Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Pohang, Gyeongbuk, 37673, South Korea.
Advanced Technology Research Center & School of Mechanical Engineering, Korea University of Technology and Education (KOREATECH), Cheonan, Chungnam, 31253, South Korea.
J Biomed Mater Res B Appl Biomater. 2020 Apr;108(3):1000-1009. doi: 10.1002/jbm.b.34452. Epub 2019 Aug 6.
Despite the potential of a collagen construct with a stiffness gradient for investigating cell-extracellular matrix (ECM) stiffness interaction or recapitulating an in vivo tissue interface, it has been developed in a limited way due to the low and poorly controllable mechanical properties of the collagen. This study proposes a novel fabrication process to achieve a compressed collagen construct with a stiffness gradient, named COSDIENT, at a level of ~ 1 MPa while maintaining in vivo ECM-like dense collagen fibrillar structures. The COSDIENT was fabricated by collagen compression followed by grayscale mask-assisted UV-riboflavin crosslinking. The collagen compression process enabled the remarkable increase in the stiffness of the collagen gel from ~ 1-10 kPa to ~ 1 MPa by physical compaction. The subsequent UV-riboflavin crosslinking with a continuous-tone grayscale mask could simply generate a gradual change of UV irradiation followed by modulating riboflavin-mediated crosslinking, thereby resulting in a continuous stiffness gradient with a range of 1.16-4.38 MPa in the single compressed collagen construct. The suggested grayscale mask-assisted photochemical crosslinking had no effect on the physical and optical properties of the original compressed collagen construct, while inducing gradual changes of chemical bonds among collagen fibrils. A skin wound healing assay with epidermal keratinocytes was finally applied as an application example of the COSDIENT to examine the effect of stiffness on the skin keratinocyte behavior.
尽管具有刚度梯度的胶原构建体具有研究细胞-细胞外基质 (ECM) 刚度相互作用或再现体内组织界面的潜力，但由于胶原的机械性能低且不易控制，因此其发展受到限制。本研究提出了一种新颖的制造工艺，可在 1 MPa 左右的水平上制造具有刚度梯度的压缩胶原构建体，命名为 COSDIENT，同时保持类似于体内 ECM 的致密胶原原纤维结构。COSDIENT 是通过胶原压缩 followed by grayscale mask-assisted UV-riboflavin crosslinking 制造的。胶原压缩过程通过物理压实使胶原凝胶的刚度从约 1-10 kPa 显著增加到约 1 MPa。随后使用连续色调灰度掩模进行的 UV-riboflavin 交联可以简单地产生 UV 照射的逐渐变化，并调节核黄素介导的交联，从而在单个压缩胶原构建体中产生 1.16-4.38 MPa 的连续刚度梯度。所提出的灰度 mask-assisted 光化学交联对原始压缩胶原构建体的物理和光学性质没有影响，同时诱导胶原原纤维之间化学键的逐渐变化。最后，应用表皮角质形成细胞的皮肤伤口愈合测定作为 COSDIENT 的应用实例，以检查刚度对皮肤角质形成细胞行为的影响。
