Electromechanical imaging of biological systems with sub-10 nm resolution

Kalinin, SV; Jesse, Stephen; Rodriguez, Brian J.; Thompson, Gary L.; Vertegel, Alexey

doi:10.1109/ise.2008.4813998

Cited by 16 publications

(22 citation statements)

References 7 publications

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“…2A), suggesting no polarization switching. This is consistent with numerous PFM measurements showing no polarity switching in collagen (26,27), and it serves as a good control. A question remains, however, on the possible contribution of injected space charges to the measured current; thus, we repeated pyroelectric measurements using a different heating rate, resulting in a different pyroelectric current (SI Appendix I, Fig.…”

Section: Resultssupporting

confidence: 90%

Ferroelectric switching of elastin

Liu

Cai

Zelisko

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 μC/cm 2 , whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications.F erroelectricity was first discovered in synthetic materials in 1920 when spontaneous polarization of Rochelle salt was found to be switchable by an external electric field (1). Ferroelectrics thus belongs to a larger class of pyroelectric materials that possess a unique polar axis, which, in turn, belongs to piezoelectrics exhibiting linear coupling between electric and mechanical fields (2). Because of these versatile properties, ferroelectric materials are promising for a wide range of technological applications in data storage, sensing, actuation, energy harvesting, and electro-optic devices (3). Biological tissues, such as bones and tendons, were first observed to be piezoelectric in 1950s (4), and shortly thereafter, pyroelectricity was discovered in a variety of biological materials as well (5, 6). Ever since then, ferroelectricity has been speculated for biological systems, and its potential physiological significance has been suggested (7). For example, it was hypothesized that the conformation transition in voltage-gated ion channels is ferroelectric in nature (8, 9). Nevertheless, indication of ferroelectricity in biological materials has only recently emerged from nanoscale piezoresponse force microscopy (PFM) studies (10-13).This work is motivated by our recent observation of PFM switching in elastin (12), which has generated quite a bit of excitement, although there is still considerable skepticism regarding the notion of biological ferroelectricity. Such reservation is understandable, given the unusual phenomenon of ferroelectric switching in biology, some ambiguities associated with PFM hysteresis, and a current lack of understanding of the basic science underpinning the switching mechanism. Indeed, there is neither macroscopic evidence of ferroelectric switching nor microscopic understan...

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Section: Resultssupporting

confidence: 90%

Ferroelectric switching of elastin

Liu

Cai

Zelisko

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…Depending of the fibril orientation, the PFM tip will either scan in direction from C-to Nterminus or in reverse direction resulting in opposite PFM phase signals. The effect of molecular orientation on piezoelectricity is also described elsewhere [22].…”

Section: Resultsmentioning

confidence: 99%

“…Additional possibilities for characterization of biological materials can be provided by another mode of SPM, piezoresponse force microscopy (PFM), which utilizes the piezoelectric behavior in biomaterials, or linear coupling between electrical and mechanical phenomena [22,23]. Piezoelectric behavior of biological systems results from the presence of proteins and other organic components, which exhibit piezoelectric activity [24][25][26][27][28][29][30].…”

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confidence: 99%

High-resolution imaging of proteins in human teeth by scanning probe microscopy

Gruverman

Rodriguez

et al. 2007

Biochemical and Biophysical Research Communications

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“…58 Furthermore, the 2010 Preface also predicted opportunities for new discoveries and breakthroughs in biological systems and strongly correlated oxides, and one of the exciting developments in the last two years is the observation of biological ferroelectricity in seashells, 22 aortic walls, 23 elastin, 24 glycine, 25 and peptide nanotubes, 26 which came more than 50 years after the closely related piezoelectricity was reported in biological tissues and 5 years after ubiquitous presence of biological piezoelectricity was established by PFM. [27][28][29][30][31] This advance is undoubtedly enabled by PFM, as vividly illustrated by Li and Zeng in their detailed studies on electromechanical coupling and ferroelectric switching of seashell in the present issue. 59 Another exciting development is recent realization of polarization reversal by mechanical stress, 32 attributed to the flexoelectric effect afforded by nanoscale Scanning Probe Microscopy (SPM) tip.…”

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confidence: 66%