Adsorption and desorption of doxorubicin on oxidized carbon nanotubes

Carbon nanotubes (CNTs) show promise as nano-drug carriers. To develop the CNT-based drug delivery systems, drug loading and release are two major issues. In this study, we systematically evaluated the adsorption and desorption of doxorubicin (DOX) on oxidized multi-walled CNTs (O-MWCNTs). Our results indicated that O-MWCNTs possessed a huge adsorption capacity for DOX (9.45 × 103 mg/g). Although the adsorption process was quite slow, the adsorption capacity kept high enough for the therapy while shortening the incubation time to 2 h (1.03 × 103 mg/g). The desorption of DOX from O-MWCNTs scarcely occurred while incubated in buffer solution at both pH 7.4 and pH 5.5, however, the lower pH did benefit the desorption. The presence of serum proteins facilitated the desorption of DOX significantly, because these proteins bound strongly to O-MWCNTs resulting in the partial surface of O-MWNCTs being occupied. Moreover, the adsorption time also affected the release of DOX from O-MWCNTs. Shortening the incubation time benefited the release of DOX. The implications to the drug loading and therapeutics of the CNT-based drug delivery systems are discussed.