Bioactive ceramics for tissue engineering and regenerative medicine derived from marine sponges

Introduction: The use of biostructures and bioceramics derived from the marine environment for several application has been proposed in the last years by different authors. Examples are the use of different marine species like coral skeletons, sea urchins and sponges as three dimensional biomatrices1-3.We have focused on the potential of bioce- ramics obtained from three marine sponges, Petrosia ficidormis (PET), Agelas oroides (AG) and Chondrosia reniformis (CR) for biomedical applications. In vitro bioactivity studies promote the precipitation of crystals of calcium phosphate (e.g. hydroxyapatite) on the surface of marine sponge derived bioceramics suggesting these as a new source of bioactive ceramics for tissue engineering and regenerative medicine (TERM) applications. Materials and methods: In these work, Sponge samples were collected in Mediterranean Sea, namely in Spanish north east coast (Petrosia fici- formis. and Agelas oroides) and Israeli coast (Chondrosia reniformis). Bi- oceramics were obtained, after sponge calcination in a furnace at 750 C for 6 hours. In vitro bioactivity of the bioceramics was evaluated by immersion in simulated body fluid (SBF), for 14 and 21 days. The structures were observed by SEM and the chemical composition was evaluated by energy dispersive x-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). Cytotoxicity studies were also performed, using the commercial Bioglass 45S5 as reference. Results: The bioceramics structures obtained after calcination present different morphological and chemical compositions, as observed by SEM-EDS (FIG. 1). PET skeleton is a 3D architecture, composed of SiO2 groups. On the other hand the inorganic part of AG and CR is a powder mainly composed of silicates. However, they also contain Ca and Mg. The microscopic observation of the ceramics crystals after immersion in SBF solution for 14 and 21 days disclosed surface crystals, with the typ- ical cauliflower-like shape characteristic of hydroxyapatite, in case of AG and CR. These crystals are composed of Ca, P and Mg as demon- strated by EDS analysis. PET on the other hand, did not reveal any crys- tal precipitation, suggesting no inherent bioactivity. FTIR confirmed the presence of characteristics peaks of carbonates and phosphates of hydroxyapatite, nxCO3 and nxPO4, after immersion of the marine ori- gin ceramics in SBF solution. XRD analysis confirms the crystallo- graphic planes of hydroxyapatite and some intermediate crystals. Finally, in vitro test results demonstrate that bioceramics from these sponges are non-cytotoxic to L929 Cells. Discussion and conclusions: The results show that bioceramics obtained from PET sponges do not possess inherent bioactivity on the contrary of AG and CR, which establish, after 14 days and 21 days of immersion in SBF solution, the formation of hydroxyapatite crystals on their surface. Observing the chemical composition of the sponges after calcination, bioactivity can be explained by the presence of calcium and magnesium groups, which allow nucleation of crystals. CR and AG ceramics show, hereafter a bioactive behavior with potential use in TERM applications, namely towards bone tissues.