Page 54 - IJB-9-2

International Journal of Bioprinting Biocompatible materials and Multi Jet Fusion

when the graft is fabricated using a pneumatic pressure- The degree of morphological change and cell lysis is
type bioprinter. This is a phenomenon that occurs because described in Table 1. All cultures treated with extracts of
the material is not uniformly extruded through the nozzle, the test sample maintain its confluent cell monolayers,
and it can be observed that the uniformity of the layer and lysed cells or toxicity was not observed. Therefore,
structure is deteriorated. When the graft was manufactured we considered there was no reactivity of the test sample.
with our screw-type bioprinter, 16 defective products out In addition, the reactivity of test sample, which did not
of 700 samples were produced, which is about 2.3% of impact the viable cells, was confirmed by quantitative
the defective rate, indicating a very low defective rate. analysis through viable cell counting (Table 5). The reagent
Based on these results, we consider that our printer and control and negative control showed no cytotoxicity, and
printing technology can improve high-quality products the positive control showed cytotoxicity in more than 70%
and productivity. cells as anticipated.

When processing polymers, various methods such as 3.7. In vivo studies of the PCL graft
injection molding and extrusion are used. The method In vivo biodegradation and stability of PCL grafts were
used in this study was 3D printing by extrusion, and evaluated (Figure 7). The grafts implanted subcutaneously
the material was discharged through the nozzle by the were harvested after 1, 3, 6, 9, and 12 months to observe the
rotational force of the screw. Kim et al. reported that a biodegradability. The molecular weight of PCL decreased
screw extrusion process is a continuous and thermally gradually over 12 months. The molecular weight reduction
and mechanically uniform manufacturing method that of PCL grafts fabricated by pneumatic pressure-type and by
fabricates product with high molecular material. It is screw-type had similar patterns. Based on the 12-month
thought that the quality and productivity of the products data, the average molecular weights were 54.5 ± 3.3% and
improved by the introduction of the printing method that 48.2 ± 1.9%, respectively, and the maximum peak molecular
can manufacture such high-quality products . weights were 61.7 ± 2.2% and 61.0 ± 2.2%, respectively,
[20]
compared to the initial point. After observing the appearance
3.6. Biocompatibility of the PCL graft of samples at 9 and 12 months after implantation, we found
According to the cytotoxicity test, all test samples showed no that the PCL grafts fabricated by pneumatic pressure-type
evidence of cell lysis or toxicity and were evaluated as grade were fractured in all samples from 9 months. On the other
0 (none) based on the criterial ISO 10993-5 (Tables 4–6). hand, the PCL graft prepared by screw-type did not have

Table 4. Results of quantitative analysis of cytotoxicity test
Well Confluent % Growth % Cells without intrac- % Rounding % Lysis Reactivity grade
monolayer inhibition ellular granulation
Test (+) 0 0 0 0 None 0
Negative control (+) 0 0 0 0 None 0
Reagent control (+) 0 0 0 0 None 0
Positive control (-) 100 100 100 100 Severe 4
(+): present, (-): absent

Table 5. Results of cytotoxicity test Table 6. Results of extraction test
Group Result of cell counting (cells/mL) Items Criteria Results
Line Test group Reagent Negative Positive Appearance It should be colorless It is colorless and
control control control and transparent, and transparent, and there
1 7.6 × 10 5 7.8 × 10 5 7.4 × 10 5 0 there should be no are no impurities.
impurities.
2 7.4 × 10 5 7.5 × 10 5 7.5 × 10 5 0
pH ≤1.5 0.8
3 7.4 × 10 5 7.7 × 10 5 7.6 × 10 5 0
Heavy metal The sample should not The sample is not
Average 7.5 × 10 5 7.7 × 10 5 7.5 × 10 5 0 be thicker than the thicker than the com-
RCC (%) 97.4 100.0 97.4 0.0 comparative solution. parative solution.
Potassium perman- ≤2.0 0.2
ganate reducible
substances

Volume 9 Issue 2 (2023) 46 https://doi.org/10.18063/ijb.v9i2.652