Page 221 - IJB-9-1

International Journal of Bioprinting Cellulose-based bio-inks for bone and cartilage TE

Table 1. Types, typical sizes, crystallinity and functions of nanocellulose
Type of nanocellulose Typical size Crystallinity Mechanical strength Characteristic
Nanofibrillated cellulose High aspect ratio; lengths: Contain both amorphous Tensile strength: 1 GPa, Good biocompatibility,
(NFC) 0.5–2 µm; diameters: and crystalline regions; Young’s modulus: 30 GPa biodegradability, water
5–60 nm crystallinity about 60% retention
Nanocrystalline High aspect ratio (~70); the Crystallization zone only; Tensile strength: 7.5 GPa, High mechanical strength,
cellulose (NCC) smallest nanoscale dimen- highly crystalline (54–88%) Young’s modulus: 120 GPa high crystallinity, good
sions of any nanocellulose; biocompatibility, biodegrad-
lengths: 0.05–0.5 µm; diam- ability
eters: 3–5 nm
Bacterial nanocellulose Lengths: several microme- Super high crystallinity (up Young’s modulus up to High water absorption, high
(BNC) ters; diameters: 20–100 nm to 95%) 70 GPa air permeability, porous
structure, good biocompati-
bility, biodegradability, high
purity, simple purification
process, expensive

in tissue engineering (TE) . In addition, numerous methods. They are further divided into three categories:
[2]
studies have reported the use of 3D bioprinting in a wide nanofibrillated cellulose (NFC), nanocrystalline cellulose
range of TE applications, particularly in the fabrication of (NCC), and bacterial nanocellulose (BNC) (Table 1). These
skin , heart , bone, and cartilage tissues . At present, 3D intrinsic properties have led to their widespread use in the
[4]
[3]
[5]
bioprinting is a rather established technique, and can be field of bone TE (Table 2).
categorized into several main methods: inkjet, extrusion,
laser-assisted, and stereolithography methods . However, 2.1. NFC
[6]
bio-ink is the most important component, particularly 2.1.1. Physicochemical properties and
in TE. Generally, several basic properties of bio-inks, preparation of NFC
including biocompatibility, printability, biodegradability, NFC is nanoscale cellulose obtained by degrading
[7]
and mechanical properties, are taken into account in TE. lignocellulosic biomass . Owing to its nanoscale size,
nanocellulose has good mechanical capabilities, strong cell
Cellulose, one of the most prevalent natural polymers, adhesion, good biocompatibility, and water retention. NFC
is a linear polymer comprising β-D-glucose. It is not is composed of many entangled nanofibers that contain
only found in plants, but also in bacteria and algae. The amorphous and crystalline regions . NFC was previously
[8]
hydrogen bond crosslink between β-D-glucose molecules prepared via high-pressure homogenization and grinding,
makes cellulose rigid, and cellulose also has high and pretreatment is necessary to produce high-caliber
biocompatibility as a natural polymer; therefore, cellulose, NFC and reduce clogging and high-energy requirements in
which is an abundant natural resource, is used to make homogenizers. The most common pretreatment methods are
bio-ink and claims an important place in the field of TE. enzymatic reactions and 2,2,6,6-tetramethylpiperidine-
[9]
Currently, nanocellulose and cellulose derivatives, which 1-oxyl free radical (TEMPO)-mediated oxidation ,
[10]
are the main forms of cellulose used in TE, are used as the which weaken the interactions between plant cell walls.
main component of TE scaffolds and often as conditioning With a typical average length of approximately 0.5–2 µm,
agents for other natural polymer inks (alginate [Alg] and an average diameter of approximately 5–60 nm, a tensile
gelatin). strength of 1 GPa, and a modulus of 30 GPa, the size and

The objective of this review is to present recent strength of NFC are mostly dependent on the source and
developments in 3D bioprinting using nanocellulose and preparation technique. Moreover, many methods have
cellulose derivatives in bone and cartilage TE that have been developed to modify the properties of NFCs. One
been developed in the last five years. We also elaborate of the examples is improving their hydrophilicity through
their potential applications in this emerging field. physical adsorption and plasma discharge, which has led to
their widespread use in various fields.
2. Nanocellulose 2.1.2. NFC 3D bioprinting in cartilage and bone repair

Nanoscale cellulose derivatives are referred to as Owing to its remarkably high fidelity and biocompatibility,
nanocellulose. Their intrinsic properties, including NFC bio-ink is a great material for 3D printing of
morphology, size, mechanical strength, and crystallinity, TE scaffolds . NFC is frequently used to modify the
[11]
are determined by various sources and preparation rheological characteristics of bio-inks and enhance their

Volume 9 Issue 1 (2023)olume 9 Issue 1 (2023)
V 213 https://doi.org/10.18063/ijb.v9i1.637