Acidic Tumor pH-Responsive Nanophotomedicine for Targeted Photodynamic Cancer Therapy

An acidic tumor pH-responsive nanophotomedicine (pH-NanoPM) for targeted photodynamic therapy (PDT) was demonstrated herein. The pH-NanoPM was prepared with a size of 110 nm by self-assembly of a pH-responsive polymeric photosensitizer (pH-PPS) consisting of pH-cleavable methoxypolyethylene glycol (pH-C-mPEG). Because the pH-C-mPEG can be detached from the nanoparticles by hydrolysis of the benzoic-imine group at the pH of an acidic tumor (6.5), the particle size and surface charge of the pH-NanoPM were changed along with the environmental pH condition. After detachment of the pH-C-mPEG, the pH-NanoPM particles became positively charged (+ 18.67 ± 1.95 mV) due to exposure of primary amine groups and decreased to a size of 40 nm. From in vitro cellular experiments with HeLa human cervical cancer cells, the pH-NanoPM exhibited enhanced cellular internalization at acidic tumor pH compared to normal pH, which led to a significant cancer cell killing effect. These results suggest that this system has the potential to be used as a new class of nanophotomedicine for targeted photodynamic cancer therapy.