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

• Femtosecond lasers can transfect a single cell through optoporation.
• Multiple cells are transfected with much lower power densities at 1550 nm.
• Calculations show that temperature gradients contribute to the mechanism.
• These mechanisms resemble those also involved in microwave biological interactions.

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. This work suggests promising opportunities for a high throughput, low cost, contactless method for laser mediated exogenous molecule delivery without the complex optics of typical single cell optoinjection, for potential integration into microscope imaging and microfluidic systems.