B.  Confocal imaging studies
To better understand how cells respond to the nanopillars, high-resolution confocal microscopy was used to image NIH 3T3 cell cytoplasm while the cells grew on the nanopillars. The spacing between the nanopillars is critical for better cell- pillar interaction. If the pillars were dense then it resulted in “bed of nails” effect on cells and cells remained suspended on the top of the pillar and did not conform around the pillars. We chose an optimized spacing of over 10µm for efficient cell penetration. Fig. 3 shows the interaction of NIH 3T3 cells on the pillars. The images clearly depict the cytoplasm exclusion effect  (dark squares/rectangles) where the nanopillars are present. The images also show that cells were penetrated completely by the nanopillars. The presence of cytoplasmic exclusion effect may mean – (a) cell membrane penetration on the nanopillars or (b) wrapping of cell membrane tightly around the nanopillar without membrane penetration.  To address this question and better understand the cell membrane conformation on the nanopillars, particularly whether nanopillars can penetrate the cell membrane, SEM imaging was done.