Marine skeletons of cuttlefish bone (CB) exhibit an interconnected porous structure with a high degree of porosity (93%) and are mainly composed of aragonitic calcium carbonate. This unique CB architecture and the easiness of hydrothermally converting calcium carbonate into calcium phosphate (CaP) materials with compositions similar to the mineral component of the bone, make CB a suitable precursor material for preparing porous scaffolds for bone repair and regeneration.
The main aim of our work was to develop a multifunctional bone graft material based on biphasic calcium phosphate (BCP) scaffolds derived from CB and then combined with different polymers to improve the brittleness and low strength, and to store drugs to then enable obtaining sustained drug release systems. CBs have been completely transformed into BCP scaffolds through hydrothermal transformation (HT). Considering the presence of trace amounts of elements, like strontium, magnesium and zinc in bone composition, the incorporations of these ionic substitutions (Sr2+, Mg2+ and/or Zn2+) in BCP scaffolds
were also attempted by partially replacing calcium into the calcium phosphates lattices during HT. The presence of the doping elements improved cell metabolic activity. Therefore, as an alternative approach, the doping elements were also introduced by coating the BCP scaffolds with sol-gel derived bioactive glass containing the doping elements. The bioactive glass coating improved the mechanical properties and the in vitro biomineralization. In addition, these scaffolds did not have a negative impact on cell metabolic activity.
To overcome the drawbacks of BCP scaffolds obtained from CB (brittleness and low strength), different polymeric coatings were applied onto their surfaces. With this purpose, two commercial polymers, poly(e-caprolactone) (PCL) and poly(DL-lactide acid) (PDLA), and two polymers synthesized in the laboratory, poly(ester amide) (PEA) and poly(ester urea) (PEU) were used. The different polymers enhanced the mechanical properties of the BCP scaffolds without compromising the original unique porous structure of CB.
The polymeric coatings, applied to the optimized BCP scaffolds doped with by partial calcium substitution with Sr2+, Mg2+ and Zn2+, did not exert any negative impact on cell metabolic activity.
The synergetic effects between BCP scaffolds and polymers were explored to develop sustainable drug delivery systems by incorporating an antibiotic. The results demonstrated that all the tested polymers exert specific influences on the drug release profiles, while conferring to the scaffolds controlled drug delivery properties. It is important to highlight that all the antibiotic loaded samples exerted antibacterial effects against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. These scaffolds can potentially be used as bone graft substitutes to improve bone regeneration and prevent bacterial biofilm formation.
Ana Sofia Neto
Third place at the 2019 ECerS Student Speech Contest
Department of materials and ceramic engineering
Campus Universitário de Santiago