Design of tunable protein-releasing nanoapatite/hydrogel scaffolds for hard tissue engineering

•The three dimensional hierarchically structured porous scaffolds are prepared.•Capability to accommodate and protect a precise quantity of a labile biomolecule.•In situ protein loading during scaffold fabrication vs. inclusion in a second step.•Valuable biocompatibility allowing osteoblast growth.

Hierarchically structured porous scaffolds based on nanocrystalline carbonated hydroxyapatite reinforced hydrogels (Gellan or Agarose) have been tested as protein release matrices while evaluation their in vitro biocompatibility. The shaping method used develops under mild conditions thus allowing the incorporation of labile substances. The Bovine Serum Albumin (BSA), employed as a model protein, has been included by using two drug-inclusion strategies: during the scaffolds preparation (in situ process) or by injection of an aqueous protein solution within (ex situ process). The release studies showed a more controlled BSA delivery when the protein was incorporated during the scaffold preparation when compared to that where the protein has been loaded in a second step (ex situ process). The release patterns can also be tailored as a function of the scaffold composition (ceramic/polysaccharide ratio and nature) as well as the drying technology employed. Biocompatibility studies demonstrated that these scaffolds, regardless of the composition, allow the culture of osteoblasts on and around the material, thus supporting the potential use of these biomaterials for bone tissue engineering.