The Study Of Fabrication And Performance Of PLLA/Lecithin Bone Tissue Engineering Scaffold

With the aging of population, demands for bone transplantation are increasing. In orderto solve the problem of supply shortage for autogenous and allogenous bone transplantation,it is necessary to develop novel bone tissue engineering scaffolds.PLLA is widely used in developing bone tissue engineering scaffold. But PLLA ishydrophobic and lacks of cellular recognition sites, which restrain further applications ofPLLA nanofibrous scaffold. In this study, we blended lecithin with PLLA, one of naturalbioactive materials to prepare scaffold to improve the hydrophilicity and biocompability ofthe scaffold. Performances of modified scaffold were investigated by SEM, XRD,ATR-FTIR, DSC, contact angle and degradation tests. After blended with lecithin(mlecithin:mPLLA≤15%) and phase separation at-24℃, scaffold still maintained the nanofibrousmorphology. The crystalline structure of scaffold was still α form. With the increase oflecithin, the hydrophilicity of scaffold was significantly improved. Lecithin acted as aplasticizer between PLLA molecule chains, decreased the degree of crystallinity. ThemBMSCs were cultured on the surface of scaffold to evaluate the biocompability of scaffold.And the attachment and proliferation of cells indicated that appropriate hydrophilicity ofscaffold could enhance the proliferation of cells significantly.Furthermore, the morphology of lecithin regulated PLLA nanofibrous scaffold wasalso investigated. When mlecihtin:mPLLA≥2.05, samples at a gelation temperature of-24℃would form nanoribbon-like structure with a depth of several hundred micrometers. Withdepth increasing, nanoribbon-like structure would transformed into nanofibrous structuregradually. And the nanoribbon-like structure would transformed into nanoplate-likestructure if the content of lecithin further increased. After lecithin added in thescaffold(mlecithin: mPLLA≥1), the crystalline structure would transform from α’ form to themore stable α form. Compared with control group, the compressive modulus of1:1groupdecreased due to lecithin acted as the platicizer. While the modulus of2.05:1group wasenhanced than1:1group because after phase separation of lecithin from the solvent system, the concentration of PLLA was increasing. With the increase of lecithin introduced into thescaffold, the protein absorption of modified groups samples fabricated at-24℃wassignificantly improved than control group fabricated at-24℃. This was partially becausethe effects of the existence of lecithin in scaffold and the increase of specific surface area.And the protein absorption of2.05:1group fabricated at room temperature, which wasconsisted of ribbon-like structure only, had no significantly difference compared withcontrol group fabricated at-24℃because the decrease of specific surface area wascounterbalanced by the existence of lecithin.After researched the morphology of samples fabricated with different concentration oflecithin, different gelation temperature, different gelation time and samples’ crystallinestructure, we speculated and concluded the forming mechanism of nanoribbon-like structure:lecithin enhanced the mobility of PLLA molecule chains, which promoted PLLA totransform into more stable α form. But if mlecithin: mPLLA≥2.05:1, the lecithin wouldaggregated at the surface of scaffold and hindered PLLA on the surface of scaffold to formnanofibrous structure at the early stage of phase separation and retained the nanoribbon-likestructure which formed at the early stage of phase separation. Controlling the surfacemorphology of PLLA nanofibrous scaffold is expected to enable the regulation of cellbehavior.