Micellar stabilized single-walled carbon nanotubes for a pH-sensitive delivery of doxorubicin

Single-walled carbon nanotubes (SWNTs) are among the promising nano-devices for delivery of therapeutic agents. Yet the drastic hydrophobic natures of SWNTs make their handling and hence application difficult. Several researches have been conducted to make them more hydrophilic and water dispersible and less toxic. Among the different approaches, dispersion methods exploit different reagents such as surfactants and block copolymers. The question is whether these so called dispersed SWNTs are stable enough and suitable for biomedical applications. Herein we aimed to functionalize SWNT surface by dioleoylphosphatidylethanolamine-polyethylene glycol (PL-PEG) and sodium deoxycholate (SDC) micelles and compare their efficacy in SWNT stabilization for biomedical application such as delivery of doxorubicin. Shortening and water dispersion of SWNTs were carried out by ultrasonication in aqueous solutions at different concentrations of SDC or PL-PEG micelle and assessed by UV-Vis-NIR spectroscopy. The stability of SWNT dispersions were assessed over the time and in the presence of salt by macroscopic observation and UV-Vis-NIR spectroscopy. Doxorubicin loading and release were carried out under different pH conditions. SWNT dispersions were stable in water for at least several weeks at room temperature, but SDC prepared dispersions were prone to agglomeration in the presence of salt and doxorubicin. The critical PL-PEG concentration for stability in physiologic conditions was about 5 times its critical micelle concentration. Doxorubicin loading was pH dependent and its release was triggered in acidic condition of tumor medium.