Novel Sol-Gel Inks for the Direct Writing of SiO2-Based Bioactive Glass Scaffolds for Tissue Engineering Applications

In this study, silicate-based, three-dimensional bioactive glass scaffolds were produced for the first time with innovative sol-gel ink-based robocasting, and their structural and morphological characterizations were performed. Additionally their, in vitro, bioactivity in simulated body fluid and phosphate-buffered saline at 37 °C was studied under static conditions. For this purpose, bare and rare earth element-containing (3 wt% Eu³⁺, Gd³⁺) silicate-based 13–93 bioactive glass gels were prepared at room temperature. Then, a hybrid gel system containing a mixture of bioactive glass gel and a temperature-sensitive hydrogel (polyethylene oxide-polypropylene oxide-polyethylene oxide tri-block-copolymer) at different ratios was used to obtain multilayered structures. After printing, the dried gel structures were calcined at 675 °C for 1 h in an air atmosphere. The results showed that the patterned, multilayered, macroporous bioactive glass scaffolds can be successfully produced using the method developed in the study. It has been understood that the structures prepared in this way can be made in much finer filament dimensions than the colloidal-based robocasting process containing bioactive glass particles. It was also shown that hydroxyapatite formation occurred on the surface of the bioactive glass scaffolds, which were kept in physiological fluids. The general results indicated that the sol-gel ink-based robocasting technique gives more promising results in preparing bioactive glass scaffolds with complex geometry than conventional colloidal ink-based robocasting. The incorporation of the studied rare earth elements was not detrimental to the printing process of the bioactive glass scaffolds.