PEG Encapsulation of Porphyrins for Cell Imaging and Photodynamic Therapy

Polyethylene glycol (PEG) encapsulation of porphyrin was designed and synthesized by introducing branched PEG substituents to the porphyrin core. Fluorescence imaging of cells was conducted to investigate the cellular uptake of these PEPPs. Results suggest that the porphyrin compound with 16 triethylene glycol chains exhibits increased cellular uptake and/or efficiency for emitting fluorescence inside the cells. The singlet oxygen yield of the porphyrin compound with 16 triethylene glycol chains is determined to be 0.93. This high singlet oxygen yield may be attributed to the large number of polyethylene glycol chains that hinder aggregation and excited-state quenching. PEPPs exhibit potential as a new class of photosensitizers for photodynamic therapy because of their water solubility, good biocompatibility, and high singlet oxygen yield. Keywords: Porphyrins, photosensitizers, singlet oxygen yields, fluorescence imaging.