title: Bone morphogenetic protein-2 binds as multilayers to a collagen delivery matrix: an equilibrium thermodynamic analysis.
abstract: Recombinant human bone morphogenetic protein-2 (rhBMP-2) promotes bone growth but must be retained at the delivery site for optimal efficacy in vivo. rhBMP-2 release from a collagen-based matrix has shown favorable pharmacokinetics. The present study assessed binding affinity and binding saturation of rhBMP-2 to a collagen matrix as a function of solution and rhBMP-2 isoform variables. Results indicate that rhBMP-2 binds to the collagen matrix with affinities on the order of 10(3) to 10(4) M(-1). Maximum binding, nu, was primarily a function of pH for heterogeneous rhBMP-2 and the extended (T(266)/T(266)) isoform. However, binding saturation of the <Q(283)/<Q(283) isoform was unaffected by pH. Overall, binding saturation was higher than the calculated saturation of a rhBMP-2 monolayer, suggesting both hydrophobic and ionic interactions in a multilayer formation. The contributions of pH and ionic strength to the linkage free energy of interaction was on the order of 1.3 kcal mol(-1) and approximately 0.3 kcal mol(-1), respectively. This thermodynamic approach can serve to optimize interactions between therapeutic proteins and delivery systems.
authors.affiliation: Formulation and Process Development, Wyeth BioPharma, One Burt Road, Andover, MA 01810, USA.
authors.forename: Randy
authors.initials: R
authors.lastname: Morin
authors.forename: David
authors.initials: D
authors.lastname: Kaplan
authors.forename: Bernardo
authors.initials: B
authors.lastname: Perez-Ramirez
mesh_terms: D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000737:chemistry* / Q000378:metabolism* / Q000493:pharmacokinetics; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D013816:Thermodynamics; D016212:Transforming Growth Factor beta / Q000737:chemistry* / Q000378:metabolism* / Q000493:pharmacokinetics
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D020033:Protein Isoforms; D016212:Transforming Growth Factor beta; D003094:Collagen