Fig. 6: ROCS microscopy of particle binding on a thermal noise level.

a TIR-ROCS images (10 ms integration time) of J774 macrophages before exposure of 100 nm glass particles, 1 min after injection and 3 min after injection. ImageJ edge finder increases visibility and high particle densities. b A 100 nm glass particle scatters less than 0.6% of incident photons. 0.03 · 0.6% of scattered photons reach the detector carrying information about particle motions. c More than 100 particles are tracked automatically within region ROI 1 after 1 and 3 min. A particular particle is marked by a red and blue circle. d Position fluctuations of particles bound to the cell surface are analyzed by the position fluctuation standard deviations σ(t). e Temporal evolution of mean fluctuation widths \(\bar{\sigma }\) and binding strengths \(\bar{\kappa }\) of ca. 260 particles after t = 1 min, 5 min and 10 min. Within 10 min, the mean binding strength \(\bar{\kappa }\) has increased about fivefold. Errors bars indicate STD. f Left: image of unlabeled cells with fluorescent-labeled particles recorded with both TIR-ROCS (at 100 Hz) and TIR-F (at 2 Hz). Particles (see 4 white/green arrows) bound to cells are visible with TIR-F (in green, shifted) and with TIR-ROCS (in white/orange). Right: ROCS image of cells with particles. ROI 3 with bright particles in front of cellular structures allowing precise 100 Hz particle tracking. Source data are provided as a Source Data file.