Biomedical Engineering Reference
In-Depth Information
prevent the magnet from suddenly moving to the ferromagnetic compartments
of the microscope. The surroundings of the microfl uidic device and permanent
magnet (objective lens, stages, microscope frame) should not contain any ferro-
magnetic materials such as nickel, iron, cobalt, nor alloys of them, because these
can affect and reduce the magnetic fi eld around the microfl uidic channels. The
magnetic fi eld intensity can be modulated in a permanent magnet system, where
the distance between the permanent magnet and the device can be manipulated
by using a linear moving stage (M-460A-XYZ; Newport Corporation, CA, USA) to
modulate the magnetic fi eld intensity acting on the microfl uidic channel [19] .
3.3.3
Measurement and Analysis
Microscaled particles (e.g., polystyrene particles) and cells can be observed by the
CCD camera, and their movement traced by using either commercialized software
(e.g., i-Solution; IMT i-Solution Inc., Vancouver, Canada) or custom-made pro-
grams coded by Matlab® and C++. The positions of the fl uorescent particles can
be easily measured using fl uorescence microscopy, and analyzed with an image
analysis program. However, those particles which do not contain fl uorescent dyes
cannot be simply distinguished from the background images, and their positions
(
x
-
y
coordinates) are rarely detectable via any automatic acquisition mode of the
software. Several steps of image processing, followed by image capture, can be
used to improve image quality and assist in the automatic measurement of the
particle positions determined by the software. If the automatic image program for
the particle position measurement is not available due to the background noise of
the images, then each image containing the particles should be analyzed manually
using programs such as ImageJ (W. Rasband, ImageJ 1.29, freeware, http://rsb.
info.nih.gov/ij/) and i-Solution.
Nanoscale particles, such as CNTs and magnetic nanoparticles, are rarely detect-
able by using a conventional CCD camera, due to their inherent small size.
Consequently, a variety of alternative analytical procedures should be applied to
determine magnetophoretic separation, including energy - dispersive X - ray spec-
troscopy ( EDS ), scanning electron microscopy ( SEM ), transmission electron
microscopy (TEM), thermogravimetric analysis (TGA), superconducting quantum
interference devices (SQUID), and Raman spectroscopy [41]. Magnetophoretic
separation can be evaluated either by an
in situ
analysis in the microfl uidic channel,
using microscopic tools (CRAIC Technologies, Inc., www.microspectra.com, San
Dimas, CA, USA), or by analyzing samples collected from the microfl uidic devices,
using the above- described techniques.
3.4
Magnetophoretic Biosensing
Among biosensor applications, a variety of sensing principles, such as detecting
the magnetic properties of target materials and/or of the magnetic micro/
