Indium Phosphide : Cadmium Free Quantum Dots for Cancer Imaging and Therapy

Fluorescent semiconductor nanoparticles, or quantum dots (QDs), have attracted a lot of attention over the past decade due to their unique optical and chemical properties. Indium phosphide (InP) QDs have emerged as a replacement for the widely used cadmium based QDs but their cytotoxity has not been well examined. Several questions vis-a-vis the InP QDs need to be addressed. Are they less toxic than CdSe/ZnS or CdTe? Are they as photoluminescent? Could they be used for imaging and photdynamic therapy (PDT)? Spin-trap electron paramagnetic resonance (EPR) spectroscopy and sulforhodamine B (SRB) viability assay indicates very low cytotoxicity in all cell lines tested, with toxicity proportional to ROS generation. Confocal microscopy showed none specific uptake of InP/ZnS concentrated in the perinuclear region. These data indicate that InP QDs are a viable alternative to cadmium-containing particles for biological applications.