Biomedical Engineering Reference
In-Depth Information
Fig. 12
AFM image of a fractured bone surface showing fi laments (
arrows
) between neighboring
fi brils (
left
). By attaching a piece of bone to the cantilever and pressing it onto another piece of
bone (
center
), forces exerted by fi laments while pulling up can be measured. Representative pull-
ing curve, where not all fi laments are broken (
top right
) and where all fi laments are broken (
bottom
right
). For details, see Fantner et al. (
2005
)
studied, showing that energy dissipation during fi bril separation is greater when
calcium ions are present. This indicates the presence of calcium-mediated sacrifi cial
bonds (Thompson et al.
2001
) in the bone between two binding regions on one
polymer, two polymers, or a polymer and a mineral plate.
6
Nanodevices for Biological Applications
6.1
Parallel Arrays Patch Clamping and Sensors
Patch clamp recording is one of the main techniques employed in electrophysiologi-
cal studies. Generally, a precisely pulled glass pipette is brought in the vicinity of a
cell of interest under an optical microscope using a micromanipulator (Sakmann
and Neher
1983
). This results in the technique being slow and having a low through-
put, making it not very suitable for use in, for instance, proteomics and drug discov-
ery development. This could be overcome using an automated on-chip patch clamp
(Xu et al.
2001
) .
An example of such an on-chip microchannel planar patch clamp device is shown
in Fig.
13
. The middle panels show a HeLa cell being introduced in the microfl uidic
system and being trapped at one of the channels. Cell deformation can be observed,
and current traces show a seal resistance of 144 MOhm (Seo et al.
2004
) . Such
devices using a cell reservoir linked to patch channels allow for simultaneous opti-
cal and electrical recording which facilitates studying the role of ion channels with
respect to cellular functions. Future devices can be designed with an improved patch
pore geometry and surface treatment to obtain a better seal necessary for single-
channel conductance studies. Since the cell reservoir is linked to many patch clamp
pores, a parallel readout is possible analyzing multiple cells simultaneously.
