Podichetty Jagdeep T, Madihally Sundararajan V
School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma, 74078.
J Biomed Mater Res B Appl Biomater. 2014 May;102(4):737-48. doi: 10.1002/jbm.b.33054. Epub 2013 Nov 21.
In this study, we tested the possibility of calculating permeability of porous scaffolds utilized in soft tissue engineering using pore size and shape. We validated the results using experimental measured pressure drop and simulations with the inclusion of structural deformation. We prepared Polycaprolactone (PCL) and Chitosan-Gelatin (CG) scaffolds by salt leaching and freeze drying technique, respectively. Micrographs were assessed for pore characteristics and mechanical properties. Porosity for both scaffolds was nearly same but the permeability varied 10-fold. Elastic moduli were 600 and 9 kPa for PCL and CG scaffolds, respectively, while Poisson's ratio was 0.3 for PCL scaffolds and ∼1.0 for CG scaffolds. A flow-through bioreactor accommodating a 10 cm diameter and 0.2 cm thick scaffold was used to determine the pressure-drop at various flow rates. Additionally, computational fluid dynamic (CFD) simulations were performed by coupling fluid flow, described by Brinkman equation, with structural mechanics using a dynamic mesh. The experimentally obtained pressure drop matched the simulation results of PCL scaffolds. Simulations were extended to a broad range of permeabilities (10(-10) m(2) to 10(-14) m(2) ), elastic moduli (10-100,000 kPa) and Poisson's ratio (0.1-0.49). The results showed significant deviation in pressure drop due to scaffold deformation compared to rigid scaffold at permeabilities near healthy tissues. Also, considering the scaffold as a nonrigid structure altered the shear stress profile. In summary, scaffold permeability can be calculated using scaffold pore characteristics and deformation could be predicted using CFD simulation. These relationships could potentially be used in monitoring tissue regeneration noninvasively via pressure drop.
在本研究中，我们测试了利用孔径和形状来计算软组织工程中使用的多孔支架渗透率的可能性。我们通过实验测量的压降以及包含结构变形的模拟来验证结果。我们分别采用盐析和冷冻干燥技术制备了聚己内酯（PCL）和壳聚糖 - 明胶（CG）支架。对显微照片进行评估以获取孔隙特征和力学性能。两种支架的孔隙率几乎相同，但渗透率相差10倍。PCL和CG支架的弹性模量分别为600 kPa和9 kPa，而PCL支架的泊松比为0.3，CG支架的泊松比约为1.0。使用一个容纳直径10 cm、厚度0.2 cm支架的流通式生物反应器来测定不同流速下的压降。此外，通过将由布林克曼方程描述的流体流动与使用动态网格的结构力学相结合，进行了计算流体动力学（CFD）模拟。实验获得的压降与PCL支架的模拟结果相匹配。模拟扩展到了广泛的渗透率范围（10^(-10) m² 至 10^(-14) m²）、弹性模量范围（10 - 100,000 kPa）和泊松比范围（0.1 - 0.49）。结果表明，在接近健康组织的渗透率下，与刚性支架相比，由于支架变形导致压降存在显著偏差。此外，将支架视为非刚性结构会改变剪切应力分布。总之，可以使用支架孔隙特征来计算支架渗透率，并且可以使用CFD模拟来预测变形。这些关系可能潜在地用于通过压降无创监测组织再生。
