Ultrasmall pH-responsive silicon phthalocyanine micelle for selective photodynamic therapy against tumor

Targeted photodynamic therapy (TPDT) based on the photosensitizers responsive for tumor microenvironment is promising because of the better anti-tumor effect and less phototoxicity against normal tissue than the traditional PDT. Nanoparticle-based stimuli-responsive photosensitizers have been widely explored for TPDT. Based on the acidic microenvironments in solid tumors, an ultrasmall pH-responsive silicon phthalocyanine nanomicelle (PSN) (smaller than 10 nm) was designed for selective PDT of tumor. PSN had high drug loading efficacy (more than 28%) and exhibited morphological transitions, enhanced fluorescence and improved singlet oxygen yield under acidic environments. PSN was renal clearable and could rapidly accumulate and be retained at tumor sites, achieving a tumor-inhibiting effect better than phthalocyanine micelle without pH response. Tumors of mice treated with PSN for PDT were completely ablated without recurrence. Thus, we have developed a phthalocyanine-based pH-responsive micelle with excellent tumor targeting ability, which is expected to realize the selective PDT of tumor.