Page 474 - IJB-10-2

International Journal of Bioprinting Bioprinting with ASCs and bioactive glass

Figure 6. Scaffold fabrication with (a) AG, (b) 1.25G, (c) 2.5G, and (d) 5G hydrogels. Implementation of dwell time (t) between successive layer depositions
aided in hydrogel recovery and made it feasible to fabricate AG and 1.25G scaffolds. Increasing the B3 glass content reduced the dwell time from 90 s to
0 s as 2.5G hydrogel scaffold could be fabricated with no dwell time. Failure to fabricate parts (dog-bone like specimen) with 5G hydrogel is also shown.

the filament recovery and thus enabled the designed soaked in DI water for 24 h to measure the swelling
scaffold fabrication. This was further tested in a complex percentage. Swelling of hydrogels indirectly represents
3D structure with internal channels mimicking a vascular the capacity of the material to absorb media and allow
network (Figure 7). cell growth and proliferation. Swelling of AG hydrogel
was increased after 24 h with the addition of B3 glass. The
Scaffolds were crosslinked with 0.1 M CaCl solution
2
for 10 min immediately after fabrication, washed, and swelling of AG scaffolds was ~36%, whereas it increased
to ~44% for 1.25G scaffolds and further to ~51% for 2.5G
scaffolds. The release of Ca and Mg ions with B3 glass
2+
2+
dissolution initiates alginate crosslinking during hydrogel
preparation (overnight stirring), and the molecular
structure was further condensed after crosslinking with
CaCl solution. Therefore, 2.5G scaffolds have a highly
2
defined and consolidated molecular structure among the
three scaffolds, and this was evident from the shrinkage
of 2.5G scaffolds (~18%) after crosslinking. After scaffolds
were soaked in DI water, they relaxed and absorbed DI
water driven by the ionic concentration gradient with
high number of ions present inside the scaffold structure
(because of glass dissolution), and no ions present in the
soaked media (DI water). Hydrogel swelling depends on
the ionic concentration of the soaking solution and the
number of ionic groups present in the hydrogel. It was
reported that increased ionic groups in hydrogel increased
its swelling ratio because of the osmotic pressure created
by the increased counterions in the hydrogel. This could
37
be the reason for the high swelling percentage observed
for 2.5G scaffolds. Higher swelling ratio for AG hydrogels
prepared with high ionic strength PBS was also reported in
Figure 7. A superior (top picture) and anterior (bottom picture) view of a a recent work and was consistent with our results.
13
complex structure fabricated by 3D extrusion printing of AG hydrogel-B3
glass composite. A second nozzle was used to extrude red dye to view In this study, small amounts of B3 glass (7.5 mg/10
the internal channel. This construct demonstrates our technique of 3D mL of DI water for 1.25G and 15 mg/10 mL of DI water
printing with two different inks.

Volume 10 Issue 2 (2024) 466 doi. 10.36922/ijb.2057