Atom Probe Tomography of Apatites and Bone-Type Mineralized Tissues

Gordon, Lyle M.; Tran, Lawrence; Joester, Derk

doi:10.1021/nn3049957

Cited by 115 publications

(128 citation statements)

References 56 publications

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“…[2] Others and we have recently expanded the use of APT to apatitic biominerals. [3][4][5] We report here on our recent discovery, by APT and correlative techniques, of a Mg-rich amorphous intergranular phase in regular enamel, and of iron-rich intergranular phases in pigmented rodent enamel (Figure 1), and the dramatic influence that these intergranular phases have on enamel mechanical properties and its resistance to acid corrosion. [6] We further discuss the localization of residual organic macromolecules, carbonate, and water in the intergranular phases and discuss the differentiation between organic and inorganic carbon (Figure 2).…”

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confidence: 87%

Chemical Imaging of Interfaces and in Interphases in Tooth Enamel

2015

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Tooth enamel is the hardest tissue in vertebrates. Optimized to withstand the forces of mastication, it is composed of hydroxylapatite (OHAp) nanowires, thousands of which are bundled into rods that are organized in a three-dimensional weave. During tooth development, a preformed organic matrix is thought to be integral to the biological control over the precipitation of an amorphous precursor phase, its transformation into hydroxylapatite, and the growth of individual OHAp nanowires in enamel. This matrix is degraded during enamel maturation, but a small amount of organics remains in the final biocomposite, where its presence and that of water affect the mechanical properties. Once the tooth has erupted, enamel is affected by caries (tooth decay), a chronic infectious disease that affects nearly 100% of adults worldwide.[1] Caries commonly begins with the demineralization of enamel by acids produced in plaque biofilms. It has long been known that the susceptibility of enamel to dissolution is greatly dependent on the presence of magnesium, carbonate, and fluoride ions. However, mapping the distribution of organic and inorganic 'trace' constituents is very challenging due to the complex 3D architecture, the importance of primarily low atomic number (Z) constituents, and the sensitivity of the sample to beam damage.Laser-pulsed atom probe tomography (APT), an imaging mass spectrometry technique of unrivalled spatial resolution (< 0.2 nm) and chemical sensitivity, allowed us to dramatically improve our understanding of the complex chemistry and structure of nano-scale organic/inorganic interfaces.[2]Others and we have recently expanded the use of APT to apatitic biominerals. [3][4][5] We report here on our recent discovery, by APT and correlative techniques, of a Mg-rich amorphous intergranular phase in regular enamel, and of iron-rich intergranular phases in pigmented rodent enamel (Figure 1), and the dramatic influence that these intergranular phases have on enamel mechanical properties and its resistance to acid corrosion. [6] We further discuss the localization of residual organic macromolecules, carbonate, and water in the intergranular phases and discuss the differentiation between organic and inorganic carbon (Figure 2). [7] References:[1] World Health Organization Media Centre,

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confidence: 87%

Chemical Imaging of Interfaces and in Interphases in Tooth Enamel

2015

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“…Laser-assisted atom probe tomography (APT) provides position and identity of atoms with sub-nanometer resolution [4]. APT was recently used to reveal nano-structures in apatites [5,6] and rodent tooth enamel [7,8]. Inspired by this work, we examined human dental enamel using APT [9] and found Mg-rich ACP nanolayers between the HAP nanowires that make up the enamel.…”

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Atom Probe Tomography of Human Tooth Enamel and the Accurate Identification of Magnesium and Carbon in the Mass Spectrum

Fontaine

Cairney

2017

Microsc Microanal

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According to the World Health Organization, 60-90% of children and nearly 100% of adults worldwide suffer from dental decay (caries), which occurs via the progressive dissolution of dental enamel. Human dental enamel is the hardest tissue in the body and plays a vital role in protecting teeth from wear and chemical attacks. It consists of a mineral phase, mainly in the form of highly oriented ribbon-like nanowires of carbonated hydroxyapatite [1].It is well established that enamel mechanical strength and fatigue resistance is derived from its hierarchical structure, which consists of periodically-arranged bundles of HAP nanowires. However, we do not yet have a full understanding of the HAP crystallization process that leads to this structure. HAP crystallization is initiated by the mineralization of an amorphous calcium phosphate (ACP) precursor [2]. It was recently proposed that magnesium (Mg) ions play a critical role in the stabilization of this ACP phase and the formation of the HAP mineral, where surface Mg ions retard the growth of HAP crystals, leading to the nanometer-sized HAP crystallites [3]. Knowledge of the distribution of Mg ions and the presence of the precursor ACP in mature human dental enamel would provide much needed information for a better understanding of enamel formation, and may eventually allow the development of strategies to enhance enamel repair and to slow or prevent caries.The investigation of such structures in human dental enamel requires high chemical sensitivity at the atomic scale. Laser-assisted atom probe tomography (APT) provides position and identity of atoms with sub-nanometer resolution [4]. APT was recently used to reveal nano-structures in apatites [5,6] and rodent tooth enamel [7,8]. Inspired by this work, we examined human dental enamel using APT [9] and found Mg-rich ACP nanolayers between the HAP nanowires that make up the enamel. We also report Mg-rich elongated precipitates and pockets of organic material among the HAP nanowires. The correct chemical identification of the atoms and molecules field-evaporated from the precipitates and other nano-scale features was particularly challenging. This is mainly due to direct Mg and C peak overlap in the enamel mass spectrum. With the increasing interest in atomic scale characterization of biominerals using APT, there is a need for accurate identification of Mg and C in the APT mass spectrum.Here we discuss the particular case of direct peak overlap between 24 Mg 2+ , 12 C + and 24 C2 2+ at 12 Dalton in human dental enamel. We show that the combined use of the isotopic distribution and spatial association with other ions enable to accurately differentiate Mg from C (Fig.1). We also highlight the contribution of Mg, carbonates and organic carbon in the different nano-scale features detected in human dental enamel (Fig.2) [10].

