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 by FeCl3. The polymer containing phosphonic acid groups could be 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 fluorescent intensity of PT-PHO shows a linear response toward Ca2+ in the range of 0.05 mol L-1 - 50 mol L-1 with a limit of detection (LOD) 44 nmol L-1. In addition, PT-PHO is low toxicity and has good biocompatibility. Thus, it could be used for imaging of lysosomal in cell and detecting of intracellular calciumion.