Surface modification of poly-l-lactic acid fibrous scaffolds by a molecular-designed multi-walled carbon nanotube multilayer for enhancing cell interactions

We presented a molecular-designed multi-walled carbon nanotube (MWCNT) layer-by-layer (LbL) multilayer on poly-l-lactic acid (PLLA) electrospun fibers for engineering cell/CNT interfaces. A stable, positively charged monolayer was created on the fiber surface by the aminolysis reaction of poly(ethylene imine) (PEI) with PLLA, followed by alternate deposition in negatively charged MWCNT and positively charged chitosan (CS). Thermogravimetric analysis indicated a sustained growth of the MWCNT during the self-assembly process. The interactions between MWCNT and polycation crucially affected the specific structure and properties of the MWCNT multilayer. MWCNT/PEI electrostatic interactions reduced the gap between MWCNTs and improved the π→π∗ transitions. However, the CS chains tended to be more serpentine than the chains of PEI molecules, which might have hindered the π→π∗ transitions. On the other hand, the electrostatic interactions might have enhanced the disorder grade of the MWCNT structure, as indicated by Raman analysis. The scaffolds maintained their fibrous and porous structure after MWCNT multilayer modification and supported fibroblast growth. The MWCNT multilayer induced cell migration toward the interior of the scaffolds. Therefore, we created a simple yet efficient method of building a CNT multilayer on three-dimensional (3D) fibrous scaffolds for enhancing cell-matrix interactions.