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International Journal of Bioprinting Nanoclay biopolymer inks for 3D printing

1. Introduction composite hydrogels becomes an emerging topic in hard
tissue regeneration. In this respect, several composite
In order to address a variety of biological problems, formulations synthesized through the encapsulation or
current research studies are focused on developing modifications of alginate-based hydrogels with additives,
multicomponent and multifunctional composite scaffolds such as inert or bioactive glasses, 21,22 hydroxyapatite, or
5,16
employing a variety of material combination and design.
nanoclays, 23-26 have been explored.
The oceans are a major renewable supply of natural In this context, our present work proposes a combined
chemicals and contain a diversity of compounds. strategy where, for the first time, alginate networks
Polysaccharides are abundant in the marine ecosystem, will be semi-interpenetrated with salecan to obtain
and their corresponding biological and physicochemical printable hydrogel formulations and further crosslinked
characteristics have encouraged their use for the creation 3D-printed alginate–salecan constructs. Salecan, which
of a wide range of biomaterials in the form of hydrogels, is a microbial marine polysaccharide extracted with a
particles, nanofibers, wafers, foams, and capsules that tolerant salt strain Agrobacterium sp. ZX09, demonstrated
have found utility in numerous sectors such as food, exceptional physical–chemical features. Among excellent
27
pharmaceuticals, membranes, and cosmetics industries. 1-3 characteristics of salecan, its rheological properties 28-30 and
Based on its availability, biocompatibility, and lack of availability to be used alongside natural 31-33 or synthetic
toxicity, alginate may be considered the most well-known polymers 34-36 are highly beneficial for our present study.
polysaccharide derived from brown seaweed. Alginate is an In recent years, our research group developed polymer
anionic linear chain biopolymer composed of mannuronate nanocomposites containing salecan for drug delivery
sequence and guluronate residues in a variety of ratios, purposes. 37,38 More recently, we have followed the
which, consequently, influences its molecular weight and possibility to synthesize solely salecan green crosslinked
physical properties. Alginate solutions have the unique materials, and further, we have investigated using salecan
4-6
ability to crosslink fast in the presence of ions (such as for the first time in additive manufacturing. 39
Ca ), which produces a cohesive hydrogel with adjustable On the other hand, nanoclays, which are categorized
2+
mechanical properties as function of alginate, crosslinker as either active components or excipients, are widely
concentrations, and incremental timing. employed in medicine and pharmaceuticals, particularly
Alginate is frequently utilized in additive for drug delivery purposes. 38,40,41 Clay nanoparticles
manufacturing. However, there are some overcoming have a strongly negatively-charged surface that is
6-8
issues due to the relatively low viscosity of alginate counterbalanced by positive metal counterions. Nanoclays
solutions which require arduous protocol adjustment to be consist of layered particles that are around 2 microns
42
able to print it in its purest form and crosslink it thereafter. in diameter and 10 nm thick. Many research studies
To improve the immediate additive manufacturing, several proved that the mechanical properties of the generated
approaches were used to overcome its limitations, including polymer–clay composites, swelling and degradation of
pre-crosslinking, rapid crosslinking during the printing the materials, and drug encapsulation and/or release are
9,10
process, and blending with other biopolymers. Alginate, all significantly modified by the addition of nanoclays into
11
6
when combined with other biomaterials, gives the scaffold the polymeric materials because clay platelets influence the
intrinsic biocompatibility, low toxicity, and moderate and synthesis process. 40,41,43-45 In addition, clay nanoparticles
controllable gelation with added divalent cations which were demonstrated to exhibit shear thinning properties to
are crucial for the encapsulation of cells or bioactive their corresponding nanocomposite hydrogels. Therefore,
compounds. In this respect, alginate was compounded with nanoclays are used in tissue engineering to produce 3D
gelatin, 12-14 chitosan, 15,16 methyl cellulose, or agarose 17-20 for scaffolds using additive manufacturing technique. The
obtaining proper hydrogel formulations that are used to presence of nanoclays also promoted osteogenesis and cell
create three-dimensional (3D) scaffolds with enhanced growth in the generated 3D-printed structures. 24-26
mechanical properties. 3D printing techniques for hydrogels offer numerous
Therefore, according to recent reports, hydrogels advantages in biomedical applications, such as
fabricated based on the combination of two or more different customization, complex geometry, and spatial control. 46-48
polymers via crosslinkers can tackle disadvantages and The principal techniques used for 3D printing are as
integrate advantages. However, the mechanical properties follows:
of the hydrogels with multiple polymer networks are (i) Extrusion-based 3D printing: This technique
still weak and cannot fully meet the requirements of 3D involves the deposition of hydrogel filaments
printing. Consequently, the development of high-strength through a fine nozzle. It offers versatility in terms

Volume 10 Issue 1 (2024) 177 https://doi.org/10.36922/ijb.0967