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Adsorption of amorphous silica nanoparticles onto hydroxyapatite surfaces differentially alters surfaces properties and adhesion of human osteoblast cells

Kalia, Priya, Brooks, Roger A., Kinrade, Stephen D., Morgan, David John, Brown, Andrew P., Rushton, Neil and Jugdaohsingh, Ravin 2016. Adsorption of amorphous silica nanoparticles onto hydroxyapatite surfaces differentially alters surfaces properties and adhesion of human osteoblast cells. PLoS ONE 11 (2) , e0144780. 10.1371/journal.pone.0144780

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Silicon (Si) is suggested to be an important/essential nutrient for bone and connective tissue health. Silicon-substituted hydroxyapatite (Si-HA) has silicate ions incorporated into its lattice structure and was developed to improve attachment to bone and increase new bone formation. Here we investigated the direct adsorption of silicate species onto an HA coated surface as a cost effective method of incorporating silicon on to HA surfaces for improved implant osseointegration, and determined changes in surface characteristics and osteoblast cell adhesion. Plasma-sprayed HA-coated stainless steel discs were incubated in silica dispersions of different concentrations (0–42 mM Si), at neutral pH for 12 h. Adsorbed Si was confirmed by XPS analysis and quantified by ICP-OES analysis following release from the HA surface. Changes in surface characteristics were determined by AFM and measurement of surface wettability. Osteoblast cell adhesion was determined by vinculin plaque staining. Maximum Si adsorption to the HA coated disc occurred after incubation in the 6 mM silica dispersion and decreased progressively with higher silica concentrations, while no adsorption was observed with dispersions below 6 mM Si. Comparison of the Si dispersions that produced the highest and lowest Si adsorption to the HA surface, by TEM-based analysis, revealed an abundance of small amorphous nanosilica species (NSP) of ~1.5 nm in diameter in the 6 mM Si dispersion, with much fewer and larger NSP in the 42 mM Si dispersions. 29Si-NMR confirmed that the NSPs in the 6 mM silica dispersion were polymeric and similar in composition to the larger NSPs in the 42 mM Si dispersion, suggesting that the latter were aggregates of the former. Amorphous NSP adsorbed from the 6 mM dispersion on to a HA-coated disc surface increased the surface’s water contact angle by 53°, whereas that adsorbed from the 42 mM dispersion decreased the contact angle by 18°, indicating increased and decreased hydrophobicity, respectively. AFM showed an increase in surface roughness of the 6 mM Si treated surface, which correlated well with an increase in number of vinculin plaques. These findings suggest that NSP of the right size (relative to charge) adsorb readily to the HA surface, changing the surface characteristics and, thus, improving osteoblast cell adhesion. This treatment provides a simple way to modify plasma-coated HA surfaces that may enable improved osseointegration of bone implants.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Cardiff Catalysis Institute (CCI)
Subjects: Q Science > QD Chemistry
Additional Information: Copyright: © 2016 Kalia et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Publisher: Public Library of Science
ISSN: 1932-6203
Funders: Engineering and Physical Sciences Research Council, National Institute of Health Research, Medical Research Council
Date of First Compliant Deposit: 30 March 2016
Date of Acceptance: 22 November 2015
Last Modified: 11 Sep 2020 09:15

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