Fig. 70. Determining the cytosolic stability of small DNA nanostructures in cellula. (A) Surface-adherent mammalian cells were individually injected with DNA structures into the cytosol. The fluorescence intensity and FRET between the three dyes was measured using confocal microscopy over the course of 60 min (B) DNA nanocrosshair with four copies of the 3-dye FRET network arranged linearly on each arm. Steady-state fluorescence spectra of the nanocrosshair with all dyes present versus individual dyes only (excitation wavelength 466 nm). (C) DNA tetrahedron with one copy of the three-dye FRET network arranged with one dye per edge. Steady-state fluorescence spectra of the tetrahedron with all dyes present versus individual dyes only (excitation wavelength 466 nm). Colored arrows in the schematics indicate D → Relay (R) and R → A FRET steps. Representative four-channel confocal image of COS-1 cells injected with (D) the nanocrosshair and (E) the tetrahedron after t = 60 min. Reproduced with permission from ref. 360 Copyright 2022 American Chemical Society.