Modification by transferrin increases the efficiency of delivery and the photodynamic effect of the quantum dot–phthalocyanine complex on A431 cells

Hybrid complexes of fluorescent nanoparticles and tetrapyrrole dyes are currently considered as promising third-generation photosensitizers for photodynamic therapy, including cancer treatment. Using nanoparticles as a platform for delivery of photosensitizers to target cells can increase the efficiency of photodynamic action. In this work, we synthesized a complex of polymer-coated CdSe/ZnS quantum dots, substituted phthalocyanines and human transferrin. Such complexes effectively enter human epidermoid carcinoma cells (A431) due to transferrin-mediated endocytosis and are localized in the perinuclear compartment. We observed an efficient excitation energy transfer from the quantum dot to phthalocyanine in the cells, which indicates stability of the complex upon its internalization. It was shown that the photodynamic activity of hybrid complexes covalently bonded to transferrin is 15% higher than the activity of unmodified hybrid complexes. Our results confirm the feasibility of using fluorescent nanoparticles to enhance the photodynamic properties of photosensitizers based on tetrapyrrole dyes.