Page 445 - IJB-9-3

International Journal of Bioprinting Gelatin-PVA crosslinked genipin bioinks for skin tissue engineering

determine the interaction of PVA and crosslinker with to 1700 cm in all hydrogels were related to the formation
-1
gelatin hydrogel. In this research, the G’ steadily drops at of amine (C-N) I, II, and III due to the interaction of
low frequencies until it reaches a minimum at a certain amine groups of GE with GNP. It was demonstrated that
frequency, at which point the modulus rises. The addition the gelatin-PVA hydrogels did not present any extra peaks
of PVA did not increase the elasticity of the gelatin in a way that implies that 3D bioprinting approach did not
hydrogel. This finding is correlated with a study by Moraes contribute to any unfavorable chemical interactions.
et al., which indicated that gelatin and PVA polymers
practically did not exhibit elastic behavior (G’) and also 4.4. Bioinks 3D microstructure and cellular
did not exhibit any phase change within the temperature compatibility
range investigated . Besides, another finding on the An appropriate porosity of skin substitute is crucial for
[65]
viscoelasticity of the gelatin-PVA hydrogel was found by wound healing application to allow efficient deposition
Gelli et al., who reported that the incorporation of PVA of ECM, and promote cell migration activity and tissue
into gelatin hydrogels decreased in the storage modulus . integration. SEM was used to determine the microporous
[66]
Moreover, the progression of stiffening and gel structure is structures of the 3D-printed hydrogels. The interconnected
confirmed by the increasing rate of G’ which is higher than pores were visible in all hydrogel groups and average pore
that of loss modulus (G”). sizes were calculated to be greater than 100 µm. A previous
study by Yannas et al. suggested that 20 – 125 m should
The crystallinity pattern of the gelatin-PVA hydrogels be the ideal pore size for reconstructing adult skin .
[71]
was evaluated using XRD, as shown in Figure 5A. Since Moreover, GE_GNP demonstrated to have the biggest pore
gelatin is a semi-crystalline polymer, there is a broad sizes among the crosslinked groups. The addition of PVA
peak in the range 10–25° (2θ) for all hydrogels. The to the gelatin hydrogels reduced their porosity. This result
gelatin-PVA hydrogels have the highest peak at (2θ) 19.5° was similar with a previous finding by Thangprasert et al.
and this finding matches a previous study by Zandraa and Labus and Radosinski, which indicated that the pore
et al. Following the incorporation of gelatin with PVA diameters of gelatin hydrogel were reduced and substantially
[67]
in the hydrogels, the crystallinity level was slightly reduced smaller by adding PVA to the gelatin hydrogels [70,72] . These
(Table 1). This occurrence was described by Swaroop results occurred due to the penetration of PVA molecules
et al., claiming that the regularity of gelatin was disrupted into the open spaces between gelatin chains. Moreover, the
by intermolecular contact . Similar results were obtained addition of GNP affected the pore diameters of gelatin-
[68]
in a recent work by Zulkiflee & Fauzi, which described how PVA hydrogels due to the formation of covalent bond. The
the addition of PVA to gelatin hydrogel would decrease number of tiny pores increased in the crosslinked polymer
crystallinity . In addition, following crosslinking with chains in the interpenetrating hydrogel as compared to the
[14]
genipin, the crystallinity of crosslinked gelatin-PVA non-crosslinked hydrogels. A previous study by Erdag et al.
hydrogels increased in comparison to non-crosslinked showed that samples with lower GNP concentrations had
hydrogels. This result was highly similar to a recent work by a higher number of tiny pores as compared to the samples
Zawani et al., which produced similar outcomes following with higher GNP concentrations . Thus, our formulations
[73]
genipin crosslinking of the hydrogels . might be able to aid in absorbing wound exudate, lower
[69]
Besides, the interaction between polymers and the risk of infection, and provide a conducive environment
functional groups of the hydrogels was characterized that promotes faster wound healing due to the presence of
using FTIR. Based on Figure 4B, both crosslinked and appropriate porosity.
non-crosslinked hydrogels exhibited distinct spectra Cell response to a toxicant or new substances and
in the region of 2750 – 3500 cm . GE_NC hydrogels the measurement of cell viability are well known as key
-1
showed vibration of C-H stretching that appeared at aspects in toxicity testing. The extrusion-based bioprinting
wavenumbers 2934.3 and 3301.98 cm that represent technique exhibited no sign of cell membrane damage after
-1
Amide A and Amide B. The hydroxyl groups (O-H) printing. The addition of different concentration of PVA
stretching in the GPVA hydrogels showed a broad peak (3% and 5%) and crosslinker (GNP) to the gelatin hydrogels
in the 2900 – 3500 cm . This result was consistent with a clearly demonstrated that no obvious cell morphological
-1
previous study by Thangprasert et al., which demonstrated changes occurred after they were encapsulated in the
that the hydroxyl group stretching formation was initiated bioinks. The live/dead assay revealed that nearly all the
by the interaction of intramolecular and intermolecular HDFs were stained green and still alive after bioprinting.
hydrogen bonds between GE and PVA . In contrast, Thus, our results demonstrated that all hydrogels could
[70]
hydrogels with greater PVA concentrations exhibited a sustain high cell viability (>90%) after 24-h extrusion,
stronger absorption peak. Moreover, the bands from 1200 indicating that the bioinks are biocompatible and less toxic

Volume 9 Issue 3 (2023) 437 https://doi.org/10.18063/ijb.677