Photosensitizing action of isomeric zinc N-methylpyridylporphyrins in human carcinoma cells

Abstract

The success of photodynamic therapy (PDT), as a minimally invasive approach, in treating both neoplastic and non-neoplastic diseases has stimulated the search for new compounds with potential application in PDT. We have previously reported that Zn(II) N-alkylpyridylporphyrins (ZnTM-2(3,4)-PyP⁴⁺ and ZnTE-2-PyP⁴⁺) can act as photosensitizers and kill antibiotic-resistant bacteria. This study investigated the photosensitizing effects of the isomers of ZnTMPyP⁴⁺ (ZnTM-2(3,4)-PyP⁴⁺) and respective ligands on a human colon adenocarcinoma cell line. At 10 μM and 30 min of illumination the isomeric porphyrins completely inhibited cell growth, and at 20 μM killed approximately 50% of the cancer cells. All these effects were entirely light-dependent. The isomers of the ZnTMPyP⁴⁺ and the respective ligands show high photosensitizing efficiency and no toxicity in the dark. Their efficacy as photosensitizers is comparable to that of hematoporphyrin derivative (HpD).

• Photosensitizers
• cancer
• photodynamic therapy
• isomeric zinc methylpyridylporphyrins
• isomeric N-methylpyridylporphyrins

Abbreviations
ZnTM-2-PyP4+	=	ortho-isomer, Zn(II) tetrakis(N-methylpyridinium-2-yl)
ZnTM-3-PyP4+	=	meta-isomer, Zn(II) tetrakis(N-methylpyridinium-3-yl)porphyrin
ZnTM-4-PyP4+	=	para-isomer, Zn(II) tetrakis(N-methylpyridinium-4-yl)
H2TM-2(3,4)-PyP4+	=	ortho(2)-, meta(3)- and para(4)-isomers of metal free ligands
PDT	=	photodynamic therapy
HpD	=	hematoporphyrin derivative
ANOVA	=	analysis of variance

Abbreviations
ZnTM-2-PyP4+	=	ortho-isomer, Zn(II) tetrakis(N-methylpyridinium-2-yl)
ZnTM-3-PyP4+	=	meta-isomer, Zn(II) tetrakis(N-methylpyridinium-3-yl)porphyrin
ZnTM-4-PyP4+	=	para-isomer, Zn(II) tetrakis(N-methylpyridinium-4-yl)
H2TM-2(3,4)-PyP4+	=	ortho(2)-, meta(3)- and para(4)-isomers of metal free ligands
PDT	=	photodynamic therapy
HpD	=	hematoporphyrin derivative
ANOVA	=	analysis of variance