Hemifusion of cells using femtosecond laser pulses

Attachment of single cells via hemifusion of cellular membranes using femtosecond laser pulses is reported in this manuscript. This is a method to attach single cells using sub-10 femtosecond laser pulses, with 800 nm central wavelength delivered from a Ti:Sapphire laser is described. A fluorescent dye, Calcein AM, was used to verify that the cell’s cytoplasm did not migrate from a dyed cell to a non-dyed cell, in order to ascertain that the cells did not go through cell-fusion process. An optical tweezer was used in order to assess the mechanical integrity of the attached joint membranes. Hemifusion of cellular membranes was successful without initiating full cell fusion. Attachment efficiency of 95% was achieved, while the cells’ viability was preserved. The attachment was performed via the delivery of one to two trains of sub-10 femtosecond laser pulses lasting 15 milliseconds each. An ultrafast reversible destabilization of the phospholipid molecules in the cellular membranes was induced due to a laser-induced ionization process. The inner phospholipid cell membrane remained intact during the attachment procedure, and cells’ cytoplasm remained isolated from the surrounding medium. The unbounded inner phospholipid molecules bonded to the nearest free phospholipid molecule, forming a joint cellular membrane at the connection point. The cellular membrane hemifusion technique can potentially provide a platform for the creation of engineered tissue and cell cultures.