Controlling Cell Behavior through the Design of Biomaterial Surfaces: A Focus on Surface Modification Techniques

A key tenet of bone tissue engineering is the development of scaffold materials that can stimulate stem cell differentiation in the absence of chemical treatment to become osteoblasts without compromising material properties. At present, conventional implant materials fail owing to encapsulation by soft tissue, rather than direct bone bonding. Here, we demonstrate the use of nanoscale disorder to stimulate human mesenchymal stem cells (MSCs) to produce bone mineral in vitro, in the absence of osteogenic supplements. This approach has similar efficiency to that of cells cultured with osteogenic media. In addition, the current studies show that topographically treated MSCs have a distinct differentiation profile compared with those treated with osteogenic media, which has implications for cell therapies.

Polymer scientists, working closely with those in the device and medical fields, have made tremendous advances over the past 30 years in the use of synthetic materials in the body. In this article we will focus on properties of biodegradable polymers which make them ideally suited for orthopedic applications where a permanent implant is not desired. The materials with the greatest history of use are the poly(lactides) and poly(glycolides), and these will be covered in specific detail. The chemistry of the polymers, including synthesis and degradation, the tailoring of properties by proper synthetic controls such as copolymer composition, special requirements for processing and handling, and mechanisms of biodegradation will be covered. An overview of biocompatibility and approved devices of particular interest in orthopedics are also covered.

Efficacy of aligned poly(l-lactic acid) (PLLA) nano/micro fibrous scaffolds for neural tissue engineering is described and their performance with random PLLA scaffolds is compared as well in this study. Perfectly aligned PLLA fibrous scaffolds were fabricated by an electrospinning technique under optimum condition and the diameter of the electrospun fibers can easily be tailored by adjusting the concentration of polymer solution. As the structure of PLLA scaffold was intended for neural tissue engineering, its suitability was evaluated in vitro using neural stem cells (NSCs) as a model cell line. Cell morphology, differentiation and neurite outgrowth were studied by various microscopic techniques. The results show that the direction of NSC elongation and its neurite outgrowth is parallel to the direction of PLLA fibers for aligned scaffolds. No significant changes were observed on the cell orientation with respect to the fiber diameters. However, the rate of NSC differentiation was higher for PLLA nanofibers than that of micro fibers and it was independent of the fiber alignment. Based on the experimental results, the aligned nanofibrous PLLA scaffold could be used as a potential cell carrier in neural tissue engineering.