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Ghosh and Yi

Figure 4. Types of biomaterials.

Figure 5. Molecular formula of agarose. The hydroxyl groups
(OH) that can be chemically altered are randomly highlighted in
light pink circles. (from ref. licensed under Creative Commons
[68]
Attribution license).
4.1.2. Alginate
Alginate is a brown algae-derived anionic polymer
composed mainly of blocked copolymers, with α-(1-4)-
L-guluronate and (1,4)-linked β -D-mannuronate residues Figure 6. Structural components of the alginate block.
arranged in different sequences and ratios depending on (A) β-(1–4)-D-Mannuronic acid; (B) α-(1–4)-L-Guluronic acid and
the alginate source [69,70] . Alginates are widely used in (C): Diagrammatic representation of biodegradable oxidized alginate
[71]
biomedical applications such as wound healing, drug used as bioink for bioprinting (from ref. Creative Commons
[72]
delivery, and tissue engineering because of their low cost Attribution-Non Commercial 3.0 Unported Licence and (from ref.
licensed under Creative Commons Attribution 3.0 license).
and biocompatibility [17,69] . The ability of alginate to make
hydrogels with characteristics analog to the ECM of qualities [75] . When cellulose chains are well organized,
tissues is the main advantage of alginate-based bioinks they form composed cellulose nanocrystals (CNC)
[70]
(Figure 6). which can improve shear-thinning behavior and enhance
mechanical strength [76] . Cellulose, as well as CNCs, are
4.1.3. Cellulose often used in bioinks because of its ability to improve
Cellulose, a very rigid polysaccharide made up of (1 the porosity of the structures, its elasticity, its ability to
– 4) linked β-D-glucopyranosyl units linked together, bind with other substances, and enhancement of bioink
plays are the primary structural substance in plant viscosity [77,78] . In addition to their biocompatibility,
cells [73,74] . Carboxymethyl cellulose is a water-soluble CNCs possess antibacterial properties, making it
form of cellulose ether that is often used to change an appealing option for the applications in wound
the density of other polymers with subpar rheological dressing [78] (Figure 7).

International Journal of Bioprinting (2022)–Volume 8, Issue 4 179