Publications

Despite advances in bone graft design and surgical techniques, bacterial infection remains a major cause of graft failure, exacerbated by the global rise in antimicrobial resistance. This has intensified the pursuit of antibioticfree strategies to prevent bacterial colonization. Among these, antibacterial surface nanotopographies have emerged as promising tools, leveraging nanoscale geometries to physically disrupt bacteria upon contact. In this study, we engineered the surface of a calcium phosphate bone graft to confer antimicrobial functionality through a dual approach: the creation of high-aspect-ratio nanotopographies and ionic doping with fluoride. Through controlled hydrolysis of alpha-tricalcium phosphate by biomimetic and hydrothermal treatments, we generated calcium deficient hydroxyapatite nanoneedle structures whose morphology and biofunctionality were tuned via fluoride incorporation. XRD and Raman spectroscopy confirmed the formation of hydroxy-fluorapatite, with phase composition and surface morphology dependent on fluoride concentration and processing parameters. Fluoride doping significantly altered nanoneedle dimensions and spacing and enhanced bactericidal activity, particularly against P. aeruginosa, and to a lesser extent S. aureus. Notably, fluoride-doping alone showed no antibacterial effects; however, when combined with nanotopography, a synergistic increase in efficacy was observed. Importantly, the antimicrobial surfaces supported the proliferation and osteogenic differentiation of SaOS-2 cells. Co-culture assays modeling pre- and post-implantation infection scenarios demonstrated robust cell adhesion and markedly reduced bacterial colonization. In conclusion, our findings present a multifunctional, synthetic bone graft with both physical and chemical antibacterial properties, offering a promising strategy to mitigate infection risks while supporting osteointegration.

JTD Keywords: Antibacterial nanotopography, Bactericidal surfaces, Biomaterials, Bone regeneration, Calcium phosphate, Cements, Coatings, Cytokines, Fluoride, Hydroxyapatite, Infections, Magnesium, Pseudomonas-aeruginosa, Setting reaction

JTD Keywords: alpha-tricalcium phosphate, cement, crystallinity, hydrolysis, hydroxyapatite, particle-size, powders, relative humidity, setting reaction, stability, tcp, vapor sorption, Calcium-phosphate, Moisture

The aim of the present work was to analyze the influence of the setting reaction on the injectability of tricalcium phosphate (TCP) pastes. Even if the injection was performed early after mixing powder and liquid, powder reactivity was shown to play a significant role in the injectability of TCP pastes. Significant differences were observed between the injection behavior of non-hardening β-TCP pastes and that of self-hardening α-TCP pastes. The differences were more marked at low liquid-to-powder ratios, using fine powders and injecting through thin needles. α-TCP was, in general, less injectable than β-TCP and required higher injection loads. Moreover, clogging was identified as a mechanism hindering or even preventing injectability, different and clearly distinguishable from the filter-pressing phenomenon. α-TCP pastes presented transient clogging episodes, which were not observed in β-TCP pastes with equivalent particle size distribution. Different parameters affecting powder reactivity were also shown to affect paste injectability. Thus, whereas powder calcination resulted in an increased injectability due to lower particle reactivity, the addition of setting accelerants, such as hydroxyapatite nanoparticles, tended to reduce the injectability of the TCP pastes, especially if adjoined simultaneously with a Na2HPO4 solution. Although, as a general trend, faster-setting pastes were less injectable, some exceptions to this rule were found. For example, whereas in the absence of setting accelerants fine TCP powders were more injectable than the coarse ones, in spite of their shorter setting times, this trend was inverted when setting accelerants were added, and coarse powders were more injectable than the fine ones.

JTD Keywords: Calcium phosphate cement, Hydroxyapatite, Injectability, Setting reaction, Tricalcium phosphate