Biomedical Engineering Reference
In-Depth Information
a
b
PLA-PEG-biotin
surface with biotin
presented on flexible
PEG chains
PC12
cells
Incubation in aq. solution
of avidin
IKVAV
= Avidin
40 µm
Wash away excess avidin
and incubate with
biotinylated ligand
c
Endothelial
cells
RGD
= Bioltinylated
ligand
200 µm
FIGURE 2.45
Microluidic.patterning.of.cell-adhesion.peptides.on.PEG.backgrounds..(From.Nikin.
Patel,.Robert.Padera,.Giles.H..W..Sanders,.Scott.M..Cannizzaro,.Martyn.C..Davies,.Robert.Langer,.
Clive.J..Roberts,.Saul.J..B..Tendler,.Philip.M..Williams,.and.Kevin.M..Shakesheff,.“Spatially.con-
trolled. cell. engineering. on. biodegradable. polymer. surfaces,”.
FASEB J.
12,. 1447,. 1998.. Figure.
contributed.by.Kevin.Shakesheff.)
polylactide-poly(ethylene glycol)-biotin repels cell adhesion and is biodegradable. A ilm of the
biotin-conjugated copolymer was droplet-cast and dried onto polystyrene. PDMS microchannels
were sealed against the coated surface and an avidin solution was allowed to ill the microchan-
nels by capillary action; avidin binding to the copolymer-biotin groups thus generated an avidin
pattern onto the copolymer background. Subsequently, the channels were lushed and removed.
When the avidin micropattern was exposed to a solution of biotinylated peptides, the peptides
were shown to attach only to the avidin-derivatized areas. IKVAV and RGD peptide sequences
were used to demonstrate the selective attachment of PC12 nerve cells and bovine aortic endo-
thelial cells, respectively, in serum-free medium. his surface engineering approach has the merit
that it is generalizable to any biotinylated ligand and any surface to which avidin physisorbs.
2.6.4 Other Cell Micropatterning Strategies
he list of cell patterning techniques does not end here. We have not even considered tech-
niques to pattern cells in 3-D, which will be reviewed in Chapter 7 when we cover Tissue
Microengineering. In the next section, we present techniques that do not it in any of the previ-
ous categories, yet they have had a notable impact in the ield of BioMEMS.
2.6.4.1 Selective Biorecognition by the Substrate
In 1998, Harold Craighead's group from Cornell University implemented the microstamped ver-
sion of “panning,” a method commonly used to sort cells. When a glass or plastic plate is coated
with antibodies against proteins present on the membrane of a certain cell type, the plate will
immunocapture
that cell type preferentially, so that the rest can be rinsed away—it's a method used
for cell sorting. he approach is ingenious: rather than relying on the cell's ability to recognize and,
thus, preferentially attach to a biomolecular micropattern, these researchers demonstrated that a
template of an antibody against
E. coli
, made by microstamping onto an unmodiied silicon surface,
selectively “captures” the bacteria in the antibody-covered areas. he concept potentially could be
