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International Journal of Bioprinting Nanoclay biopolymer inks for 3D printing

Figure 3. Storage modulus (G’) and loss modulus (G”) as a function of frequency for the crosslinked 3D-printed hydrogel-based samples.

The storage (G’) and loss (G”) moduli, registered for method. The addition of clay nanoparticles increased the
the crosslinked 3D hydrogel-based structures, are shown elastic moduli, showing that the nanocomposites were
in Figure 3 as a function of frequency. The moduli of the stiffer than the neat biopolymer sample (AV2). Thus, the
equilibrium swollen samples were determined using the elastic moduli values for the synthesized alginate–salecan
frequency sweep method. It is essential to note that for nanocomposite materials were 7.28 × 10 for AV2C1,
3
3
all the samples under investigation, G’ is higher than G” 12.06 × 10 KPa for AV2C2, 11.39 × 10 KPa for AV2C3,
3
3
over the whole frequency range of 0.1 to 5 Hz, attesting and 7.34 × 10 KPa for AV2C4, all of which were greater
the crosslinked condition of the resulting 3D structures. than the elastic modulus of the uncompounded alginate–
Additionally, the addition of clay nanoparticles and the salecan sample (AV2, 5.21 × 10 KPa). These values are
3
rise in their concentration in the formulations used for 3D comparable to the elastic moduli of soft tissues (brain, skin,
printing resulted in an increase in the storage modulus G’ and muscles). 63-66 The nanoparticles are likely to impede
and loss modulus G”, respectively. This event suggested that the movement of the biopolymer networks, according to
clay nanoparticle interfered in the crosslinking mechanism the findings, which are consistent with earlier research
and 3D-printed composite hydrogels were becoming more on polymer–clay nanocomposites. 40,44,67 Following that,
rigid and able to tolerate higher mechanical stress. the samples with the highest clay concentration showed a
The acquired results are consistent with prior research little decline, demonstrating that an optimal clay content
investigations that demonstrate the creation of more stiff (of ~5 and 7%wt.) is required to achieve larger elastic
biomaterials by combining biopolymeric networks or moduli. This effect could be explained by the dispersion
adding inorganic components. Thus, Serafin et al. showed of nanoclay particles within the alginate–salecan matrix,
that the mechanical characteristics are noticeably improved which is more pronounced with low clay concentrations,
when collagen is combined with gelatin or hyaluronic as indicated by XRD analyses, as well as the remodeling of
40,55
acid. The same group found that the storage modulus the internal structure under applied mechanical stress.
60
increases as the amount of inorganic partner increases in In summary, the nanocomposite samples demonstrated
the collagen–gelatin matrix. Furthermore, as the frequency augmented mechanical stability compared with the neat
was raised, both moduli—storage and loss—increased as biopolymer sample, which is critical when the material is
well. The hydrogels continue to exhibit an elastic response projected for applications that are subjected to mechanical
as a result, and the storage modulus continues to be greater stress.
than the loss modulus. Other studies have demonstrated
61
also how the addition of clay to polymeric matrices had 3.6. Microscopy analyses
a favorable impact on the rheological and mechanical SEM analyses of freeze-dried 3D structures were also
properties of the produced nanocomposites. 57,62 carried out to investigate their morphology when created
with various compositions. The macrostructure underwent
The reduced moduli/elastic moduli were determined visible changes as a result of the viscosity of the probe as
from nanoindentation results using the Oliver–Pharr observed from SEM images presented in Figure 4. Thus,

Volume 10 Issue 1 (2024) 187 https://doi.org/10.36922/ijb.0967