Bone Morphogenetic Protein 2 (BMP-2) Aggregates Can be Solubilized by Albumin-Investigation of BMP-2 Aggregation by Light Scattering and Electrophoresis.

Julius Sundermann,Holger Zagst,Heike Bunjes,Hermann Wätzig,Judith Kuntsche

doi:10.3390/pharmaceutics12121143

Julius Sundermann, Holger Zagst + Show 3 more

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https://doi.org/10.3390/pharmaceutics12121143

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Abstract

Bone morphogenetic protein 2 (BMP-2) has a high tendency to aggregate at physiological pH and physiological ionic strength, which can complicate the development of growth factor delivery systems. The aggregation behavior in differently concentrated BMP-2 solutions was investigated using dynamic and static light scattering. It was found that at higher concentrations larger aggregates are formed, whose size decreases again with increasing dilution. A solubilizing effect and therefore less aggregation was observed upon the addition of albumin. Imaged capillary isoelectric focusing and the simulation of the surface charges of BMP-2 were used to find a possible explanation for the unusually low solubility of BMP-2 at physiological pH. In addition to hydrophobic interactions, attractive electrostatic interactions might be decisive in the aggregation of BMP-2 due to the particular distribution of surface charges. These results help to better understand the solubility behavior of BMP-2 and thus support future pharmaceutical research and the development of new strategies for the augmentation of bone healing.

Highlights

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGF-β) family and are well known for their osteoinductive potential [1]
The transport of Bone morphogenetic protein 2 (BMP-2) to distant cells can be enabled by protein–protein binding with chordin, which leads to solubilization of the protein [2]
As BMP-2 is known to have the ability to renature after chaotropic denaturation [8], it was concluded that urea solutions were not chaotropic enough to provide a substantial BMP-2 solubilization during iciEF

Summary

Introduction

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGF-β) family and are well known for their osteoinductive potential [1]. The transport of BMP-2 to distant cells can be enabled by protein–protein binding with chordin, which leads to solubilization of the protein [2]. In the marketed BMP-2 formulation, the basic disulfide-bridged homodimeric protein, which has an isoelectric point (pI) of 8.5 [4] and a size of 26 kDa [5], is buffered at pH 4.5 after reconstitution. At this pH, the protein has a strong positive charge and is considered to be largely soluble. The formation of large BMP-2 aggregates (>1 μm) can be induced by increasing the pH from 4.5 to 6.5 in the marketed formulation INFUSE® [7]

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