Cellular behavior of human mesenchymal stem cells cultured on single-walled carbon nanotube film Chor Yong Tay, Haigang Gu, Wen Shing Leong, Haiyang Yu, Hua Qiong Li, Boon Chen Heng, Hosea Tantang, Say Chye Joachim Loo, Lain Jong Li, Lay Poh Tan * Division of Materials Technology, School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore ARTICLE INFO Article history: Received 18 August 2009 Accepted 18 November 2009 Available online 24 November 2009 ABSTRACT The influences of carboxylic functionalized single-walled carbon nanotubes (SWCNTs) on cell adhesion, spreading and cell lineage commitment of human mesenchymal stem cells (hMSCs) were evaluated. hMSCs were cultured on a thin mesh like layer of SWCNTs with a vertical height of less than 100 nm. The influence of the SWCNT film was significant on the cell spreading and focal adhesion distribution. Cells spread better on a SWCNT film as com- pared to cover slip (control), resulting in larger cell area and have higher occurrence of fil- opodia (microspikes) at the cell boundaries. Cytoskeleton arrangement was observed to be less orientated in the cells cultured on a SWCNT film as compared to control. Neurogenic markers such as nestin, glial fibrillary acidic protein and microtubule associated protein 2 genes were transiently upregulated (a process where cellular components, in this case RNA, is increased in response to external variable) over the first week while genes indicative of osteogenesis remained at its nominal level. These results suggest that nano roughness alone is sufficient to modulate cellular behavior and early stage of stem cell lineage com- mitment without the aid of an induction medium. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Carbon nanotubes (CNTs), consisting of cylindrical graphene sheets of nanometer diameter, have been the focus of consid- erable research in various fields such as chemistry, physics, electronics and materials science due to their high electrical conductivity, high chemical stability, extremely high mechan- ical strength and modulus [1,2]. In recent years, scientists have begun using CNTs to formulate different carbon mor- phologies and exploring new applications of CNTs, such as field emitters, sensors, polymer composites and nanoscale electrode arrays [3–5]. Their unique electrical and optical properties make CNTs widely used in bio-electronic devices, bio-sensors and bio-probes. CNTs have also been used for the delivery of small molecules, DNA, proteins and vaccines [6–8] as well as tissue engineering for support of cell growth [9–11]. The biocompatibility and cytotoxicity of CNTs have been researched extensively. Mooney et al. [12] reported that CNT suspension has good biocompatibility with mesenchymal stem cells (MSCs) and supported proliferation as well as dif- ferentiation of MSCs in the presence of induction medium, while CNT substrates show good cell viability and adhesion [12–20]. However, contradictory results have also been reported. For instance, Zhu et al. [21] demonstrated that mul- ti-walled CNTs can induce DNA damage in mouse embryonic stem cells, while single-walled CNTs (SWCNTs) can induce accelerated oxidative stress, resulting in the formation of free radicals and accumulation of peroxidative products in human epidermal keratinocytes [22,23]. The results from Jia et al. [24] 0008-6223/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2009.11.031 * Corresponding author: Fax: +65 6790 9081. E-mail address: lptan@ntu.edu.sg (L.P. Tan). CARBON 48 (2010) 1095 – 1104 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/carbon