Rinker Torri E, Philbrick Brandon D, Temenoff Johnna S
W.H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 313 Ferst Drive, 30332 Atlanta, GA, USA.
W.H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, 313 Ferst Drive, 30332 Atlanta, GA, USA; Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 315 Ferst Drive, 30332 Atlanta, GA, USA.
Acta Biomater. 2017 Jul 1;56:91-101. doi: 10.1016/j.actbio.2016.12.042. Epub 2016 Dec 21.
Development of multifunctional biomaterials that sequester, isolate, and redeliver cell-secreted proteins at a specific timepoint may be required to achieve the level of temporal control needed to more fully regulate tissue regeneration and repair. In response, we fabricated core-shell heparin-poly(ethylene-glycol) (PEG) microparticles (MPs) with a degradable PEG-based shell that can temporally control delivery of protein-laden heparin MPs. Core-shell MPs were fabricated via a re-emulsification technique and the number of heparin MPs per PEG-based shell could be tuned by varying the mass of heparin MPs in the precursor PEG phase. When heparin MPs were loaded with bone morphogenetic protein-2 (BMP-2) and then encapsulated into core-shell MPs, degradable core-shell MPs initiated similar C2C12 cell alkaline phosphatase (ALP) activity as the soluble control, while non-degradable core-shell MPs initiated a significantly lower response (85+19% vs. 9.0+4.8% of the soluble control, respectively). Similarly, when degradable core-shell MPs were formed and then loaded with BMP-2, they induced a ∼7-fold higher C2C12 ALP activity than the soluble control. As C2C12 ALP activity was enhanced by BMP-2, these studies indicated that degradable core-shell MPs were able to deliver a bioactive, BMP-2-laden heparin MP core. Overall, these dynamic core-shell MPs have the potential to sequester, isolate, and then redeliver proteins attached to a heparin core to initiate a cell response, which could be of great benefit to tissue regeneration applications requiring tight temporal control over protein presentation.
Tissue repair requires temporally controlled presentation of potent proteins. Recently, biomaterial-mediated binding (sequestration) of cell-secreted proteins has emerged as a strategy to harness the regenerative potential of naturally produced proteins, but this strategy currently only allows immediate amplification and re-delivery of these signals. The multifunctional, dynamic core-shell heparin-PEG microparticles presented here overcome this limitation by sequestering proteins through a PEG-based shell onto a protein-protective heparin core, temporarily isolating bound proteins from the cellular microenvironment, and re-delivering proteins only after degradation of the PEG-based shell. Thus, these core-shell microparticles have potential to be a novel tool to harness and isolate proteins produced in the cellular environment and then control when proteins are re-introduced for the most effective tissue regeneration and repair.
为了实现更全面地调节组织再生和修复所需的时间控制水平，可能需要开发能够在特定时间点隔离、分离并重新递送细胞分泌蛋白的多功能生物材料。为此，我们制备了核壳结构的肝素-聚乙二醇（PEG）微粒（MPs），其基于PEG的可降解外壳能够在时间上控制载有蛋白质的肝素MPs的递送。核壳MPs通过再乳化技术制备，每个基于PEG的外壳中肝素MPs的数量可以通过改变前体PEG相中肝素MPs的质量来调节。当肝素MPs负载骨形态发生蛋白-2（BMP-2）后再封装到核壳MPs中时，可降解的核壳MPs引发的C2C12细胞碱性磷酸酶（ALP）活性与可溶性对照相似，而非可降解的核壳MPs引发的反应则显著较低（分别为可溶性对照的85 + 19%和9.0 + 4.8%）。同样，当形成可降解的核壳MPs后再负载BMP-2时，它们诱导的C2C12 ALP活性比可溶性对照高约7倍。由于BMP-2增强了C2C12 ALP活性，这些研究表明可降解的核壳MPs能够递送具有生物活性的、载有BMP-2的肝素MP核心。总体而言，这些动态核壳MPs具有隔离、分离并随后重新递送附着在肝素核心上的蛋白质以引发细胞反应的潜力，这对于需要对蛋白质呈现进行严格时间控制的组织再生应用可能具有极大的益处。
组织修复需要对强效蛋白质进行时间控制的呈现。最近，生物材料介导的细胞分泌蛋白结合（隔离）已成为一种利用天然产生蛋白质的再生潜力的策略，但该策略目前仅允许立即放大和重新递送这些信号。本文介绍的多功能、动态核壳肝素-PEG微粒通过基于PEG的外壳将蛋白质隔离到蛋白质保护的肝素核心上，克服了这一限制，将结合的蛋白质暂时与细胞微环境隔离，并仅在基于PEG的外壳降解后重新递送蛋白质。因此，这些核壳微粒有可能成为一种新型工具，用于利用和隔离细胞环境中产生的蛋白质，然后控制何时重新引入蛋白质以实现最有效的组织再生和修复。
