TY - JOUR
T1 - Phosphate Functional Groups Improve Oligo[(Polyethylene Glycol) Fumarate] Osteoconduction and BMP-2 Osteoinductive Efficacy
AU - Olthof, Maurits G.L.
AU - Tryfonidou, Marianna A.
AU - Liu, Xifeng
AU - Pouran, Behdad
AU - Meij, Björn P.
AU - Dhert, Wouter J.A.
AU - Yaszemski, Michael J.
AU - Lu, Lichun
AU - Alblas, Jacqueline
AU - Kempen, Diederik H.R.
N1 - Funding Information:
The authors acknowledge the financial support from the National Institutes of Health (R01 AR45871 and R01 EB03060), the AO Foundation (AO startup grant S-15-46K), the Dutch Arthritis Foundation (LLP12 and LLP22), and Anna-NOREF foundation. Furthermore, the authors thank Nynke Ankringa from the Department of Veterinary Pathology of the University of Utrecht for analyzing histology, and Loek Loozen, Michiel Croes, and Marianne K. E. Koolen from the Department of Orthopedic Surgery of the University Medical Center Utrecht for assisting with the surgery.
Publisher Copyright:
© Copyright 2018, Mary Ann Liebert, Inc.
PY - 2018/5
Y1 - 2018/5
N2 - 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.
AB - 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.
KW - bone morphogenetic protein 2
KW - bone tissue engineering
KW - oligo[(polyethylene glycol) fumarate]
KW - osteoconduction
KW - phosphate functional groups
UR - http://www.scopus.com/inward/record.url?scp=85047192757&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85047192757&partnerID=8YFLogxK
U2 - 10.1089/ten.tea.2017.0229
DO - 10.1089/ten.tea.2017.0229
M3 - Article
C2 - 29065776
AN - SCOPUS:85047192757
SN - 1937-3341
VL - 24
SP - 819
EP - 829
JO - Tissue Engineering - Part A
JF - Tissue Engineering - Part A
IS - 9-10
ER -