Indocyanine green-loaded N-doped carbon quantum dot nanoparticles for effective photodynamic therapy and cell imaging of melanoma cancer: in vitro, ex vivo and in vivo study.

Background: Indocyanine Green (ICG) as an agent for photodynamic therapy (PDT) of melanoma cancer has low quantum yield, short circulation half-life, poor photo-stability, and tendency to aggregation.

Purpose: N-doped carbon quantum dot (CQD) nanoparticle was applied to encapsulate ICG and overcome ICG obstacle in PDT with simultaneous cell imaging property.

Methods: CQD was prepared using hydrothermal method. Cell culture study and In vivo assessments on C57BL/6 mice containing melanoma cancer cells was performed.

Results: Results showed that CQD size slightly enhanced from 24.55 nm to 42.67 nm after ICG loading. Detection of reactive oxygen species (ROS) demonstrated that CQD improved ICG photo-stability and ROS generation capacity upon laser irradiation. Cell culture study illustrated that ICG@CQD could decrease survival rate of melanoma cancer cells of B16F10 cell line from 48% for pure ICG to 28% for ICG@CQD. Confocal microscopy images approved more cellular uptake and more qualified cell imaging ability of ICG@CQD. In vivo assessments displayed obvious inhibitory effect of tumor growth for ICG@CQD in comparison to free ICG on the C57BL/6 mice. In vivo fluorescence images confirmed that ICG@CQD accumulates remarkably more than free ICG in tumor region. Finally, ICG@CQD was proposed as an innovative nanocarrier for PDT and diagnosis.