Piezoelectric Effect in Human Bones Studied in Nanometer Scale

Abstract

The piezoelectric effect has been studied in wet and dry human bones using a piezoresponse force microscope (PFM). It allowed to measure piezoelectric response with nanometer scale resolution directly in a collagen matrix and to obtain a piezoresponse image near the Haversian channel. Dielectric response and dc conductivity have been measured. Theoretical calculations taking into account the inhomogeneity of the electric field under the PFM tip apex and its screening in highly conductive bone samples were performed for obtaining the piezoelectric coefficient in the bone collagen.Ferroelectric phenomena have been observed in many biological materials. The origin of these fundamental physical properties is ascribed to high structural ordering of biological systems at any level that is a low symmetry configuration of elementary cells based of their helical or chiralic dissymmetry. Linear electrooptic effect has been found in nerve fibers. 1 Dielectric spectroscopy studies of oriented purple membranes showed that bacteriorhodopsin, which is an integral membrane protein, possesses a significant electrical dipole moment and demonstrates a liquid crystal-like ferroelectric behavior. 2 This experiment was a direct confirmation of the theoretical model of ion channels in a biological membrane 3,4 acting as electric switches between ferroelectric (closed, insulating) and paraelectric (open, ion-conducting) states. Plants and animal and human tissues (protein amino acids, pineal gland of brain, bones, skin, tendon, etc.) reveal pronounced piezoelectric 5,6 and pyroelectric properties. 7-9 Reports on the observation of pyroelectric effect 7-9 was a first evidence of the existence of macroscopic spontaneous electrical polarization in bones. Application of an ac electric field to the cortical human bone allowed to observe reversal of the spontaneous polarization by recording dielectric hysteresis loop. 10 Both piezoelectric and pyroelectric phenomena were related to collagen, which is an organic crystalline matrix of the bone composed from strongly aligned polar organic protein molecules. 11 It was proposed that the piezoelectric effect plays an important physiological role in bone growth, remodeling, and fracture healing. 12In this paper we report on studies of piezoelectric effect in moist and dry human bones by the use of a piezoresponse force microscope (PFM). It allowed both to measure piezoelectric response with nanometer scale resolution directly in a collagen matrix and to obtain a piezoresponse image near the Haversian channel. Theoretical calculations, taking into account the inhomogeneity of the electric field under the PFM tip apex and screening of the applied electric field, were performed for obtaining the piezoelectric coefficient in bone collagen.Human adult humerus and tibia diaphysial fragments were used for sample preparation. Bones were supplied by The Israeli National Bone Bank at the Chaim Sheba Medical Center. All the bones were obtained from young (<45 years of age) individuals during organ harvesting a...

Electromechanical imaging of biological systems with sub-10nm resolution

“…Thus, understanding of the fundamental mechanisms of electromechanical coupling in biological systems necessitates studies on the level of a single structural element, such as protein fibril in the calcified and connective tissues, a task still not achieved despite several attempts. 8 Here, we demonstrate electromechanical imaging and microstructural analysis of dentin and enamel in a human tooth with sub-10 nm resolution using vertical and lateral piezoresponse force microscopy ͑PFM͒. In PFM, a conductive tip is brought into contact with the surface, and the piezoelectric response is detected as the first harmonic component, A 1 , of the tip deflection, A = A 0 + A 1 cos͑ t + ͒, induced by the application of the periodic bias V tip = V dc + V ac cos͑ t͒ to the tip.…”

Компьютерные Исследования Наноструктур Гидроксиапатита, Их Особенности И Свойства

“…Finally, it is also worth noting, that the value of the polarization and the surface charge density (P ~ 0.0038 C/m 2 ) obtained in view of the general law of the electromechanical coupling (that is the connection between polarization and piezoelectric coefficients, inherent of all ferroelectrics) [63,64] leads to the value of the piezoelectric coefficient of the order of d ~ 15.7 pm/V, which only twice larger than values ~ 7.62-8.48 pC/N (or pm/V) measured by Halperin et al on tibia bone samples by piezoresponse force miscroscopy [64,65]. As we discussed above (section 2.2) such deviation could occur by averaging the registered piezoelectric signal from different grains with various local polar states, fluctuated in crosssection of the native tibia bones samples.…”

Local piezoresponse and polarization switching in nucleobase thymine microcrystals

“…The latter value is in a good agreement with the experimental data obtained by PFM and is comparable with those of other organic and biological molecular structures. [64][65][66][67] As it is clear from the introduced model, the d zz coefficient has a very strong asymmetry for the field applied along OY axis, as shown in Table II.…”