Biomedical Engineering Reference
In-Depth Information
11
Second-Harmonic
Generation Imaging
of Self-Assembled
Collagen Gels
11.1 Introduction ......................................................................................245
11.2 Background........................................................................................246
Collagen Structural Properties • Collagen Gel Self-Assembly •
Optical Properties of Collagen Gels • Image Processing
11.3 SHG Imaging of Acellular Collagen Gels .....................................249
Introduction • Quantification of Collagen Fiber Shape from Second-
Harmonic Images • Effects of Collagen Fiber Size on Second-
Harmonic Signal • Effects of Acellular Collagen Gel Concentration
on Second-Harmonic Signal • Effect of Collagen Fiber Orientation
on SHG • Quantification of Collagen Network Architecture from
Second-Harmonic Images • Determining Mechanical Relationships
in Acellular Gels from Second-Harmonic Images • Summary: SHG
Imaging of Acellular Collagen Gels
11.4 SHG Imaging of Cellularized Collagen Gels................................259
Introduction • Effect of Gel Contraction on SHG Images • SHG
Image Texture Simulation • Multiphoton Image Parameters Are
Sensitive to Cellularized Gels Microstructure • Skewness and SC of
SHG and TPF Signals Predict
E
of Cellularized Gels • Summary
11.5 Conclusions....................................................................................... 264
Acknowledgments ....................................................................................... 264
References......................................................................................................265
Christopher B. Raub
University of California,
Irvine
Bruce J. Tromberg
University of California,
Irvine
Steven C. George
University of California,
Irvine
11.1 introduction
The biological molecules that exhibit second-harmonic generation (SHG) include fibrillar collagens,
myosin, microtubules, silk, and cellulose [1-4]. Laser scanning microscopy (LSM) allows for nonin-
vasive and nondestructive three-dimensional imaging of the SHG signal from biological samples pos-
sessing second-harmonic-generating molecules [5-9]. As an optical signal, SHG is uniquely sensitive to
the spatial organization of generating dipoles [10-14], allowing for quantitative and selective structural
characterization of second-harmonic-generating tissue. Numerous optical and structural parameters
have been derived from the SHG signal, from which inferences can be made about tissue structural,
compositional, optical, and mechanical properties [15-26].
This chapter focusses on SHG signal imaging studies of hydrogels composed of acid-solubilized type
I collagen. Self-assembled silk and cellulose scaffolds that generate second-harmonic signal have also
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