Visualizing biointerfaces in three dimensions: electron tomography of the bone–hydroxyapatite interface

Abstract

A positive interaction between human bone tissue and synthetics is crucial for the success of boneregenerative materials. A greater understanding of the mechanisms governing bone-bonding is often gained via visualization of the bone -implant interface. Interfaces to bone have long been imaged with light, X-rays and electrons. Most of these techniques, however, only provide low-resolution or two-dimensional information. With the advances in modern day transmission electron microscopy, including new hardware and increased software computational speeds, the high-resolution visualization and analysis of three-dimensional structures is possible via electron tomography. We report, for the first time, a threedimensional reconstruction of the interface between human bone and a hydroxyapatite implant using Z-contrast electron tomography. Viewing this structure in three dimensions enabled us to observe the nanometre differences in the orientation of hydroxyapatite crystals precipitated on the implant surface in vivo versus those in the collagen matrix of bone. Insight into the morphology of biointerfaces is considerably enhanced with three-dimensional techniques. In this regard, electron tomography may revolutionize the approach to high-resolution biointerface characterization.

High-resolution three-dimensional probes of biomaterials and their interfaces

“…Numerous studies report the formation of an apatite layer between bone and implant, up to 1000 mm in thickness [36,[47][48][49], commonly accepted to occur through a dissolution-reprecipitation process [47]. Composition and orientation of this layer is debated to date [50][51][52][53][54][55].…”

“…While ET has had roots in the biological and materials science fields dating back over 40 years, the interdisciplinary domain of biomaterials, in particular biomaterials in contact with biological matter, has not seen its use until very recently [36].…”

“…It also confirmed that the orientation of HA crystals in the bone matrix is parallel to the implant surface, which is consistent with the collagen-banding pattern being visible perpendicular to the surface in STEM projections. Full videos of the tilt series and three-dimensional reconstruction are available in our previous work [36].…”

Biomimetic Hydroxyapatite Deposition on Titanium Oxide Surfaces for Biomedical Application

“…5) [47]. Viewing this structure in three dimensions enabled observation of visualization of nanometre differences in the orientation of hydroxyapatite crystals precipitated on the implant surface in vivo versus those in the collagen matrix of bone.…”

“…Three dimensional reconstruction of the interface between human bone and a hydroxyapatite implant using Z-contrast electron tomography with FIB slice. [47] (A) (B)…”