Visualizing molecular polar order in tissues via electromechanical coupling

Electron microscopy (EM) and atomic force microscopy (AFM) techniques have long been used to characterize collagen fibril ordering and alignment in connective tissues. These techniques, however, are unable to map collagen fibril polarity, i.e., the polar orientation that is directed from the amine t...

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Bibliographic Details
Published in:Journal of structural biology 2012-12, Vol.180 (3), p.409-419
Main Authors: Denning, Denise, Alilat, Sofiane, Habelitz, Stefan, Fertala, Andrzej, Rodriguez, Brian J.
Format: Article
Language:English
Subjects:
Animals
Atomic force microscopy
Collagen
Collagen - chemistry
Extracellular Matrix - chemistry
Eye - chemistry
Eye tissues
Microscopy, Atomic Force
Microscopy, Electron
Molecular Imaging
Piezoelectricity
Piezoresponse force microscopy
Polar ordering
Rats
Swine
Tail - chemistry
Tendon
Tendons - chemistry
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Summary:Electron microscopy (EM) and atomic force microscopy (AFM) techniques have long been used to characterize collagen fibril ordering and alignment in connective tissues. These techniques, however, are unable to map collagen fibril polarity, i.e., the polar orientation that is directed from the amine to the carboxyl termini. Using a voltage modulated AFM-based technique called piezoresponse force microscopy (PFM), we show it is possible to visualize both the alignment of collagen fibrils within a tissue and the polar orientation of the fibrils with minimal sample preparation. We demonstrate the technique on rat tail tendon and porcine eye tissues in ambient conditions. In each sample, fibrils are arranged into domains whereby neighboring domains exhibit opposite polarizations, which in some cases extend to the individual fibrillar level. Uniform polarity has not been observed in any of the tissues studied. Evidence of anti-parallel ordering of the amine to carboxyl polarity in bundles of fibrils or in individual fibrils is found in all tissues, which has relevance for understanding mechanical and biofunctional properties and the formation of connective tissues. The technique can be applied to any biological material containing piezoelectric biopolymers or polysaccharides.
ISSN:1047-8477
1095-8657
DOI:10.1016/j.jsb.2012.09.003