Pyrene functionalized molecular beacon with pH-sensitive i-motif in a loop

In this work, we present a spectral characterization of pH-sensitive system, which combines the i-motif properties with the spatially sensitive fluorescence signal of pyrene molecules attached to hairpin ends. The excimer production (fluorescence max. similar to 480 nm) by pyrene labels at the ends of the molecular beacon is driven by pH-dependent i-motif formation in the loop. To illustrate the performance and reversible work of our systems, we performed the experiments with repeatedly pH cycling between pH values of 7.5 +/- 0.3 and 6.5 +/- 0.3. The sensor gives analytical response in excimer-monomer switching mode in narrow pH range (1.5 pH units) and exhibits high pH resolution (0.1 pH unit). (C) 2015 Elsevier B.V. All rights reserved.