Fluorescence turn-on detection of DNA based on the aggregation-induced emission of conjugated poly(pyridinium salt)s

Herein, a new conjugated poly(pyridinium salt), poly{(4,4'-(1,4-phenylene)bis(2,6-diphenylpyridinium))-co-N-butyl-3,6-carbazolylene ditosylate} (Poly1), exhibits aggregation-induced emission (AIE) characteristics. It is weakly emissive in solution but highly luminescent in the aggregate state. A fluorescence turn-on biosensor for calf thymus DNA (ctDNA) detection and quantification is developed by taking advantage of complexation-induced aggregation of Poly1, which increases the polymer fluorescence in aqueous solution. It was found that the fluorescence intensity of Poly1 in ethanol-phosphate buffer solution (2 mM, pH 7.4) (v/v 1 : 1) was increased up to about 2.4 folds when the concentration of ctDNA increased from 0 to 95 mu M along with the blue-shift of the emission peak from 604 to 586 nm. In the concentration range from 0 to 60 mu M, the ratio of the increase in photoluminescent intensity at 604 nm in the presence of ctDNA (I-ctDNA - I-0) to that in the absence of ctDNA (I-0) is linearly proportional to the concentration of ctDNA with a correlation coefficient of 0.997. The detection limit was calculated to be of 1.2 mu M based on the results of fluorescence titration.