Mechanism of Enhanced Strontium Uptake into Calcite via an Amorphous Calcium Carbonate Crystallization Pathway

Littlewood, Janice L.; Shaw, Samuel; Peacock, Caroline L.; Bots, Pieter; Trivedi, Divyesh; Burke, Ian T.

doi:10.1021/acs.cgd.6b01599

Cited by 70 publications

(77 citation statements)

References 61 publications

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“…Additionally, the rates of conversion from amorphous to crystalline solids are known to be slow relative to rates of aragonite precipitation (Bots et al, ; Ihli et al, ), and thus unlikely to maintain the extremely rapid early larval calcification (Maeda‐Martinez, ; Waldbusser et al, ). Finally, amorphous solids tend to have less specificity for the elementally pure form of the crystal than crystalline antecedents (Littlewood et al, ), which is in contradiction to our observation of initially greater Ca‐specificity followed by less specificity of the precipitate composition (Figure ). Our results therefore suggest that the PDI shell is not formed through an ACC precursor mechanism.…”

Section: Discussioncontrasting

confidence: 99%

Mechanisms to Explain the Elemental Composition of the Initial Aragonite Shell of Larval Oysters

Haley

Hales

Brunner

et al. 2018

Geochem Geophys Geosyst

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Calcifying organisms face increasing stress from the changing carbonate chemistry of an acidifying ocean, particularly bivalve larvae that live in upwelling regions of the world, such as the coastal and estuarine waters of Oregon (USA). Arguably the first and most significant developmental hurdle faced by larval oysters is formation of their initial prodissoconch I (PDI) shell, upon which further ontological development depends. We measured the minor metal compositions (Sr/Ca, Mg/Ca) of this aragonitic PDI shell and of post‐PDI larval Crassostrea gigas shell, as well as the water they were reared in, over ∼20 days for a May and an August cohort in 2011, during which time there was no period of carbonate under‐saturation. After testing various methods, we successfully isolated the shell from organic tissue using a 5% active chlorine bleach solution. Elemental compositions (Sr, Mg, C, N) of the shells post‐treatment showed that shell Sr/Ca ranged from 1.55 to 1.82 mmol/mol; Mg/Ca from 0.60 to 1.11 mmol/mol, similar to the few comparable published data for larval oyster aragonite compositions. We compare these data in light of possible biomineralization mechanisms: an amorphous calcium carbonate (ACC) path, an intercellular path, and a direct‐from‐seawater path to shell formation via biologically induced inorganic precipitation of aragonite. The last option provides a mechanistic explanation for: (1) the accelerated precipitation rates of biogenic calcification in the absence of a calcifying fluid; (2) consistently elevated precipitation rates at varying ambient‐water saturation states; and (3) the high Ca‐selectivity of the early larval calcification despite rapid precipitation rates.

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Section: Discussioncontrasting

confidence: 99%

Mechanisms to Explain the Elemental Composition of the Initial Aragonite Shell of Larval Oysters

Haley

Hales

Brunner

et al. 2018

Geochem Geophys Geosyst

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“…On the other hand, amorphous structures have high ability to accommodate ions and molecules. Indeed, enhanced Sr 2+ uptake in calcite via an amorphous precursor pathway has been demonstrated [65]. Recently, the synergic effect of Sr 2+ and Mg 2+ on amorphous calcium phosphate stabilization [66] has been reported and shown to retard its conversion into HA.…”

Section: The Impact Of Sr 2+ On the Pathway Of Ha Mineralizationmentioning

confidence: 99%

Formation of stable strontium-rich amorphous calcium phosphate: Possible effects on bone mineral

