Nonlinear elastic properties of polyacrylamide gels: implications for quantification of cellular forces.
Nonlinear elastic properties of polyacrylamide gels: implications for quantification of cellular forces.
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DOI：
10.3233/bir-2009-0540
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发表时间：
2009
期刊：
影响因子：
1.1
通讯作者：
Tracqui P
中科院分区：
文献类型：
--
作者：
Boudou T;Ohayon J;Picart C;Pettigrew RI;Tracqui P
由于其可调的机械性能，聚丙烯酰胺凝胶（PAG）经常被用于研究细胞粘附和迁移的细胞外基质刚度的反应。由于已知这些反应在很大程度上取决于细胞收缩性和基质机械阻力之间的张力平衡，因此PAG的机械性质的精确知识变得非常重要。利用微管抽吸技术，我们首先展示了PAG的非线性弹性行为，然后成功地模拟了它的原始应变能函数。该函数取决于泊松比和两个材料参数，这已明确相关的丙烯酰胺和双丙烯酰胺的浓度。这些结果的影响已被强调的牵引力显微镜实验，其中细胞力定量来自嵌入PAG珠位移。我们发现，考虑PAG作为一个线性弹性介质往往显着低估牵引力的基板位移大于2 μm。有趣的是，我们还表明，在细胞牵引力实验中目前使用的细胞力幅度和PAG刚度范围内，有限尺寸效应对于PAG基底厚度低于60 μm变得至关重要。因此，我们通过一个新的本构律改进的PAG非线性力学性能的表征可能会对生物实验产生重大影响，这些细胞外基质经历大的应变。
Because of their tunable mechanical properties, polyacrylamide gels (PAG) are frequently used for studying cell adhesion and migratory responses to extracellular substrate stiffness. Since these responses are known to heavily depend on the tensional balance between cell contractility and substrate mechanical resistance, a precise knowledge of PAG’s mechanical properties becomes quite crucial. Using the micropipette aspiration technique, we first exhibited the nonlinear elastic behavior of PAG and then successfully modeled it by an original strain-energy function. This function depends on the Poisson’s ratio and on two material parameters, which have been explicitly related to acrylamide and bis-acrylamide concentrations. Implications of these results have been highlighted with regard to traction force microscopy experiments where cellular force quantification is derived from displacements of beads embedded in PAG. We found that considering PAG as a linear elastic medium tends to significantly underestimate traction forces for substrate displacements larger than 2 μm. Interestingly, we also showed that in the range of cellular force amplitude and PAG stiffness currently used in cell traction force experiments, finite size effects become critical for PAG substrate thickness below 60 μm. Thus, our improved characterization of PAG nonlinear mechanical properties through a new constitutive law could have significant impact onto biological experimentations where such extracellular substrates experience large strains.