Green and facile synthesis of highly biocompatible carbon nanospheres and their pH-responsive delivery of doxorubicin to cancer cells

Developing an efficient nanoparticulate drug-delivery system with a sub-100 nm diameter plays a crucial role in delivering antitumor drugs into cancer cells and improving their therapeutic efficacy. Carbon spheres, due to their large surface areas, unique surface properties and ease of functionalization, can generally deliver a large quantity of therapeutic agents to the target disease sites. In this study, spherical carbon nanoparticles with uniform size (71 nm) and regular shape were synthesized by hydrothermal reaction of bacterial cellulose nanofibers (30–50 nm), which had been achieved by a microorganism synthesis. Then using a simple acidification treatment, we could obtain carbon nanospheres with high drug loading capacity (the drug encapsulation efficiency was found to be about 93.4% and the drug loading efficiency (DL) reached about 52.3%). Meanwhile, the carbon nanospheres also exhibited good pH sensitivity in drug delivery. The results of in vitro experiments demonstrate that the carbon nanospheres prepared played an important part in the increase of the intracellular drug concentration and delayed-efficacy of the drug effect, which make them a promising platform for the delivery of other therapeutic agents beyond DOX.