The Process And Properties Of HA Porous Scaffold By Freeze Drying With An Eletrostatic Field

Osseous tissue engineering is a new method to therapy bone defect. HA scaffold has introduced extensively interests. Porous HA has been generally accepted and the scaffold is biocompatible, biodegradable.A novel route using directional solidification of an aqueous HA slurry with and electrostatic field for fabricating aligned porous HA scaffold was demonstrated. The porous HA scaffolds with lamellar pores structure were fabricated by freeze-drying. The properties including pores morphology, size, and distribution were investigated; drying time was investigated; the compressive intension was tested by Instron5565 material testing.The results show that by changing the process parameters, the porosity can be transformed in the range from 45% to 85%, and the pore size can be transformed between 100μm and 800μm. The scaffolds are characterized by well-defined pore connectivity. The pore size of HA scaffold were controlled by freeze temperature, when the temperatures were-20℃,-50℃and-80℃respectively, the pore sizes were 570～630μm,440～380μm,330～290μm. With the increasing of cooling temperature, the pore size gradually becomes smaller. The slurry concentration played an important role preparing of the scaffolds. HA scaffold with lamellar pore can't obtain when the slurry concentration was less than 5% or over than 60%. When the direction of electrostatic field and temperature gradient (1.3℃/cm) is identical, aligned pore microstructure was obtained; when the direction of electrostatic field and temperature gradient (2℃/cm) is vertical, the most tilt angle was 74°.The result of drying time shows that the chamber condition for drying has a best qualification. It was that drying temperature was 5℃and press was 40Pa. Relationship between dying time (T/℃) and slurry concentration (X/%) was agree with the following equality: T=91.9-1.54X. The result of compressive test shows the relationship between compressive strength and porosity was agree with the following equality:σ=σfe-cp. The compressive strength of scaffolds which exhibit 45% porosity and 100μm pore size can reach about 6.7MPa. The absorbance of porous scaffold with 250μm and 65% porosity was 0.26 Arbit.unit, which was higher than compact HA ceramic.