Fig. 1: Screening metal sensing dyes as a visual reporter for LAMP amplification.

For each dye, the color of triplicate LAMP reactions is shown for before (left column) and after (middle column) the LAMP reaction with either lambda DNA (1 ng) or without (NTC). LAMP amplification was confirmed by real-time curves (right column; 1 cycle = 15”). The difference in visible dye color reduces the real time fluorescence emitted by the dsDNA binding dye, and thus the Y-axis for the real time curves is different due to automatic scaling by the software. Each dye was tested either without Mn²⁺ or with two concentrations of Mn²⁺ (100 and 800 µM). The labels for these three conditions are color-coded the same as their corresponding real-time curves. The best visual detection condition for each dye is highlighted in a dotted rectangle. a 75 μM 5-Bromo-PAPS. b 75 μM 5-Nitro-PAPS. c 200 μM PAR. d 80 μM HNB. e 100 μM EBT. In reactions with 800 µM Mn²⁺, the amplification was significantly impaired, as shown in the real-time column of a–c. In addition, such limited amplification combined with the high concentration of Mn²⁺ could not produce a color change after 40 min incubation time (middle column in a, b) likely due to insufficient production of PPi.