Carbon Nanotubes as Intracellular Carriers for Multidrug Resistant Cells Studied by Capillary ElectrophoresisLaserInduced Fluorescence

Fluorescently labeled carbon nanotube probes (CNTP) are prepared by derivatizing oxidized (o )-MWNTs with a fluorescein dye. Capillary electrophoresis coupled with laser-induced fluorescence (CE-LIF) detection is used to separate and detect CNTP in multidrug-resistant cells (K562A) and the parent cells (K562S). CE-LIF and flow cytometry investigation reveal that the CNTP can traverse the membranes in both cell lines without being pumped out by P-glycoprotein. The CE-LIF method is also useful for quantitative analysis of CNT in single cells, enabling drug delivery and multidrug resistance (MDR) studies. Moreover, toward quantifying the intracellular uptake of oxidized (o )-SWNTs with anchored Rhodamine123 (Rho123), fluorescence-quenching of Rho123 is measured by micellar electrokinetic chromatography coupled with LIF detection. Enhanced uptake of Rho123 in multidrug-resistant leukemia cells can be achieved with the aid of the o -SWNTs carriers. Besides being able to overcome MDR, o -SWNTs are shown to be excellent intracellular carriers possessing large adsorption capacity and prolonged release ability. Finally, it is demonstrated that o -SWNTs are safe for biological applications at concentrations of up to 40 �g/mL.