A metal mediated specific poly(cyclotriphosphazene- co -curcumin) fluorescent micro-probe for tetracycline sensing

The extensive use of tetracycline antibiotics (TCs) renders their widespread in the environment that may cause bacterial resistance. Thus, detection of residual TCs and understanding of their broader roles and impacts in the environment and soil ecology are is of critical significance. This paper describes the investigation of a Mg (II)-specific fluorescent micro-probe (PCC–Mg) based on cyclotriphosphazene (Cpz) and curcumin for classical TC•HCl sensing with a low detection limit of 29 nM and a fast response time of less than 10 s. The sensing mechanism is presumably attributed to specific Mg 2+ binding with TCs since the fluorescence enhancement is not observed in the absence of Mg 2+ and not influenced by the presence of several metal ions and anions. The binding of Mg 2+ to curcumin/TC and the formation of TC-metal-curcumin ternary complex can be concluded with NMR and mass spectrometry. Moreover, for the purpose of easy applications, test strips are made to render visual detection of TC with noticeable and selective fluorescence enhancement. The formation of the ternary complex between Cur from the popular herb Curcuma longa and TC from Streptomyces spp. mediated by metal ions also hints a potential role of microbiolochemical-phytochemical interactions in maintaining biodiversity and equilibria in soil microecology.