Spectroscopic studies of pyridil and methoxyphenyl porphyrins in homogeneous and Pluronic®-based nanostructured systems

Abstract

Spectroscopic properties of Porphyrins TPyP (tetra(4-pyridil)porphyrin), TMPP (tetrakis(4-methoxypheny) porphyrin) and its zinc metaled derivatives porphyrins Zn-TPyP and Zn-TMPP respectively, were studied in homogeneous and micro heterogeneous systems, comprising nanostructured Pluronic® copolymeric micellar systems, as a promising drug delivery systems for the porphyrins investigated. Physico-chemical properties such as, hydrophobicity degree, self- aggregation in solvents of different polarities and water/ethanol mixtures (monofasic binary), as well as kinetics profile and isotherm binding, molecular organization, [Formula: see text] and relative localization in neutral micellar systems. The hydrophobic character was the key to relative drug location in the micellar systems. In homogenous solvents systems the porphyrins presented relatively high values of molar absorptivity and low values of [Formula: see text]. The K[Formula: see text] values obtained are modulated by the structure of porphyrins, state of aggregation, as well as, structure and macro molecular self-organization of copolymers. Fluorescence quenching studies have shown that porphyrins in F-127 are located in a less hydrophobic region than the porphyrins in P-123, which are located preferentially in a deeper micellar microenvironment. The zinc porphyrins showed high values of K[Formula: see text]. Thus, the association of the porphyrins with specific binding sites of micellar systems is strongly modulated by the presence of the metal coordinated to the porphyrinic ring.