Hettiaratchi Marian H, Chou Catherine, Servies Nicholas, Smeekens Johanna M, Cheng Albert, Esancy Camden, Wu Ronghu, McDevitt Todd C, Guldberg Robert E, Krishnan Laxminarayanan
1 The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia .
2 School of Chemistry and Biochemistry, Georgia Institute of Technology , Atlanta, Georgia .
Tissue Eng Part A. 2017 Jul;23(13-14):683-695. doi: 10.1089/ten.tea.2016.0507. Epub 2017 Mar 24.
Tissue engineering strategies involving the in vivo delivery of recombinant growth factors are often limited by the inability of biomaterials to spatially control diffusion of the delivered protein within the site of interest. The poor spatiotemporal control provided by porous collagen sponges, which are used for the clinical delivery of bone morphogenetic protein-2 (BMP-2) for bone regeneration, has necessitated the use of supraphysiological protein doses, leading to inflammation and heterotopic ossification. This study describes a novel tissue engineering strategy to spatially control rapid BMP-2 diffusion from collagen sponges in vivo by creating a high-affinity BMP-2 sink around the collagen sponge. We designed an electrospun poly-ɛ-caprolactone nanofiber mesh containing physically entrapped heparin microparticles, which have been previously demonstrated to bind and retain large amounts of BMP-2. Nanofiber meshes containing 0.05 and 0.10 mg of microparticles/cm demonstrated increased BMP-2 binding and decreased BMP-2 release in vitro compared with meshes without microparticles. However, when microparticle-containing meshes were used in vivo to limit the diffusion of BMP-2 delivered by using collagen sponges in a rat femoral defect, no differences in heterotopic ossification or biomechanical properties were observed. Further investigation revealed that, although BMP-2 binding to heparin microparticles was rapid, the presence of serum components attenuated microparticle-BMP-2 binding and increased BMP-2 release in vitro. These observations provide a plausible explanation for the results observed in vivo and suggest that competitive protein binding in vivo may hinder the ability of affinity-based biomaterials to modulate growth factor delivery.
涉及体内递送重组生长因子的组织工程策略通常受到生物材料无法在感兴趣部位空间控制所递送蛋白质扩散的限制。用于临床递送骨形态发生蛋白-2（BMP-2）以促进骨再生的多孔胶原海绵所提供的时空控制不佳，因此需要使用超生理剂量的蛋白质，这导致了炎症和异位骨化。本研究描述了一种新型组织工程策略，即通过在胶原海绵周围创建高亲和力的BMP-2汇来在体内空间控制BMP-2从胶原海绵的快速扩散。我们设计了一种电纺聚己内酯纳米纤维网，其中含有物理包裹的肝素微粒，先前已证明这些微粒能结合并保留大量BMP-2。与不含微粒的网相比，含有0.05和0.10毫克微粒/平方厘米的纳米纤维网在体外表现出增强的BMP-2结合和减少的BMP-2释放。然而，当在大鼠股骨缺损中使用含微粒的网来限制通过胶原海绵递送的BMP-2扩散时，未观察到异位骨化或生物力学性能的差异。进一步研究表明，尽管BMP-2与肝素微粒的结合很快，但血清成分的存在会减弱微粒与BMP-2的结合并增加体外BMP-2的释放。这些观察结果为体内观察到的结果提供了合理的解释，并表明体内竞争性蛋白质结合可能会阻碍基于亲和力的生物材料调节生长因子递送的能力。
