Figure 2.

Fluorescence of HNB and result of LAMP detection using the dry reagents in the glass pad. (a) Schematic representation of the experimental process for reaction pad testing and analysis. Screening of reaction pads, optimization of drying additive, and other experiments on a single reaction pad were performed following this process. According to the experimental purpose, the composition of each solution was changed frequently. (b) Colorimetric and fluorescence image of negative (-) and positive (+) LAMP solution containing HNB dye for comparison in solution and on the glass pad. Negative: no template DNA; positive: Streptococcus pneumoniae genomic DNA. (c) Fluorescence of HNB in liquid and in the glass pad as a function of Mg²⁺ concentration. The concentration of MgSO₄ was changed in the reaction buffer (without LAMP reaction). (d) Selection of additives for the dry condition. Reagents including HNB, LAMP primer, Bst polymerase and additive were dried in the glass pad. LAMP reaction was performed using the dry reagents, and the stabilization effect of additives in the glass pad was shown using the S/N ratio. S, fluorescent intensity of the LAMP reaction pad; N, fluorescent intensity of the control pad, which contained the same reagents without primers. (e) Fluorescence signal of HNB-treated glass pad according to Mg²⁺ concentration. The signal from the dry condition was affected by PVA. Measurement of fluorescence in (c), (d), and (e) was repeated three times and error bars represent standard deviation of these results.