Nanoscale characterization of isolated individual type I collagen fibrils: polarization and piezoelectricity

Abstract

Piezoresponse force microscopy was applied to directly study individual type I collagen fibrils with diameters of approximately 100 nm isolated from bovine Achilles tendon. It was revealed that single collagen fibrils behave predominantly as shear piezoelectric materials with a piezoelectric coefficient on the order of 1 pm V(-1), and have unipolar axial polarization throughout their entire length. It was estimated that, under reasonable shear load conditions, the fibrils were capable of generating an electric potential up to tens of millivolts. The result substantiates the nanoscale origin of piezoelectricity in bone and tendons, and implies also the potential importance of the shear load-transfer mechanism, which has been the principle basis of the nanoscale mechanics model of collagen, in mechanoelectric transduction in bone.

Electromechanical properties of dried tendon and isoelectrically focused collagen hydrogels

“…Piezoresponse force microscopy (PFM), a technique developed initially to image domains in ferroelectric materials by measuring bias-induced surface deformations [27], has recently been employed to study electromechanical coupling in biological systems [28]. PFM is capable of investigating in-plane and out-of-plane piezoelectric response from biosystems at the nanoscale, including collagen [29][30][31][32][33]. Minary-Jolandan and Yu have observed shear piezoelectricity in single collagen type I fibrils using PFM [31,32].…”

“…PFM is capable of investigating in-plane and out-of-plane piezoelectric response from biosystems at the nanoscale, including collagen [29][30][31][32][33]. Minary-Jolandan and Yu have observed shear piezoelectricity in single collagen type I fibrils using PFM [31,32]. With PFM, not only can fibril alignment be investigated through normal AFM surface topography and deflection images, but the amplitude of the piezoelectric signal and the polarity of the fibrils can be imaged.…”

Piezoelectricity in collagen type II fibrils measured by scanning probe microscopy

“…When the piezoelectric signals are calibrated via geometric scaling, 42 the measured shear coefficient for type I is in the same range as reported previously. 12 The increase in piezoelectric signal for type I cannot be attributed to tip wear, etc., as type II was investigated prior to type I using the same tip. Type I collagen was also prepared using the type II protocol to ensure the preparation methods used were not responsible for the differences observed.…”

“…While the link between charge and cellular interactions is not well understood, previous studies investigating cellular adhesion and growth on poled hydroxyapatite suggest that surface charge influences cellular response. 11 The piezoelectric properties of collagen type I have been studied at scales ranging from the macroscale 1 to, more recently, the nanoscale 12 with the advent of piezoresponse force microscopy (PFM). 13,14 Collagen type I is a shear piezoelectric with a polarization along the fibril length (corresponding to an amine (N) to carboxyl (C) polarity).…”

Preface to Special Topic: Invited Papers from the International Symposium on Piezoresponse Force Microscopy and Nanoscale Phenomena in Polar Materials, Aveiro, Portugal, 2009

“…The early imaging applications were the harbinger of current advances in PFM-based probes, ranging from ferroelectrics and multiferroics [20][21][22] to III-V nitrides 23,24 to polymers, [25][26][27][28][29] and biological systems, [30][31][32][33] and recently to strongly correlated oxides 34,35 and energy storage and conversion materials. timely appearance as an important scientific event.…”