A novel molecular probe sensing polynuclear hydrolyzed aluminum by chelation-enhanced fluorescence

Abstract

A novel molecular probe (P2) sensing polynuclear hydrolyzed aluminum by chelation-enhanced fluorescence was described, which was prepared from 1,1'-(1,4-phenylene)bis(7-methyl-1,3,5-octanetrione) and 2-aminomethylpyridine. P2 showed a strong fluorescence response to Al(III) when excited by the optimized wavelength of 400nm and the λmax,em at 505nm indicated a hypsochromic shift of 11nm to that of free P2, but Cu(II) was observed to quench the fluorescence intensity to nearly zero. The P2–Al(III) complex indicated the best fluorescence response at a pH near 7 and there might be a relevance to the amphoteric property of the aluminum hydroxide. The emission intensity at 505nm continued to increase until the mole ratio of [Al(III)]/[P2] reached a value of 13 and no stoichiometry was observed during the process, which implied that the sensing target of the P2 probe was not the free aluminum ion but the polynuclear hydrolyzed aluminum. The binuclear hydrolyzed aluminum compounds were selected as model target molecules to simulate the energy-minimized structure of the P2–Al(III) complex to confirm the CHEF mechanism. The enhanced fluorescent images of HeLa cells incubated with 1μM P2 and 5μM Al(III) were obtained.