The effect of the addition of a polyglutamate motif to RGD on peptide tethering to hydroxyapatite and the promotion of mesenchymal stem cell adhesion

A. A. Sawyer, D. M. Weeks, S. S. Kelpke, Michael Scott McCracken, S. L. Bellis

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

Mimicking endogenous bone-binding proteins, RGD peptides have been synthesized with polyacidic amino acid domains in order to ionically tether the peptides to bone-like synthetic biomaterials, including hydroxyapatite (HA). However, a direct comparison of unmodified RGD with polyacidic-conjugated RGD has not been performed, and thus a benefit for the acidic domain has not been established. We evaluated the peptide/HA bond of RGD peptides with and without an attached polyglutamate sequence (E7), as well as examined mesenchymal stem cell (MSC) adhesion and morphology as they were affected by the conjugated peptide. We found that significantly more E7RGD was bound to HA than RGD at all coating concentrations tested, and moreover, more E 7RGD was retained on the HA surface even after extended washing in serum-free media. Consistent with in vitro results, higher levels of E 7RGD than RGD remained on HA that had been implanted in vivo for 24 h, indicating that the polyacidic domain improved peptide-binding efficiency. At several peptide concentrations, E7RGD increased cell adhesion compared to RGD surfaces, establishing a biological benefit for the E 7 modification. In addition, HA pre-coated sequentially with low-density E7RGD (1-10 μg/ml) and serum (FBS) stimulated cell adhesion and spreading, compared to either coating alone, suggesting that an ionic linkage allows for the potential adsorption of serum proteins to unoccupied sites, which may be important for bone formation in vivo. Collectively, these results suggest that tethering peptides to HA via a polyglutamate domain is an effective method for improving the peptide/HA bond, as well as for enhancing MSC adhesion.

Original languageEnglish (US)
Pages (from-to)7046-7056
Number of pages11
JournalBiomaterials
Volume26
Issue number34
DOIs
StatePublished - Dec 1 2005

Fingerprint

Polyglutamic Acid
Cell adhesion
Durapatite
Stem cells
Mesenchymal Stromal Cells
Hydroxyapatite
Cell Adhesion
Peptides
Bone
Bone and Bones
Coatings
arginyl-glycyl-aspartic acid
Serum-Free Culture Media
Biocompatible Materials
Osteogenesis
Washing
Adsorption
Blood Proteins
Biomaterials
Carrier Proteins

Keywords

  • Bone
  • Cell adhesion
  • Cell spreading
  • Hydroxyapatite
  • Mesenchymal stem cell
  • RGD peptide

ASJC Scopus subject areas

  • Bioengineering
  • Ceramics and Composites
  • Biophysics
  • Biomaterials
  • Mechanics of Materials

Cite this

The effect of the addition of a polyglutamate motif to RGD on peptide tethering to hydroxyapatite and the promotion of mesenchymal stem cell adhesion. / Sawyer, A. A.; Weeks, D. M.; Kelpke, S. S.; McCracken, Michael Scott; Bellis, S. L.

In: Biomaterials, Vol. 26, No. 34, 01.12.2005, p. 7046-7056.

Research output: Contribution to journalArticle

Sawyer, A. A. ; Weeks, D. M. ; Kelpke, S. S. ; McCracken, Michael Scott ; Bellis, S. L. / The effect of the addition of a polyglutamate motif to RGD on peptide tethering to hydroxyapatite and the promotion of mesenchymal stem cell adhesion. In: Biomaterials. 2005 ; Vol. 26, No. 34. pp. 7046-7056.
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AU - Weeks, D. M.

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AU - Bellis, S. L.

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AB - Mimicking endogenous bone-binding proteins, RGD peptides have been synthesized with polyacidic amino acid domains in order to ionically tether the peptides to bone-like synthetic biomaterials, including hydroxyapatite (HA). However, a direct comparison of unmodified RGD with polyacidic-conjugated RGD has not been performed, and thus a benefit for the acidic domain has not been established. We evaluated the peptide/HA bond of RGD peptides with and without an attached polyglutamate sequence (E7), as well as examined mesenchymal stem cell (MSC) adhesion and morphology as they were affected by the conjugated peptide. We found that significantly more E7RGD was bound to HA than RGD at all coating concentrations tested, and moreover, more E 7RGD was retained on the HA surface even after extended washing in serum-free media. Consistent with in vitro results, higher levels of E 7RGD than RGD remained on HA that had been implanted in vivo for 24 h, indicating that the polyacidic domain improved peptide-binding efficiency. At several peptide concentrations, E7RGD increased cell adhesion compared to RGD surfaces, establishing a biological benefit for the E 7 modification. In addition, HA pre-coated sequentially with low-density E7RGD (1-10 μg/ml) and serum (FBS) stimulated cell adhesion and spreading, compared to either coating alone, suggesting that an ionic linkage allows for the potential adsorption of serum proteins to unoccupied sites, which may be important for bone formation in vivo. Collectively, these results suggest that tethering peptides to HA via a polyglutamate domain is an effective method for improving the peptide/HA bond, as well as for enhancing MSC adhesion.

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