An Eco-Friendly Substitute of Calcium Nitrate for the Sol-Gel Preparation of pH-Neutral Bioactive Glass

Bioactive glasses (BGs) are a class of biomaterials with outstanding performance, widely used in clinical applications. The sol-gel method has been proven effective for preparing BGs that meet clinical requirements. Traditionally, calcium nitrate is used as the calcium precursor in this method; however, it produces environmentally harmful nitrogen oxides, which require additional removal steps and increase costs. In this study, a novel approach is introduced by using calcium oxide solution in ethylene glycol (CEG) as an alternative calcium precursor for the preparation of a newly developed pH-neutral phosphosilicate calcium. This method yields products with properties nearly identical to those produced with calcium nitrate. Importantly, the CEG route does not involve any hazardous compounds, making it a more environmentally friendly and cost-effective alternative to conventional methods.