Alendronate-loaded gelatin microparticles as templating agents for macroporous magnesium phosphate-based bone cements

Magnesium phosphate-based cements (MPCs) have recently attracted great attention as materials for bone repair. However, the lack of macroporosity, fundamental for cells permeation and bone ingrowth, is one of the main limitations hampering MPCs full exploitation. In this work gelatin microparticles are exploited as templating agents for the creation of macroporosities in MPCs. In addition, gelatin particles were loaded with a well-recognized drug for the treatment of osteoporosis, alendronate, to locally release the therapeutic agent. Gelatin microparticles of different size were prepared with a simple water-in-oil emulsion method and included in MPCs at various concentrations. The properties of both the MPCs and the final material were characterized by assessing the composite in terms of injectability, setting time, infrared spectroscopy, scanning electron microscopy and confocal Raman microscopy. The MPC-gelatin composites were then incubated in water at physiological temperature, to promote the dissolution of the gelatin, obtain a macroporous cement, and release gelatin and alendronate. The obtained results show that gelatin microparticles have a twofold action as they allow for the formation of MPC with an interconnected and hundreds of µm-sized porosity and the local release of alendronate, resulting in a material with ideal features for bone repair.