Page 284 - IJB-10-1

International Journal of Bioprinting Scaffolds manufacturing by fused deposition modeling

Table 1. P(3HB-co-3HHx) characteristics according to the supplier
Characteristic Value Units Standard
Melt flow index (MFI) 1 g/10 min ISO 1133-2 (160°C and 2.16 kg)
Density 1.20 g/cm 3 ISO 1183-1
Melting temperature 124 °C ISO 11357
Glass transition temperature (T ) 1 °C ISO 11357
g
Young’s modulus 0.9 GPa EN ISO 527
Strain at break 21 % EN ISO 527
Vicat 62 °C ISO 1133-5

biocompatibility and bone regeneration capacity to the addition, rheological studies were performed to measure
neat polymer. From the mechanical point of view, ceramic the viscosity changes in each processing stage. The main
materials can act as a reinforcement, leading to an increase novelty focuses on the assessment of the changes that
of stiffness of the polymer composite. In addition, the take place during a hydrolytic degradation process of
composites are more ductile than the ceramic material. the material. In this sense, different studies have been
40
Of note, increasing HA contents in PLA resulted in conducted by other authors that measure the cell adhesion,
higher biocompatibility and bioactivity of PLA, or cell but the effect on the physical properties over the immersion
proliferation enhancement in the case of PCL as matrix. 41,42 time has not been deeply investigated. In this case, scaffolds
were fabricated and immersed in phosphate-buffered saline
The development of scaffold structures for bone
regeneration process is a current trend, and different (PBS) at 37°C up to 8 weeks. To monitor the changes that
kinds of studies have been carried out to improve bone took place during the immersion, compression mechanical
regeneration process. During the healing process, blood properties, changes in the weight of the sample and changes
43
and cells can penetrate the porous structure in order to in the pH of the medium were measured.
start bone formation. Depending on the manufacturing
44
technique employed for the obtention of the scaffold, 2. Materials and methods
different properties will be obtained. As Eltom et al. propose, 2.1. Materials
scaffolds were conventionally manufactured by freeze- Commercial-grade P(3HB-co-3HHx) (Ercros® PH 110)
drying, solvent casting, gas foaming, electrospinning, or supplied by Ercros S.A. (Barcelona, Spain) in pellet
thermal-induce phase separation, but with the grow of form (cylindrical shape with an average of 3 mm length
additive manufacturing techniques, different approaches and 2 mm diameter) were used as polymer matrix of
have been made to develop scaffolds with rapid prototyping the nanocomposites. The main characteristics of the
techniques. In this sense, the development of scaffolds polymer, according to the supplier, are reported in Table 1.
45
made by FDM has been conducted in different polymeric Commercially available nHA, purchased from Merck
matrix like PLA, PCL, and also P(3HB-co-3HHx). 23,39,46 (Madrid, Spain) (Ref: 677418) was used as filler for the
In addition, the combination of biopolymers with ceramic nanocomposites. According to the supplier, this nHA has
fillers to enhance the tissue regeneration has been a surface area of higher than 9.4 m /g, as determined by
2
investigated. 47,48 In most cases, only the cell adhesion over Brunauer–Emmet–Teller (BET) analysis, and a molecular
the scaffold is studied but in some cases, the study of the weight of 502.31 g/mol. The particle size was lower than
mechanical performance of the scaffold is also conducted. 49 200 nm and the purity was reported to be equal to or
The main aim of this work is the development of higher than 97%. The employed material is a polymer with
nanocomposites prepared from P(3HB-co-3HHx) and nHA, low melt flow index (MFI), so the temperature profile and
targeting the development of bioactive and biodegradable screw speed must be adjusted properly in order to obtain
materials for 3D printing of medical devices. In this work, a good-quality filament. Other authors have reported the
standard tensile specimens with 100% infill and different employment of polymers with MFI values close to the one
infill directions were 3D-printed to assess the mechanical employed in this study. 50,51
properties of the developed nanocomposites. In addition,
the effect of all the processing stages was analyzed by thermal 2.2. Preparation of nanocomposites
tests, such as differential scanning calorimetry (DSC) and The matrix and the filler were dried at 80°C in an air-
thermogravimetry analysis (TGA), to measure the changes circulating oven (Industrial Marsé, S.A., Barcelona, Spain)
in enthalpy and main characteristic temperatures. In for 24 h. Subsequently, the correct amount of each material

Volume 10 Issue 1 (2024) 276 https://doi.org/10.36922/ijb.0156