Biocompatible Aza-BODIPY-Biotin Conjugates for Photodynamic Therapy of Cancer

With an objective to develop efficient photosensitizers to cancerous tissues, we synthesized two novel biocompatible sensitizers based on aza-BODIPYs incorporated with heavy atoms and biotin moieties. The bioconjugates DPR2a and DPR2b exhibited a favorable absorption range (600-750 nm) with excellent triplet-state quantum yields (up to 79%) and singlet oxygen generation yields (up to 75%). In vitro photobiological investigations employing MDA-MB-231 breast cancer cell lines exhibited rapid cellular uptake, negligible dark toxicity, and high photocytotoxicity. The mechanism of cell death of these systems was predominantly due to the mitochondrial damage, leading to apoptosis mediated via the generation of singlet oxygen-triggered reactive oxygen species. The in vivo studies with the representative conjugate DPR2a employing female NOD/SCID mice models showed inhibition in tumor growth and significantly decreased tumor volume post photodynamic therapy (PDT) treatment. Our results validate that both DPR2a and DPR2b with iodine incorporation exhibit favorable and superior photophysical and photobiological aspects and demonstrate thereby their potential applications in imaging and PDT of cancer.