Page 155 - IJB-9-3

International Journal of Bioprinting LPBF of AKM/PEEK biological composite

Table 1. HT-LPBF parameters for the fabrication of PEEK and 5 days, a cell counting kit-8 (CCK-8) assay was conducted.
its composites The absorbance at 450 nm was measured with a microplate
reader. The bioactivity of the AKM/PEEK composites
Processing parameters Values was evaluated in in vitro mineralization experiments. The
Layer thickness 0.1 mm samples were soaked in SBF (pH = 7.4) for 7 days. The
Laser scanning speed 1600–2400 mm/s apatite formation on the surface was observed by SEM.
Laser scanning speed of counter 3000 mm/s
hatch spacing 0.2 mm 3. Results and discussion
Laser power 25 W
3.1. Characteristics and HT-LPBF processability of
Laser power of counter 6 W
AKM/PEEK powder
The particle morphology and size distributions are shown
in Figure 1. As shown in Figure 1a and c, the morphology of
Testing Machine (INSTRON 5982). The tensile samples PEEK powder is relatively regular with some subspherical
were prepared according to ISO-5272/1BA. To ensure the particles, while the overall shape of ball-milled AKM
reliability of data, four samples were tested in each group. powder is similar to the block with sharp angles and
The microstructure of powders (pure PEEK, composites wrinkles. As the matrix of composite powder, PEEK has
with 5 wt%, 10 wt%, and 15 wt% AKM) and the fracture a morphology conducive to the flowability of the powder.
cross-sections of the tensile samples were observed by a Figure 1b and d show the particle size distributions of the
field-emission electron microscope (SEM; JSM-7600F, PEEK and the AKM, respectively. The particle size of PEEK
DOLEE, Japan). Before observation, the samples were is mainly distributed in 10–120 μm, while the particle size
sputter-coated by platinum for 300 s. An energy dispersive of AKM is less than 20 μm. The distribution range of PEEK
spectroscopy (EDS) was utilized to observe the distribution powder is suitable for the HT-LPBF process . The smaller
[45]
of elements. The thermal properties of the pure PEEK particle size of AKM is beneficial to widen the particle
and the composites were tested by differential scanning size distribution and increase the packing density of the
calorimetry (DSC; PerkinElmer Instruments, USA). N was composite powder, but the interface combination between
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used as a protective gas in the DSC tests. The temperature AKM and PEEK needs further clarification.
rose from room temperature to 380°C by a heating rate
of 10°C/min and then decreased to room temperature To observe the interface combination between AKM
by a cooling rate of 10°C/min. The thermogravimetric and PEEK particles, the composite powder with 15 wt%
analysis (TGA; Pyris1 TGA, PerkinElmer Instruments, AKM was observed by SEM, as shown in Figure 2. The
USA) was performed to test the thermal decomposition elemental surface distribution was also tested to observe
properties of powders. The TGA test was conducted in an the distribution of the AKM particles. The results showed
air environment, in which the PEEK can be completely that tiny AKM particles were evenly attached to the surface
decomposed at 850°C. The temperature rose from room of the PEEK particle, thereby avoiding the aggregation of
temperature to 850°C by a heating rate of 10°C/min. The AKM particles and promoting uniform distribution. No
crystalline structures of composite powders and HT-LPBF- obvious aggregation phenomenon was found, and this
fabricated samples were tested by an X-ray diffractometer was proven by the element distribution detected by EDS,
(XRD; X’Pert3 powder, PANalytical B.V., the Netherlands) as shown in Figure 2. The Si, Mg, O, and Ca elements
with Cu Kα radiation (λ = 1.543 Å). The θ/θ scanning presented uniform distributions, suggesting that the AKM
mode was conducted from 10° to 60° at a speed of 10°/min. powder was uniformly dispersed in the composite.
The biocompatibility of the AKM/PEEK composites To further investigate the HT-LPBF processability
was evaluated by rat bone marrow stromal cells (BMSCs). of the composite powders, thermal property tests were
The samples used in biological experiments were tablets performed because the melting and crystallization
(φ6 × 2 mm ). The BMSCs were digested with 0.25% properties of powders have a great influence on the HT-
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trypsin after growing to 70% confluence and then were LPBF process. To study the thermal properties of the
diluted to a cell suspension of 3 × 10 /mL. The suspension composite powders, TGA and DSC tests were carried out,
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was added to a 96-well plate with a content of 100 μL per as shown in Figure 3. According to the thermogravimetric
well, and then placed in an incubator (37°C, 5% CO ) for curve and its differential curve, PEEK and its AKM
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24 h. Tablets fabricated by composite powders were put in composite powders with different weight ratios
a DMEM-F12 (Hyclone, USA) medium. The BMSCs were experienced a nearly consistent thermal decomposition
transferred to the medium and cultured in an incubator process. Even if the AKM content increased, the powder
(37°C, 5% CO ). After being cultured for 1 day, 3 days, and kept undergoing an initial decomposition at about 480°C.
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Volume 9 Issue 3 (2023) 147 https://doi.org/10.18063/ijb.699