Influence of nanoporosity on the nature of hydroxyapatite formed on bioactive calcium silicate model glass

For hard tissue regeneration, the bioactivity of a material is measured by its ability to induce the formation of hydroxyapatite (HA) under physiological conditions. It depends on the dissolution behavior of the glass, which itself is determined by the composition and structure of glass. The enhance...

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Published in:Journal of biomedical materials research. Part B, Applied biomaterials Applied biomaterials, 2019-05, Vol.107 (4), p.886-899
Main Authors: Thamma, Ukrit, Kowal, Tia, Falk, Matthias, Jain, Himanshu
Format: Article
Language:English
Subjects:
Bioglass
Biological activity
Biomedical materials
Calcium
Calcium ions
Calcium silicates
Calcium transport
Carbonation
Diffusion rate
Glass substrates
Growth rate
Hydroxyapatite
Materials research
Materials science
Plates (structural members)
Porosity
Regeneration
Sintering (powder metallurgy)
Size distribution
Sol-gel processes
Tissue engineering
X ray photoelectron spectroscopy
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Summary:For hard tissue regeneration, the bioactivity of a material is measured by its ability to induce the formation of hydroxyapatite (HA) under physiological conditions. It depends on the dissolution behavior of the glass, which itself is determined by the composition and structure of glass. The enhanced HA growth on nanoporous than on nonporous glass has been attributed by some to greater specific surface area (SSA), but to nanopore size distribution by others. To decouple the influence of nanopore size and SSA on HA formation, we have successfully fabricated homogeneous 30CaO-70SiO (30C70S) model bioactive glass monoliths with different nanopore sizes, yet similar SSA via a combination of sol-gel, solvent exchange, and sintering processes. After incubation in PBS, HA, and Type-B carbonated HA (HA/B-CHA) form on nanoporous monoliths. The XPS, FTIR, and SEM analyses provide the first unambiguous demonstration of the influence of nanopore size alone on the formation pathway, growth rate, and microstructure of HA/CHA. Due to pore-size limited diffusion of PO , two HA/CHA formation pathways are observed: HA/CHA surface deposition and/or HA/CHA incorporation into nanopores. HA/CHA growth rate on the surface of a nanoporous glass monolith is dominated by the pore-size limited transport of Ca ions dissolved from nanoporous glass substrates. Furthermore, with increasing nanopore size, HA/CHA microstructures evolve from needle-like, plate-like, to flower-like appearance. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 886-899, 2019.
ISSN:1552-4973
1552-4981
DOI:10.1002/jbm.b.34184