Page 498 - IJB-10-2

International Journal of Bioprinting Mineralization of 3D-printed PHA scaffolds

present in the polymer. By virtue of its biocompatibility of Machinery and Materials, Daejeon, Korea). The PHA
2
and biodegradability, PHA has been increasingly used in scaffold was printed using a nozzle size of 400 µm, printing
medical applications, such as those involving bone scaffolds speed of around 500 mm/min, pneumatic pressure of 80
and implants. Notably, PHA exhibits lower acidity and kPa, and temperature of 180°C. The printing process was
4,7
generates fewer inflammatory degradation products than completed in <40 min to prevent thermal denaturation
existing degradable polymers, such as polylactic acid (Figure S1 in Supplementary File).
(PLA), indicating its potential in mitigating cytotoxicity
issues. 2.2. Surface functionalization of the PHA scaffold
with pDA and a mineralized PHA scaffold with HA
Three-dimensional (3D) bioprinting facilitates new The PHA scaffold was coated with pDA and HA. pDA was
bone formation by enabling the fabrication of complex dissolved in 10 mM Tris-HCl buffer at a concentration of 2
3D scaffold structures that offer mechanical support and mg/mL and stirred for 1 h. The printed PHA scaffold was
utilize a wide range of materials, including biocompatible soaked in a solution containing pDA and stirred for 24 h
polymers. 3D printing techniques comprise various at room temperature. The scaffold coated with pDA was
1–3
categories, including extrusion-based, jetting-based, and washed at least three times in deionized water and then
vat photopolymerization-based printing. Depending on dried in vacuum at 40°C for 24 h.
the material characteristics and the desired structure,
different types of 3D bioprinting technologies can be HA was produced using a 5× simulated body fluid
applied in tissue engineering or the medical field. 8-11 (SBF) solution (Biosesang, Korea). The composition of the
+
+
In particular, extrusion-based printing involves the 5× SBF solution is as follows: Na , 710 mM; K , 25 mM;
2-
-
2+
3-
fused filament fabrication (FFF) method, which utilizes Mg , 7.7 mM; Cl , 739.7 mM; HCO , 21 mM; HPO ,
4
2-
thermoplastic materials. The material is heated and melted 5 mM; and SO , 2.5 mM. The PHA scaffolds with pDA
4
within the 3D printer, then systematically layered to create were soaked in the SBF solution, which was stirred at room
a 3D structure. Extrusion-based printing is widely used for temperature for 72 h. The biopolymers with pDA and HA
shaping various thermoplastic polymers due to its ease of were rinsed at least three times to remove the residue and
use and the lack of solvent requirements. PHA is known then dried (Figure 1).
to be highly suitable for fabricating scaffolds through 3D 2.3. Surface characterization of functionalized
printing, owing to its thermoplastic property, excellent biopolymer scaffold
processability, and ability to provide appropriate physical The surface morphology of the printed biopolymer with
properties. 12,13 However, PHAs are naturally resistant to pDA and HA coatings was investigated using scanning
moisture (i.e., are water-insoluble), which can interfere electron microscopy (SEM; Sirion, FEI, USA). The
with host cell attachment, growth, and differentiation in wettability of the biopolymers was evaluated based on
the context of bone regeneration. 4,13 the contact angle (Contact Angle Meter DM 210; Kyowa
In this study, 3D-printed PHA scaffolds were Kirin, Inc., Tokyo, Japan). A 4 µL droplet was placed on the
functionalized with bioactive molecules to enhance their surface of the samples, and the contact angle was measured
biological performance. The surface of a 3D-printed after 30 s.
PHA scaffold was coated with polydopamine (pDA) and 2.4. Physiochemical characterization of the
hydroxyapatite (HA) using a straightforward technique. biopolymer scaffold
Immersion was the only step required for creating the pDA Attenuated reflectance-infrared (ATR-IR) spectroscopy
and HA coatings, thus providing a simple and rapid process. was used to measure the chemical composition of PHA and
pDA supports cell adhesion and enhances calcination pDA at a resolution of 4 cm . The chemical composition
-1
for bone remodeling. Biomineralization with HA, which of the samples was determined using X-ray photoelectron
is compositionally similar to the mineral phase of bone, spectroscopy (XPS) for the identification of specific
enhances the osteogenic differentiation of osteoblast-like chemical elements (C, O, N, Ca), using a monochromatic
cells. Thus, the pDA and HA coatings further advance the Al-Kα radiation source with an X-ray beam spot size of 400
potential applications of PHA scaffolds in osteogenesis.
µm. The phase of the calcium phosphate of HA that formed
2. Materials and methods on the scaffold surface was identified using X-ray diffraction
(XRD) over the 2θ range of 25–50°. Thermogravimetric
2.1. Biopolymer scaffold fabrication analysis (TGA) was used to investigate the influence of
PHA (molecular weight: 257 kDa; CJ CHEILJEDANG, pDA and HA on the degradation temperature and thermal
Seoul, Korea) was fabricated using an extrusion-based stability of the biopolymer. The samples were heated from
printing approach with a 3D bioprinter (Korea Institute 25°C to 850°C at a rate of 10°C/min.

Volume 10 Issue 2 (2024) 490 doi: 10.36922/ijb.1806