Page 182 - IJB-8-4

A Review on Bioinks and their Application in Plant Bioprinting
conducted to generate new bioinks or bioink composites In vitro synthesis from plant cell cultures could
with improved cell viability, proliferation, permeability, meet the growing demand for plant-derived components,
and bioprintability to expand bioprinting techniques such as secondary metabolites, in medicine, and cosmetic
into the field of plant biology. Nevertheless, plant-based industries. However, further research is needed to
biomaterials and printing plant parts are slowly making improve process efficiency, which green bioprinting can
advances in the area of bioprinting. Although, most plant potentially accelerate through the design of a specified
cells are totipotent, that is, they have a strong potential immobilization matrix to enable the local and time-
to develop a tissue scaffold that acts as the precursor resolved analysis and modulation of substrate diffusion
for an organ. From that organ, an entire plant can be routes. The effects of cell immobilization on secondary
generated, even if the environmental conditions are metabolite production and extraction should thus be
unfavorable . Despite cell totipotency, new plant cell- further investigated.
[18]
related discoveries in the field of bioprinting research Secondary metabolites derived from plants are
are currently lacking. Moreover, the primary challenge beneficial in pharmaceutical, food, and purely aesthetic
to successful plant tissue printing is the lack of safe and additives. Immobilization can increase productivity
intricate microarchitectures designed to mimic natural by ensuring appropriate environmental conditions for
biological functions . cells ; thus, various cell immobilization strategies
[19]
[28]
Plants have been extensively studied since have been used for plant cells, such as encapsulation in
the earliest times, and various essential chemical hydrogel beads (such as agarose, gelatin, alginate, and
compounds with tremendous medicinal potential have pectate), binding on the substrate surface of synthetic
been uncovered . Microorganisms, such as bacteria foams or fibers, and trapping hollow fibers in filter
[20]
or viruses, can be countered with a well-functioning membranes . The use of the bioprinting approach, that
[29]
immune system. Therefore, stimulating the body’s natural is, cell encapsulation in hydrogels through computer
defensive mechanism toward infections has been shown aided design based 3D printing, can advance the progress
to be an effective technique. Alkaloids, polysaccharides, toward the success of a structured plant cell-laden 3D
glycosides, terpenoid lactones, and flavonoids are scaffold. The immobilization of plant cells in organized
important phytochemicals that have been linked to plant hydrogel matrices may allow the collection of spatially
immunomodulation activities . These phytochemicals and temporally resolved data to analyze the impact of
[20]
may serve as key compounds in the development of safe the immobilization matrix and culture conditions on
and effective immunomodulators for the treatment and secondary metabolite release. This would provide a better
prevention of viral illnesses. Natural products have been understanding of hydrogel-entrapped plant cell cultures.
shown to influence the immune system in nonspecific The fabrication of structured plant cell-laden hydrogel
ways. Plant extracts have been widely studied for their matrices by bioprinting could also enable the realization
potential immunomodulatory characteristics in various of architectures with defined macropore sizes and shapes
regions of the world . For example, Acorus calamus that may be modified to induce specific conditions for
[21]
rhizome extract inhibits the proliferation of various plant cell cultures to produce large amounts of secondary
human and mouse cell lines. As a result, plants are metabolites. This is expected to increase productivity,
frequently referred to as immunomodulators, which are make harvesting without cell loss easier, and allow the
chemicals that alter the immune system’s reaction to a co-cultivation of cells derived from different species or
threat . Immunomodulators modulate and strengthen even different taxonomic classifications. Furthermore,
[22]
the immune system, preparing it for any threat . Plant such structured immobilization matrices could be easily
[23]
cells possess cell walls (CWs) while animal cells possess integrated into bioreactors (fixed-bed reactors), and two-
cell membranes, which allow them to be more flexible. stage processes consisting of proliferative and production
Conversely, the CW is more useful for protecting the phases, which are promising for plant cells, could be
internal organ system. easily established.
Recently, the green bioprinting concept was In addition, the present plant-based biomaterial
established following the effective use of an extrusion- production processes are inefficient and have unsustainable
based bioprinting methodology developed for printing requirements . A new strategy for plant-based biomaterial
[30]
human cells for manufacturing photosynthetic microalgae- production has been proposed by Beckwith et al. which
laden hydrogel scaffolds [24-26] . Green bioprinting refers significantly eliminates or reduces inefficiencies during
to printing plant cells or other plant-based fabrication. pre-processing and agricultural stages. The feasibility
Primarily, green bioprinting is a promising emerging of targeted culture strategies has been demonstrated
immobilization technology for plant cells that can allow using a Zinnia elegans model system . Gel-mediated
[30]
the development of new bioprocesses and monitoring cell cultures can be used to generate tunable plant-based
systems for secondary metabolite production . constructs to mimic isolated plant tissues in pre-defined
[27]

174 International Journal of Bioprinting (2022)–Volume 8, Issue 4