Fullerene as a transporter for doxorubicin investigated by analytical methods and in vivo imaging

Carbon nanomaterials, including fullerenes, exhibit not only unique structure and electronic properties but also a significant potential to serve as radical scavengers and/or anti-oxidants. Their conjugation with anticancer drugs such as doxorubicin (DOX) may help to balance severe negative side effects of these cytostatics and also improve the delivery of the drug taking advantage of the enhanced cellular uptake, selectivity to cancer cells, and pH regulated release. In this study, the fullerene (C60) surface was oxidized by concentrated nitric acid, which enabled simple DOX-fullerene conjugation based on π-π stacking and hydrophilic interactions with carboxylic groups. The strength of this noncovalent binding is pH dependent. At a low pH, the amino group of DOX is protonated, however at a higher pH, the amino group is deprotonated, resulting in stronger hydrophobic interactions with the fullerene walls. CE and HPLC were employed for characterization of resulting complexes. The cell toxicity of the conjugates was evaluated using Staphylococcus aureus and finally they were administered into the chicken embryo to assess the applicability for in vivo imaging.