Chemical Modifications of Porous Carbon Nanospheres Obtained from Ubiquitous Precursors for Targeted Drug Delivery and Live Cell Imaging

Cost-effective anti-cancer drug delivery vehicles that can ensure controlled and targeted transportation of drug molecules are pertinent to modern day biomedical applications. Minimally toxic 9-13 nm diameter porous carbon nanospheres (PNs) were synthesized by oxidative cutting of porous carbon matrices (PCs) obtained by carbonization of pasture grass, human hair and sucrose. Among them, the grass derived PNs (PN-G) with superior surface area, porosity and graphitic content demonstrate a significant loading of the drug both by chemical binding and physisorption. Polyethylenimine (PEI) and folic acid (FA) functionalization maintain therapeutic efficacy of the drug doxorubicin (DOX) to the targeted folate receptor (FR) overexpressed human cervical cancer cells (HeLa) and human breast cancer cells (MDA-MB-231) through receptor mediated endocytosis whereas FR deficient normal cells (human embryonic kidney 293) exhibit substantially lower endocytosis under identical conditions. Moreover, upon loading cell-impermeable propidium iodide (PI), the PNs display superior activity toward near-infrared (NIR) live cell imaging in HeLa cells whereby due to a higher binding affinity of PI with the nucleic acids, the PI-to-PN energy transfer quenched fluorescence is recovered. This dual functionality of controlled and targeted drug delivery and photobleaching resistant live cell imaging by the cost-effective PNs has larger implications in nanomedicine research and technology. Porous carbon nanospheres derived from abundant resources act as highly efficient and cost-effective nanocarriers for targeted anticancer drug delivery and live cell imaging.