Tissue Microengineering - Introduction to BioMEMS - page 380

UV light
Photomask
Prepolymer solution
Hydrogel unit
Glass slide
Mineral oil

b

Phase-contrast Fluorescence

Pipette tip

d

Petri dish

FITC-
dextran

UV light

a

Hydrogel
units

Mineral oil

Prepolymer solution

Nile red

Photomask

Glass slide

e

Hydrogel
unit

Prepolymer solution

Random Branched

c

Secondary
photocross-
linking

Red cells

f g

Linear Offset

Hydrogel
aggregate

Green
cells

200 µm

200 µm

FIGURE 7.6 Fabrication.of.cell-laden.microgels..(From.Yanan.Du,.Edward.Lo,.Shamsher.Ali,.and.
Ali.Khademhosseini,.“Directed.assembly.of.cell-laden.microgels.for.fabrication.of.3D.tissue.con-
structs,”. Proc. Natl. Acad. Sci. U. S. A. ,. 105,. 9522-9527,. 2008.. Copyright. (2008). National.
Academy.of.Sciences,.U..S..A.)

7.1.2 Skin Microengineering
On a cellular level, the skin is not lat—it contains deep invaginations (termed rete ridges )
that play a crucial role in maintaining the skin's mechanical integrity and lexibility. In 2000,
a group led by Jef Morgan, then at the Shriners Burns Hospital in Boston, fabricated micro-
molded collagen analogs of the basal lamina ( Figure 7.7a and b ) to test the levels of diferentia-
tion of keratinocytes compared with keratinocytes cultured on lat collagen layers. heir results
showed diferentiation and stratiication of the keratinocytes cultured in deep ridges ( Figure
7.7c ), suggesting that the ridges provide a diferentiation cue for keratinocytes in the normal
process of skin growth. Because, until now, implanted artiicial skin has not contained rete

a

500 µm

Collagen/GAG dermal analog

b c

50 µm 100 µm

FIGURE 7.7 Microfabricated. rete. ridges.. (From. George. D.. Pins,. Mehmet. Toner,. and. Jeffrey. R..
Morgan,.“Microfabrication.of.an.analog.of.the.basal.lamina:.Biocompatible.membranes.with.com-
plex.topographies,”. FASEB J. ,.14,.593-602,.2000..Figure.contributed.by.Mehmet.Toner.)