Biomineralization of calcium phosphate revealed by in situ liquid-phase electron microscopy

Xiaoyue Wang,Jie Yang,Kathryn Grandfield,Leyla Soleymani,Carmen M Andrei

doi:10.1038/s42004-018-0081-4

Xiaoyue Wang, Jie Yang + Show 3 more

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https://doi.org/10.1038/s42004-018-0081-4

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Journal: Communications Chemistry	Publication Date: Nov 13, 2018
Citations: 36	License type: open-access

Affiliation: McMaster University

Abstract

Calcium phosphate biomineralization is essential to the formation of bones and teeth, and other pathological calcifications. Unravelling the mechanism of calcium phosphate nucleation and growth contributes significantly to understanding diseases caused by pathological mineralization, and also to designing biomimetic materials with suitable properties. Recently, calcium phosphate was proposed to mineralize following a non-classical crystal growth pathway of pre-nucleation cluster aggregation. Liquid-phase transmission electron microscopy allows dynamic processes to be recorded continuously inside liquid. Here we present direct evidence, based on continuous monitoring in liquid, to confirm that calcium phosphate mineralization from simulated body fluid occurs by particle attachment, shown with nanoscale spatial resolution and sufficient temporal resolution. This work may lay the foundation for future investigation of mineralization in other relevant biological systems in humans and vertebrates.

Highlights

Calcium phosphate biomineralization is essential to the formation of bones and teeth, and other pathological calcifications
Understanding the mineralization process of Calcium phosphates (CaP) will aide in unveiling biomineralization mechanisms of healthy tissues such as bone, dentin and cementum, pathological calcifications, and contribute towards research in applied sciences related to human health, such as the development of biomimetic materials and realization of mineralization mechanisms toward synthetic implant systems[5,7]
It has been proposed that the existence of Amorphous calcium phosphate (ACP) pre-nucleation clusters decreases the energy barrier to nucleation and enables biominerals, such as CaP, to mineralize following a non-classical crystal growth process defined as crystallization by particle attachment[14]

Summary

Introduction

Calcium phosphate biomineralization is essential to the formation of bones and teeth, and other pathological calcifications. Liquid-phase transmission electron microscopy (LP-TEM), with the ability to record events in confined liquid between two electron-transparent membranes with nanoscale spatial resolution and real-time temporal resolution[17,18], is a promising technique to image dynamic nucleation and growth process of CaP. This approach has been used to study the nucleation and growth of CaCO314,15,19 and provides direct experimental evidence for the existence of formation pathways through the transformation of amorphous or crystalline precursors[16]. In spite of these challenges, approaches focused on varying solution chemistry—use of radical scavengers and additives, tuning solution pH, and changing the solvent type—or electron beam conditions— lowering electron dose rate, varying imaging mode, and tuning the accelerating voltage—have shown to be effective in reducing the interference of electron beam with imaging or the process under investigation[26]

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