The greatest challenge of using additive manufacturing to reproduce the complex hierarchical structure of biological tissue is the limited resolution of current 3-D bioprinters. The most common techniques–extrusion, laser desorption, and aerosol jet deposition–struggle to create features smaller than 100 µm because it approaches the size of individual cells. Further constraining the minimum resolution is the tendency of bioinks to spread following deposition. We therefore present an enhanced bioprinting technique that overcomes these limitations through the use of a microfluidic printer head. It contains a network of fine channels that processes fluids in the laminar flow regime, where shear, temperature, mass transfer, and concentration profiles can be precisely controlled. A coaxial flow device with four channels was used to synthesize a cell scaffold of collagen and hyaluronic acid. A solution of collagen, HA, and fibrinogen was mixed with a solution of chitosan, FeCl<sub>3</sub>, and N-Ethyl-N′-(3-dimethylaminopropyl)carbodiimide (EDC) to generate internal fibril alignment and hollow channels with dimensions that extended far below the resolution of the bioprinter. The 30 x 30 x 5 mm constructs mimicked the helicoidal organization of heart muscle. Design of Experiments (DOE) then determined the concentrations, mix ratios, and flow rates needed to reproduce the elastic modulus of human myocardium along the direction of extrusion. Using 2-photon microscopy, we observed cell surface localization of alpha5 integrin-eGFP (a reporter for cell adhesion) and cell viability at day 7 (live/dead assay) in Chinese hamster ovary (CHO) and cardiac fibroblasts cells grown in the matrix. Our results demonstrate that the HA/collagen/fibrinogen matrix offers cell-matrix adhesion motifs and is biocompatible with multiple mammalian cell lines.

Microfluidic 3-D printing of hierarchically structured biomaterials for myocardial tissue constructs

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.