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Bioprinting with collagen
from spinal cord injury, they cultivated NSC 3D bioprinting depends on collagen concentration
on the surface of scaffolds. Next, scaffolds in a solution. Only high concentrations of collagen
were implanted into transsection lesions in T10 (more than 20 mg/ml) in single-component
of the spinal cord in rats. Two months after, a collagen bioinks allow increasing the accuracy
significant recovery of locomotor functions was of printing. At present, there are only a few
observed. commercially available concentrated collagen
bioinks – Lifeink (35 mg/ml, Advanced
®
3.6 Cornea Biomatrix, USA) and Viscoll (80 mg/ml, Imtek,
®
Cornea bioprinting is one of the new approaches Russia). One of the distinctive characteristics of
in tissue engineering . The extracellular matrix these bioinks is the possibility to add not only cells
[46]
of the native cornea consists of almost 90% of I but also any components of the extracellular matrix
type collagen. This is why bioinks for artificial to their composition. This allows to bioprint an
cornea also must contain collagen. The bioprinting artificial cell-laden matrix, which can be required
of cornea through the extrusion method allows by a researcher to solve a specific problem.
controlling the thickness and geometrical Despite the absence of sufficient data on the
properties of a printed structure. For example, behavior of mammalian cells in dense collagen
Isaacson et al. have printed a corneal like cell- hydrogels, a large number of scientists are
[47]
laden structure. As a bioink, they used a mixture concerned that cells will inevitably collapse in
of SA and methacrylated type I collagen with dense collagen hydrogels during cultivation.
[17]
encapsulated corneal keratocytes. Cell survival in However, primary tests have debunked those
the printed structures during 7-day cultivation was concerns. It was found that fibroblasts retain their
high viability in high-density collagen gels (up to
at a high level. Similar results on cell survival were 40 mg/ml). These results lead the way to some new
obtained in AG, collagen, and corneal stromal studies devoted to the behavior of cells in high-
keratocytes bioinks . density collagen hydrogels, their proliferation and
[48]
These studies show that it will be possible to migration activity, differentiation, functionality
create an artificial cornea in the future. However, retention, as well as the creation of various
in vitro experiments do not give sufficient scaffolds using 3D printing technology with their
information for it. For this case, more studies that subsequent colonization with cells in various
imply 3D bioprinting of different versions of the fields of tissue engineering.
artificial cornea will have to be tested in vivo.
Acknowledgments
4 Concluding remarks and future perspectives
This work was funded by the Foundation for
For the last few years, there was significant Assistance to Small Innovative Enterprises
progress in 3D bioprinting and adaptation of (FASIE), Project no. 44700.
collagen solutions to the needs of this technology.
Without any doubt, the combination of collagen- Conflicts of interest
based bioink and 3D bioprinting has great potential
in the manufacture of artificial organs and tissues The authors declare that they have no conflicts of
for tissue engineering and regenerative medicine. interest.
Table 1 provides a list of existing variants of References
collagen-based bioinks that could be used for
such purposes. However, the development in this 1. Xia Z, Jin S, Ye K, 2018, Tissue and organ 3D bioprinting. SLAS
direction is very slow. It is mostly connected with Technol, 23:301–314. DOI: 10.1177/2472630318760515.
the absence of easily-accessible collagen bioinks 2. Nagarajan N, Dupret-Bories A, Karabulut E, et al., 2018,
which would correspond to requirements of the Enabling personalized implant and controllable biosystem
“perfect” bioink. The applicability of collagen for development through 3D printing. Biotechnol Adv, 36:521–

24 International Journal of Bioprinting (2020)–Volume 6, Issue 3