A Fluorogenic Hydrazino-Pictet-Spengler Reaction in Live Cells

Lipid peroxidation generates diverse aldehydic lipids associated with oxidative stress and signaling, yet methodologies capable of their detection in live cells are currently lacking. Here, we report a fluorogenic hydrazino-Pictet-Spengler (HIPS) probe for lipidic aldehydes "FLipA-HIPS" that generates bright, wash-free fluorescent reaction products in vitro and in cellulo. FLipA-HIPS is essentially nonfluorescent but reacts with aldehydes to give an environmentally sensitive fluorophore with a higher quantum yield in SDS micelles as compared to aqueous buffer alone. FLipA-HIPS reacts with lipidic aldehydes to give 10- to 25-fold higher fluorescence intensities than reactions containing either short-chain aliphatic or aromatic aldehydes in aqueous buffer. Confocal microscopy shows that live cells pretreated with potassium bromate or the aldehydic phospholipid "POVPC" display rapid and selective FLipA-HIPS staining that co-localizes with the endoplasmic reticulum (ER), consistent with the ER's known role in accumulating lipidic aldehydes. These results demonstrate that HIPS reactions can exhibit useful fluorogenic properties for aldehyde biosensing applications in live cells.