92 M. C. W. Chen and K. C. Cheung
Figure 5.2. Comparison of natural cell and tissue morphology cultured on 2-D and 3-D
substrates.
14
spatial variability can interfere in signaling between cells.
17
The small dimensions
of microfluidic devices offer short diffusion lengths and better control of the
microenvironment.
Second, by providing a three-dimensional scaffold for cell organization,
hydrogels offer attachment points and mechanical support to cells seeded inside.
Atthesametime,theporousgelmatrixallows the delivery of nutrients and
removal of waste products from the cells through diffusion.
Miniaturizing to the microscale offers advantages in scaling.
18,19
For example,
the low Reynolds numbers imply laminar ow, where diffusive effects dominate.
Enzyme analysis, immunoassays, and DNA analysis or PCR can be conducted in
much smaller timescales compared to macroscale systems. Microfluidic systems
which integrate cell culture and characterization will contribute to improved cul-
ture conditions which will more closely resemble the physiological environment,
and by permitting tracking of small cell numbers or individual cells, advance work
in areas such as stem cell research or drug discovery.
5.2 HYDROGELS
A variety of three-dimensional cell culture matrices, or scaffolds, have been
developed for tissue engineering applications. Tissue engineering uses living
cells to restore or maintain the function of tissue and organs, and involves cell
biology, materials science, and medicine.
20
Scaffolds have been used as implant
materials as well as in vitro cell culture materials.
14
Implantable materials should
be biodegradable and should match the properties of the surrounding tissue,
whether it be bone or skin. Cell culture scaffolds should approximate the ECM
as closely as possible.
SO13997_text.indd 100SO13997_text.indd 100 26/01/2011 3:50 PM26/01/2011 3:50 PM

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