Author:
Apkarian Robert P.,Wright Elizabeth R.,Seredyuk Victor A.,Eustis Susan,Lyon L. Andrew,Conticello Vincent P.,Menger Fredric M.
Abstract
The micro- and nanoarchitectures of water-swollen hydrogels were
routinely analyzed in three dimensions at very high resolution by two
cryopreparation methods that provide stable low-temperature specimens
for in-lens high magnification recordings. Gemini surfactants (gS),
poly-N-isopropylacrylamides (p-NIP Am), and elastin-mimetic di- (db-E)
and triblock (tb-E) copolymer proteins that form hydrogels have been
routinely analyzed to the sub-10-nm level in a single day. After they
were quench or high pressure frozen, samples in bulk planchets were
subsequently chromium coated and observed at low temperature in an
in-lens field emission SEM. Pre-equilibrated planchets
(4–40°C) that hold 5–10 μl of hydrogel facilitate
dynamic morphological studies above and below their transition
temperatures. Rapidly frozen samples were fractured under liquid
nitrogen, low-temperature metal coated, and observed in-lens to assess
the dispersion characteristics of micelles and fragile colloidal
assemblies within bulk frozen water. Utilizing the same planchet
freezing system, the cryoetch-HRSEM technique removed bulk frozen water
from the hydrogel matrix by low-temperature, high-vacuum sublimation.
The remaining frozen solid-state sample faithfully represented the
hydrogel matrix. Cryo- and cryoetch-HRSEM provided vast vistas of
hydrogels at low and intermediate magnifications whereas high
magnification recordings and anaglyphs (stereo images) provided a
three-dimensional prospective and measurements on a molecular level.
Publisher
Cambridge University Press (CUP)
Cited by
31 articles.
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