White precipitate of magnesium pyrophosphate forms in the LAMP reaction solution as a by-product of the amplification reaction [5] . Therefore, after amplification, we first precipitated the magnesium pyrophosphate to the bottom of the reaction tube by centrifugating the LAMP reaction solution for 10 seconds using a small desk-top centrifuge (6,000 rpm). Then, 4 µl of PEI solution adjusted to the desired concentration was added to the supernatant to form an insoluble DNA-cationic polymeric polymer complex at room temperature. A pellet was formed by immediately centrifuging it for 10 seconds using the same centrifuge. A fluorescent image of the pellet was photographed with a fluorescence microscope (VB-G05, Keyence Corporation) equipped with a Handy UV Lamp (wavelength: 365 nm; Vilber Lourmat) and a UV blocking filter (NEO Dynamic L-400, MARUMI Optical Co., Ltd.). Since the magnesium pyrophosphate precipitate was nonfluorescent, it had no effect at all on visualization of pellet fluorescence. To investigate the effect of ionic strength on precipitation titration, aqueous KCl was added to the reaction solution after the LAMP reaction so that it was the prescribed concentration.