Investigating the possible use of a tetra (hydroxyphenyl) porphyrin as a fluorescence probe for the supramolecular detection of phospholipids

The present work explores the interest of using the 5,10,15,20-tetrakis(3-hydroxyphenyl)- 21H,23H-porphin (m-THPP), a commercially available porphyrin, as a polarity probe for the detection of phospholipids. Feasibility of the process was first tested by direct fluorimetry and it was established that emission enhancement in the presence of lipids was maximum for a methanol content of 15% (v/v), a neutral pH (6-8), and a probe concentration of 2x10-7M in the working solution. Detection with m-THPP in these conditions presents higher response factor but shorter linear range than diphenylhexatriene (DPH), the reference dye for the supramolecular detection of lipids. Insights on the mechanism of m-THPP - lipid association demonstrated that, at high lipid concentrations, porphyrin is associated to lipid assemblies in monomer form and located in the interior of bilayer; in low lipid content, porphyrin aggregates co-exist with the monomer. Finally it was assessed that the method can be successfully coupled with micro-bore liquid chromatography.