Fabrication And Performance Of Porous PLLA Scaffold

Using biomaterials to fabricate porous scaffold for tissue engineering is one of the core problems in tissue engineering. In this paper, porous poly l-lactic acid (PLLA) scaffold and porous PLLA-hydroxyapatite (HA) composite scaffold were fabricated by modified solvent casting/porogen leaching method using ice particulates as porogen, basic performances of the scaffolds were also researched.Porous PLLA scaffolds were fabricated using salt, ammonium bicarbonate and ice particulates as porogen, respectively, no porogen remained in the scaffold prepared only using ice as porogen and the morphology of pores was spherical. The result of cell experiment showed that the porous scaffold has good biocompatibility and no cytotoxicity when the ice porogen was used, so the ice particulate is a good kind of porogen for fabricating method of porous scaffold. A mathematical model of freeze-drying was established, on the base of analyzing the influencing factors on freeze-drying, a novel freeze-drying device was designed, in which the heat and mass transmission during freeze-drying process were improved and the freeze-drying efficiency raised. A liquid-solid extraction technique was used instead of freeze-drying technique to fabricate porous scaffold and the preparing period was shortened obviously. However, during the fabrication the porous PLLA scaffold contracted and distorted obviously.The effect of technical factors on morphology of porous PLLA scaffold was researched using orthogonal experiment. Ice size determined the pore size but had no effect on porosity of porous scaffold, porosity and degree of connection was increased when increasing of ice's mass fraction, porosity was increased while degree of connection was decreased when increasing chloroform. A method using"porosity connection ratio"to estimate degree of pore's connection of single pore and the whole scaffold was established elementary.PLLA-HA composite porous scaffold was fabricated. Compressive strength of porous scaffold was increasing with HA's mass fraction increasing, but it was decreasing with HA's mass fraction increasing when HA's mass fraction was greater than some value. SEM observe showed that HA powders were agglomerated in porous scaffold and became more serious with HA's mass fraction increasing. No obvious effect on HA powders agglomergation was caused by ultrasonic vibration, so no obvious compressive strength increasing was observed. Hydrophilicity of porous scaffold was obviously different from that of membrane, no effectively improvement of hydrophilicity was observed with HA's mass fraction increasing. Surface coating with chitosan or surface alkali hydrolysis treatment were used to improve hydrophilicity of porous composite scaffold. The result showed that only alkali hydrolysis treatment improved the hydrophilicity of whole porous composite scaffold. Hydrophilicity of porous scaffold was gradually improved with the increase of immersing time in simulation body fluid (SBF). Based on correlative surface physics and chemistry theory, a model was established, hydrophobicity of porous scaffold compared to membrane and superhydrophilicity of porous scaffold after surface modification can be explained using this model.During the whole in vitro degradation period, no obvious structure change and selfcatalysis was happened in all kinds of porous scaffold. The compressive strength increased in a shorttime initially and decreased with the time prolonged. Degradation speed of porous PLLA-HA scaffold after surface modification was more rapid than porous PLLA scaffold and porous PLLA-HA scaffold.