Cell interactions at the nanoscale: piezoelectric stimulation

Nanometric movements of the substrate on which endothelial cells are growing, driven by periodic sinusoidal vibration from 1 Hz to 50 Hz applied by piezo actuators, upregulate endothelin-1 and Kruppel-like factor 2 expression, and increase cell adhesion. These movements are in the z (vertical) axis and ranges from 5 to 50 nm and are similar in vertical extent to protrusions from the cells themselves already reported in the literature. White noise vibrations do not to produce these effects. Vibrational sweeps, if suitably confined within a narrow frequency range, produce similar stimulatory effects but not at wider sweeps. These effects suggest that coherent vibration is crucial for driving these cellular responses. In addition to this, the applied stimulations are observed to be close to or below the random seismic noise of the surroundings, which may suggest stochastic resonance is being employed. The stimulations also interact with the effects of nanometric patterning of the substrates on cell adhesion and Kruppel-like factor 2 and endothelin-1 expression thus linking cell reactions to nanotopographically patterned surfaces with those to mechanical stimulation.