Immobilization of a phosphonated analog of matrix phosphoproteins within cross-linked collagen as a templating mechanism for biomimetic mineralization

Li Sha Gu, Young Kyung Kim, Yan Liu, Kei Takahashi, Senthil Arun, Courtney E. Wimmer, Raquel Osorio, Jun Qi Ling, Stephen Warwick Looney, David Henry Pashley, Franklin Chi Meng Tay

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

Immobilization of phosphoproteins on a collagen matrix is important for the induction of intrafibrillar apatite mineralization. Unlike phosphate esters, polyphosphonic acid has no reactive sites for covalent binding to collagen amine groups. Binding of poly(vinyl phosphonic acid) (PVPA), a biomimetic templating analog of matrix phosphoproteins, to collagen was found to be electrostatic in nature. Thus, an alternative retention mechanism was designed for immobilization of PVPA on collagen by cross-linking the latter with carbodiimide (EDC). This mechanism is based on the principle of size exclusion entrapment of PVPA molecules within the internal water compartments of collagen. By cross-linking collagen with EDC, a zero length cross-linking agent, the sieving property of collagen is increased, enabling the PVPA to be immobilized within the collagen. The absence of covalent cross-linking between PVPA and collagen was confirmed by Fourier transform infrared spectroscopy. Based on these results, a concentration range for immobilized PVPA to template intrafibrillar apatite deposition was established and validated using a single layer reconstituted type I collagen mineralization model. In the presence of a polyacrylic acid-containing mineralization medium optimal intrafibrillar mineralization of the EDC-cross-linked collagen was achieved using 500 and 1000 μg ml -1 PVPA. The mineralized fibrils exhibited a hierarchical order of intrafibrillar mineral infiltration, as manifested by the appearance of electron-dense periodicity within unstained fibrils. Understanding the basic processes in intrafibrillar mineralization of reconstituted collagen creates opportunities for the design of tissue engineering materials for hard tissue repair and regeneration.

Original languageEnglish (US)
Pages (from-to)268-277
Number of pages10
JournalActa biomaterialia
Volume7
Issue number1
DOIs
StatePublished - Jan 1 2011

Fingerprint

Biomimetics
Phosphoproteins
Collagen
Immobilization
Acids
Apatites
carbopol 940
Apatite
Periodicity
Fourier Transform Infrared Spectroscopy
Tissue Engineering
Collagen Type I
phosphonic acid
Static Electricity
Tissue engineering
Infiltration
Amines
Minerals
Regeneration
Electrostatics

Keywords

  • Cross-linking
  • Intrafibrillar mineralization
  • Reconstituted collagen
  • Size exclusion
  • Templating analog

ASJC Scopus subject areas

  • Biotechnology
  • Biomaterials
  • Biochemistry
  • Biomedical Engineering
  • Molecular Biology

Cite this

Immobilization of a phosphonated analog of matrix phosphoproteins within cross-linked collagen as a templating mechanism for biomimetic mineralization. / Gu, Li Sha; Kim, Young Kyung; Liu, Yan; Takahashi, Kei; Arun, Senthil; Wimmer, Courtney E.; Osorio, Raquel; Ling, Jun Qi; Looney, Stephen Warwick; Pashley, David Henry; Tay, Franklin Chi Meng.

In: Acta biomaterialia, Vol. 7, No. 1, 01.01.2011, p. 268-277.

Research output: Contribution to journalArticle

Gu, Li Sha ; Kim, Young Kyung ; Liu, Yan ; Takahashi, Kei ; Arun, Senthil ; Wimmer, Courtney E. ; Osorio, Raquel ; Ling, Jun Qi ; Looney, Stephen Warwick ; Pashley, David Henry ; Tay, Franklin Chi Meng. / Immobilization of a phosphonated analog of matrix phosphoproteins within cross-linked collagen as a templating mechanism for biomimetic mineralization. In: Acta biomaterialia. 2011 ; Vol. 7, No. 1. pp. 268-277.
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AU - Kim, Young Kyung

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AU - Takahashi, Kei

AU - Arun, Senthil

AU - Wimmer, Courtney E.

AU - Osorio, Raquel

AU - Ling, Jun Qi

AU - Looney, Stephen Warwick

AU - Pashley, David Henry

AU - Tay, Franklin Chi Meng

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AB - Immobilization of phosphoproteins on a collagen matrix is important for the induction of intrafibrillar apatite mineralization. Unlike phosphate esters, polyphosphonic acid has no reactive sites for covalent binding to collagen amine groups. Binding of poly(vinyl phosphonic acid) (PVPA), a biomimetic templating analog of matrix phosphoproteins, to collagen was found to be electrostatic in nature. Thus, an alternative retention mechanism was designed for immobilization of PVPA on collagen by cross-linking the latter with carbodiimide (EDC). This mechanism is based on the principle of size exclusion entrapment of PVPA molecules within the internal water compartments of collagen. By cross-linking collagen with EDC, a zero length cross-linking agent, the sieving property of collagen is increased, enabling the PVPA to be immobilized within the collagen. The absence of covalent cross-linking between PVPA and collagen was confirmed by Fourier transform infrared spectroscopy. Based on these results, a concentration range for immobilized PVPA to template intrafibrillar apatite deposition was established and validated using a single layer reconstituted type I collagen mineralization model. In the presence of a polyacrylic acid-containing mineralization medium optimal intrafibrillar mineralization of the EDC-cross-linked collagen was achieved using 500 and 1000 μg ml -1 PVPA. The mineralized fibrils exhibited a hierarchical order of intrafibrillar mineral infiltration, as manifested by the appearance of electron-dense periodicity within unstained fibrils. Understanding the basic processes in intrafibrillar mineralization of reconstituted collagen creates opportunities for the design of tissue engineering materials for hard tissue repair and regeneration.

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