(209c) Toxicity of Non-Cd-Based Fluorescent Nanoparticles for Biomedical Imaging

Fluorescent nanoparticles have a unique potential for biomedical imaging because of their small size and unique fluorescent properties, including resistance to photobleaching, narrow emission bandwidth, and broad excitation spectra. However, the current gold standard nanoparticles for biomedical imaging, quantum dots, contain cadmium, a carcinogen and neurotoxin, which is released upon photooxidation yielding epigenetic changes, apoptosis, and cell death. Toxicity has severely hindered the application of quantum dots in the clinic, even in a diagnostic capacity. Here, we examined toxicity behaviors of two alternative fluorescent nanoparticles: carbon dots and Mn-doped ZnSe quantum dots, comparing them to commercial quantum dots. Carbon dots were examined as bare, water soluble nanoparticles and in poly(lactide-co-glycolide) (PLGA) polymer nanocomposites, whereas Mn-doped ZnSe quantum dots were investigated with an organic surface coating, a water-soluble surface coating, and a polymer micelle surface coating. Four tests were used to assess cell health and possible pathways of cell death in human liver cells: an MTT assay for viability, a TUNEL assay for apoptosis, LIVE/DEAD screening for necrosis, and a test for production of reactive oxygen species (ROS). In addition, we examined particle sensitivity to photooxidation, a suspected cause of ion release and resulting toxicity. It was determined that carbon dots exhibit ~2-20X less toxicity than commercial quantum dots, and that coatings greatly enhance particle resistance to photooxidation.