Structural effects of incorporating Cu⁺ and Cu²⁺ ions into silicate bioactive glasses using molecular dynamics simulations

Copper oxide containing bioactive glasses have drawn attention because of their unique properties as biomaterials for targeted tissue engineering applications. This is due to their ability to act as stimulants for new tissue formation. In the present manuscript, we aim to study the structure and properties of copper incorporated bioactive glass 45S5 using molecular dynamic simulations using newly parameterized interaction potentials for Cu⁺-O and Cu²⁺-O oxides. The role of copper oxides in 45S5 glasses was elucidated by studying a series of glasses with compositions 46.1 mol% SiO₂, 26.9 mol% CaO, 24.4 mol% Na₂O, and 2.6 mol% P₂O₅ in which CuO (10, 15, and 20 mol%) was progressively substituted for Na₂O. The local environment of Cu⁺ and Cu²⁺ ions within the glasses was explored and the ratio was calculated theoretically. The findings indicate that both Cu⁺ ions with a three-fold coordination and Cu²⁺ ions coordinated by six oxygen atoms participate in the silica network as network modifiers. The impact of Cu⁺ and Cu²⁺ ions on the overall glass network connectivity was likely to be small. The ratio of Cu⁺ : Cu_total has been found to increase with an increase in the content of CuO in the structure of the studied glasses. In the computational study of the glasses, the network connectivity was used to predict their bioactivity. From our study, it was concluded that incorporating Cu⁺ and Cu²⁺ ions in the structure of 45S5 glasses favours the bioactivity of these glasses.