Resorbable 3D printed scaffolds for bone regeneration

ARAOZ, BEATRIZ; HERMIDA, ÉLIDA B.

Darmstadt

Congreso; Materials Science Engineering (MSE-2018); 2018

Resorbable 3D printed scaffolds for bone regenerationThe aim of this work was to obtain 3D printed scaffolds that mimics the extracellular matrix of bone with suitable mechanical properties that actively participates in bone healing. The addition of a bioactive glass to a biocompatible and resorbable polymer gives a biodegradable composite that stimulates the response of the organism to regenerate bone. Scaffolds morphology must enhance cell adhesion, proliferation, differentiation and organization in a normal tissue configuratio. In particular, the layer-by-layer 3D printing technique is a fast and reproducible process to obtain a complex construct. It could reproduce custom made scaffolds from medical images obtained by CT or/and MRI of the own patient.Filaments for the printing process were made combining Bioglass 45S5 (BG) and/or a porogen agent (salt) with polyhydroxybutyrate-co-valerate (PHBV). The powders were dried in an air-circulating oven and extruded in a Parallel Twin-Screw Extruder. Barrel-temperature profile and screw speed were set up to achieve high quality output, that is, to minimize thermal degradation and to ensure homogenous mixing of the components. To obtain the scaffolds, test specimens were designed according to ASTM standards and printed by the solid fusion deposition technique (FFD) in a 3D printer. Filaments and scaffolds morphology was observed by SEM. The pristine PHBV filaments showed no porosity at the micro and nano scale. However, the addition of micronized salt grains during the extrusion process led to a homogeneous mixture (PHBV-salt) that conferred porosity to the filament after dissolving salt in distillated water. A hierarchical distribution of interconnected pores between 500 nm - 500 μm was observed, leading to a promising structure for proliferation and migration of osteoblasts that could contribute to regenerate the bone structure. The combination of PHBV-salt-BG in a filament produce a homogeneous distribution of those three materials evidencing a successful mixing process. Contact angle measurements shown that the hydrophilicity of scaffolds increased with the BG content.Mechanical properties of filaments and printed scaffolds were measured in a Dynamic Mechanical Analyzer. PHBV and PHBV-salt filaments had mechanical properties similar to those of ABS (thermoplastic polymer widely used in 3D printing) being suitable for FFD. In the printed constructs the elastic modulus (tensile and compression mode) depended on the printing pattern. Moreover, the elastic response was similar to the trabecular bone one.As a preliminary study of in vitro bioactivity of materials, filaments and scaffolds were treated in SBF solution at 37 ºC for different periods of time. Then those were studied by SEM-EDS and DRX. Results shown that filaments and scaffolds containing BG lead to a HA-like layer formation and almost no degradation was observed within the first 8 weeks of treatment. The biological evaluation of the scaffolds ? according to ISO10993-5? showed low cytotoxicity on fibroblasts cells.All results mentioned above remark two main features of the compounds. On one side, its suitability for 3D printing by FFD and on the other, the morphology of the printed scaffold that emulates the extracellular bone matrix and promotes the adhesion and proliferation of fibroblasts and osteoblasts.