Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2018 May 1;6(5):915-946.
doi: 10.1039/c7bm00765e.

Bioinks for 3D bioprinting: an overview

P Selcan Gungor-Ozkerim  1 , Ilyas Inci, Yu Shrike Zhang, Ali Khademhosseini, Mehmet Remzi Dokmeci
Affiliations
Review

Bioinks for 3D bioprinting: an overview

P Selcan Gungor-Ozkerim et al. Biomater Sci. .

Abstract

Bioprinting is an emerging technology with various applications in making functional tissue constructs to replace injured or diseased tissues. It is a relatively new approach that provides high reproducibility and precise control over the fabricated constructs in an automated manner, potentially enabling high-throughput production. During the bioprinting process, a solution of a biomaterial or a mixture of several biomaterials in the hydrogel form, usually encapsulating the desired cell types, termed the bioink, is used for creating tissue constructs. This bioink can be cross-linked or stabilized during or immediately after bioprinting to generate the final shape, structure, and architecture of the designed construct. Bioinks may be made from natural or synthetic biomaterials alone, or a combination of the two as hybrid materials. In certain cases, cell aggregates without any additional biomaterials can also be adopted for use as a bioink for bioprinting processes. An ideal bioink should possess proper mechanical, rheological, and biological properties of the target tissues, which are essential to ensure correct functionality of the bioprinted tissues and organs. In this review, we provide an in-depth discussion of the different bioinks currently employed for bioprinting, and outline some future perspectives in their further development.

PubMed Disclaimer

Conflict of interest statement

Conflicts of interest

The authors declare no conflict of interests in this work.

