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A Review on Bioinks and their Application in Plant Bioprinting
To produce the bioink, sodium alginate was first 5.2. Hybrid bioink
dissolved in distilled water at a concentration of 4%
(w/v) [126] . Using a 25 mL hypodermic syringe and a 5.2.1. Textile biocomposites with photosynthetic properties
#21 needle, the polymer solution was dropped into the Single-cell photosynthetic microalgae, which absorb
gelation media comprising a 250 mL CaCl solution at CO and release O as a byproduct, have been utilized in
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a defined concentration (w/v) under continuous stirring recent years. They have their own set of requirements like
at room temperature. The beads were then cured in the living organisms, including the need for an appropriate
gelation medium for 15 min, removed and washed with pH, light, temperature, and nutrient supply [128] . The
distilled water, and then dried at 30°C in a debris room. construction and fabrication procedures for these unique
Beads crosslinked with BaCl and AlCl were made in the “living organisms” could be reevaluated. For example,
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same way. Notably, the drying process affects the stability biogel printing has become popular in the area of material
of beads. The porosity of the beads decreases when they research, with potential applications in food industries
partially dry. The complete dehydration of the beads can and pharmaceuticals, wherein experiments are ongoing
cause surface cracking, which can make the beads more to optimize the assimilation of living cells into digital
prone to surface erosion when rehydrated. The swelling printing methods [129,130] .
and deterioration indices are thus likely to be affected. Kappa-carrageenan, chitosan, Aloe Vera, and a clay-
Furthermore, water in hydrogel exists in two states: based (Auro clay) binder have all been used as biogel
bound water and free water. As a result, it is possible that matrices for printing (Table 3).
when the beads were dried at 30°C, free water may escape To prepare this type of ink cell, the eukaryotic green
while the bound water remains; hence, crosslinking microalga Chlorella vulgaris (paraphylum Chlorophyta)
ions may be present when the beads are hydrated. The is often used in conjunction with the selected microalga
distance between the syringe and the gelation medium, because it is considerably more resilient than other
the number of drops of polymer solution falling into the microalgae and cyanobacteria. In addition, these cells
gelation media per minute, and the temperature were all are compatible with a variety of environments, including
kept consistent throughout the experiment. office and large public buildings, which provide a uniform
Algal cells derived from TAP-algae were then high-intensity light cycle, vast surface area, and constant
introduced into the hydrogel. The TAP-algae solution was temperatures.
prepared [115] . Fresh liquid TAP media was used for the algal To create the foundation of the bio-gel matrix, at
cells during the preparation of the TAP-algae solution. Since room temperature, kappa-carrageenan (from >99.9%
it included fresh nutrients rather than accumulated cellular pure powder) has been added to a dilution series of BG11
waste elements like methane and free radicals, the fresh
medium was perfect for cell development [127] . Following
the preparation of algal cells, cells were transferred into
the previously prepared hydrogel. The hydrogel bioink
(used to print algae-containing hydrogel filters) had a
cell concentration of 150,000 cells mL . This prepared
−1
hydrogel was used to print the filters on a 10 cm Petri dish
(Figure 16). The filters were in the shape of square disks
with a length of 25 mm and a thickness of 1.5 mm and
included 8 holes with a diameter of 2 mm each. The printing
speed was 6 mm s , while the extrusion pressure was 95 psi
−1
to deposit layers with a thickness of 0.1 mm. After printing,
5 mm of 4% w/v CaCl solution was added to the petri
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dish holding the printed filter for 2 min to allow alginate
crosslinking [127] . Crosslinking generates chemical linkages
between the polymer chains of the printed filters, allowing Figure 16. Schematic of the production of the macro- or
the retention of their printed shape (Figure 15). After mesoporous periodic artificial micro leaf structures using a 3D
crosslinking was completed, liquid TAP media were poured direct writing technique. First, SiO nanospheres and DBSA are
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over the filters to allow algal cell proliferation. The algal added to prepared TIA solutions. Then, soluble linear chains are
formed, resulting in a homogeneous sol-gel ink with adequate
cells containing the filters were placed at room temperature rheological properties that may flow through a micronozzle.
for 4 days below light bulbs once they had proliferated. After solidification, calcination, and etching with hot potassium
This is the 1 time that the 3D printing of algae- hydroxide (KOH), a hierarchical porous micro lattice structure is
st
infused hydrogel filters has been utilized to remove formed. Reprinted with permission from Chem. Mater. 2018, 30, 3,
copper from contaminated water [125] . 799–806. Copyright 2018 American Chemical Society [148] .

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