Improved Bone Morphogenetic Protein-2 Retention in an Injectable Collagen Matrix Using Bifunctional Peptides

Paul T Hamilton,Michelle S Jansen,R Edward Benson,Joseph C Gile,Shrikumar A Nair,Hanne Grøn,Jonathan A Hodges,Wayne F Beyer,Sathya Ganesan,Robin Hyde-Deruyscher,Fabrizio Gelain

doi:10.1371/journal.pone.0070715

Abstract

To promote healing of many orthopedic injuries, tissue engineering approaches are being developed that combine growth factors such as Bone Morphogenetic Proteins (BMP) with biomaterial carriers. Although these technologies have shown great promise, they still face limitations. We describe a generalized approach to create target-specific modular peptides that bind growth factors to implantable biomaterials. These bifunctional peptide coatings provide a novel way to modulate biology on the surface of an implant.Using phage display techniques, we have identified peptides that bind with high affinity to BMP-2. The peptides that bind to BMP-2 fall into two different sequence clusters. The first cluster of peptide sequences contains the motif W-X-X-F-X-X-L (where X can be any amino acid) and the second cluster contains the motif F-P-L-K-G. We have synthesized bifunctional peptide linkers that contain BMP-2 and collagen-binding domains. Using a rat ectopic bone formation model, we have injected rhBMP-2 into a collagen matrix with or without a bifunctional BMP-2: collagen peptide (BC-1). The presence of BC-1 significantly increased osteogenic cellular activity, the area of bone formed, and bone maturity at the site of injection. Our results suggest that bifunctional peptides that can simultaneously bind to a growth factor and an implantable biomaterial can be used to control the delivery and release of growth factors at the site of implantation.

Highlights

7.9 million fractures occur each year in the United States alone, and approximately 10% of fractures exhibit delayed or impaired healing [1]
Phage display was performed against immobilized recombinant human BMP-2 (rhBMP-2) with 10 different peptide libraries, representing over 10 billion peptide sequences
The consensus sequence among the peptides indicates that all the peptides within a sequence cluster are binding to the same site on Bone Morphogenetic Proteins (BMP)-2, and the common amino acids that make up the motif are responsible for the specific interactions with BMP-2

Summary

Introduction

7.9 million fractures occur each year in the United States alone, and approximately 10% of fractures exhibit delayed or impaired healing [1]. Bone morphogenetic proteins (BMPs) are osteogenic growth factors that have been shown to stimulate new bone formation and fracture healing [2,3]. Recombinant human BMP-2 (rhBMP-2) has been shown to accelerate healing of open tibial fractures [4], and rhBMP-7 has been used to treat tibial nonunions [5]. These clinical applications, require open surgical procedures to insert the BMP–loaded carrier. Supraphysiological amounts of BMPs are required to promote bone formation due to the growth factor’s rapid diffusion away from its carrier [6,7]. The use of high doses, raises concerns about bone formation away from the site and impact on nearby tissues and organs [8]; in accordance, rhBMP-2 use has been linked to a variety of serious adverse events [9]

Methods

Results

Conclusion