Biomedical Engineering Reference
In-Depth Information
(6)
Stir the clear solution again at 60 °C for 12 h to ensure complete coupling
between the polymer and dodecylamine.
(7)
Cool back down to RT and evaporate the remaining solvent with a rotary
evaporator that leaves a pale yellow, solid amphiphilic polymer.
(8)
Transfer the polymer to a nitrogen filled glove box (< 0.1 ppm O
2
) and
dissolve in anhydrous CHCl
3
(25 mL) to give a monomer unit concentra-
tion of 0.8 M.
(9)
Store the amphiphilic polymer solution in a glass vial in the glove box until use.
Part 2. Coating the Si nanocrystals with polymer
101
(1)
In a 50 mL round bottom flask mix the amphiphilic polymer stock solu-
tion (0.8 M monomer units in CHCl
3
, 53 µL) and alkyl-Si NMs at 3.0 mg/
mL in anhydrous CHCl
3
, 0.40 mL, and anhydrous CHCl
3
(2.55 mL). You
may use other NMs as well.
(2)
Vortex the mixture and stir with magnetic stirrer for 15 min at RT.
(3)
Remove the solvent by rotary evaporation to yield a yellow Si-polymer
film on the inner wall of the flask.
(4)
Add aqueous sodium borate buffer (SBB) (50 mM borate, 2.0 mL, pH 12)
and stir for 15 min at RT to disperse the Si-polymer.
(5)
Add 13.0 mL DI water to dilute the NMs.
(6)
Pass the suspension through a 0.2-µm pore syringe filter (Corning, PES
membrane) followed by a 0.1-µm pore syringe filter (Whatman, inorganic
membrane).
(7)
Place the filtered nanocrystal solution in an ultracentrifugation filter
(Amicon Ultra, regenerated cellulose membrane, 50 kDa MWCO) and
centrifuge at 4000
g
for 4 min at RT.
(8)
Discard the colorless filtrate and retain the concentrated NMs solution
above the membrane.
(9)
Dilute the NMs solution with 15.0 mL sterile-filtered phosphate buffered
saline (PBS, 150 mM, pH 7.4).
(10)
Repeat the ultracentrifugation two more times using PBS to dilute the
retained NMs solution.
(11)
Store the final aqueous NMs solution in a glass vial under ambient condi-
tions until use.
(12)
Characterize the amphiphilic polymer coated NMs.
Hessel and coworkers used X-ray diffraction (XRD), attenuated total reflec-
tance FTIR (ATR-FTIR) spectra (400-4000 cm
−1
), and X-ray photoelectron
spectroscopy (XPS) to characterize the surface composition and to demonstrate
that the amphiphilic polymer successfully coated the NM surface. A UV-vis
spectrophotometer, PL, and photoluminescence excitation (PLE) were used to
establish the optical properties. Zeta potential was measured by laser Doppler
anemometry using a Zetasizer Nano ZS instrument (Malvern). TEM and DLS
are good nondestructive instruments to establish physical characteristics of
NMs (
Figure 3.4
).
