Phosphate Functional Groups Improve Oligo[(Polyethylene Glycol) Fumarate] Osteoconduction and BMP-2 Osteoinductive Efficacy

Maurits G.L. Olthof, Marianna A. Tryfonidou, Xifeng Liu, Behdad Pouran, Björn P. Meij, Wouter J.A. Dhert, Michael J Yaszemski, Lichun Lu, Jacqueline Alblas, Diederik H.R. Kempen

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Off-the-shelf availability in large quantities, drug delivery functionality, and modifiable chemistry and mechanical properties make synthetic polymers highly suitable candidates for bone grafting. However, most synthetic polymers lack the ability to support cell attachment, proliferation, migration, and differentiation, and ultimately tissue formation. Incorporating anionic peptides into the polymer that mimics acidic proteins, which contribute to biomineralization and cellular attachment, could enhance bone formation. Therefore, this study investigates the effect of a phosphate functional group on osteoconductivity and BMP-2-induced bone formation in an injectable and biodegradable oligo[(polyethylene glycol) fumarate] (OPF) hydrogel. Three types of OPF hydrogels were fabricated using 0%, 20%, or 40% Bis(2-(methacryloyloxy)ethyl) phosphate creating unmodified OPF-noBP and phosphate-modified OPF-BP20 and OPF-BP40, respectively. To account for the osteoinductive effect of various BMP-2 release profiles, two different release profiles (i.e., different ratios of burst and sustained release) were obtained by varying the BMP-2 loading method. To investigate the osteoconductive effect of phosphate modification, unloaded OPF composites were assessed for bone formation in a bone defect model after 3, 6, and 9 weeks. To determine the effect of the hydrogel phosphate modification on BMP-2-induced bone formation, BMP-2 loaded OPF composites with differential BMP-2 release were analyzed after 9 weeks of subcutaneous implantation in rats. The phosphate-modified OPF hydrogels (OPF-BP20 and OPF-BP40) generated significantly more bone in an orthotopic defect compared to the unmodified hydrogel (OPF-noBP). Furthermore, the phosphate functionalized surface-enhanced BMP-2-induced ectopic bone formation regardless of the BMP-2 release profile. In conclusion, this study clearly shows that phosphate functional groups improve the osteoconductive properties of OPF and enhanced BMP-2-induced bone formation. Therefore, functionalizing hydrogels with phosphate groups by crosslinking monomers into the hydrogel matrix could provide a valuable method for improving polymer characteristics and holds great promise for bone tissue engineering.

Original languageEnglish (US)
Pages (from-to)819-829
Number of pages11
JournalTissue Engineering - Part A
Volume24
Issue number9-10
DOIs
StatePublished - May 1 2018

Keywords

  • bone morphogenetic protein 2
  • bone tissue engineering
  • oligo[(polyethylene glycol) fumarate]
  • osteoconduction
  • phosphate functional groups

ASJC Scopus subject areas

  • Bioengineering
  • Biochemistry
  • Biomaterials
  • Biomedical Engineering

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  • Cite this

    Olthof, M. G. L., Tryfonidou, M. A., Liu, X., Pouran, B., Meij, B. P., Dhert, W. J. A., Yaszemski, M. J., Lu, L., Alblas, J., & Kempen, D. H. R. (2018). Phosphate Functional Groups Improve Oligo[(Polyethylene Glycol) Fumarate] Osteoconduction and BMP-2 Osteoinductive Efficacy. Tissue Engineering - Part A, 24(9-10), 819-829. https://doi.org/10.1089/ten.tea.2017.0229