Surface Engineering of Nano-fibrous Biodegradable Poly(L-lactic acid) Scaffolds for Tissue Engineering
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Surface Engineering of Nano-fibrous Biodegradable Poly(L-lactic acid) Scaffolds for Tissue Engineering Xiaohua Liu, Youngjun Won, and Peter X. Ma Biological and Materials Sciences Department, University of Michigan, Ann Arbor, MI 48109-1078, U.S.A. ABSTRACT The architectural design and surface properties of scaffolds are important aspects in tissue engineering. The porous scaffolds accommodate cells and guide their growth, while the surface nature of the scaffolds can directly affect cell attachment, proliferation, and ultimately neo tissue regeneration. In this work, a highly porous poly(L-lactic acid) (PLLA) scaffold with nanofibrous pore wall architecture has been fabricated by mimicking the structure of natural collagen using a novel thermally induced phase separation method developed in our group. A universally effective surface modification method was developed, and gelatin was successfully grafted onto the surface of nano-fibrous PLLA scaffolds by entrapment procedure. The surface composition, morphology, and properties were examined using ATR-FTIR, XPS and SEM. The surface coverage of gelatin on the PLLA surface was as high as 39.4%. MC3T3-E1 osteoprogenitor cells were cultured for 6 weeks in solid-walled PLLA scaffolds, nano-fibrous PLLA scaffolds, and surface-modified nano-fibrous PLLA scaffolds, respectively. The osteoblasts proliferated in all three types of scaffolds, but the cell numbers were always significantly higher in the surfacemodified nano-fibrous scaffolds than in the other two types of scaffolds, and the cell numbers in nano-fibrous scaffolds were higher than that in the solid-walled scaffolds. These results demonstrate that the surface-modified nano-fibrous architecture could serve as a superior scaffold for tissue engineering. INTRODUCTION The architectural design and surface properties of scaffolds are important aspects in tissue engineering [1-4]. A desired architecture of scaffolds enhances protein adsorption, nutrient exchange, and metabolic waste removal. In addition, the interactions between cells and materials take place on the pore surface of the scaffolds, thus the surface properties of scaffolds can directly affect cells attachment, proliferation, and eventually neo tissue regeneration. Collagen is a natural extracellular matrix component of many tissues, and its fibrillar structure has long been noticed to be important for cell attachment, proliferation, and neo tissue regeneration. However, there are some limitations in using collagen as scaffolding for tissue engineering. As a natural material, there is less control over the mechanical properties, biodegradability, and batch to batch consistency. Pathogen transmission and immuno-rejection associated with collagen from animal and cadaver sources are also concerns. To mimic the fine fibrous architecture of collagen and overcome the above disadvantages, our group has developed
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a novel thermally induced phase separation technique to fabricate synthetic nano-fibrous matrices [5-7]. These matrices have nano-fibers
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