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“…APT is specifically adept at characterizing nanomaterials with internal organic-inorganic interfaces, due to its elemental sensitivity and spatial accuracy. We recently demonstrated this capability in biological minerals in the magnetite cusp of the chiton tooth [4] and vertebrate bone and dentin [5].We report here on the characterization of native equine spleen ferritin using APT. Greene et al recently used APT to analyse ferritin as a model for characterizing biological materials using APT.…”

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Towards Atom Probe Tomography of Hybrid Organic-Inorganic Nanoparticles

Gordon¹,

Cohen²,

Joester³

2013

Microsc Microanal

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Surface functionalization of inorganic nanoparticles is widely used to modify material properties for a variety of applications including medical therapies and diagnostics. While inorganic nanoparticles may be characterized via electron microscopy and X-ray scattering, study of hybrid nanomaterials and, in particular, buried interfaces is very challenging. Here we discuss the application of atom probe tomography (APT) to imaging organic-inorganic interfaces of biological nanoparticles, ferritin, as a model system. Ferritin is a structurally well-characterized protein, critical across biology to store some 4500 iron atoms and transport iron as mineralized Fe (III) [1]. This 24-subunit 12 nm protein has a spherical 8 nm core into which Fe (II) enters and is subsequently oxidized.APT is uniquely capable of providing the necessary chemical and structural insight at the atomic scale by directly probing the location and chemical identity of the atoms within a small sample of material. APT consists of a field-ion microscope coupled to a time-of-flight mass spectrometer, providing chemical and three-dimensional positional information of ions successively field evaporated from a sharp sample. The advent of ultraviolet laser pulsing has widely enlarged the scope of APT to include a range of insulating materials, including hybrid organic-inorganic materials [3]. APT is specifically adept at characterizing nanomaterials with internal organic-inorganic interfaces, due to its elemental sensitivity and spatial accuracy. We recently demonstrated this capability in biological minerals in the magnetite cusp of the chiton tooth [4] and vertebrate bone and dentin [5].We report here on the characterization of native equine spleen ferritin using APT. Greene et al. recently used APT to analyse ferritin as a model for characterizing biological materials using APT. In this work, researchers used a solidified organic/salt matrix, which contained numerous ferritin complexes [6]. These APT tips of dense ferritin/salt deposits were able to undergo APT, providing a proof of concept through mass spectrometry results. However, they were unable to characterize individual proteins and their experiments suffered from drastic tip bending, preventing meaningful reconstructions [6]. To image individual ferritin protein complexes, we deposited a dilute solution of native equine spleen ferritin onto a silicon post coated with Au-Pd (Figure 1) [7]. Further encapsulation of the adsorbed molecules with Au-Pd and subsequent focused ion beam milling allowed for the fabrication of APT sample tips. This method allowed for a small number of ferritin complexes to be characterized. This work not only allows for resolution and characterization of ferritin, but also shows our ability to use APT to characterize discrete nanoparticles.Atom probe tomography characterizes ferritin as spherical accumulations of iron and oxygen surrounded by carbon and nitrogen. Creating an isoconcentration surface we can identify the iron-rich core within the ferritin protein (Figure ...

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Atom Probe Tomography of Apatites and Bone-Type Mineralized Tissues

Cited by 115 publications

References 56 publications

Chemical Imaging of Interfaces and in Interphases in Tooth Enamel

Chemical Imaging of Interfaces and in Interphases in Tooth Enamel

Atom Probe Tomography of Human Tooth Enamel and the Accurate Identification of Magnesium and Carbon in the Mass Spectrum

Towards Atom Probe Tomography of Hybrid Organic-Inorganic Nanoparticles

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