Atomic-scale investigation of zinc/strontium Co-doped 45S5 bioglass: A molecular dynamics simulation investigation on dissolution behavior

This study presents an atomic-scale investigation into the dissolution behavior and structural evolution of Zinc/Strontium (Zn/Sr) co-doped 45S5 bioglass using Molecular Dynamics (MD) simulations. The primary objective was to elucidate how the substitution of Calcium (Ca) with Strontium (Sr), in the presence of Zinc (Zn), influences the network connectivity (NC), structural homogeneity, and degradability of bioactive glasses (BGs). Results indicate that the dominant structural unit remains Q 2 , consistent with the characteristic structure of 45S5 bioglass. As SrO content increases, a slight rise in the fraction of Q 2 species was observed, suggesting a more pronounced chain-like structure. Interestingly, while the calculated NC exhibited an increasing trend with Sr substitution, other key metrics told a different story. The total bond density (F net ) decreased significantly with higher SrO content, indicating a reduction in overall structural strength. Furthermore, the study evaluated structural homogeneity using the R-factor, revealing that increasing SrO content enhances the structural uniformity of the glass, bringing it closer to the homogeneity of the Sr-free control sample. The structural insights were experimentally validated through the evaluation of the 45-ZS5 sample, which demonstrated significant bioactivity despite the co-doping of Zn and Sr. This confirms that the structural modifications induced by Zn/Sr substitution do not compromise the material’s biological function. Collectively, these findings suggest that in the 45-ZS5 sample, the reduction in bond strength and density, coupled with improved structural homogeneity, optimizes the degradability of the BGs. This enhanced degradability promotes more uniform ion release, thereby improving the therapeutic efficiency and bioactivity of Zn/Sr-co-doped 45S5 bioglass.