title: A hydrogel bioink toolkit for mimicking native tissue biochemical and mechanical properties in bioprinted tissue constructs.
abstract: Advancement of bioprinting technology is limited by the availability of materials that both facilitate bioprinting logistics as well as support cell viability and function by providing tissue-specific cues. Herein we describe a modular hyaluronic acid (HA) and gelatin-based hydrogel toolbox comprised of a 2-crosslinker, 2-stage polymerization technique, and the capability to provide tissue specific biochemically and mechanically accurate signals to cells within biofabricated tissue constructs. First, we prepared and characterized several tissue-derived decellularized extracellular matrix-based solutions, which contain complex combinations of growth factors, collagens, glycosaminoglycans, and elastin. These solutions can be incorporated into bioinks to provide the important biochemical cues of different tissue types. Second, we employed combinations of PEG-based crosslinkers with varying molecular weights, geometries (linear, 4-arm, and 8-arm), and functional groups to yield hydrogel bioinks that supported extrusion bioprinting and the capability to achieve final construct shear stiffness values ranging from approximately 100 Pa to 20 kPa. Lastly, we integrated these hydrogel bioinks with a 3-D bioprinting platform, and validated their use by bioprinting primary liver spheroids in a liver-specific bioink to create in vitro liver constructs with high cell viability and measurable functional albumin and urea output. This hydrogel bioink system has the potential to be a versatile tool for biofabrication of a wide range of tissue construct types.
  
  
  CONCLUSIONS
  Biochemical and mechanical factors both have important implications in guiding the behavior of cells in vivo, yet both realms are rarely considered together in the context of biofabrication in vitro tissue construct models. We describe a modular hydrogel system that (1) facilitates extrusion bioprinting of cell-laden hydrogels, (2) incorporates tissue-specific factors derived from decellularized tissue extracellular matrix, thus mimicking biochemical tissue profile, and (3) allows control over mechanical properties to mimic the tissue stiffness. We believe that employing this technology to attend to both the biochemical and mechanical profiles of tissues, will allow us to more accurately recapitulate the in vivo environment of tissues while creating functional 3-D in vitro tissue constructs that can be used as disease models, personalized medicine, and in vitro drug and toxicology screening systems.
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA. Electronic address: askardal@wakehealth.edu.
authors.forename: Aleksander
authors.initials: A
authors.lastname: Skardal
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: Mahesh
authors.initials: M
authors.lastname: Devarasetty
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: Hyun-Wook
authors.initials: HW
authors.lastname: Kang
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: Ivy
authors.initials: I
authors.lastname: Mead
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: Colin
authors.initials: C
authors.lastname: Bishop
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Shupe
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: Sang Jin
authors.initials: SJ
authors.lastname: Lee
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: John
authors.initials: J
authors.lastname: Jackson
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: James
authors.initials: J
authors.lastname: Yoo
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: Shay
authors.initials: S
authors.lastname: Soker
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest University Health Sciences, Winston-Salem, NC, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Atala
mesh_terms: D000418:Albumins / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D062028:Bioprinting / Q000379:methods*; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000494:pharmacology*; D011092:Polyethylene Glycols / Q000737:chemistry; D012212:Rheology / Q000187:drug effects; D012996:Solutions; D018874:Spheroids, Cellular / Q000166:cytology / Q000187:drug effects; D034421:Sus scrofa; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds / Q000737:chemistry*; D014022:Tissue Survival / Q000187:drug effects; D014508:Urea / Q000378:metabolism
chemical_list: D000418:Albumins; D012996:Solutions; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols; D014508:Urea
keywords: Bioink; Bioprinting; Elastic modulus; Extracellular matrix; Hydrogel