Fluorescence microscopic quantification of DNA with α,β,γ,δ-tetrakis[4-(trimethylammonium)phenyl]porphine by a ring-like deposition technique Original Research Article

A ring-like deposition technique is proposed to quantify trace amounts of DNA. Because of the capillary effect of solvent, which compensates for the evaporative loss at the contact line of a nanoliter sample droplet on a hydrophobic surface, materials of the droplet can be carried to the edge of the drop spot, and a ring-like deposit (RLD) can occur. It was found that a fluorescent deposit of α,β,γ,δ-tetrakis[4-(trimethylammonium)phenyl]porphine can occur on a dimethyldichlorosilane (DMCS)-modified glass slide, and the fluorescence emission of the deposit can be greatly enhanced by DNA. Linear responses were obtained between the maximum enhanced fluorescence intensity (ΔImax) and amount of calf thymus DNA (ctDNA) in the range 0.10–3.00 pmol, and fish sperm DNA (fsDNA) in the range 0.20–3.00 pmol. Limits of determination are 6.8 fmol ctDNA and 19 fmol fsDNA.