Effect of porogen agent on the size, shape, and structure of porous hydroxyapatite scaffolds

The modification of hydroxyapatite (HA) scaffolds into spherical forms can prevent inflammatory responses and promote faster bone growth compared to irregular scaffolds. HA must possess a porous structure with a porosity value to support bone regeneration. Droplet extrusion is the most widely applied and simplest method to produce hydroxyapatite scaffolds in liquid air systems. Therefore, the addition of carbon black as porogen was aimed to increase the porosity of HA scaffolds.

At present work, the synthesis of porous HA scaffold was carried out in two stages: synthesis of HA powder and fabrication of spherical HA scaffold. The materials used were Ca(OH)₂ from local limestone, H₃PO₄, ammonia solution, ethanol, natrium alginate, acetic acid, pharmaceutical-grade chitosan, carbon black, and deionized water. We investigated the influence of carbon black with a concentration variation of 0.5%, 1%, and 1.5 wt.% as a porogen agent on the size and shape, porosity, and mechanical properties of porous hydroxyapatite scaffolds.

The scaffolds’ size varied from 1180 to 1359 µm, and the shape quantified by the sphericity factor (SF) of droplets was generally smaller than 0.05. The addition of CB indicating enhanced porosity up to 64% showed mesopores of 2.3–2.5 nm diameters with good pore interconnecting channels. The compressive strength of scaffolds is consistent with the characteristics of trabecular bone.

The results suggest that carbon black was feasible to be used as a porogen agent in preparation of porous hydroxyapatite scaffolds for dental filler.