title: Heparin microparticle effects on presentation and bioactivity of bone morphogenetic protein-2.
abstract: Biomaterials capable of providing localized and sustained presentation of bioactive proteins are critical for effective therapeutic growth factor delivery. However, current biomaterial delivery vehicles commonly suffer from limitations that can result in low retention of growth factors at the site of interest or adversely affect growth factor bioactivity. Heparin, a highly sulfated glycosaminoglycan, is an attractive growth factor delivery vehicle due to its ability to reversibly bind positively charged proteins, provide sustained delivery, and maintain protein bioactivity. This study describes the fabrication and characterization of heparin methacrylamide (HMAm) microparticles for recombinant growth factor delivery. HMAm microparticles were shown to efficiently bind several heparin-binding growth factors (e.g. bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (FGF-2)), including a wide range of BMP-2 concentrations that exceeds the maximum binding capacity of other common growth factor delivery vehicles, such as gelatin. BMP-2 bioactivity was assessed on the basis of alkaline phosphatase (ALP) activity induced in skeletal myoblasts (C2C12). Microparticles loaded with BMP-2 stimulated comparable C2C12 ALP activity to soluble BMP-2 treatment, indicating that BMP-2-loaded microparticles retain bioactivity and potently elicit a functional cell response. In summary, our results suggest that heparin microparticles stably retain large amounts of bioactive BMP-2 for prolonged periods of time, and that presentation of BMP-2 via heparin microparticles can elicit cell responses comparable to soluble BMP-2 treatment. Consequently, heparin microparticles present an effective method of delivering and spatially retaining growth factors that could be used in a variety of systems to enable directed induction of cell fates and tissue regeneration.
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, 315 Ferst Drive, Atlanta, GA 30332, USA.
authors.forename: Marian H
authors.initials: MH
authors.lastname: Hettiaratchi
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, 315 Ferst Drive, Atlanta, GA 30332, USA.
authors.forename: Tobias
authors.initials: T
authors.lastname: Miller
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, 315 Ferst Drive, Atlanta, GA 30332, USA; The Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA 30332, USA.
authors.forename: Johnna S
authors.initials: JS
authors.lastname: Temenoff
authors.affiliation: The Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA 30332, USA; The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, GA 30332, USA.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Guldberg
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, 315 Ferst Drive, Atlanta, GA 30332, USA; The Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, Atlanta, GA 30332, USA. Electronic address: todd.mcdevitt@bme.gatech.edu.
authors.forename: Todd C
authors.initials: TC
authors.lastname: McDevitt
mesh_terms: D000178:Acrylamides / Q000737:chemistry; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000494:pharmacology; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism*; D002478:Cells, Cultured; D016503:Drug Delivery Systems / Q000379:methods; D006493:Heparin / Q000737:chemistry* / Q000494:pharmacology; D051379:Mice; D053758:Nanoparticles / Q000737:chemistry*; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000378:metabolism; D023822:Tissue Engineering; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D000178:Acrylamides; D001672:Biocompatible Materials; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D006493:Heparin; C496354:Fgfr2 protein, mouse; D051497:Receptor, Fibroblast Growth Factor, Type 2; D000469:Alkaline Phosphatase; C045985:methacrylamide
keywords: Alkaline phosphatase; Bone morphogenetic protein; Bone tissue engineering; Glycosaminoglycan; Heparin; Microparticle