Biomaterials for MEMS

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 flow, 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