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International Journal of Bioprinting Bioprinting cell-laden protein-based hydrogel

concentrations showed viability greater than 90% (1, 3, strategies, engineering a print head or a hand-held printer
and 7 days). Therefore, they demonstrated that the photo- with digital control for direct tissue repair is one of the
crosslinkable cdECM-based bioinks could be successfully promising clinical applications. Indeed, via utilizing the
engineered for auricular cartilage reconstruction while scanned lesions’ 3D reconstructions, bioprinting is capable
exhibiting favorable printability and structural stability. of accurately delivering GFs, cells, and biomaterial-based
Toward the same goal, cartilage acellular matrix scaffolds to repair the lesion with different thicknesses and
(CAM) bioinks containing silk fibroin were engineered shapes. Equipping bioprinters with microfluidic printing
for bioprinting from porcine cartilage by a team of heads can also enable smooth and rapid switching across
scientists [237] . In the first step, CAM-silk scaffolds were various bioink reservoirs in the printing process, making it
crosslinked with methanol only, 100 mM 1-ethyl- simpler in order to recapitulate the native tissues’ biological
3-(-3-dimethylaminopropyl) carbodiimide/N- intricacy. Another point that should be considered in the
hydroxysuccinimide (EDC/NHS) in water (EDC-W), or bioprinting is the design of a gradient scaffold that can
80% methanol (EDC-M) for 12 h. Subsequent to incubation be seamlessly transferred from the cartilage layer to the
for 7 days in collagenase, the printed CAM-silk scaffolds bone layer while maintaining the distinct properties and
illustrated significant changes in shape and weight. A non- functions of each tissue. This has made some progress, but
crosslinked CAM-silk scaffold collapsed after 1 day of more efforts are needed, especially with merging bioprinting
treatment with collagenase 0.2%. At the end of incubation technologies and co-bioprinting of several bioinks.
period, the extruded structures completely dissolved, Moreover, the practicability and commercial availability
and the methanol- and EDC-W-treated groups displayed of bioinks and cells should be considered, including their
analogous degradation characteristics after 3 to 5 days. In cost, source, shelf-life, and approval by the Food and Drug
contrast, EDC-M could preserve the printed scaffolds well. Administration (FDA). Another direction is combining
The EDC-M-treated scaffolds did not degrade after 7 days, bioprinting techniques to meet different current obstacles,
and EDC-W scaffolds retained ~20% of their initial weight. which is grabbing considerable attention among scientists.
For instance, the employment of bioprinting approaches
5. Challenges and perspectives with diverse resolutions can be used to imitate the aspects of
natural biological systems, which are operating on various
Within the context of bioprinting approaches, classified scales. Moreover, evaluating the cellular functions after
based on the cells format and the number of cells generated and during bioprinting will benefit the broad applicability
during the bioprinting process, an unmet need still exists, and future success of bioprinting strategies. Last but not
which is related to the cell damage due to the shear stress least, the continual optimization of bioprinting factors,
during the bioprinting procedure. Furthermore, bioinks the evolution of bioprinting equipment like imaging used
with enhanced cell shielding features are not largely for single-cell sorting, and the modification of bioink
explored. In this regard, scholars are merging experimental formulations like cellular density are ongoing trends to
investigations with probabilistic models to improve make bioprinting approaches more advanced, precise, and
our understanding of how cells get encapsulated into relevant to certain requirements.
droplets in bioprinting and develop novel bioinks having
the right balance of rheological characteristics for stress Protein-based materials are among the most promising
shielding and printability. The applications of the present sources for the bioinks’ formulations utilized in bioprinting
single-cell bioprinting techniques are limited owing to strategies. Nonetheless, as with all the materials that are
multiple issues. To begin with, although the efficiency and developed from biologics, there can be batch-to-batch
reliability of the single-cell encapsulation are significantly variations in these materials, and thus the bioinks made
improved, the single-cell printing’s overall throughput from them. Hence, it is of cardinal importance to establish
is still low. Secondly, current printing methods typically well-defined and strict protocols for the concentration,
rely on the single-cell droplets’ printing within an open purification, and extraction of the employed proteins to
environment, causing deviation and interference in the provide reliable and reproducible outcomes. Additionally,
following analysis. In other methods of bioprinting, one selecting the best accessible method of sterilization
major obstacle is associated with reproducing a highly can serve an essential role in guaranteeing the final
complex set of cell–matrix and cell–cell interactions, bioink’s safety and ideal properties. On the one hand,
which are needed to guarantee sufficient organ functions. proteins originating from xenogeneic sources represent
Besides, some of the developed bioinks containing several a potential ethical concern and could increase the risk
populations of cells have failed to replicate the native ECM of pathogen transmission. On the other hand, allogeneic
microenvironment in the body, a bottleneck that remains to sources of proteins pose extra difficulty in the source
be addressed. Concerning the perspectives of bioprinting material’s availability, particularly taking into account

Volume 9 Issue 6 (2023) 488 https://doi.org/10.36922/ijb.1089