Shear-thinning sacrificial ink for fabrication of Biosilicate® osteoconductive scaffolds by material extrusion 3D printing

Abstract

Osteoconductive scaffolds are required to stimulate and enhance the regenerative potential of cells in bone tissue engineering applications. Additive manufacturing (AM), popularly known as 3D printing, has been widely used to fabricate these porous structures. In this study, bioceramic scaffolds based on highly bioactive glass-ceramic (Biosilicate®) were developed and characterized using a hydrogel as sacrificial ink for material extrusion 3D printing. A paste containing Biosilicate as solid filler was developed from a sacrificial ink whose formulation is based on poly(ethylene glycol) (PEG-400) with 7.5% (w/w) Laponite® nanoclay as rheological modifier. Initially, the rheological behaviors of the sacrificial ink (PL) and of the ceramic paste with 70% (v/v) Biosilicate (PL-BioS) were evaluated. Viscosity of the PL increased with addition of Biosilicate, showing a shear-thinning behavior appropriate to material extrusion 3D printing. After that, samples were 3D printed and dried at 20 and 50 °C. The dimensional characteristics of the samples were evaluated and compared, and showed that drying at 20 °C resulted in lower degree of shrinkage and mass loss before sintering. Preliminary heating stage microscopy tests were performed to define the sintering parameters, and then the scaffolds were sintered at 900 °C for 5 h at a heating rate of 1 °C/min. The sintered scaffolds were analyzed by FTIR, XRD, and SEM. These characterizations showed that the PL was eliminated from the structure with no significant change in scaffold composition, which remained intact after this process, and that the residual Laponite improved scaffold strength with formation of micropores internally to the filaments. An in vitro biological study confirmed the nontoxic behavior of the developed scaffolds on NHI-3T3 fibroblast-like cells, showing suitable cell adhesion, growth and proliferation on their surface, which are associated with good osteoconductive properties. In conclusion, the use of PL gels combined with Biosilicate is promising for ceramic ink formulation, considering that shear-thinning materials facilitate the 3D printing process. Moreover, preliminary mechanical and biological results reveal the potential of the sintered scaffolds for use in bone tissue engineering.