Visualizing Molecular Polar Ordering in Tissues via Electromechanical Coupling

Electromechanical coupling in piezoelectric biopolymers may play a role in, e.g., load-dependent bone remodeling, however, little is actually known regarding the effect of electrical stimuli on the chemistry and functionality of biosystems, particularly at the nanoscale. A first step in this direction is an assessment of the piezoelectric properties of biological tissues, and in particular of the polar ordering of the molecular constituents. To determine the existing polar architecture in biological tissues, piezoresponse force microscopy (PFM) is employed. PFM is widely used to probe electromechanical phenomena in inorganic and organic piezoelectric and ferroelectric materials, and in recent years has been employed to study piezoelectric biomaterials. Here, using a combination of the vertical and lateral PFM, we distinguish the molecule orientation in individual collagen fibrils in several collagenous tissues, including rat tail tendon and porcine eye tissues. This technique could be useful in improving our current understanding of cell signaling and mechanotransduction.