A novel phosphonic acid functional polythiophene fluorescent sensor for Ca2+ and its live cell imaging

Calcium ions are indispensable to various physiological activities of the body, so the detection of calcium ions is very important. In this work, a new water-soluble polythiophene derivative poly{((thiophene-3,4-diylbis(oxy))bis(propane-3,1-diyl))bis(phosphonic acid)} (PT-PHO) was designed and synthesized via oxidative polymerization with FeCl3. The polymer containing phosphonic acid groups could be used as a "turn off" fluorescent sensor for Ca2+ detection. Under optimal conditions, PT-PHO exhibits high selectivity and sensitivity to detect Ca2+ among metal ions. The fluorescence intensity of PT-PHO shows a linear response toward Ca2+ in the range of 0.05-50 mu mol L-1 with a limit of detection (LOD) of 44 nmol L-1. In addition, PT-PHO has low toxicity and good biocompatibility. Thus, it could be used for imaging lysosomes in cells and detecting intracellular calcium ions.