Page 49 - IJB-9-2

International Journal of Bioprinting Biocompatible materials and Multi Jet Fusion

2.3. Characterization of the grafts Table 2. Test method of extraction test
The morphology of the grafts was examined by scanning Parameter items Test methods
electron microscopy (Hitachi) operating at 15 kV .
[14]
Appearance Observe with the naked eye.
Additionally, the mechanical properties of the PCL pH Test according to the test method for
grafts were measured by performing tensile tests and plastic pharmaceutical containers.
bending tests using a universal testing machine (Force Heavy metal Test according to Method 1 of the Metal
tester MCT-2150, A&D Company limited) with a 1 kN- Test Method in the Korean Pharmaco-
maximum load cell at a cross-head speed of 10 mm/ poeia. Take 10 mL of the extract and
min. add 2 mL of lead standard solution to
the comparative solution.
Differential scanning calorimetry (Q10) analysis Potassium permanganate- Take 20 mL of extract and control solu-
was used to measure the crystallinity. The samples were reducible substances tion and carry out the test according to
heating at rate of 10°C/min from 0°C to 100°C in N2 the test method for plastic pharmaceuti-
(-70°C–100°C). The enthalpy of fusion of 100% crystalline cal containers.
PCL (∆H_m^0) is 139.5 J/g. The percent crystallinity of
samples was calculated using the formula as follows: 2.6. In vivo studies
% Crystallinity = (∆H_m)/(∆H_m^0 )×100 All animals (Sprague Dawley [SD] rats, male, 7 weeks,
200–300 g) were cared for according to methods approved
Concordance with the original image of the graft was by the Institutional Animal Care and Use Committee
evaluated. For this evaluation, a 3D structure including (IACUC No. 2020-0019 and 2021-0010) at SMG-SNU
a curved surface was designed and then printed. After Boramae Medical Center, Seoul, Republic of Korea.
scanning the printed structure, its size was compared with
the size of the design drawing. The degradation pattern of the PCL graft in the body
was observed. After being subcutaneously implanted in
2.4. Evaluation of the uniformity and defective rate the SD rats, the graft was harvested at 3 months, 6 months,
The uniformity of the microstructure of the graft was 9 months, and 12 months to observe the appearance
evaluated. After measuring the thickness of the layer at and microstructure. In addition, the molecular weight
random, the standard deviation was calculated. and tensile strength at 12 months were measured by gel
permeation chromatography (Waters) and universal
The defective rate of the sample was investigated by
measuring the size of the prepared graft, and by observing testing machine, respectively.
the microstructure, samples exceeding 10% from the 2.7. Statistical analysis
standard value were counted. All the samples were assayed in triplicates, and the results
The size and thickness were measured using a vernier obtained were expressed in standard deviations (SD)
caliper, and the microstructure was observed using a above and below the mean (mean ± SD). All statistical
microscope. analyses were carried out with analysis of variance using
Prism software. Results were considered to be statistically
2.5. Biocompatibility tests significant when the P-value was less than 0.05.
The cytotoxicity test of the PCL graft was evaluated
according to ISO10993 guidelines. It was performed using 3. Results and discussion
mouse fibroblast (L-929 mouse fibroblast cells). High- 3.1. Screw extrusion 3D bioprinter
density polyethylene film (Hatano Research Institute)
and ZDEC Polyurethane film (Hatano Research Institute) Table 3. Specifications of screw extrusion-type bioprinter
were used for negative control and positive control,
respectively . Items Specifications
[15]
In order to investigate whether impurities were mixed Structure of printer Orthogonal structure
in the printing process, an extraction test was performed Temperature range 30–200°C
(Table 2). The items include appearance, pH, heavy metal, Bed size 100 × 100 × 100 mm
and potassium permanganate-reducible substances, Conveying device GT2 belt
and the test was conducted according to the “Korean Maximum printing speed 0–20 mm/s
Pharmacopoeia-Containers-Plastics Physicochemical test”
guidelines. Extraction was carried out at a rate of 3 cm Rotational speed 100–1000 mm/s
2
(surface area)/mL at 50 ± 2°C for 72 hours. Minimum movement distance 12.5 µm

Volume 9 Issue 2 (2023) 41 https://doi.org/10.18063/ijb.v9i2.652