Faculty of Applied Sciences, University Politehnica of Bucharest, RO-060042, Romania. Center for Advanced Laser Technologies (CETAL), National Institute for Laser, Plasma and Radiation Physics, Magurele, Bucharest, RO-077125, Romania.
Biofabrication. 2018 Feb 5;10(2):025009. doi: 10.1088/1758-5090/aaa718.
A major limitation of existing 3D implantable structures for bone tissue engineering is that most of the cells rapidly attach on the outer edges of the structure, restricting the cells penetration into the inner parts and causing the formation of a necrotic core. Furthermore, these structures generally possess a random spatial arrangement and do not preserve the isotropy on the whole volume. Here, we report on the fabrication and testing of an innovative 3D hierarchical, honeycomb-like structure (HS), with reproducible and isotropic arhitecture, that allows in 'volume' migration of osteoblasts. In particular, we demonstrate the possibility to control the 3D spatial cells growth inside these complex architectures by adjusting the free spaces inside the structures. The structures were made of vertical microtubes arranged in a mulitlayered configuration, fabricated via laser direct writing by two photons polymerization of the IP-L780 photopolymer. In vitro tests performed in MG-63 osteoblast-like cells demonstrated that the cells migration inside the 3D structures is conducted by the separation space between the microtubes layers. Specifically, for layers separation between 2 and 10 μm, the cells gradually penetrated between the microtubes. Furthermore, these structures induced the strongest cells osteogenic differentiation and mineralization, with ALP activity 1.5 times stronger, amount of calcified minerals 1.3 times higher and osteocalcin secretion increased by 2.3 times compared to the other structures. On the opposite, for layers separation less than 2 μm and above 10 μm, the cells were not able to make interconnections and exhibited poor mineralization ability.
现有的用于骨组织工程的 3D 可植入结构的一个主要局限性是，大多数细胞迅速附着在结构的外边缘，限制了细胞向内部的渗透，并导致形成坏死核心。此外，这些结构通常具有随机的空间排列，并且整个体积不保持各向同性。在这里，我们报告了一种创新的 3D 分级、蜂窝状结构（HS）的制造和测试，该结构具有可重复和各向同性的架构，允许成骨细胞在“体积”中迁移。特别是，我们证明了通过调整结构内部的自由空间，可以控制这些复杂结构内部的 3D 空间细胞生长。这些结构由排列在多层结构中的垂直微管组成，通过双光子聚合 IP-L780 光聚合物的激光直写制造而成。在 MG-63 成骨样细胞的体外测试中，证明了细胞在 3D 结构内的迁移是通过微管层之间的分离空间进行的。具体来说，对于层间距为 2 至 10 μm，细胞逐渐渗透到微管之间。此外，这些结构诱导了最强的细胞成骨分化和矿化，碱性磷酸酶（ALP）活性增强了 1.5 倍，矿化矿物质的量增加了 1.3 倍，骨钙素分泌增加了 2.3 倍，与其他结构相比。相反，对于层间距小于 2 μm 和大于 10 μm 的结构，细胞无法进行连接，并且表现出较差的矿化能力。
