Unexpected potential of fluoroquinolones in photooxidative polymerization

Fluoroquinolones (FQs), such as lomefloxacin (LX) and fleroxacin (FX), are effective photochemical initiators. When thionine, pyrrole and aniline were photosensitized by LX under UV and oxygen, they polymerized into nanodots and nanofibers after irradiation. Tetrakis-5,10,15,20-(4-aminophenyl)porphyrin (TAPP) underwent similar polymerization in CH₂Cl₂ when FX was incorporated. LX and FX defluorinated during the irradiation. Incorporating oxygen could accelerate the reaction. Reactive oxygen species, such as hydrogen peroxide, were likely to be generated in this case and initiate the polymerization. The FQ-induced polymerization showed potential in photochemical and electrochemical applications. When the resultant poly(thionine) nanoparticles were modified on ITO conductive glass squares as electrodes, they could mediate electron transfer for hydrogen peroxide. The forward reaction rate constant was estimated to be 1 × 10³ M^-1 s ^-1 at pH 7. The thionine derivatives could also serve as a molecular adhesive for glucose oxidase. Thanks to these properties, the electrodes, after further modified with glucose oxidase, could function as a glucose sensor. The sensitivity to glucose reached a level as low as μM. Besides thionine, pyrrole showed promise for photolithography. When paper strips were treated with LX and pyrrole, the strips could function as photographic films. FQs are thus shown to be useful photosensitizers, not just notorious photocarcinogens.