et al. 2019

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a b s t r a c tBone, tooth enamel, and dentin accumulate Sr 2+ , a natural trace element in the human body. Sr 2+ comes from dietary and environmental sources and is thought to play a key role in osteoporosis treatments. However, the underlying impacts of Sr 2+ on bone mineralization remain unclear and the use of synthetic apatites (which are structurally different from bone mineral) and non-physiological conditions have led to contradictory results. Here, we report on the formation of a new Sr 2+ -rich and stable amorphous calcium phosphate phase, Sr(ACP). Relying on a bioinspired pathway, a series of Sr 2+ substituted hydroxyapatite (HA) that combines the major bone mineral features is depicted as model to investigate how this phase forms and Sr 2+ affects bone. In addition, by means of a comprehensive investigation the biomineralization pathway of Sr 2+ bearing HA is described showing that not more than 10 at% of Sr 2+ , i.e. a physiological limit incorporated in bone, can be incorporated into HA without phase segregation. A combination of 31 P and 1 H solid state NMR, energy electron loss spectromicroscopy, transmission electron microscopy, electron diffraction, and Raman spectroscopy shows that Sr 2+ introduces disorder in the HA culminating with the unexpected Sr(ACP), which co-exists with the HA under physiological conditions. These results suggest that heterogeneous Sr 2+ distribution in bone is associated with regions of low structural organization. Going further, such observations give clues from the physicochemical standpoint to understand the defects in bone formation induced by high Sr 2+ doses. Statement of SignificanceUnderstanding the role played by Sr 2+ has a relevant impact in physiological biomineralization and provides insights for its use as osteoporosis treatments. Previous studies inspired by the bone remodelling pathway led to the formation of biomimetic HA in terms of composition, structures and properties in water. Herein, by investigating different atomic percentage of Sr 2+ related to Ca 2+ in the synthesis, we demonstrate that 10% of Sr 2+ is the critical loads into the biomimetic HA phase; similarly to bone. Unexpectedly, using higher amount leads to the formation of a stable Sr 2+ -rich amorphous calcium phosphate phase that may high-dose related pathologies. Our results provide further understanding of the different ways Sr 2+ impacts bone.⇑ Corresponding authors at

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“…Indeed, the use of an amorphous precursor facilitates the incorporation of inclusions, which then remain entrapped in the calcium carbonate phase during and after its crystallization. Accordingly, numerous bioinspired studies have addressed the potential utility of an amorphous precursor, using ACC as the precursor for synthesizing calcite with a high level of inclusion incorporation . That is how Mg‐calcite, whose formation is kinetically and thermodynamically disfavored, was successfully synthesized from crystallization of Mg‐rich ACC (Mg‐ACC) …”

Section: Introductionmentioning

confidence: 99%

Experimental and Theoretical Insights into the Bioinspired Formation of Disordered Ba‐Calcite

Seknazi

Levy

Polishchuk

et al. 2018

Adv Funct Materials

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Calcite has the ability to host large amounts of intracrystalline inclusions, a phenomenon that is known to be the case in biominerals and has been demonstrated in bioinspired synthetic systems. In this study, barium ion is focused on as the inclusion. Highly substituted Ba-calcite possesses disordered carbonate orientations, characteristic of 3 3 R R m m symmetry. It is shown that calcite experiences an order-disorder transition, in which the carbonate groups undergo progressive loss of their rotational order with increasing amounts of incorporated Ba, and reach complete rotational disorder for a critical amount of Ba. This transition is characterized and a theoretical model justifying the influence of Ba is proposed. Moreover, the disordered 3 3 R R m m Ba-substituted calcite has been previously identified as a high-temperature phase or as a highly metastable room-temperature phase. Those descriptions are challenged by successfully synthesizing it under slow-rate conditions and by studying its thermal behavior, and it is concluded that the fully disordered Ba-calcite is stable, whereas the transitional, partially disordered Ba-calcite phase is metastable.

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Mechanism of Enhanced Strontium Uptake into Calcite via an Amorphous Calcium Carbonate Crystallization Pathway

Cited by 70 publications

References 61 publications

Mechanisms to Explain the Elemental Composition of the Initial Aragonite Shell of Larval Oysters

Mechanisms to Explain the Elemental Composition of the Initial Aragonite Shell of Larval Oysters

Formation of stable strontium-rich amorphous calcium phosphate: Possible effects on bone mineral

Experimental and Theoretical Insights into the Bioinspired Formation of Disordered Ba‐Calcite

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