Bio-Degradation Studies of Fluorescent Defects in Carbon Nanotube Hosts

Carbon nanotubes (CNTs) have been enormously used in various fields because of their unique mechanical, optical and electronic properties. The rapid developments of the CNT applications have raised concerns of their impacts on the environment and human health, urging the investigations of CNT degradation. Among different types of CNTs, single-wall carbon nanotubes (SWCNTs) emit at the short-wave infrared (SWIR) that pertains low tissue scattering and low autofluorescence, making them ideal candidates for in vivo imaging applications such as disease targeting and real-time cell trackings. The clinical use of fluorescent SWCNTs carries the ‘post-diagnosis’ issues including long-term retention and chronic toxicity, to the patients. For example, long-term accumulation of SWCNTs in certain tissues, such as the liver and lungs, may lead to the development of inflammation-related diseases, including fibrosis. We believe that the prompt solution to these issues would be the development of bio-degradable fluorescent SWCNTs. Here, we report faster degradations of fluorescent defect-containing SWCNTs in biological systems. Fluorescent defects in SWCNTs are known to increase the particle emission brightness and move their excitation and emission peaks to longer wavelengths. We performed comprehensive studies of how various defect conditions, ROS species and cell types affect the degradation efficiency. Our results indicate that the hollow-core, single-atomic layer nature of the SWCNTs combined with degradable fluorescent defects could be better SWIR fluorophores for clinical uses compared to solid-core inorganic fluorophores and organic nanodots.