Page 197 - IJB-10-1

International Journal of Bioprinting Nanoclay biopolymer inks for 3D printing

with higher concentrations of salecan, and further clay, polysaccharide or clay peaks. These modifications may be
the pores macrostructure is better defined as a result of explained by the overlapping of the component’s peaks and
increased viscosities and consequently, printing stability as also the possible interactions between the various groups
compared to probes with lower concentrations of salecan, of the components (COOH and OH groups from alginate,
without clay or with low clay concentrations. As a result, OH groups from salecan, and OH from clay edges), as
as the ink formulations were less viscous, the 3D-printed shown in previous studies. 38,44,70 Thus, FTIR analyses
constructs began to collapse under the weight of the confirmed that the structural changes of alginate–salecan
printed layers. biopolymer matrix occurred after clay inclusion with
interactions between components and slight peak shifts
The surface observed when examining the 3D depending on clay concentration.
structures was relatively smooth. With the addition of clay,
there was a change in the surface morphology, specifically, X-ray diffraction analyses presented in Figure 6
some roughness caused by clay particulate agglomeration also indicated changes in the structure of the semi-
in the composition. These became more visible when the interpenetrated biopolymeric matrices as well as of their
concentration of clay in the hydrogel matrix was increased. nanocomposites. XRD curve of the AA0 pristine alginate
The most noticeable feature of SEM images is that printed sample revealed by the existence of two diffraction peaks
probes had distinct filaments, which were more visible at 2θ ~13° and ~ 22°, respectively. These weak and broad
at higher concentrations of salecan as well as clay in the peaks are generally ascribed to a rather amorphous
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hydrogel ink. Furthermore, the filaments in the layered structure of alginate. The bi-component samples also
samples attached very effectively to one another. showed a typical salecan peak-of-diffraction at 20°, which
rose with increasing microbial polysaccharide content.
Taken together, by modifying the concentration of As a result, the X-ray curves revealed a partly crystalline
salecan and nanoclay in the original biopolymer sample, structure with a dominating amorphous phase, which
the morphology of the 3D constructions can be tailored to was ascribed to hydrogen-bonding interactions between
obtain 3D constructs with enhanced printing fidelity and polysaccharides COOH and OH functional groups on
structure stability. alginate and salecan polysaccharides. These results were
consistent with FTIR findings which demonstrated
3.7. Structural analyses, FTIR and XRD biopolymeric chains interactions, too. Furthermore,
The results of FTIR spectrophotometric analyses presented prior investigations in which salecan polysaccharide
in Figure 5 have shown the characteristic peaks for alginate was mixed with other natural polymers, such as agarose,
and salecan as well as changes or shifts of these specific chitosan, κ-carrageenan, and xanthan gum, also revealed
peaks depending on the composition of the materials. modifications in the resulted biopolymer matrices. 33,72-74
Sodium alginate presented the following commonly known
wavelengths: ~1017 cm for the C-O-C and C-OH bonds, The existence of the specific peak of nanoclay around 2θ
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~1600 cm for asymmetrical stretching vibration of COO - ~4–7° was confirmed in the XRD profile of polysaccharide-
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group, ~1420 cm for symmetrical COO group stretching based nanocomposites. This peak underwent some changes
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vibration, and ~2900 cm for CH symmetric stretching in intensity and width, indicating an advanced dispersal
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vibration. In the case of the alginate–salecan sample of clay platelets in biopolymer matrix, mostly at low clay
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investigation, the FTIR curves revealed a slightly modified concentrations. Changes in inter-basal distance may
peak spanning around 1019 cm , which was attributed suggest biopolymer molecules insertion between silicate
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to alginate–salecan chain interactions considering that lamella and the formation of mainly intercalated structures,
salecan generally exhibits the characteristic C-OH a fact strongly related with the rheological behavior of
absorption band corresponding to the glucopyranose the nanocomposites inks. Moreover, the findings are in
ring from the polysaccharide structure in the mentioned accordance with prior research that demonstrated that
area. 39,68,69 adding nanoclay particles to polymeric systems increases
the matrix’s crystallinity, which in turn has an impact on
FTIR tests on nanocomposites based on alginate and the swelling phenomena. 55
salecan confirmed the presence of biopolymer-specific
peaks along with the specific peaks of the clay, namely, 3.8. Evaluation of the internal morphology of the
vibrations of Si-O-Si at ~1000 cm , Al-Si-O at 450–620 cm , 3D-printed object by computed tomography
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and OH in the range of 3400–3600 cm . However, Computed tomography (CT) analysis was performed in
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certain changes in the shape of the FTIR curve may be order to depict the internal morphology of the 3D-printed
seen between 1007 and 1020 cm , especially the presence object and to investigate whether the chemical composition
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of a sharper peak with a minor shift from the assigned variation influenced the architecture. Moreover,
Volume 10 Issue 1 (2024) 189 https://doi.org/10.36922/ijb.0967