Production of ceramic alumina scaffolds via ceramic stereolithography with potential application in bone tissue regeneration

Scaffolds are devices that mimic the characteristics of the extracellular matrix; they are highly porous, with well-distributed and interconnected pores. Tissue engineering proposes scaffolds as an alternative treatment for different diseases and injuries affecting bone tissue. Triply periodic minimal surfaces (TPMS) are geometric structures whose characteristics fit well with the scaffold's requirements. Ceramic stereolithography enables the production of these complex geometries with high precision using ceramic materials. Alumina (Al2O3) is a well-known ceramic material appreciated for its chemical and mechanical stability properties. The biomedical use of alumina as an alternative to replace metallic parts in bone components has been increasing. In this work, a suspension of alumina particles in a photopolymerizable resin is developed in order to be implemented in the printing of ceramic scaffolds with TPMS-type geometries by ceramic stereolithography for potential biomedical applications. The resin used was characterized in a different work by TGA and FTIR (Duque et al., 2023) and is acrylic in nature, also the alumina particles were characterized by DTP and XRD, these are micrometer sized and a showed an α-alumina phase with a high degree of crystallinity. The rheological behavior of the suspension was studied with ceramic load percentages of 35, 40, and 50 vol% in order to choose the most favorable conditions for piece printing. The three suspensions presented low viscosities, being the 50 vol% sample the one that presented the highest viscosity, with an average value of 0.77 Pa s. These viscosities were suitable for the ceramic stereolithography printing process. The 50 vol% suspension was characterized by TGA and DSC and did not show any difference compared to the resin without particles. Scaffolds with TPMS Gyroid and Schwartz P geometry were obtained by ceramic stereolithography and characterized morphologically and mechanically before and after sintering. The thermal treatment was successful. The polymer-ceramic scaffolds before sintering exhibited better compression resistance than the sintered ones. Fully ceramic scaffolds with gyroid geometry showed compressive strength values of 0.4 MPa, which is comparable to human trabecular bone. The best compression resistance was for the samples with the gyroid geometry. Since the 50 vol% sintered scaffolds with gyroid geometry showed better mechanical results, they were impregnated with propolis extracts from the Arauca region of Colombia in order to evaluate their antimicrobial activity against the standard strains Staphylococcus aureus (ATCC 29212) and Escherichia coli (ATCC 25922). The evaluated scaffolds exhibited better antibacterial activity against the S. aureus strain. After sintering, the 50Al scaffolds were submitted to a degradation test in phosphate-buffered saline (PBS) to assess the chemical stability of the alumina. The results indicated that the samples maintained their initial weight throughout the testing period, with measurements taken on days 1, 5, 8, and 12 showing no significant changes in weight loss percentage. This stability suggests that the alumina scaffolds possess robust chemical resistance under the tested conditions.