/cholate cocktail that enabled us to differentiate these two drugs and rapidly measure their concentrations when present together. Additionally, a Tb³⁺-cholate gel-based paper sensor was developed to detect and quantify them in a single drug containing system with a limit of detection (LOD) well below 100 nM.