3D printing of strontium-enriched biphasic calcium phosphate scaffolds for bone regeneration.

Calcium phosphate (CaP) scaffolds doping with therapeutic ions are one of the focuses of recent bone tissue engineering research. Among the therapeutic ions, strontium stands out for its role in bone remodeling. This work reports a simple method to produce Sr-doped 3D-printed CaP scaffolds, using Sr-doping to induce partial phase transformation from ß-tricalcium phosphate (ß-TCP) to hydroxyapatite (HA), resulting in a doped biphasic calcium phosphate (BCP) scaffold. Strontium carbonate (SrCO3) was incorporated in the formulation of the 3D-printing ink, studying ß-TCP:SrO mass ratios of 100:0, 95:5, and 90:10 (named as ß-TCP, ß-TCP/5-Sr, and ß-TCP/10-Sr, respectively). Adding SrCO3 in the 3D-printing ink led to a slight increase in viscosity but did not affect its printability, resulting in scaffolds with a high printing fidelity compared to the computational design. Interestingly, Sr was incorporated into the lattice structure of the scaffolds, forming hydroxyapatite (HA). No residual SrO or SrCO3 were observed in the XRD patterns of any composition, and HA was the majority phase of the ß-TCP/10-Sr scaffolds. The addition of Sr increased the compression strength of the scaffolds, with both ß-TCP/5-Sr and ß-TCP/10-Sr performing better than the ß-TCP. Overall, ß-TCP/5-Sr presented higher mineralized nodules and mechanical strength, while ß-TCP scaffolds presented superior cell viability. The incorporation of SrCO3 in the ink formulation is a viable method to obtain Sr-BCP scaffolds. Thus, this approach could be explored with other CaP scaffolds aiming to optimize their performance and the addition of alternative therapeutic ions.

Bioglass-based scaffolds coated with silver nanoparticles: Synthesis, processing and antimicrobial activity.

Over the past few years, several tridimensional synthetic bone grafts, known as scaffolds, are being developed to overcome the autologous grafts limitations. Among the materials used on the production of scaffolds, the 45S5 bioglass stands out due to its capacity of bonding to hard and soft tissues. Silver nanoparticles are well-known for their antimicrobial properties and their incorporation on the scaffold may promote its antimicrobial response, avoiding microorganism proliferation on the materials surface. This study proposes a simple way to coat 45S5 bioglass-based scaffolds with silver nanoparticles. The scaffolds were obtained by the sponge replication technique and the silver nanoparticles were incorporated by soaking under ultrasonic stirring. The antimicrobial activity of the scaffolds was analyzed against three different microbial strains: S. aureus, P. aeruginosa, and C. albicans. Due to the heat treatment during the scaffold production, the bioglass crystalized mainly in a sodium calcium silicate phase, forming a glass-ceramic scaffold. The silver nanoparticles were coated in a well-distributed manner throughout the scaffold, while avoiding their aggregation. The coated scaffold inhibited the growth of all the analyzed microorganism. Therefore, the use of ultrasonic stirring to coat the bioglass scaffold with silver nanoparticles showed to be an efficient way to promote its antimicrobial response.