Microfluidic 3D Printing of a Photo-Cross-Linkable Bioink Using Insights from Computational Modeling

Abstract

Three-dimensional (3D) bioprinting of photo-cross-linkable hydrogel precursors has attracted great interest in various tissue engineering and drug screening applications, as the biochemical and biophysical properties of the resultant hydrogel structures can be tuned spatiotemporally to provide cells with physiologically relevant microenvironments. In particular, these bioinks benefit from great biofunctional versatility that can be designed to direct cells toward a desired behavior. Despite significant progress in the field, the 3D printing of cell-laden photo-cross-linkable bioinks with low polymer concentrations has remained a challenge, as rapidly stabilizing these bioinks and transforming them to hydrogel filaments is hindered by their low viscosity. Additionally, reaching an optimized print condition has often been challenging due to the large number of print parameters involved in 3D bioprinting setups. Therefore, computational modeling has occasionally been employed to understand the impact of various print parameters and reduce the time and resources required to determine these effects in experimental settings. Here, we report a novel 3D bioprinting strategy for fabricating hydrogel fibrous structures of gelatin methacryloyl (GelMA) with superior control over polymer concentration, particularly in a relatively low range from ∼1% (w/v) to 6% (w/v), using a microfluidic printhead. The printhead features a coaxial core–sheath flow, coupled with a photo-cross-linking system, allowing for the in situ cross-linking of GelMA and the generation of hydrogel filaments. A computational model was developed to determine the optimal ranges of process parameters and inform about the diffusive and fluid dynamic behavior of the coaxial flow. The cytocompatibility of the biofabrication system was determined via bioprinting cell-laden bioinks containing U87-MG cells. Notably, the established pipeline from computational modeling to bioprinting has great potential to be applied to a wide range of photo-cross-linkable bioinks to generate living tissues with various material and cellular characteristics.

Review on Porous Scaffolds Generation Process: A Tissue Engineering Approach

“…-Not for complex geometrical shapes. deposition of filaments can be alternated with UV irradiation, 131 in this procuring the stability of the previous layer before depositing the next one. This technique has been explored using GelMA 135 and PEGDA.…”

“…(c) 3D bioprinting extrusion with a light source adapted to cross-link photo-cross-linkable hydrogel. Reproduced from ref . Copyright 2021 American Chemical Society.…”

“…Adaptation of a UV cross-linking device in the bioprinter is useful for photosensitive hydrogels, as shown in Figure c. The deposition of filaments can be alternated with UV irradiation, in this procuring the stability of the previous layer before depositing the next one. This technique has been explored using GelMA and PEGDA .…”

Diffusion‐Based 3D Bioprinting Strategies

“…The effects of different core and sheath concentrations and flow rates on the predicted concentration profiles were investigated to determine optimal printing parameters for stable filament formation. [118] Besides diffusion inside coaxial nozzles, FEM has been employed in extrusion bioprinting to predict diffusion-induced gelation. In one demonstration, the diffusion of graphene oxide (GO) into an elastin-like recombinamer (ELK1) ink at different time points after extrusion was predicted using FEM.…”

Hydrogels for Tissue Engineering: Addressing Key Design Needs Toward Clinical Translation

“…Aspect Biosystems’ microfluidic bioprinter allows for rapid switching between multiple cell-laden hydrogels and contains a microfluidic junction enabling mixing of crosslinkers with precursor polymers (e.g., alginate and calcium) shortly before extrusion ( Figure 5A ) ( Dickman et al, 2020 ). By modifying the crosslinking and precursor polymer solutions, this microfluidic chip can also bioprint chemically crosslinkable thrombin ( Abelseth et al, 2019 ; Lee et al, 2019 ) or photo-crosslinkable bioinks ( Mirani et al, 2021 ). In general, microfluidics bioprinting benefits from the wide array of operations that can be performed on a microfluidic chip prior to bioprinting, allowing for highly controlled and dynamic mixing of multiple components over time.…”