Page 472 - IJB-10-2

International Journal of Bioprinting Bioprinting with ASCs and bioactive glass

Figure 4. Viscoelastic behavior of AG hydrogels. (a) The physical behavior of hydrogels immediately after overnight stirring in a beaker kept on a 40°C
hot plate. Flowability of hydrogels stopped with increased B3 glass content (at 2.5G). 2.5G, 5G, and 10G hydrogels exhibit a solid-like behavior. (b) Storage
modulus (G’) and (c) loss modulus (G’’) as a function of Strain percentage at room temperature before crosslinking with CaCl for alginate-gelatin gels
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without glass and with different B3 glass weight percentages. (d) G’ and G’’ for 2.5G, and (e) G’ and G’’ for 5G.

of 100 s shear rate. For example, steady-state viscosity of 2.5G hydrogels. Six-layered scaffolds measuring 15 × 15 ×
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2.5G hydrogel at t = 0 s was ~7000 Pa·s, and its recovered 1 mm were fabricated. The printing parameters used to
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viscosity value between 160 and 220 s was at ~2000 Pa·s. fabricate scaffolds along with the printability matrix for
This behavior was noticed in hydrogels with high B3 glass different hydrogels are shown in Table 1. Hydrogels were
content (>2.5 wt.%) and believed to have occurred due to first tested for their extrudability through a syringe at
the loss of material between plates during tests at shear rate different air pressures with different nozzle tips. Although
of 100 s . The recovery time results provided a satisfactory all hydrogel types were extrudable using different tip sizes
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representation of the recovery behavior as they confirmed ranging from internal diameter of 250 µm to 580 µm,
the printability of all hydrogels with and without B3 glass the extrusion of highly viscous 5G and 10G hydrogels
addition. The recovery behavior of 10G hydrogel is not required high air pressures, extrudate was uneven, and
shown in Figure 5 because of its inhomogeneity and high consistent filament formation was not feasible. In part, this
material loss during recovery tests even at low shear rates. could be due to inhomogeneous mixture of alginate and
gelatin components in 5G and 10G hydrogels. Addition of
3.2. Fabrication, swelling, and mechanical more glass meant availability of more Ca ions to initiate
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property assessment alginate crosslinking before achieving a homogeneous
The determination of viscosity and material recovery composite hydrogel. Moreover, utilizing higher air
times enabled scaffold fabrication with AG, 1.25G, and pressures would damage the cells in the hydrogel, and large

Volume 10 Issue 2 (2024) 464 doi. 10.36922/ijb.2057