Brown Ashley C, Baker Stephen R, Douglas Alison M, Keating Mark, Alvarez-Elizondo Martha B, Botvinick Elliot L, Guthold Martin, Barker Thomas H
The School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, United States.
Department of Physics, Wake Forest University, Winston-Salem, NC 27109, United States.
Biomaterials. 2015 May;49:27-36. doi: 10.1016/j.biomaterials.2015.01.010. Epub 2015 Feb 11.
Protein based polymers provide an exciting and complex landscape for tunable natural biomaterials through modulation of molecular level interactions. Here we demonstrate the ability to modify protein polymer structural and mechanical properties at multiple length scales by molecular 'interference' of fibrin's native polymerization mechanism. We have previously reported that engagement of fibrin's polymerization 'hole b', also known as 'b-pockets', through PEGylated complementary 'knob B' mimics can increase fibrin network porosity but also, somewhat paradoxically, increase network stiffness. Here, we explore the possible mechanistic underpinning of this phenomenon through characterization of the effects of knob B-fibrin interaction at multiple length scales from molecular to bulk polymer. Despite its weak monovalent binding affinity for fibrin, addition of both knob B and PEGylated knob B at concentrations near the binding coefficient, Kd, increased fibrin network porosity, consistent with the reported role of knob B-hole b interactions in promoting lateral growth of fibrin fibers. Addition of PEGylated knob B decreases the extensibility of single fibrin fibers at concentrations near its Kd but increases extensibility of fibers at concentrations above its Kd. The data suggest this bimodal behavior is due to the individual contributions knob B, which decreases fiber extensibility, and PEG, which increase fiber extensibility. Taken together with laser trap-based microrheological and bulk rheological analyses of fibrin polymers, our data strongly suggests that hole b engagement increases in single fiber stiffness that translates to higher storage moduli of fibrin polymers despite their increased porosity. These data point to possible strategies for tuning fibrin polymer mechanical properties through modulation of single fiber mechanics.
基于蛋白质的聚合物通过调节分子水平的相互作用，为可调谐天然生物材料提供了一个令人兴奋且复杂的领域。在此，我们展示了通过纤维蛋白天然聚合机制的分子“干扰”，在多个长度尺度上改变蛋白质聚合物结构和力学性能的能力。我们之前报道过，通过聚乙二醇化的互补“钮扣B”模拟物与纤维蛋白聚合“孔b”（也称为“b口袋”）的结合，可以增加纤维蛋白网络的孔隙率，但有点自相矛盾的是，也会增加网络刚度。在此，我们通过表征从分子到本体聚合物的多个长度尺度上钮扣B - 纤维蛋白相互作用的影响，探索这一现象可能的机制基础。尽管其与纤维蛋白的单价结合亲和力较弱，但在接近结合系数Kd的浓度下添加钮扣B和聚乙二醇化钮扣B，都会增加纤维蛋白网络的孔隙率，这与报道的钮扣B - 孔b相互作用在促进纤维蛋白纤维横向生长中的作用一致。在接近其Kd的浓度下添加聚乙二醇化钮扣B会降低单个纤维蛋白纤维的伸长率，但在高于其Kd的浓度下会增加纤维的伸长率。数据表明，这种双峰行为是由于钮扣B（降低纤维伸长率）和聚乙二醇（增加纤维伸长率）的各自贡献。结合基于激光阱的纤维蛋白聚合物微观流变学和本体流变学分析，我们的数据强烈表明，孔b的结合增加了单纤维的刚度，尽管孔隙率增加，但这转化为纤维蛋白聚合物更高的储能模量。这些数据指出了通过调节单纤维力学来调整纤维蛋白聚合物力学性能的可能策略。
