Physical, mechanical and in vitro evaluation of a novel cement based on akermantite and dicalcium phosphate dihydrate phase

Magnesium containing calcium silicates have recently shown that they are promising materials for various biomedical application with potential use in the form of bulk ceramic, composite scaffold or coatings on metallic substrates. A novel akermanite (AK; Ca2MgSi2O7)/dicalcium phosphate dihydrate (DCPD, CaHPO4. H2O) cement mixture was tested in this work in order to produce an alternative AK/DCPD biocement for orthopedic applications. For comparison, we have prepared two cements mixed with 2.5 wt% NaH2PO4 solution (labeled as NaH2PO4 cement) and with the solution composed of organic 2.5 wt% citric acid a 2.5 wt% trisodium citrate (citrate cement) respectively. The results demonstrated only a partial dissolution of AK, regardless of the type of liquid used. On the other hand, the DCPD was completely hydrolyzed much faster in the citrate cement. The final hydration product was an amorhous quarternary phase of CaO-MgO-SiO2-P2O5 composition with the remaining unreacted akermanite embeded in the cement matrix. The highest early compressive strength was observed in the citrate cement (33 MPa), but much lower value was measured in NaH2PO4 cement (7 MPa) after 1 d setting. Different cell responses have been observed when the cells were cultured on the surfaces of cement substrates. While the NaH2PO4 cement demonstrated high proliferation activity of osteoblast, the citrate cement showed strong cytotoxic cell response, probably as a result of higher concentration of citrates on the cement surface, which can negatively affect the attachment and proliferation of osteoblastic cells.