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In-Lens Cryo-High Resolution Scanning Electron Microscopy: Methodologies for Molecular Imaging of Self-Assembled Organic Hydrogels

Published online by Cambridge University Press:  01 August 2003

Robert P. Apkarian ,
Elizabeth R. Wright ,
Victor A. Seredyuk ,
Susan Eustis ,
L. Andrew Lyon ,
Vincent P. Conticello  and
Fredric M. Menger
Robert P. Apkarian
Affiliation:
Integrated Microscopy and Microanalytical Facility, Emory University, Atlanta, GA 30322
Elizabeth R. Wright
Affiliation:
Integrated Microscopy and Microanalytical Facility, Emory University, Atlanta, GA 30322 Department of Chemistry, Emory University, Atlanta, GA 30322 Department of Materials Science and Engineering, University of Southern California, Los Angeles, CA 90089
Victor A. Seredyuk
Affiliation:
Department of Chemistry, Emory University, Atlanta, GA 30322
Susan Eustis
Affiliation:
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332
L. Andrew Lyon
Affiliation:
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332
Vincent P. Conticello
Affiliation:
Department of Chemistry, Emory University, Atlanta, GA 30322
Fredric M. Menger
Affiliation:
Department of Chemistry, Emory University, Atlanta, GA 30322
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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.

Keywords

in-lens cryo-HRSEMcryoetchhydrogelsacrylamidesproteinssurfactants
Type
High Resolution Cryo-SEM
Information
Microscopy and Microanalysis , Volume 9 , Issue 4 , August 2003 , pp. 286 - 295
Copyright
© 2003 Microscopy Society of America

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