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International Journal of Bioprinting Evolution of bioprinting

also achieved by reprogramming cells for differentiation again published in abundance. A large number of articles
into cardiomyocytes and endothelial cells . 3D printing focus on the characterization of hydrogels, impressions of
[91]
of central nervous system structures, which is difficult to small parts of organs that, thanks to all the advances made
achieve due to the high complexity of the central nervous each year, are becoming more functional, and, above all,
system, was made possible on a small scale using the small additions, modifications, or changes in the materials
microscale continuous projection printing. With these to make bioprinted constructs as similar as possible to real
biomimetic scaffolds, regeneration of damaged axons from biological structures. In addition, articles related to robotic-
the spinal cord of mice was achieved, which synapse with assisted in situ bioprinting started to emerge, thanks to the
the neural progenitor cells of the scaffold . generation of new robots capable of correctly positioning
[92]
“Tumor-on-a-chip,” in which the reconstruction of a the nozzles for dexterous and precise bioprinting [102] .
glioblastoma tumor from patient-derived cells reproduces Also, as an example of progress in this field, pancreatic
the structure, biochemistry, and biophysical properties of islets were bioprinted using extracellular decellularized
the native tumor, was then developed and could be used for composite bioinks and subsequently implanted in mouse
identifying effective treatments . An in situ skin bioprinter models; it was observed that there were no inflammatory
[93]
was also developed, where skin layers were printed directly reactions, and the neovascular processes started in week 8
[103]
onto the patient, resulting in rapid wound closure, reduced of the experiment, and the cell viability was 120% .
shrinkage, and accelerated re-epithelialization . Many of the aforementioned studies continue to be
[94]
carried out and evolve, leading to the development of new
It has been shown that the imprinting of cartilage
extracellular matrix scaffolds, GelMA, and mesenchymal protocols with important changes that bring us ever closer
to the reality of using bioprinting in medicine on a routine
stem cell-derived exosomes can be an effective treatment for basis (Figure 4).
osteoarthritis by regulating disease-causing mitochondrial
function and facilitating cartilage regeneration . In
[95]
addition, the design of biomimetic muscles created by 3D 4. Main applications of bioprinting
printing with tissue-derived cells and bioinks has been 4.1. Tissue regeneration
found to improve the treatment of irrecoverable volumetric The worldwide shortage of organ and tissue donors, owing
muscle wasting .
[96]
the high demand for organs and tissues and the need for using
The year of 2020 has seen a shortfall of original research immunosuppressants for a long time after implantation,
papers because of the COVID-19 pandemic, and most of is a problem that needs to be addressed [104] . Therefore,
the articles on this topic were review articles. the use of bioprinting is increasingly being considered a
The topic of most recent review articles revolves around possible solution to this problem, whereby transplants are
4D bioprinting, which integrates the concept of time as created from the patient’s own cells, obviating the need for
the fourth dimension within traditional 3D bioprinting a donor or the use of various immunosuppressants that
technology and facilitates the fabrication of functional and could induce negative side effects. To create tissues using
complex biological architectures . This is made possible bioprinting, three central approaches, namely biomimicry,
[97]
by the fact that such 3D-printed structures are able to autonomous self-assembly, and microtissue building
[105]
produce changes in their structure after receiving a certain blocks, are considered .
stimulus. Apart from that, reviews on bioprinting in the (i) Biomimicry. Biomimicry involves the fabrication
study of the complex tumor microenvironment, with a of identical reproductions of the cellular and
better understanding of its functionality and the goal to extracellular components of a tissue or organ [106] .
tailor personalized treatment for each patient, also started (ii) Autonomous self-assembly. Autonomous self-
to accumulate [98,99] .
assembly relies on the cell as the main driver of
The use of poloxamer composites in bioprinting histogenesis, directing the composition, localization,
was first proposed due to their bioactivity, temperature- functional, and structural properties of the tissue [107] .
dependent self-assembly, thermo-reversible behavior, and (iii) Microtissue building blocks. Microtissue building
physicochemical properties, which make them promising block is defined as the smallest structural and
drug carriers and good mimics of various tissue types [100] . functional component of a tissue. There are two
Also in 2020, the bioprinting of a meniscus that fulfilled the main strategies: first, self-assembled cell spheres
necessary characteristics to be implanted was achieved [101] .
(similar to microtissues) are assembled into a
Throughout 2021 and 2022, reviews and studies on the macrotissue using biologically inspired design and
use of decellularized cellular matrix in bioprinting were organization [108] ; second, accurate, high-resolution

Volume 9 Issue 4 (2023) 373 https://doi.org/10.18063/ijb.742