Patterned carbon nanotubes as a new three-dimensional scaffold for mesenchymal stem cells.

We investigated the cellular adhesive features of mesenchymal stem cells (MSC) on non-coated and collagen coated patterned and vertically aligned carbon nanotube (CNT) structures mimicking the natural extra cellular matrix (ECM). Patterning was achieved using the elasto-capillary induced by water treatment on the CNT arrays. After confirmation with specific markers both at transcript and protein levels, MSCs from different passages were seeded on either collagen coated or non-coated patterned CNTs. Adhesion and growth of MSCs on the patterned CNT arrays were examined using scanning electron microscopy image analysis and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-tetrazolium bromide (MTT) assays. The highest MSC count was observed on the non-coated patterned CNTs at passage zero, while decreasing numbers of MSCs were found at the later passages. Similarly, MTT assay results also revealed a decrease in the viability of the MSCs for the later passages. Overall, the cell count and viability experiments indicated that MSCs were able to better attach to non-coated patterned CNTs compared to those coated with collagen. Therefore, the patterned CNT surfaces can be potentially used as a scaffold mimicking the ECM environment for MSC growth which presents an alternative approach to MSC-based transplantation therapy applications.

Simultaneous growth of self-patterned carbon nanotube forests with dual height scales.

In this study, we report on a unique, one-step fabrication technique enabling the simultaneous synthesis of vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with dual height scales through alcohol catalyzed chemical vapor deposition (ACCVD). Regions of VA-MWCNTs with different heights were well separated from each other leading to a self-patterning on the surface. We devised a unique layer-by-layer process for application of catalyst and inhibitor precursors on oxidized Si (100) surfaces before the ACCVD step to achieve a hierarchical arrangement. Patterning could be controlled by adjusting the molarity and application sequence of precursors. Contact angle measurements on these self-patterned surfaces indicated that manipulation of these hierarchical arrays resulted in a wide range of hydrophobic behavior changing from that of a sticky rose petal to a lotus leaf.