In the present book, after briefly summarizing recent literature concerning modification and applications of these materials, several recent developments of bio-composites containing silica nanoparticles or calcium sulphate intended for bone regeneration are reported. The composites are characterized with respect to their chemical-physical and mechanical properties. Their bio-compatibility and capacity to induce the osteoblastic phenotype in human bone marrow mesenchymal stem cells have been assessed. The authors focus on two particular systems based on either natural or synthetic bio-polymers with different biofillers: alginate/chitosan blends with calcium sulphate and poly(-caprolactone) with silica nanoparticles.