Synthesis and Photodynamic Activity of Vitamin–Chlorin Conjugates at Nanomolar Concentrations against Prostate Cancer Cells

[Image: see text] 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.