Automated Closed-System Expansion of Pluripotent Stem Cell Aggregates in a Rocking-Motion Bioreactor.

Pluripotent stem cell suspension aggregates have proven to be an efficient and phenotypically stable means for expansion and directed differentiation. Bioreactor systems with automation of perfusion, fluidization, and gas exchange are essential for scaling up pluripotent stem cell cultures. Since stem cell pluripotency and differentiation are affected by both chemical and physical signals, we investigated a low-shear method for the expansion of cells in a rocking-motion bioreactor.

Plasma membrane temperature gradients and multiple cell permeabilization induced by low peak power density femtosecond lasers.

Calculations indicate that selectively heating the extracellular media induces membrane temperature gradients that combine with electric fields and a temperature-induced reduction in the electropermeabilization threshold to potentially facilitate exogenous molecular delivery. Experiments by a wide-field, pulsed femtosecond laser with peak power density far below typical single cell optical delivery systems confirmed this hypothesis. Operating this laser in continuous wave mode at the same average power permeabilized many fewer cells, suggesting that bulk heating alone is insufficient and temperature gradients are crucial for permeabilization.