New role of oil red O in detection of double stranded DNA

Oil red O (ORO) is a commonly used dye for the tissue staining, which recognizes nitroglycerin and cholesterol esters. In this paper, we describe an unexpected finding that ORO can be fluorescently lighted up upon meeting dsDNA with emission peak localized at 600 nm, although it almost does not fluoresce by itself. This property triggered us to test its potential as a dsDNA fluorescence probe. The interaction of dsDNA and ORO was demonstrated by spectral and thermodynamic analysis and several other means. The fluorescence of ORO was gradually increased following the addition of dsDNA, which showed linear response toward dsDNA in the concentration range from 0.02 to 0.64 mg/mL with a detection limit of 0.69 μg/mL. Moreover, ORO showed excellent selectivity when testing with a variety of dsDNA-like biomolecules. Besides, ORO resisted photobleaching and worked very well under biological background. Altogether, we propose here a new nucleic acid lighting up fluorescence probe for double stranded dsDNA detection.