Figure 1.
Elaboration steps: grafting of an ATRP (Atom Transfer Radical Polymerization) initiator on a glass surface (2) is followed by NIPAM polymerization (3), yielding a polymer brush which is selectively removed by UV irradiation (4).
APTES: 3-aminopropyl-triethoxysilane, BMPB: 2-bromo-2-methylpropionyl bromide, PNIPAM: poly(N-isopropylacrylamide).
Figure 2.
Brush growth characterization:
(a) Brush dry thickness polymerization time, for
M. (b)
for 1 min polymerization. Error bars are of the symbols size and correspond to a typical
nm variation in thickness observed between samples elaborated under the same nominal conditions.
Figure 3.
Force-distance curves measured on a water immersed PNIPAM brush ( nm), at two temperatures below and above the polymer LCST (see labels on main panel).
It can be seen that the range of steric, repulsive forces due to the presence of the brush is markedly reduced at 37C, and that the hard-wall repulsion at high temperature occurs at a distance close to the dry thickness of the brush, indicating almost full expulsion of the solvent from the PNIPAM layer above its LCST. Inset: scheme of the SFA experimental configuration.
Figure 4.
UV irradiation time for brushes of initial thickness 82 nm (blue), 65 nm (green), and 54 nm (red).
Figure 5.
Phase contrast image of annular and triangular patterns obtained by UV photoablation of PNIPAM.
The light grey regions have been irradiated by deep UV, where the polymer have been removed. Image size is 473355
m
.
Figure 6.
Protein adsorption on micropatterns:
(a) Fibronectin adsorption into V-shaped patterns (V arms of length 40 m and width 10
m). Inset: fluorescence intensity profile along the blue line drawn in main panel. (b) Wide field image of stained fibronectin adsorbed on V-shaped patterns, showing large scale homogeneity. Image size: 2200
1664
m (taken with a 4× objective on an Olympus IX70 microscope. Reduced contrast quality is due to the low NA of the objective).
Figure 7.
Phase contrast images of cells adhered on square (up), triangular (middle), and rectangular-shaped patterns (down).
Scale bar is 80 m.
Figure 8.
Cell adhesion on PNIPAM micropatterns:
A/ Fibronectin and fibrinogen-A546 coating on micropatterned PNIPAM glass surface (red). Scale bar is 15 m. B/ individual MEF cells plated on pentagon, annulus, triangle or square-shaped fibronectin micropatterns. Cells were fixed and stained with phalloidin to reveal F-actin filaments (green). Scale bar represents 15
m. C/ Average distributions of actin (fire), built from the overlay of 10 images for each shape. The average distribution highlights the reproducibility of the distributions shown in B/ and enhances the spatial distribution of F-actin bundles along micropattern border regions. Scale is 15
m.
Figure 9.
Thermally-induced cell detachment:
(A) and (B): Sequences of cells detaching as temperature is lowered (images 6767
m, dry brush thickness
nm). The time stamp gives the time elapsed since the surfaces were taken out of the incubator. The rightmost image in each line shows the free pattern after full cell detachment. (A) cell initially adhered on a circular pattern. Imposed temperature is 21
C. (B) cell initially adhered on a hexagonal pattern. Imposed temperature is 26
C. (C): sketch of the polymer chains swelling inducing cell detachment.