Water-soluble phthalocyanines selectively bind to albumin dimers: A green approach toward enhancing tumor-targeted photodynamic therapy

Targeted delivery of therapeutic agents is of particular interest in the field of cancer treatment. However, there is an urgent need for developing clinically promising targeting approaches that can be readily administered in a green manner. Methods: Five phthalocyanine derivatives bearing different anionic and cationic groups were designed and synthesized. Then, their binding affinity with albumin were studied using gel assays, optical spectra and computational simulation. Finally, in vitro and in vivo fluorescence imaging and photodynamic therapy (PDT) evaluations were carried out. Results: The two positively charged compounds could selectively bind to albumin dimer over albumin monomer, while the three negatively charged phthalocyanines could bind to both albumin monomer and dimer. Following systemic administration, the phthalocyanines show improved tumor accumulation via transport by natural albumin. PDT evaluations indicate that one of the positively charged compounds, ZnPcN₄, shows outstanding phototherapeutic efficacy against tumors in preclinical models. Conclusion: Our findings demonstrate that the use of water-soluble phthalocyanines as photosensitizers and in vivo albumin as a natural carrier may provide a green and efficient approach for tumor-targeted imaging and therapy.