Direct ink writing of hydroxyapatite based paste scaffolds for absorption-release of drug solutions

The demand for new processes of production, materials and applications of medication has changed significantly. In particular, there is a growing need for the development of methodologies to delivery active compounds with specific properties for patient-specific drugs with customized dosages, shapes, and release profiles. Three-dimensional bioprinting (3D) emerges as a promising technology, as it enables the creation of structures with high precision, low cost, and the potential to incorporate therapeutic agents.

In this study we developed a hydroxyapatite-based paste suitable for direct-ink-writing (DIW) 3D printing, with a view to producing relatively porous, multi-layered scaffolds that allow the incorporation of antibiotics.

The methodology adopted to obtain these structures consisted of using the 3D syringe extrusion printing technique, based on digital CAD models of varying complexity, which were subsequently rendered and adjusted with optimized printing parameters. This process allowed the creation of hydroxyapatite-based structures with controlled internal and external structure, ensuring a good mechanical stability even when doped with antibiotics. The optimization of the paste was ensured with a specific ratio: 37,5% of hydroxyapatite, 38% of sucrose, 0,5% of sodium alginate and 24% of water w/w. After printing, the scaffolds were impregnated with antibiotics and evaluated in a bacterial culture environment, one containing Escherichia coli and the other in the presence of Staphylococcus aureus, gram-negative and gram-positive microorganisms, respectively.

The results demonstrated that DIW 3D printing of the hydroxyapatite paste was successful, producing stable scaffolds that were suitable for drug solution absorption. Antibiotic impregnation was successful, as the structures exhibited activity against the tested bacteria. This approach has potential to be a promising strategy to develop controlled drug delivery systems that may assist in prevent ant treat localized infections.