<i>In vivo</i> activation of NCL probe by luciferase and nitroredictase expressing <i>E</i>.<i>coli</i> in a mouse model of thigh infection.

<p>(A). Luminescence over 4 h from <i>E</i>. <i>coli luc+</i> infected quadriceps (5 × 10<sup>4</sup>–5 × 10<sup>7</sup> bacteria) after IP injection of 0.8 mg NCL probe (200 μL of 10 mM solution in PBS). (B). Luminescence over 4 h from <i>E</i>. <i>coli luc+</i> infected quadriceps (5 × 10<sup>7</sup> bacteria) following IP injection of 0.8 mg of probe or 0.63 mg of luciferin (200 μL of 10 mM solution in PBS). (C). Luminescence imaging of mice over 24 h bearing 5 × 10<sup>7</sup> bacteria, treated with various (0.08, 0.8 and 1.6 mg) NCL probe concentrations (200 μL of 1, 10 and 20 mM solutions of NCL in PBS). As a positive control, mice were injected with equal amounts of <i>E</i>. <i>coli</i> MG1655 expressing lux luciferase that doesn't require exogenous substrate for light production [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131037#pone.0131037.ref044" target="_blank">44</a>]. The signal was collected over 24 h, n = 3 per group.</p>