A casting based process to fabricate 3D alginate scaffolds and to investigate the influence of heat transfer on pore architecture during fabrication

The fabrication of 3-dimensional (3D) tissue scaffolds is a competitive approach to engineered tissues. An ideal tissue scaffold must be highly porous, biocompatible, biodegradable, easily processed and cost-effective, and have adequate mechanical properties. A casting based process has been developed in this study to fabricate 3D alginate tissue scaffolds. The alginate/calcium gluconate hydrogel was quenched in a glass mold and freeze dried to form a highly porous tissue scaffold whose tiny pores retain the shape of the ice crystals during quenching. Knowing that the water in the alginate hydrogel would form ice crystals if frozen and that different cooling conditions may dramatically influence the pore architecture, the speed and direction of the heat transfer in freeze drying hydrogel were examined with regard to pore size and orientation. The pore architecture at the different locations of the fabricated scaffolds was characterized using scanning electron microscopy. The fabricated scaffolds consist of pores that are highly interconnected, with a diameter about 200 µm (average diameter of a capillary) to permit blood vessel penetration. It also has been found that the pore size, orientation, and uniformity are significantly affected by the condition of heat transfer during freeze drying. Tailoring the pore architecture of the scaffolds is feasible by controlling heat transfer. This study provides an insight on pore architecture formation and control by altered process parameters.