Silk fibroin reactive inks for 3D printing crypt-like structures

A reactive silk fibroin ink formulation designed for extrusion three-dimensional (3D) printing of protein-based hydrogels at room temperature is reported. This work is motivated by the need to produce protein hydrogels that can be printed into complex shapes with long-term stability using extrusion...

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Bibliographic Details
Published in:	Biomedical materials (Bristol) Vol. 15; no. 5; p. 055037
Main Authors:	Heichel, Danielle L, Tumbic, Julia A, Boch, Marisa E, Ma, Anson W K, Burke, Kelly A
Format:	Journal Article
Language:	English
Published:	England 01-09-2020
Subjects:	Alginates - chemistry Animals Bioprinting - methods Bombyx Caco-2 Cells Cell Adhesion Cell Proliferation Coculture Techniques Fibroins - chemistry Humans Hydrogels - chemistry In Vitro Techniques Microscopy, Confocal Microscopy, Fluorescence Myofibroblasts - metabolism Nanocomposites Oscillometry Printing, Three-Dimensional Rheology Robotics Silk - chemistry Spectrometry, Fluorescence Spectroscopy, Fourier Transform Infrared Temperature Tissue Engineering - methods Tissue Scaffolds - chemistry Tyrosine - analogs & derivatives Tyrosine - chemistry Water
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Summary:	A reactive silk fibroin ink formulation designed for extrusion three-dimensional (3D) printing of protein-based hydrogels at room temperature is reported. This work is motivated by the need to produce protein hydrogels that can be printed into complex shapes with long-term stability using extrusion 3D printing at ambient temperature without the need for the addition of nanocomposites, synthetic polymers, or sacrifical templates. Silk fibroin from the Bombyx mori silkworm was purified and synthesized into reactive inks by enzyme-catalyzed dityrosine bond formation. Rheological and printing studies showed that tailoring the peroxide concentration in the reactive ink enables the silk to be extruded as a filament and printed into hydrogel constructs, supporting successive printed layers without flow of the construct or loss of desired geometry. To enable success of longer-term in vitro studies, 3D printed silk hydrogels were found to display excellent shape retention over time, as evidenced by no change in construct dimensions or topography when maintained for nine weeks in culture medium. Caco-2 (an intestinal epithelial cell line) attachment, proliferation, and tight junction formation on the printed constructs was not found to be affected by the geometry of the constructs tested. Intestinal myofibroblasts encapsulated within reactive silk inks were found to survive shearing during printing and proliferate within the hydrogel constructs. The work here thus provides a suitable route for extrusion 3D printing of protein hydrogel constructs that maintain their shape during printing and culture, and is expected to enable longer-term cellular studies of hydrogel constructs that require complex geometries and/or varying spatial distributions of cells on demand via digital printing.
ISSN:	1748-605X
DOI:	10.1088/1748-605x/ab99d4