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International Journal of Bioprinting Comparison of different 3D printing technologies

Although this test is not decisive to know if the hydrogel Table 1. Contact angle results for the hydrogels studied
is going to present a correct cell viability, it does show us, at Material Temperature (°C) Contact angle (°)
a low economic cost, other interesting characteristics:
GelMA 5% Ambient 116
(i) Pressure that needs to be applied for a drop of
hydrogel to be released. The greater the amount of 30 54
pressure generated, the greater the original forces 40 51
inside the syringe, so cell survival may be reduced. GelMA 10% Ambient 120
(ii) Viscosity of the hydrogel. Although this test does 30 109
not allow us to quantify the viscosity of the hydrogel 40 37
or its gelation, it does allow us to visually predict ColMA (Cs = 5) 9 32
which hydrogels are going to present a greater state 15 31
of gelation. This is a very important characteristic to ColMA (Cs = 10) 9 45
obtain a correct printability. 15 46
(iii) Hydrogel wettability. It is related to cell adhesion and HAMA 5% 9 46
spreading . Ambient 42
[32]
Table 1 shows the results obtained. 30 40
Both Matrigel and ColMA with different concentrations 40 40
could not be analyzed at the temperature of 25°C in the Matrigel 9 45
room where the experiment was carried out, as both 15 48
crosslink at a temperature above 15°C. Ten percent GelMA
at a temperature of 40°C showed an interesting contact performing the sessile drop method and when using it
angle, but a printing temperature above 37°C would subject as a bioink in the bioprinter. Due to its low bioprinting
the cells to high stress leading to cell death. Collagen-based temperature, this hydrogel is not suitable for cell-loaded
materials had very low viscosity above 30°C, which made bioprinting, but the good results obtained in the sessile
them difficult to bioprint. Therefore, their combination drop method indicate that it is suitable for subsequent
with other materials should be considered. loading of cells into the bioprinter-generated structure,
because the contact angles are between 35° and 80°.
In view of the results in Table 1, the most interesting
hydrogels for obtaining good viability and cell proliferation 3.2.2. Filament collapse test
are 5% GelMA, ColMA with a target concentration of The aim of this test is to analyze the deflection of the
10 mg/mL, 5% HAMA, and Matrigel, so the rest of the hydrogel filament to be analyzed for different distances.
hydrogels, because they presented worse characteristics in For this purpose, a platform has been developed with the
this first test, were discarded in this study. same dimensions as a Petri dish, made up of pillars that are
Matrigel is a material that requires low temperature for progressively spaced one unit apart (Figure 3).
its maintenance, as it polymerizes at room temperature. This platform was designed using Inventor, printed
Therefore, its temperature must be low both when with PLA, and coated with resin. This platform, designed

Figure 3. Design of the platform for the collapse test using Inventor. Source: own elaboration.

Volume 9 Issue3 (2023) 30 https://doi.org/10.18063/ijb.680