Structural, thermal, in vitro degradation and cytocompatibility properties of P₂O₅-B₂O₃-CaO-MgO-Na₂O-Fe₂O₃ glasses

Borophosphate glasses with compositions of (48 − x)P₂O₅-(12 + x)B₂O₃-14CaO-20MgO-1Na₂O-5Fe₂O₃ (where x = 0, 3, 8 mol%) were prepared via a melt-quenching process. The effects of replacing P₂O₅ with B₂O₃ on the structural, thermal, degradation properties and cytocompatibility were investigated. Fourier transform infrared (FTIR) spectroscopy analysis confirmed the existence of BO₃ triangular units and BO₄ tetrahedral units within all the glasses with an increase of B/P ratio from 0.25 to 0.5. The BO₄ units within the glass structure were observed to cause an increase in density (ρ) as well as glass transition (T_g) temperature and to decrease the crystallisation temperature (T_c). A decrease in thermal stability which indicated by process window was also observed in the case of substitution of P₂O₅ with B₂O₃. Degradation analysis of the glasses indicated that the dissolution rate increased with the addition of B₂O₃. The decrease in the thermal stability and chemical durability were attributed to the increase of BO₃ units, which could increase crystallisation tendency and be easily hydrolysed by solution. The effect of boron addition on the cytocompatibility of the glasses was analysed using Alamar Blue and alkaline phosphatase (ALP) assays and DNA quantification. MG63 osteosarcoma cells cultured in direct contact with the glass samples surface for 14 days showed better cytocompatibility, compared to the tissue culture plastic (TCP) control group. In summary, the glass formulation with 12 mol% B₂O₃ presented the best cytocompatibility and thermal stability, thus could be considered for continuous fibre fabrication in future research and downstream activities.