Page 193 - IJB-10-5

International Journal of Bioprinting Structural design of D-surface scaffolds

dried at 60°C for 4 h. The composite pellets were collected thickness in a radial pattern was established. The gradient
through a water bath and subsequently granulated. The thickness was in the range of 0.8–1.2 and 0.9–1.6 mm,
blends were dried in an oven at 60°C for 8 h. The PBAT/ respectively. The diameter of the cylinder was 15 mm,
PLA were then fabricated into filaments using a filament and the height was 18 mm. The other graded model
extruder. The extruder barrel heating zone was set at a had a set gradient thickness along the z-axis. The cube
range of 190–210°C. The PBAT/PLA specimens were 3D size had a dimension of 20 × 20 × 20 mm. The gradient
printed using a near-end FFF 3D printer. thickness was set in the range of 0.6–1.8, 0.8–1.6, and

2.3. Design of homogeneous and graded bone 1.0–1.4 mm, respectively. After designing using Rhino
scaffold structures software, the generated models were exported as STL
The bone scaffold structures were designed based on files and then imported into CURA 5.4 software for
minimal D-surface structures. Homogeneous and graded slicing and FFF printing. To compare the load-bearing
minimal D-surface structures were mathematically and energy absorption capacity, the relative density of the
approximated using the implicit method. The equation for homogeneous and graded models was kept the same.
D-surface structures is presented as Equation 1. 29
2.4. Platelet-rich plasma preparation and loading
in scaffolds
ϕD (x, y, z) = sin (ωx) sin (ωy) sin (ωz) + Blood was extracted from adult rabbits through cardiac
sin (ωx) cos (ωy) cos (ωz) + cos (ωx) (1) puncture under aseptic conditions. Approximately 4 mL
sin (ωy) cos (ωz) + cos (ωx) cos (ωy)
sin (ωz) = C of extracted blood was centrifuged at room temperature
to obtain three distinct phases, including the platelet-poor
where x, y, and z represent spatial coordinates. The layer, buffy-coat PRP, and erythrocytes (from the top to
structure was generated as the solution of the level-set bottom layer). The two upper layers were transferred to
function ϕ = C. The solid model of the surface was created a fresh tube and centrifuged according to the following
by extracting the zero-level set surface C = 0 for Equation 1. program: acceleration for 30 s, 2700 rpm for 2 min, 2400
The homogeneous D-surfaces were creased by Rhino 7.4 rpm for 4 min, 2700 rpm for 4 min, and 3000 rpm for 3 min.
software and presented in Figure 1. For the homogeneous The superficial plasma was discarded, and the remaining
D-surfaces, samples with the wall thickness of 1.0 mm and precipitated platelets were collected as PRP.
sample with the wall thickness of 1.2 mm were fabricated. To keep the factor bioactivity, PRP was fabricated just
Each group had three parallel specimens. Specifically, an before use and loaded on the 3D-printed scaffolds. Before in
extension field was generated using the implicit function, vitro and in vivo biological tests, 1 mL of PRP was extracted
and a sheet surface model was generated. using a syringe and dropped on the sterilized scaffolds. The
For the graded D-surfaces, two kinds of models were scaffolds were placed in a sterilized vacuum drying oven
established. Firstly, a cylindrical model with gradient for 2 h to facilitate PRP infiltration into the scaffolds.

Figure 1. The model of uniform and graded diamond minimal surfaces. The graded cylindrical model is radially distributed across the wall thickness, and
the graded cube has a gradient thickness vertically distributed from top to bottom.

Volume 10 Issue 5 (2024) 185 doi: 10.36922/ijb.3416