Page 467 - IJB-10-2

International Journal of Bioprinting Bioprinting with ASCs and bioactive glass

cells for extrusion-based bioprinting techniques. No one initiate the crosslinking of alginate-based hydrogels.
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3
material offers both the required rheological and biological Recently, investigators added copper or niobium to
properties, and therefore, it is a common practice to create a bioactive glass and then printed with hydrogel in order
composite hydrogel to suit specific bioprinting application. to fabricate a fast-recovering and printable construct. 23,24
Other researchers used borate-based bioactive glass to
Alginate has been extensively used as synthetic
extracellular matrix (ECM) that mimics native human improve the printability of AG hydrogels by increasing the
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tissues for more than three decades. Alginate is derived stiffness of the printed construct.
4,5
from algae that crosslinks in the presence of divalent Previously, we investigated cell viability in a
cations such as Ca and Mg and is suitable for bioprinting 3D-bioprinted AG-glass composite hydrogel, using a
2+
2+
applications. As alginate exhibits poor cell adhesion and recently FDA-approved borate-based bioactive glass (13-
6
proliferation due to the lack of arginine-glycine-aspartate 93B3 glass, referred to as B3) and human adipose stem
(RGD) tripeptide sequences, it is functionalized to include cells (ASCs). The B3 glass is particularly attractive due
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7,8
RGD peptide sequence in its molecular structure. An to its high dissolution rate and angiogenic ability. 27-29 This
alternative approach is to add gelatin to alginate to prepare specific glass composition has demonstrated an ability to
a composite hydrogel to enhance the hydrogel’s ability heal difficult-to-treat diabetic wounds, a capability thought
to support cell adhesion and rheological properties for to stem from their angiogenic properties. However, the
extrusion-based bioprinting techniques. 9-14 Despite being exact reasons for their effectiveness and the underlying
unstable at physiological temperatures, gelatin improves mechanisms involved are still not entirely clear. One recent
the printability of the composite alginate+gelatin (AG) study showed that an increased collagen III/collagen I
hydrogel at room temperature due to the thermoreversible ratio for ASCs with B3 glass exposure could establish one
9
gel–sol transition behavior of gelatin. AG hydrogels have possible mechanism for wound-healing behavior with B3
been evaluated by researchers in different weight ratios to glass.
30
improve rheological properties at room temperature to ASCs are extracted from the stromal vascular fraction
facilitate printability without affecting the cell viability. 10,14 of subcutaneous fat, which is more accessible and
Researchers have also pursued media ionic strength involving a less invasive procedure than acquiring their
modification and deposition at ~10°C, instead of room bone marrow counterpart, the more commonly studied
temperature, to improve printability. Despite good bone-derived mesenchymal stem cells. 31-33 Additionally,
13
viability (~90%) with epidermal stem cells, sheep stem
cells, and aortic smooth muscle cells in the above studies, they yield a greater number of cells after isolation than
the main challenges that remain for AG hydrogel are to bone-derived mesenchymal stem cells and have a higher
proliferative capacity. For these reasons, in addition to
achieve: (i) printability at room temperature, (ii) controlled their differentiation, angiogenic, and therapeutic abilities,
degradation of alginate, and (iii) slower dissolution of they are increasingly used in tissue engineering strategies.
gelatin for improved viability over time.
In this study, we: (i) examined how the rheological
Until the late 2000s, a material was considered
bioactive upon formation of a hydroxyapatite-like layer characteristics of AG hydrogel are enhanced by adding B3
microparticles, (ii) identified the optimal range of B3 glass
on its surface to bond with hard tissue (bone) upon in bioprinting AG hydrogels and ASC viability, and (iii)
implantation. 15,16 Recently, the definition of “bioactive” evaluated the stability of AG hydrogel and the dissolution
has expanded, and the bioactive glass dissolution products of gelatin under these conditions.
have been increasingly investigated for vascularization,
wound healing, cardiac, lung, and nerve tissue engineering 2. Materials and methods
applications in addition to traditional bone repair and
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teeth applications. The research on bioactive glasses has 2.1. Cell culture
evolved to produce glass compositions that are highly Frozen vials of human ASCs were thawed and plated in
resorbable based on borate (B O ) network instead of complete cell culture media (CCM) and incubated at 37°C
3
2
traditional silicate (SiO ) network. 18-20 The dissolution of with 5% humidified CO . To ensure that the findings were
2
2
bioactive glasses depends not only on the durability of the universal and not unique to a single donor, ASCs from
main glass-forming network (e.g., SiO or B O ) and the three different unrelated donors (LaCell, New Orleans, LA,
3
2
2
overall glass composition, but it also depends on several USA) were tested in all experiments. More details about
other factors such as residual stresses during heat treatment the ASC culture conditions and media requirements can
and surface roughness. It is known that borate glass be found in our previous work. 34,35 CCM was prepared
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dissolves at a faster rate compared to Bioglass , and the with alpha minimum essential media (α-MEM) by adding
®
2+
calcium (Ca ) ions released during glass dissolution could 10% fetal bovine serum, 1% 100× L-glutamine, and
Volume 10 Issue 2 (2024) 459 doi. 10.36922/ijb.2057