Vancomycin release kinetics from Mg-Ca silicate porous microspheres developed for controlled drug delivery

In this work, sol-gel derived bredigite (MgCa7Si4O16), akermanite (MgCa2Si2O7), and diopside (MgCaSi2O6) porous microspheres were loaded with vancomycin, and the release kinetics of this drug from them was evaluated. In this regard, mathematical models of Higuchi, Peppas, Baker-Lonsdale, Hixson-Crowell, first order, and zero order were considered in terms of linear and nonlinear regression analyses. Using the goodness of fitting correlation coefficients, the number of release stages was determined, and then diffusion- and degradation-controlled mechanisms were assigned to each stage. It was found that the diopside microspheres presented a two-step diffusional drug delivery. For akermanite and bredigite, an initial burst diffusion-controlled release followed by a sustained mixed-mode release mechanism of diffusion and degradation was identified, with the domination of the latter especially for bredigite.