Microtubule guiding in a multi-walled carbon nanotube circuit

Dielectrophoretic alignment of carbon nanotubes: theory, applications, and future

Carbon nanotubes (CNTs) are nominated to be the successor of several semiconductors and metals due to their unique physical and chemical properties. It has been concerning that the anisotropic and low controllability of CNTs impedes their adoption in commercial applications. Dielectrophoresis (DEP) is known as the electrokinetics motion of polarizable nanoparticles under the influence of nonuniform electric fields. The uniqueness of this phenomenon allows DEP to be employed as a novel method to align, assemble, separate, and manipulate CNTs suspended in liquid mediums. This article begins with a brief overview of CNT structure and production, with the emphasize on their electrical properties and response to electric fields. The DEP phenomenon as a CNT alignment method is demonstrated and graphically discussed, along with its theory, procedure, and parameters. We also discussed the side forces that arise in DEP systems and how they negatively or positively affect the CNT alignment. The article concludes with a brief review of CNT-based devices fabricated using DEP, as well as the method's limitations and future prospects.

Microtubule cytoskeleton-disrupting activity of MWCNTs: applications in cancer treatment

Microtubules and carbon nanotubes (CNTs), and more particularly multi-walled CNTs (MWCNTs), share many mechanical and morphological similarities that prompt their association into biosynthetic tubulin filaments both, in vitro and in vivo. Unlike CNTs, microtubules are highly dynamic protein polymers that, upon interaction with these nanomaterials, display enhanced stability that has critical consequences at the cellular level. Among others, CNTs prompt ectopic (acentrosomal) microtubule nucleation and the disassembly of the centrosome, causing a dramatic cytoskeletal reorganization. These changes in the microtubule pattern trigger the generation of ineffective biomechanical forces that result in migration defects, and ultimately in spindle-assembly checkpoint (SAC) blockage and apoptosis. In this review, we describe the molecular mechanism involved in the intrinsic interference of CNTs with the microtubule dynamics and illustrate the consequences of this effect on cell biomechanics. We also discuss the potential application of these synthetic microtubule-stabilizing agents as synergetic agents to boost the effect of classical chemotherapy that includes spindle poisons (i.e. paclitaxel) or DNA interfering agents (5-fluorouracil)-, and list some of the advantages of the use of MWCNTs as adjuvant agents in preventing cell resistance to chemotherapy.

Guiding neural extensions of PC12 cells on carbon nanotube tracks dielectrophoretically formed in poly(ethylene glycol) dimethacrylate

The PC12 cell line has been widely used as an in vitro model for studying neuronal differentiation and identifying the factors affecting the process. It has the ability to differentiate in the presence of nerve growth factor (NGF), resulting in neural extensions called dendrites and axons. In this study, first the impact of randomly distributed multi-walled carbon nanotubes (MWCNTs) in poly(ethylene glycol) dimethacrylate (PEGDMA) on PC12 cell differentiation was investigated in terms of neurite length, number of neurite per cell and differentiation marker gene expression profile. Then, dielectrophoretically aligned MWCNTs in PEGDMA was used to guide and support the neuronal differentiation of PC12 cells in the presence of NGF. The method is expected to be useful in revealing the nanotopographical role in fundamental studies and understanding of nanotopographical effects for biomedical applications on nerve regeneration.

A schematic illustration of the strategy used to create a microenvironment consisting of micropatterns and CNT tracks. The new microenvironment allowed roughly positioning of PC12 cells and guidance of neural extensions.

Different Microtubule Structures Assembled by Kinesin Motors

The microtubule-kinesin system is used to form microtubule-based structures via microtubule gliding motility. On the kinesin-coated surface, the microtubules can be easily assembled into stable micro- and nanostructures like circles and microtubule bundles using the streptavidin-biotin system. Furthermore, these microtubules structures can still retain performance with kinesin motor movement in spite of different velocities. Collisions bear responsibility for the majority of events leading to circle formation. By taking advantage of biological substances, some micro- or nanostructures, which are difficult to fabricate by artificial processes, can be easily obtained.