Spectroscopic characterization of porphyrin supramolecular aggregates on poly-lysine and their application to quantitative DNA determination

Using UV-Vis absorption, fluorescence emission and resonance light scattering (RLS) measurements, we have shown that, under the appropriate conditions, a supramolecular complex is formed between the anionic meso-tetrakis(4-sulfonatophenyl)porphine (H2TPPS) and the protonated form of poly-lysine. Such assembly is characterized by an almost complete quenching of the porphyrin's fluorescence. The addition of DNA, which is a poly-anion, causes a displacement of the porphyrin bound to the poly-cationic matrix with consequent increase in the fluorescence intensity of the solution. Therefore, since the variation in fluorescence emission is linearly related to the concentration of DNA added, we have investigated the possibility of employing such a supramolecular system in a simple and rapid method for the quantitative determination of DNA in solution.