Graphitic
carbon nitride (also known as g-CN or g-C3N4) has the intrinsic ability to generate electron–hole
pairs under visible light illumination, resulting in the generation
of reactive oxygen species (ROS). We report g-CN quantum dots (g-CNQDs)
as a standalone photodynamic transducer for imparting significant
oxidative stress in glioma cells, manifested by the loss of mitochondrial
membrane potential. With an optimized treatment time, visible light
source, and exposure window, the photodynamic treatment with g-CNQDs
could achieve ∼90% cancer cell death via apoptosis. The g-CNQDs,
otherwise biocompatible with normal cells up to 5 mg/mL, showed ∼20%
necrotic cancer cell death in the absence of light due to membrane
damage induced by a charge shielding effect at the acidic pH prevailing
in the tumor environment. Acute toxicity analysis in C57BL/6 mice
with intravenously injected g-CNQDs at a 20 mg/kg dose showed no signs
of inflammatory response or organ damage.