Page 182 - IJB-10-4

International Journal of Bioprinting Effects of structure on the interbody cage

its degradation process and mechanical properties was the Beijing University of Chemical Technology, as
also investigated. The primary objective of this study is demonstrated in Figure 2A. Based on the fused deposition
to provide theoretical and technical support for further principle, the melt differential 3D printer could overcome
research and development, design, and clinical application the constraints of other existing 3D printers on the
of novel spinal interbody fusion cages. shape, attributes, and group allocation ratio of printing
materials by the application of a precision screw for
2. Materials and methods material plasticization and feeding. The cage was designed
and modeled using SolidWorks in conjunction with the
2.1. Preparation of composite materials vertebral shape. Print paths were planned using Simplify
In this experiment, PCL (50 kDa, Perstorp, Sweden) was 3D. A 0.5 mm nozzle was applied to perform a 0° and
utilized as the substrate, and 25 wt% HA (60 nm, Nanjing 90° rectilinear infill pattern. Two filling rates, 60% and
Duly Biotech Co., Ltd, China) was compounded to generate 40%, were designed to alter the aperture in the horizontal
composite particles for the creation of biodegradable spinal direction. Three angle-changing schemes were devised,
interbody fusion cages. As shown in Figure 1, PCL pellets where the beam filling angle was changed after printing 1,
were premixed with HA powder at a mass ratio of 3:1 2, and 4 layers sequentially at the same angle, to realize the
and then co-extruded and pelletized using a twin-screw variation of the vertical aperture, as shown in Figure 2B.
extruder (LJPS, Zhangjiagang City Lianjiang Machinery Table 1 demonstrates how the two structural parameters
Co., Ltd, China). The screw speed was set to 25 rpm. were orthogonally merged to generate six meso-structural
Four temperature gradients were established with the first interbody fusion cages. The printing temperature was set
segment T1 set at 60°C in the feed zone, followed by T2 to 90°C, the printing layer height was set to 0.32 mm, and
and T3 increasing by 10°C each, and the final segment T4 the printing speed was set to 3.5 mm/s.
at the same temperature as T3, set at 90°C for the die head.
HA/PCL (3.0 ± 0.5 mm) pellets (25 wt%) were generated 2.3. In vitro degradation test
following melting, cooling, and pelletizing. Due to the low melting point of PCL (60°C), artificial
simulated body fluid (SBF), instead of phosphate-buffered
2.2. Design and manufacturing of degradable solution (PBS), was used as the soaking solution in this
interbody fusion cages experiment to conduct accelerated degradation tests in a
The interbody fusion cage was manufactured in this 37°C environment and to identify the porous cage model
experiment employing a melt differential 3D printer that matches the growth of bone tissue most closely. The
specialized for biomedical materials developed by following was the test protocol:

Figure 1. Manufacturing of 25 wt% HA/PCL composites.

Volume 10 Issue 4 (2024) 174 doi: 10.36922/ijb.1996