Transferrin as a potential carrier in photodynamic therapy (PDT) and cell phototoxicity induced by Cr(phen)33+.

GARCIA P; CAVALLO N; LLORENS DE LOS RIOS C; PERRONE A; SILVERO J.; ; ARGUELLO G; CABANILLAS A

Mar del Plata, Buenos Aires. Argentina

Congreso; LVII Reunion Cientifica Anual Sociedad Argentina de Investigacion Clinica (SAIC).; 2012

SAIC

Phenantrolinic chromium (III) complexes have been studied as possible photosensitizers to Photodynamic Therapy (PDT).  The photochemical and photophysical properties of these complexes, make them important compounds to be studied. It is speculated that the Cr(III) complexes have to be carried inside the cell to perform the effect. Our aim was to study the association of the Transferrin (Trf) with Cr(phen)33+ and its potential capability of transportation to the inner cell.    We also studied the toxicity of Cr(phen)33+ in its fundamental and excited state induced by LED irradiation at 472nm.  In order to assess the possible association Trf-Cr(phen)33+, we used Bhatthacharrya`s equation to measure the binding constant (Kb) between the complex and the Trf at different pHs, from 7.40 to 5.40.  We used circular dichroism (CD) to evaluate whether the complex induced changes in secondary and tertiary structure of HoloTrf.  By MTT assay, we studied changes in MDA-MB231 (breast carcinoma) cell viability induced by different concentrations of Cr(III) complex (with or w/o Trf).   The results show that the Kb Trf-Cr(phen)33+, is dependent on pH, being lower at more acidic pHs (5,40) compatible with endosomal compartments, suggesting that the complex could be released in the inner cell.  From CD experiments, we show that the protein in presence of the complex doesn’t suffer conformational changes, indicating that the TrfReceptor is able to recognize HoloTrf as well as HoloTrf-Cr(phen)33+. Cell Viability diminished significantly when the complex is associated to the Trf.  It also diminished from 0.942 to 0.797 (relative values) by 10µM of complex in irradiated cells, which first show that the excited state of the complex induced a higher degree of cytotoxicity than the fundamental state.    The results imply that Trf is a potential carrier of Cr (III) complexes for PDT.