Artificially-induced organelles are optimal targets for optical trapping experiments in living cells

Optical trapping supplies information on the structural, kinetic or rheological properties of inner constituents of the cell. However, the application of significant forces to intracellular objects is notoriously difficult due to a combination of factors, such as the small difference between the refractive indices of the target structures and the cytoplasm. Here we discuss the possibility of artificially inducing the formation of spherical organelles in the endoplasmic reticulum, which would contain densely packed engineered proteins, to be used as optimized targets for optical trapping experiments. The high index of refraction and large size of our organelles provide a firm grip for optical trapping and thereby allow us to exert large forces easily within safe irradiation limits. This has clear advantages over alternative probes, such as subcellular organelles or internalized synthetic beads.This research was partly funded by the Spanish Ministry of Education and Science (FIS2010-16104, BFU-2009-07186 and BFU2012-33932) as well as by the regional authorities of Catalonia – ACC1Ó (VALTEC G614828324059231). C. L.-Q. acknowledges an APIF grant from the University of Barcelona and a A. F. an FI grant from the Generalitat de Catalunya (regional authorities of Catalonia).Peer reviewe