Polypeptide-based artificial erythrocytes conjugated with near infrared photosensitizers for imaging-guided photodynamic therapy

Photodynamic therapy (PDT) combining with near infrared (NIR) imaging is attractive. However, the intrinsic hypoxia in tumor and consumption of oxygen during treatment will decrease PDT. Here an artificial red cell was prepared using polypeptides conjugated hemoglobin as an oxygen carrier. A NIR photosensitizer-brominated 4,4-difluoro-4-bora-3a,a-diaza-s-indacene (BODIPY-Br₂) possessing both high fluorescence emission and singlet oxygen generation efficiency was synthesized and also conjugated to polypeptides to achieve NIR imaging-guided PDT. In vitro studies performed on HepG2 cancer cells verified the oxygen carrier, cancer tracing and curing abilities of the as-prepared polymeric nanoparticles. Even under hypoxia condition, it also obviously increases the cell killing rate when exposed light at a low energy (25 mW/cm², 10 min). Meanwhile, the fluorescence of BODIPY in NPs would light up cells for real-time imaging. These results show the potential of the biocompatible and biodegradable P-Hb-B NPs for enhancement of simultaneous tracing and treating of cancer.