Towards local electromechanical probing of cellular and biomolecular systems in a liquid environment

Abstract

Electromechanical coupling is ubiquitous in biological systems, with examples ranging from simple piezoelectricity in calcified and connective tissues to voltage-gated ion channels, energy storage in mitochondria, and electromechanical activity in cardiac myocytes and outer hair cell stereocilia. Piezoresponse force microscopy (PFM) originally emerged as a technique to study electromechanical phenomena in ferroelectric materials, and in recent years has been employed to study a broad range of non-ferroelectric polar materials, including piezoelectric biomaterials. At the same time, the technique has been extended from ambient to liquid imaging on model ferroelectric systems. Here, we present results on local electromechanical probing of several model cellular and biomolecular systems, including insulin and lysozyme amyloid fibrils, breast adenocarcinoma cells, and bacteriorhodopsin in a liquid environment. The specific features of PFM operation in liquid are delineated and bottlenecks on the route towards nanometre-resolution electromechanical imaging of biological systems are identified.

Ferroelectric or non-ferroelectric: Why so many materials exhibit “ferroelectricity” on the nanoscale

“…347,348 Piezoelectric displacement is linearly proportional to applied voltage = . The forces are probed with a sinusoidal voltage Vac superimposed on a dc bias Vdc,…”

Biological Ferroelectricity Uncovered in Aortic Walls by Piezoresponse Force Microscopy

“…Piezoresponse force microscopy (PFM) is a powerful tool to probe electromechanical coupling in piezoelectric and ferroelectric systems at nanoscale [20–23], and in recent years, it has been applied to study a variety of biological tissues and materials. These include human bones [24] and teeth [25], tooth dentin and enamel [26,27], collagen fibrils [28–30], and insulin and lysozyme amyloid fibrils, breast adenocar-cinoma cells, and bacteriorhodopsin [31], as summarized in a recent review [22]. While these studies unambiguously established piezoelectricity in biological tissues at nanoscale, biological ferroelectricity remains elusive.…”

Glucose Suppresses Biological Ferroelectricity in Aortic Elastin

“…[25]. PFM, a powerful tool to probe the biological electromechanics at nanoscale [20,21,26–31], was used to measure the piezoelectric effect of the elastin, by applying an ac voltage through the conductive atomic force microscopy tip to excite the piezoelectric vibration of the sample under both vertical and lateral modes [32]. The thickness of the PFM sample is approximately 0.62 mm, and a typical PFM scan is shown in Fig.…”