Surface Engineering of Nano-Fibrous Poly(L-Lactic Acid) Scaffolds via Self-Assembly Technique for Bone Tissue Engineering

The architectural design and surface properties of scaffolds are important in tissue engineering. The porous scaffolds provide the environment to accommodate cells and guide their growth. The surface nature of the scaffolds affect cell attachment, proliferation, and ultimately neo tissue regeneration. In this work, a highly porous Poly(L-lactic acid) (PLLA) scaffold with nano-fibrous architecture has been fabricated to mimic the structure of natural collagen using a novel thermally induced phase separation method developed in our group. The electrostatic layer-by-layer self-assembly technique was applied to incorporate gelatin onto the surface of nano-fibrous PLLA (NF-PLLA) scaffolds. The surface composition, morphology, and properties were examined using ATR-FTIR, XPS, SEM and contact angle measurements. The amount of gelatin on a NF-PLLA film was controlled by the number of assembled polyelectrolyte bilayers, and increased linearly with the bilayer number after the first two bilayers. The contact angle decreased upon surface modification, indicating improvement in hydrophilicity. MC3T3-E1 osteoprogenitor cells were cultured on these surface-modified films and scaffolds. The cell number on the surface-modified NF-PLLA film was significantly higher than that on the control 4 h and 24 h after cell seeding, and increased with the number of bilayers. Furthermore, the osteoblasts proliferated at a higher rate and were more evenly distributed on surface-modified NF-PLLA scaffolds than on the control scaffolds. These results demonstrated that the electrostatic self-assembly was a powerful technique to modify three dimensional scaffold surfaces, and the surface-modified nano-fibrous scaffolds were advantageous for cell adhesion and proliferation.