Multi-casting approach for vascular networks in cellularized hydrogels

Abstract

Vascularization is essential for living tissue and remains a major challenge in the field of tissue engineering. A lack of a perfusable channel network within a large and densely populated tissue engineered construct leads to necrotic core formation, preventing fabrication of functional tissues and organs. We report a new method for producing a hierarchical, three-dimensional (3D) and perfusable vasculature in a large, cellularized fibrin hydrogel. Bifurcating channels, varying in size from 1 mm to 200–250 µm, are formed using a novel process in which we convert a 3D printed thermoplastic material into a gelatin network template, by way of an intermediate alginate hydrogel. This enables a CAD-based model design, which is highly customizable, reproducible, and which can yield highly complex architectures, to be made into a removable material, which can be used in cellular environments. Our approach yields constructs with a uniform and high density of cells in the bulk, made from bioactive collagen and fibrin hydrogels. Using standard cell staining and immuno-histochemistry techniques, we showed good cell seeding and the presence of tight junctions between channel endothelial cells, and high cell viability and cell spreading in the bulk hydrogel.

Fabrication of microfluidic chips using controlled dissolution of3Dprinted scaffolds

“…[ 38 ] Moreover, the ability of eISR to smooth the surface of 3D printed curved ABS channels greatly enhances the drawback of having void spaces typically existing at the edges of 3D printed layers of ABS using FDM. [ 35,40 ] Finally, eISR could be used to produce round channels with different diameters to compose vasculature systems [ 41 ] in one microfluidic device, which is difficult to fabricate using FDM 3D printers only.…”

Recent Progress in Biomimetic Additive Manufacturing Technology: From Materials to Functional Structures

“…The channels are fully 3D, hierarchical, and customizable due to the CAD‐based model design. The results show good cell seeding with the presence of tight junctions between channel endothelial cells, as well as high cell viability and spreading in the bulk hydrogel (Figure g) . Another 3D‐printing process is to use direct extrusion of hydrogel microparticles within a supporting slurry to build 3D structures (Figure h) .…”

“…g) 3D printing of a hydrogel channel and cell in the channel. Reproduced with permission . Copyright 2017, The Royal Society Publishing.…”

3D Printable Vascular Networks Generated by Accelerated Constrained Constructive Optimization for Tissue Engineering

“…It is of note that each unit cell in the CCO model is supported with its own terminal, therefore producing a uniform pressure distribution in the perfusion space, which leads to biomimetic vascular networks. This is in contrast to networks fabricated via 3D printing methods where the perfusion space is typically supplied through a series of one-dimensional channels [30], [43], [44] leading to variation in pressure across the perfusion space. Further, the space occupied by connections between inlet and terminal one-dimensional channels will produce unsupported regions within the tissue construct.…”

“…Perfect depth balance can be achieved by using a spacefilling fractal [26], but the suitability of fractals for large-scale organs is debatable [27]- [29]. Notably, manufactured models which have been designed to achieve uniform depth balance have only been shown to supply a line or plane of points [30], [31].…”