Engineering interconnected 3D vascular networks in hydrogels using molded sodium alginate lattice as the sacrificial template

Abstract

Engineering 3D perfusable vascular networks in vitro and reproducing the physiological environment of blood vessels is very challenging for tissue engineering and investigation of blood vessel function. Here, we engineer interconnected 3D microfluidic vascular networks in hydrogels using molded sodium alginate lattice as sacrificial templates. The sacrificial templates are rapidly replicated in polydimethylsiloxane (PDMS) microfluidic chips via Ca⁺²-crosslinking and then fully encapsulated in hydrogels. Interconnected channels with well controlled size and morphology are obtained by dissolving the monolayer or multilayer templates with EDTA solution. The human umbilical vein endothelial cells (HUVECs) are cultured on the channel linings and proliferated to form vascular lumens. The strong cell adhesion capability and adaptive response to shear stress demonstrate the excellent cytocompatibility of both the template and template-sacrificing process. Furthermore, the barrier function of the endothelial layer is characterized and the results show that a confluent endothelial monolayer is fully developed. Taken together, we develop a facile and rapid approach to engineer a vascular model that could be potentially used in physiological studies of vascular functions and vascular tissue engineering.

Coaxial nozzle-assisted 3D bioprinting with built-in microchannels for nutrients delivery

“…Joshua Hammer et al [27] presented a process to fabricate hydrogels with microchannellike porosity in which stimuli-responsive calcium alginate microfilaments served as sacrificial materials for fluidic channels and were encapsulated within photocrosslinkable hydrogels composed of methacrylated gelatin (Gel-MA). Wang et al [28] described a method using a crosslinked sodium alginate as a biocompatible sacrificial template to fabricate interconnected 3D microfluidic vascular networks in hydrogels. The sacrificial templates are rapidly replicated in PDMS microfluidic chips via Ca 2þ -crosslinking, fully encapsulated in hydrogels, and then the interconnected 3D microfluidic channels were generated by dissolving the template with EDTA solution.…”

Freestanding 3-D microvascular networks made of alginate hydrogel as a universal tool to create microchannels inside hydrogels

“…In previous reports, it has been frequently discussed that the dissolving of sacrificial templates inside the cell-laden gel may hurt the cells. 29,31,33,50 However, continuous efforts until now have not yet fully addressed this common problem, probably because of the inherent drawback of the strategy that involves microfabrication process in the presence of the live cells. For instance, in a recent report, Huang and his co-workers tried to reduce the damage to cells caused by the fabrication process by using a biocompatible sacrificial template made of sodium alginate; however, the reagent used for dissolving the template, ethylenediaminetetraacetic acid (EDTA), is not biocompatible.…”

“…For instance, in a recent report, Huang and his co-workers tried to reduce the damage to cells caused by the fabrication process by using a biocompatible sacrificial template made of sodium alginate; however, the reagent used for dissolving the template, ethylenediaminetetraacetic acid (EDTA), is not biocompatible. 50,51 In another work, Chen et al reported a smart design using a 3-D-printed carbohydrate glass sacrificial template that dissolves in water; however, although this template can be removed by a biocompatible buffer, the dissolution of carbohydrate will cause osmotic shock that damages the cells. 31 Thus, the authors needed to coat the carbohydrate glass lattice with a thin layer of poly(D-lactide-co-glycolide) (PDLGA); and because the template was highly hygroscopic, it had to be reinforced by dextrans, and stored at 45 C or in a vacuum chamber before use.…”

“…After that, the gel-coated copper scaffold was immersed in 1 M CaCl 2 solution for further electrolysis to dissolve most of the copper. The remaining copper was dissolved completely in 0.1 M FeCl 3 solution at 50 C for 1 h. Finally, the Fe 3þ ions in the alginate tubules were replaced by Ca 2þ ions (1 M CaCl 2 and 0.02 M EDTA, pH 5) at 50 C for 1 h.…”

“…It is worth noting that there were two types of non-printing methods to create microtubes: one was to cast from capillary tubes, and the other was to form tubes through microfluidic laminar flow. 36,50 Neither of the methods were suitable for generating branched tube networks like in our work. Besides, other materials and biomolecules could be pre-loaded in our hydrogel tubular networks by mixing them with the alginate solution beforehand, and the thickness of the tubule wall could be easily controlled by tuning the time span of electrolysis.…”