Using Self-Assembled Monolayers to Pattern ECM Proteins and Cells on Substrates - Methods in Molecular Biology: Extracellular Matrix Protocols - page 204

2.3.2.2. [1-[(M ETHYLCARBONYL ) THIO ] UNDEC -11 YL ] TRI ( ETHYLENE GLYCOL )

Dissolve 0.6 g (2 mmol) of the previous compound in 20 mL of freshly
distilled THF; add 10 mg of recrystallized 2, 2'-azobisisobutyronitrile (Aldrich)
and 1.4 mL (20 mmol) of thiolacetic acid (Aldrich) and irradiate for 6-8 h with
a 450-W medium-pressure mercury lamp (Ace Glass) filtered through Pyrex.
Check that the reaction has reached completion before work-up. Take out a
0.1-mL aliquot, reduce under pressure and take an NMR spectrum. The signal
from the protons of the alkene group at = 4.8-6 ppm should disappear if the

reaction has gone to completion. Concentrate the reaction mixture and purify
( R f = 0.3): a typical yield is approx 80%. 1 H NMR (250 MHz)

δ

1.2 (broad
singlet, 14 H), 1.6 (multiplet, 4 H), 2.3 (singlet, 3 H), 2.85 (triplet, 2 H, J = 7 Hz),
3.45 (triplet, 2 H, J = 7 Hz), 3.5-3.75 (multiplet, 12 H).

δ

2.3.2.3. (1-M ERCAPTOUNDEC -11- YL ) TRI ( ETHYLENE GLYCOL )
Dissolve 0.4 g (1 mmol) of the previous compound in 2 mL of freshly dis-
tilled dichloromethane and 8 mL of degassed (argon or nitrogen for 30 min)
methanol. Add 0.9 mL (1.2 mmol) of 1.3 M sodium methoxide (Aldrich) in
degassed methanol. After 45 min, bring the reaction mixture to neutral pH
using DL-camphor-10-sulfonic acid (Aldrich), concentrate and purify ( R f = 0.25);
a typical yield is 50 %. 1 H NMR (250 MHz) 1.1 (broad singlet, 14 H), 1.2

(triplet, 1 H, J = 7 Hz), 1.5 (multiplet, 4H), 2.3 (singlet, 3 H), 2.5 (quartet, 2 H,
J = 7 Hz), 3.0 (broad singlet, 1 H), 3.4 (triplet, 2 H, J = 7 Hz), 3.5-3.75 (mul-
tiplet, 12 H).

δ

3. Methods
3.1. Micropattern Stamping Procedure
1. Lay substrate on clean and flat surface, with gold facing upwards. Take care not

to scratch the surface with sharp forceps, or by placing substrate upside down. If
there is dust visible on the substrate, blow gently with pressurized air or nitrogen.

2. Rinse the PDMS stamp with ethanol and blow off vigorously with a stream of

pressurized air or nitrogen for at least 10 s. If any dust remains on the stamp,
repeat this procedure.

3. Dip a Q-tip into a 2-m M solution of hexadecanethiol in ethanol and gently paint

a layer of the solution onto the PDMS stamp. Use a stream of air or nitrogen to
gently evaporate the ethanol off the stamp.

4. Gently place the stamp face down onto the gold-coated substrate. Allow the stamp

to adhere. This step may require putting gentle pressure on the stamp to press it
against the substrate. Let the fully adhered stamp remain on the substrate for at
least 10 s.

5. Using forceps, gently peel away the stamp from the substrate, being certain not to

smear the stamp against the substrate or to let the stamp re-adhere to the sub-
strate.