Characterization of Engineered Scaffolds with Spatial Prevascularized Networks for Bulk Tissue Regeneration.

Despite significant progress in the fabrication of prevascularized networks over the past decade, a number of challenges remain. One of the most relevant issues is the lack of three-dimensional (3D) structures, which limits the clinical applications of the engineered scaffolds. Another problem is the complexity of prevascularized networks in engineered scaffolds, which is still less than that of human tissues, especially in the case of mature and bulk tissues. Thus, there is still the need to develop more flexible methods to better simulate the structure of natural tissues. In this work, we used a versatile sacrificial template method to fabricate bulk scaffolds with spatial prevascularized networks. Soft poly(vinyl alcohol) (PVA) filaments were used to print the sacrificial template, and the receiving platform was a stepped shaft, allowing the sacrificial template to have a complex 3D structure. The obtained template was embedded into gelatin and microbial transglutaminase (mTG). The inner PVA template could be extracted from the enzymatic cross-linking system, and an engineered scaffold with spatial prevascularized networks was obtained. In vitro experiments demonstrated that the fabrication process is biocompatible with cells.

A Versatile Method for Fabricating Tissue Engineering Scaffolds with a Three-Dimensional Channel for Prevasculature Networks.

Despite considerable advances in tissue engineering over the past two decades, solutions to some crucial problems remain elusive. Vascularization is one of the most important factors that greatly influence the function of scaffolds. Many research studies have focused on the construction of a vascular-like network with prevascularization structure. Sacrificial materials are widely used to build perfusable vascular-like architectures, but most of these fabricated scaffolds only have a 2D plane-connected network. The fabrication of three-dimensional perfusable branched networks remains an urgent issue. In this work, we developed a novel sacrificial molding technique for fabricating biocompatible scaffolds with a three-dimensional perfusable branched network. Here, 3D-printed poly(vinyl alcohol) (PVA) filament was used as the sacrificial material. The fused PVA was deposited on the surface of a cylinder to create the 3D branched solid network. Gelatin was used to embed the solid network. Then, the PVA mold was dissolved after curing the hydrogel. The obtained architecture shows good perfusability. Cell experiment results indicated that human umbilical vein endothelial cells (HUVECs) successfully attached to the surface of the branched channel and maintained high viability after a few days in culture. In order to prevent deformation of the channel, paraffin was coated on the surface of the printed structure, and hydroxyapatite (HA) was added to gelatin. In conclusion, we demonstrate a novel strategy toward the engineering of prevasculature thick tissues through the integration of the fused PVA filament deposit. This approach has great potential in solving the issue of three-dimensional perfusable branched networks and opens the way to clinical applications.

[A pilot study of three dimensional printing of human bone marrow stem cells (hBMSCs)].

PURPOSE: To establish a three-dimensional biological printing technique of hBMSCs. METHODS: The hBMSCs were regularly isolated and cultured, and adjusted to the density of 1x10(6)/mL single cell suspension. Then these cells were labeled by PI fluorescence marker, and transferred by rapid prototype biological printer. Deposition spots were 300microm apart at X-axis, 500microm at Y-axis, 50microm at Z-axis, and then observed by laser confocal microscope. RESULTS: This technique could deposit cells with good spatial control. In three-dimensional layer, each "cell ink" drop contained 15-35 hBMSCs post-transfer, and achieved accurate distribution with spots distributed 300microm apart at x-axis, 500microm at y-axis and 50microm at Z-axis. CONCLUSIONS: This study indicates that hBMSCs can be effectively delivered by a rapid prototype printer with speed and accuracy. Application of three dimensional printing is of great importance in tissue engineering bone.