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Amorphous polyphosphate–hydroxyapatite: A morphogenetically active substrate for bone-related SaOS-2 cells in vitro

Paper ID Volume ID Publish Year Pages File Format Full-Text
158 11 2016 10 PDF Available
Title
Amorphous polyphosphate–hydroxyapatite: A morphogenetically active substrate for bone-related SaOS-2 cells in vitro
Abstract

There is increasing evidence that inorganic calcium-polyphosphates (polyP) are involved in human bone hydroxyapatite (HA) formation. Here we investigated the morphology of the particles, containing calcium phosphate (CaP) with different concentrations of various Na–polyP concentrations, as well as their effects in cell culture. We used both SaOS-2 cells and human mesenchymal stem cells. The polymeric phosphate readily binds calcium ions under formation of insoluble precipitates. We found that addition of low concentrations of polyP (<10 wt.%, referred to the CaP deposits) results in an increased size of the HA crystals. Surprisingly, at higher polyP concentrations (>10 wt.%) the formation of crystalline HA is prevented and amorphous polyP/HA hybrid particles with a size of ≈50 nm are formed, most likely consisting of polyP molecules linked via Ca2+ bridges to the surface of the CaP deposits. Further studies revealed that the polyP–CaP particles cause a strong upregulation of the expression of the genes encoding for two marker proteins of bone formation, collagen type I and alkaline phosphatase. Based on their morphogenetic activity the amorphous polyP–CaP particles offer a promising material for the development of bone implants, formed from physiological inorganic precursors/polymers.Statement of significanceHydroxyapatite (HA) is a naturally occurring mineral of vertebrate bone. Natural HA, a bio-ceramic material which is crystalline to different scale, has been used as a biomaterial to fabricate scaffolds for in situ bone regeneration and other tissue engineering purposes. In contrast to natural HA, synthetic apatite is much less effective. In general, while HA is bioactive, its interaction and biocompatibility with existing bone tissue is low. These properties have been attributed to a minimal degradability in the physiological environment. In the present study we introduce a new Ca–phosphate (CaP) fabrication technology, starting from calcium chloride and dibasic ammonium phosphate with the HA characteristic Ca/P molar ratio of 10:6 and report that after addition >10% (by weight) of polyphosphate (polyP) amorphous CaP/HA samples were obtained. Those samples elicits strong morphogenetic activity let us to conclude that polyP/HA-based material might be beneficial for application as bone substitute implant.

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Keywords
Polyphosphate; Microparticles; Hydroxyapatite; Collagen type I; Alkaline phosphatase; Morphogenetic activity
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Amorphous polyphosphate–hydroxyapatite: A morphogenetically active substrate for bone-related SaOS-2 cells in vitro
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Publisher
Database: Elsevier - ScienceDirect
Journal: Acta Biomaterialia - Volume 31, February 2016, Pages 358–367
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us