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Poly(γ-glutamic acid)/silica hybrids with calcium incorporated in the silica network by use of a calcium alkoxide precursor

Poly(γ-glutamic acid)/silica hybrids with calcium incorporated in the silica network by use of a calcium alkoxide precursor
Poly(γ-glutamic acid)/silica hybrids with calcium incorporated in the silica network by use of a calcium alkoxide precursor
Current materials used for bone regeneration are usually bioactive ceramics or glasses. Although they bond to bone, they are brittle. There is a need for new materials that can combine bioactivity with toughness and controlled biodegradation. Sol‐gel hybrids have the potential to do this through their nanoscale interpenetrating networks (IPN) of inorganic and organic components. Poly(γ‐glutamic acid) (γ‐PGA) was introduced into the sol‐gel process to produce a hybrid of γ‐PGA and bioactive silica. Calcium is an important element for bone regeneration but calcium sources that are used traditionally in the sol‐gel process, such as Ca salts, do not allow Ca incorporation into the silicate network during low‐temperature processing. The hypothesis for this study was that using calcium methoxyethoxide (CME) as the Ca source would allow Ca incorporation into the silicate component of the hybrid at room temperature. The produced hybrids would have improved mechanical properties and controlled degradation compared with hybrids of calcium chloride (CaCl2), in which the Ca is not incorporated into the silicate network. Class II hybrids, with covalent bonds between the inorganic and organic species, were synthesised by using organosilane. Calcium incorporation in both the organic and inorganic IPNs of the hybrid was improved when CME was used. This was clearly observed by using FTIR and solid‐state NMR spectroscopy, which showed ionic cross‐linking of γ‐PGA by Ca and a lower degree of condensation of the Si species compared with the hybrids made with CaCl2 as the Ca source. The ionic cross‐linking of γ‐PGA by Ca resulted in excellent compressive strength and reduced elastic modulus as measured by compressive testing and nanoindentation, respectively. All hybrids showed bioactivity as hydroxyapatite (HA) was formed after immersion in simulated body fluid (SBF).
0947-6539
8149-8160
Poologasundarampillai, Gowsihan
eb107fef-363a-4bf4-a845-ff83d93037f4
Yu, Bobo
1b14306f-9d25-4d74-a7ad-863d9d31abc7
Tsigkou, Olga
32ad58e6-8bec-4c80-ad04-dce7ef5caa0b
Wang, Daming
912aa2b1-b80b-42db-afcc-4a753197a523
Romer, Frederik
78473760-5d63-472a-ab97-2e5ca3645a98
Bhakhri, Vineet
de3d26ca-96cb-4a3c-a8ea-491d9cd1255c
Giuliani, Finn
189bf26d-11af-4441-bf1d-a5d48ee9f6d0
Stevens, Molly M.
2af17549-764e-4c18-a316-f7dc790398e0
Mcphail, David S.
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Smith, Mark E.
abd04fbf-5f56-459d-89ec-e51ab2598c09
Hanna, John V.
20ab8960-4ac0-41c7-bc4a-a40195717a51
Jones, Julian R.
be62105e-98fc-40ff-95cb-16afc9f3b512
Poologasundarampillai, Gowsihan
eb107fef-363a-4bf4-a845-ff83d93037f4
Yu, Bobo
1b14306f-9d25-4d74-a7ad-863d9d31abc7
Tsigkou, Olga
32ad58e6-8bec-4c80-ad04-dce7ef5caa0b
Wang, Daming
912aa2b1-b80b-42db-afcc-4a753197a523
Romer, Frederik
78473760-5d63-472a-ab97-2e5ca3645a98
Bhakhri, Vineet
de3d26ca-96cb-4a3c-a8ea-491d9cd1255c
Giuliani, Finn
189bf26d-11af-4441-bf1d-a5d48ee9f6d0
Stevens, Molly M.
2af17549-764e-4c18-a316-f7dc790398e0
Mcphail, David S.
26e659c5-747a-4f81-9144-2e4fbcc49556
Smith, Mark E.
abd04fbf-5f56-459d-89ec-e51ab2598c09
Hanna, John V.
20ab8960-4ac0-41c7-bc4a-a40195717a51
Jones, Julian R.
be62105e-98fc-40ff-95cb-16afc9f3b512

Poologasundarampillai, Gowsihan, Yu, Bobo, Tsigkou, Olga, Wang, Daming, Romer, Frederik, Bhakhri, Vineet, Giuliani, Finn, Stevens, Molly M., Mcphail, David S., Smith, Mark E., Hanna, John V. and Jones, Julian R. (2014) Poly(γ-glutamic acid)/silica hybrids with calcium incorporated in the silica network by use of a calcium alkoxide precursor. Chemistry - A European Journal, 20 (26), 8149-8160. (doi:10.1002/chem.201304013).

Record type: Article

Abstract

Current materials used for bone regeneration are usually bioactive ceramics or glasses. Although they bond to bone, they are brittle. There is a need for new materials that can combine bioactivity with toughness and controlled biodegradation. Sol‐gel hybrids have the potential to do this through their nanoscale interpenetrating networks (IPN) of inorganic and organic components. Poly(γ‐glutamic acid) (γ‐PGA) was introduced into the sol‐gel process to produce a hybrid of γ‐PGA and bioactive silica. Calcium is an important element for bone regeneration but calcium sources that are used traditionally in the sol‐gel process, such as Ca salts, do not allow Ca incorporation into the silicate network during low‐temperature processing. The hypothesis for this study was that using calcium methoxyethoxide (CME) as the Ca source would allow Ca incorporation into the silicate component of the hybrid at room temperature. The produced hybrids would have improved mechanical properties and controlled degradation compared with hybrids of calcium chloride (CaCl2), in which the Ca is not incorporated into the silicate network. Class II hybrids, with covalent bonds between the inorganic and organic species, were synthesised by using organosilane. Calcium incorporation in both the organic and inorganic IPNs of the hybrid was improved when CME was used. This was clearly observed by using FTIR and solid‐state NMR spectroscopy, which showed ionic cross‐linking of γ‐PGA by Ca and a lower degree of condensation of the Si species compared with the hybrids made with CaCl2 as the Ca source. The ionic cross‐linking of γ‐PGA by Ca resulted in excellent compressive strength and reduced elastic modulus as measured by compressive testing and nanoindentation, respectively. All hybrids showed bioactivity as hydroxyapatite (HA) was formed after immersion in simulated body fluid (SBF).

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e-pub ahead of print date: 18 May 2014
Published date: 23 June 2014

Identifiers

Local EPrints ID: 440900
URI: http://eprints.soton.ac.uk/id/eprint/440900
ISSN: 0947-6539
PURE UUID: 6f57a8e4-58bc-4823-a444-2dd9e5de2cfa

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Date deposited: 22 May 2020 16:34
Last modified: 22 May 2020 16:37

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Contributors

Author: Gowsihan Poologasundarampillai
Author: Bobo Yu
Author: Olga Tsigkou
Author: Daming Wang
Author: Frederik Romer
Author: Vineet Bhakhri
Author: Finn Giuliani
Author: Molly M. Stevens
Author: David S. Mcphail
Author: Mark E. Smith
Author: John V. Hanna
Author: Julian R. Jones

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