The synthesis and characterization of biotinylated chlorin photosensitizer and the corresponding zinc and indium complexes are described for potential applications in photodynamic therapy (PDT) for cancer. Phototoxicity of the biotin-chlorin conjugate and the metallated complexes was determined in colon carcinoma CT26 cell lines known to overexpress biotin (Vit B7) receptors. Cell survival assay indicated that the biotinylated chlorin and indium complex showed increased cell growth inhibition than the zinc complex and the starting chlorin (methyl pheophorbide). Fluorescence microcopy studies revealed the generation of apoptotic cells upon light irradiation of colon cells treated with the indium complex. Targeting biotin receptors in cancer cells can improve specificity of photosensitizers for PDT applications.
Phototoxicity response of synthesized vitamin–chlorin
conjugates
and their zinc and indium complexes was determined in the human PC-3
prostate cancer cell line, which was previously demonstrated to overexpress
vitamin receptors on the cell surface. Pantothenic acid (Vit B5) and
lipoic acid (or thioctic acid) were covalently linked to methyl pheophorbide
(a chlorophyll derivative) and subsequently metallated with zinc and
indium. Cell survival assay indicated that the vitamin–chlorin
conjugates have better photodynamic activity against the PC-3 prostate
cancer line at the nanomolar concentration range than the commercially
available starting precursor methyl pheophorbide. Fluorescence and
transmission electron microscopy studies indicated some formation
of apoptotic cells and cytoplasmic vacuoles of photosensitized prostatic
cells. Targeting vitamin receptors in prostatic cancer cells can be
utilized to enhance specificity of photosensitizers for photodynamic
therapy applications.
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