Figures

Fig. 1
Fig. 1
Schematic representation of the main 3D bioprinting technologies. (a) Inkjet/droplet bioprinting. (b) Extrusion-based bioprinting. (c) Laser-assisted bioprinting. Reproduced with permission Copyright Nature Publishing Group, 2014.
Fig. 2
Fig. 2
Schematic diagrams of thermoresponsive gelation and the corresponding shear elastic (G′) and loss moduli (G″) measured as a function of temperature for: (a) pure GelMA, and (b) fibroblast-laden GelMA bioinks. Reprinted with permission Copyright John Wiley & Sons, Inc., 2014.
Fig. 3
Fig. 3
The process of 3D-bioprinting of cell-encapsulated constructs by using silk-gelatin as a bioink. Reprinted with permission Copyright Elsevier, 2014.
Fig. 4
Fig. 4
Bioprinting process of a 3D structure with built-in microchannels by using an alginate bioink. Physical cross-linking process was utilized via calcium ions. Reprinted with permission Copyright Elsevier, 2015.
Fig. 5
Fig. 5
Schematic representation of laser-assisted bioprinting. Reprinted with permission Copyright IOP Publishing, 2014.
Fig. 6
Fig. 6
The gelation process of HA grafted with pNIPAAM. Reprinted with permission Copyright Elsevier, 2014.
Fig. 7
Fig. 7
Robotic and manual printing of 3D constructs by using an agarose bioink under fluorocarbon. (a) Top and (b) side view of printed cell-laden constructs. (c) 3D construct mimicking a vascular bifurcation that was printed while submerged in perfluorotributylamine. (d) Printed cylinders without cells. Reprinted with permission Copyright IOP Publishing, 2013.
Fig. 8
Fig. 8
Utilizing various dECM bioinks for bioprinting 3D tissue constructs. (a) Heart tissue construct was printed with only heart dECM (hdECM). (b) Cartilage and adipose tissues were printed with cartilage dECM (cdECM) and (c) adipose dECM (adECM), respectively, and in combination with PCL framework (scale bar, 5 mm). Reprinted with permission Copyright Nature Publishing Group, 2014.
Fig. 9
Fig. 9
Adipose tissue obtained by surgery and used as a bioink after a decellularization process for soft tissue reconstruction. Reprinted with permission Copyright Elsevier, 2015.
Fig. 10
Fig. 10
Employing multiple PEG-based bioinks with tunable cross-linking properties. (a) Strategy of formulation of printable bioinks comprised of acrylate-based cross-linkers (crosslinker 1), alkyne-based cross-linkers (crosslinker 2), thiolated HA, thiolated gelatin, and unmodified HA and gelatin. (b) Implementation of bioprintable hydrogel bioinks: the bioink formulation was prepared and spontaneously cross-linked through thiol-acrylate binding, resulting in a soft, extrudable material. Lastly, the bioprinted structures were fused, stabilized, and brought to the target stiffness. Reprinted with permission Copyright Elsevier, 2015.
Fig. 11
Fig. 11
PEG-based cell-laden bioinks. (a) Polymer or polymer mixtures in linear (gelatin), branched (4-arm PEG amine), or multifunctional form. The red circles represent amines, blue triangles represent methacrylate groups, and the yellow stars indicate SVA groups of PEGX. (b) PEGX can be linear or multiarm and can have various chain lengths. (c) Cells can be encapsulated by (d) mixing with polymers and PEGX to form the bioink. (e) Alternatively, secondary cross-linking can be performed to increase mechanical strength following the printing step. (f) By changing the reactive groups of PEGX, polymers of other functional groups can be cross-linked. Purple polygons represent thiols, cross-linkable with maleimide PEGX (pink squares) and green ellipses represent alkynes, cross-linkable with azide PEGX (orange pentagon). (g) Printing process of PEGX bioink method and corresponding phase: PEGX with or without cells were mixed within the polymer solution and loaded into the printing cartridge. After gel formation and stable mechanical properties were achieved, gels could be 3D printed into multilayer constructs. Reprinted with permission Copyright John Wiley & Sons, Inc., 2015.
Fig. 12
Fig. 12
Rigid and biocompatible PEG-alginate-nanoclay blend bioinks and different 3D bioprinted constructs. (a) Various 3D constructs were printed using a bioink (from left to right: hollow cube, hemisphere, pyramid, twisted bundle, the shape of an ear, and a nose with food dye). (b) A mesh made of hydrogels was printed and was used to host HEK cells. (c) Viability of cells in a collagen hydrogel infused into the 3D printed mesh of the PEG-alginate-nanoclay bioink material. (d) Viability of the cells through 7 d culture. (e) A printed bilayer mesh (top layer red, bottom layer green) was uniaxially stretched up to three times of its initial length. Relaxation of the sample after stretching shows almost complete recovery of its original shape. (f) A printed pyramid underwent a compressive strain of 95% while returning to its original shape after relaxation. Reprinted with permission Copyright John Wiley & Sons, Inc., 2015.
Fig. 13
Fig. 13
Use of cell-aggregate-based bioinks and related bioprinting strategies. (a) Bioprinter (general view); (b) multiple bioprinter nozzles; (c) tissue spheroids based bioink before dispensing; (d) tissue spheroids during dispensing; (e) continuous dispensing in air; (f) continuous dispensing in fluid; (g) digital dispensing in air; (h) digital dispensing in fluid; (i) scheme of bioassembly of tubular tissue constructs using bioprinting of self-assembled tissue spheroids illustrating sequential steps of layer-by-layer tissue spheroid deposition and tissue fusion processes. Reprinted with permission Copyright Elsevier, 2009.
Fig. 14
Fig. 14
Aggregate of MEF cells used as a bioink for bioprinting an aorta-like structure while the hydrogel served as a support. Reprinted with permission Copyright John Wiley & Sons, Inc., 2015.
Fig. 15
Fig. 15
Preparation and generation of a conductive bioink. (a) A scheme of coagulation reaction of DNA/HA-coated CNT-based bioinks. (b) Viscosity results of a conductive CNT-based bioink. (c) 3D printing of a bioink on a PDMS mold. (d) SEM image shows porous structure of the printed samples. (e) Mechanical test results of printed fibers after swelling. (f) Cyclic voltammetry curves of printed fibers in PBS. (g) Impedance measurements of printed CNT-based microfibers in PBS. (h) Structure of printed fibers inside cell-laden GelMA hydrogels. (i) Top view of GelMA hydrogel shows the printed fibers inside the construct. (j) Immunostaining results of cardiomyocytes encapsulated in GelMA after 10 days including printed fibers for sarcomeric α-actinin (green), cell nuclei (blue), and Cx-43 (red). Reprinted with permission Copyright John Wiley & Sons, Inc., 2016.
Fig. 16
Fig. 16
(a) Schematic diagrams of the two-step gelation mechanism of bioinks: thermoresponsive gelation of gelatin and the irreversible chemical gelation of alginate at the polymer level. (b) Printing of heated hydrogel precursor including living cells onto a cold substrate. (c) First gelation step by decreasing the temperature, which resulted in solidification of the gelatin. (d) After printing the whole construct, it was immersed in a CaCl2 solution to cross-link the alginate within the hydrogel precursor mixture. This procedure was performed in a cold environment to preserve the stability of the construct until chemical cross-linking was completed. (e) Long-term stability was ensured by the cross-linked alginate and then the cooling plate was removed. Reprinted with permission Copyright Elsevier, 2014.
Fig. 17
Fig. 17
The use of phages as a nanobioink. The nano-filamentous M13 bacteriophage was genetically engineered to present cell-adhesive peptides on its major protein. (a) Target genes were inserted into the gVIII region, leading to close proximity to the N-terminus of pVIII. The resulting circular DNA was then transformed into E. coli, creating the engineered M13 phages, which were identified by DNA sequencing. (b) Schematic diagram of an M13 phage displaying a regularly spaced, dense array of biochemical motifs, including both the integrin-binding segment (GRGDS) and the Ca2+- binding segment (DDYD). (c) Schematic diagram of a bioink (target cells + RGD-phages + alginate) and a 3D cell-laden construct printed using the phage-based bioink. Reprinted with permission Copyright Elsevier, 2016.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Bajaj P, Schweller RM, Khademhosseini A, West JL and Bashir R, Annu. Rev. Biomed. Eng, 2014, 16, 247–276. - PMC - PubMed
    1. Groll J, Boland T, Blunk T, Burdick JA, Cho D-W, Dalton PD, Derby B, Forgacs G, Li Q, Mironov VA, Moroni L, Nakamura M, Shu W, Takeuchi S, Vozzi G, Woodfield TBF, Xu T, Yoo JJ and Malda J, Biofabrication, 2016, 8, 013001. - PubMed
    1. Murphy SV and Atala A, Nat. Biotechnol, 2014, 32, 773–785. - PubMed
    1. Zhang YS, Yue K, Aleman J, Mollazadeh-Moghaddam KM, Bakht SM, Dell’Erba V, Assawes P, Shin SR, Dokmeci MR, Oklu R and Khademhosseini RA, Ann. Biomed. Eng, 2017, 45, 148–163. - PMC - PubMed
    1. Zhang YS, Duchamp M, Oklu R, Ellisen LW, Langer R and Khademhosseini A, ACS Biomater. Sci. Eng, 2016, 2, 1710–1721. - PMC - PubMed