pH-Dependent Cancer-Directed Photodynamic Therapy by a Water-Soluble Graphitic-Phase Carbon Nitride-Porphyrin Nanoprobe.

Theranostic photodynamic nanomaterials suffer from poor water solubility and nontargeted toxicity. A water-soluble graphitic-phase carbon nitride-based material (g-C3 N4 ) conjugated to a positively charged porphyrin P2 (conjugating concentration: 60 μm mg-1  mL-1 ) is shown to be a new concept of photodynamic therapeutic agent (g-C3 N4 -P2). The pH-sensitive emission of g-C3 N4 is the driving force for the generation of 1 O2 from g-C3 N4 -P2. The amount of 1 O2 /light generated from a photosensitizer porphyrin can be controlled by the pH-sensitive emission of g-C3 N4 at acidic pH (pH 4-6), especially under acidic conditions mimicking those of tumor tissue, and thus has the potential to be utilized as a cancer-selective PDT agent.