Structural and functional imaging with carbon nanotube AFM probes

Abstract

Atomic force microscopy (AFM) has great potential as a tool for structural biology, a field in which there is increasing demand to characterize larger and more complex biomolecular systems. However, the poorly characterized silicon and silicon nitride probe tips currently employed in AFM limit its biological applications. Carbon nanotubes represent ideal AFM tip materials due to their small diameter, high aspect ratio, large Young's modulus, mechanical robustness, well-defined structure, and unique chemical properties. Nanotube probes were first fabricated by manual assembly, but more recent methods based on chemical vapor deposition provide higher resolution probes and are geared towards mass production, including recent developments that enable quantitative preparation of individual single-walled carbon nanotube tips [J. Phys. Chem. B 105 (2001) 743]. The high-resolution imaging capabilities of these nanotube AFM probes have been demonstrated on gold nanoparticles and well-characterized biomolecules such as IgG and GroES. Using the nanotube probes, new biological structures have been investigated in the areas of amyloid-beta protein aggregation and chromatin remodeling, and new biotechnologies have been developed such as AFM-based haplotyping. In addition to measuring topography, chemically functionalized AFM probes can measure the spatial arrangement of chemical functional groups in a sample. However, standard silicon and silicon nitride tips, once functionalized, do not yield sufficient resolution to allow combined structural and functional imaging of biomolecules. The unique end-group chemistry of carbon nanotubes, which can be arbitrarily modified by established chemical methods, has been exploited for chemical force microscopy, allowing single-molecule measurements with well-defined functionalized tips.

Chemical force microscopy: probing chemical origin of interfacial forces and adhesion

“…CFM was further advanced in the Lieber laboratory by using carbon NTs as AFM probes [27] and a review of this work is available [31]. The small size of the Shortened NT, as is NT + 5 mM benzylamine NT + 5 mM ethylenediamine in pH 6 buffer containing 50 mM carbodiimide, 2h Shortened NT as is Shortened NT as is [27,28,31] probe and the capability of chemical functionalization make nanotube tips ideal for trying to achieve the ultimate lateral resolution in CFM; however, the commercial availability and massproduction of such probes remain a problem.…”

Carbon Nanotube-Based Nanomechanical Sensor: Theoretical Analysis of Mechanical and Vibrational Properties

“…However, the poorly characterized silicon and nitride probe tips currently employed in AFM limit some applications since conventional silicon tips can easily break during an impact on the scanned surface. CNTs are potentially ideal materials for AFM probe application due to their robust mechanical properties and well-defined geometry such as a small diameter and high aspect ratio [47][48][49]. There were some reports on the use of CNT probes tip increase the sensitivity and the resolution in the AFM.…”

Advances of Nanotechnology in the Stem Cells Research and Development

“…Carbon nanotubes can be functionalized to achieve improved properties and functions such as biocompatibility and biomolecular recognition capabilities [86][87]. Protein-conjugated carbon nanotubes can across the cellular membrane and enter into cytoplasm and cell nucleus [88][89].…”