Carbon nanotubes (CNTs) were reported to cause severe toxicity in in vivo and in vitro studies. On the other hand, CNTs has the potential as a mechanism for drug delivery across the blood brain barrier due to its nano-sized dimensions. The present preliminary study examined the cytotoxic effect of CNTs in serum-free and serum-containing EMEM medium on neuroblastoma cells growth. The MTS assay showed that CNTs did not cause any cytotoxicity at concentrations below 0.1 mg/mL at 24 and 48 h incubation in serum-containing EMEM medium. This finding suggested that below 0.1 mg/mL, CNTs can be used as a mechanism for drug delivery for the treatment of neuronal cancer. However, CNTs showed slighty toxic towards neuroblastoma cells at concentration 0.1 mg/ml at 48h incubation in serum-free EMEM medium. This finding indicates that the present of serum play a role for toxicity effect of CNTs in cells.

Single-walled carbon nanotubes (SWCNT) were synthesized by using a simple evaporating method and a double furnace system. Ethanol was chosen as a carbon precursor because it has an evaporating temperature of 78 °C and was reported to produce a high purity of CNTs. Evaporated ethanol can be used as a precursor for carbon nanotubes (CNTs) synthesis. Ethanol was evaporated at 80 °C and channeled directly into a double furnace system. Furnace 1 was maintained at 180 °C and furnace 2 was set at 700 °C, 800 °C and 900 °C. The CNTs were then characterized by thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and Raman spectroscopy. Helical CNTs were observed at 700°C, webs of hollow tubes at 800 °C, and long tube structures at 900 °C based on FESEM. The diameter of CNTs that were synthesized ranged between 54 - 200 nm. Raman spectrum revealed that the G-band was 1590 cm-1 and the D-band was about 1350 cm-1. SWCNT was determined by RBM (radial breathing mode) to be between 200 - 300 raman shifts (cm-1). The modified CVD (chemical vapor deposition) system set up in the present study is successfully used for large scale synthesis of CNTs from an aqueous precursor such as ethanol.

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Carbon nanotubes (CNTs) are widely used in fields as diverse as engineering, physics and medicine. CNTs unique physical properties and strength play a major part in such a wide application. However, there have been concerns on the deleterious effects of CNTs as a delivery tool for therapeutic proteins, peptides and genes in biomedicine. CNTs disturb normal neuronal function, and accumulate and cause brain damage. Unfunctionalized CNTs were reported to cause toxicity in cells rather than functionalized CNTs. Thus, effects of CNTs on cells should be rigorously tested. In the present study, unfunctionalized multiwall CNTs were introduced to human neuroblastoma (SH-SY5Y) cells to investigate the toxicity effect. The neurotoxicity test showed that cell viability was above 80 % for CNT at 100 pg/ ml 1 mg/ ml. The neuroprotective test revealed that viability of cells was less than 40 % and 50 % at 1 μg/ ml - 1 mg/ ml and 1 pg/ml - 100 ng/ ml concentration range, respectively. The number of viable cells was decreased, with increase in the concentration of CNT using a reactive oxygen species (ROS) test. These findings provide useful information in elucidating the inhibitory effect of CNTs as a tool of drug delivery.

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