Piezoelectricity in hydrated frozen bone and tendon

Abstract

THE piezoelectric property of connective tissue may play a role in regulating the patterns of tissue growth¹. Most piezoelectric measurements, however, deal with dried tissue^2–4. Observations of stress-generated voltages from hydrated connective tissue are generally insufficient to establish that the voltages are of piezoelectric origin, because of complications resulting from streaming potentials and electrode effects^5–7. A report of the non-existence of piezoelectricity in hydrated collagen at room temperature⁸ has been criticised⁹. Use of the converse effect is most desirable in studying biological piezoelectricity⁹, but for hydrated tissue the high electrical conductivity of water interferes with the establishment of an electric field inside the sample^2,4. We therefore hydrated and then froze our connective tissue samples taking advantage of the reduced conductivity of ice compared with that of water. Our results establish the existence of the piezoelectric effect in bone and tendon under physiological conditions of moisture, but at a non-physiological temperature (−25° C).