Characterizing Environmental Factors that Impact the Viability of Tissue-Engineered Constructs Fabricated by a Direct-Write Bioassembly Tool

Abstract

Tissue engineering combines the fields of medicine and engineering to build replacement tissue capable of restoring, maintaining, or improving damaged tissue. Researchers have recently developed techniques to fabricate tissue in which both the cells and matrix have a carefully defined architecture. This report details studies evaluating the use of a direct-write, 3-dimensional (3D) bioassembly tool (BAT) capable of extruding cells and matrix into spatially organized, 3D constructs. This system has been characterized by its ability to fabricate viable 2-dimensional and 3D constructs containing up to 2 separate cellular solutions suspended in type I collagen. The effects of various environmental factors, such as extrusion pressure, humidity, and stage heating, were examined with respect to the viability of the extruded cells. The data indicate that the system parameters required to extrude cells suspended in collagen do not adversely affect the viability of those cells. Maintaining a high humidity, especially when stage heat was applied, is critical in maintaining the viability of the printed cells. These results demonstrate that the BAT is capable of spatially organizing separate cellular solutions into a defined architecture; however, when cells were extruded in a supporting matrix of 3.0 mg/mL type I collagen, it was not possible to consistently generate adjacent, touching, but nonoverlapping lines of separate solutions. Thus, when a fabrication system such as BAT is used to generate complex, 3D viable constructs, the supporting matrix for the cells should be carefully chosen on the basis of such characteristics as its rate of polymerization and stiffness.

Determinants of Microvascular Network Topologies in Implanted Neovasculatures

“…Printed microvascular constructs were prepared using the BioAssembly Tool (BAT) 20 . The BAT is composed of a computer-controlled stage, that permits independent X and Y translation with 500 nm resolution, and a Z translational print head independently controlled with the same resolution.…”

3D Bioprinting of Vascularized, Heterogeneous Cell‐Laden Tissue Constructs

“…[ 32 ] Others have reported that the applied pressure, nozzle diameter, cell type, and environmental conditions infl uence cell viability after printing. [ 33,34 ] Another important parameter is the total build time required to fabricate the desired engineered tissue construct. We anticipate that there is a maximum time over which these cell-laden inks can be stored in the ink reservoir prior to being harmed.…”

Microfluidic techniques for development of 3D vascularized tissue

“…Two predominant approaches have arisen from the bioprinting technology, specifically those based on inkjet printing [100–104] and mechanical extruders [105, 106]. Inkjet printing is a versatile, robust and a cost effective method, as it relies on direct printing of individual or pockets of cells.…”

“…Bioprinting can be utilized for generating small and intermediate diameter blood vessels using mechanical extruder-based techniques [105, 106]. In these approaches the exact purpose of the mechanical extruders is to place the ‘bio-ink’ or multicellular aggregated particles (that could be made of multiple cell types) with a defined composition into a supporting structure or ‘bio-paper’.…”