Tuning the microstructure and biodegradation of three-phase scaffolds for bone regeneration made of PCL, Zein, and HA

The aim of this study has been the design of novel multi-phase porous scaffolds with bi-modal pore size distributions and controlled biodegradation rate for bone tissue engineering (bTE), via a gas foaming–leaching approach. Poly("-caprolactone) (PCL) has been melt mixed with thermoplastic zein (TZ) and hydroxyapatite particle, to pre- pare multi-phase PCL–TZ and PCL–TZ–HA composites suitable to be further pro- cessed for the fabrication of 3D porous scaffolds. To this aim, these systems have been gas foamed by using CO2 as blowing agent and, subsequently, soaked in H2O to leach out the plasticizer from the TZ. This combined process allows the formation of an interpenetrated micro- and macro-porosity network within the samples. The effect of the different formulations on the micro-structural properties and in vitro biodegradation of the scaffolds has been investigated, and the results correlated to the mechanisms involved in the formation of the bi-modal pore structure. Results demonstrated that the multi-phase nature of the biomaterials prepared as well as their composition signifi- cantly affect the micro-structural properties and biodegradation rate of the scaffolds. The optimal selection of the processing conditions may allow for the design of multi- phase 3D porous scaffolds suitable for bTE.