The effect of sinusoidal AC electric stimulation of 3D PCL/CNT and PCL/β-TCP based bio-composites on cellular activities for bone tissue regeneration

Various physical stimulations have been widely applied to tissue regenerative applications. In particular, for bone tissue regeneration, several experimental studies have reported that electric stimulation can enhance the mineral formation in cultured osteoblasts and even alter the pattern of gene expression, promoting bone tissue formation. However, to date, for rapid-prototyped polycaprolactone (PCL)-based composites of pure PCL and dispersed materials including carbon nanotubes and beta-tricalcium phosphate (TCP), the effect of electric stimulation on various cellular activities has not been analyzed. Here, a sinusoidal AC electric field (55 +/- 8 mV cm(-1) and 60 Hz) between parallel electrodes was applied to three-dimensional scaffolds (pure PCL, PCL/CNT-0.2 wt%, and PCL/beta-TCP-20 wt%) cultured with osteoblast-like cells (MG63) 30 min per day for 14 days. When exposed to electric stimulation, alkaline phosphatase and calcium mineralization were enhanced in all scaffolds, and the PCL/beta-TCP scaffold in particular showed the highest improvement in bone mineralization compared with other scaffolds. In this work, we surmised that the improvement may have been due to chemical precipitation of the calcium ions from the PCL/beta-TCP scaffolds. To evaluate the effect of the released calcium ions from the composite scaffold, we observed the cellular behavior (cellular contraction) of proliferated cells under electric stimulation. The results indicate that in addition to the applied electric field conditions, the scaffold materials are also an important parameter for successful electric stimulation.