Imaging by highly stable near-infrared luminescence by single-walled carbon nanotubes

we used single-walled carbon nanotubes (SWNTs) as a tool for high-bandwidth intracellular tracking. SWNTs are stiff quasi–one-dimensional tubular all-carbon nanostructures with diameters of ~1 nm and persistence lengths above 10 μm. Individual semiconducting SWNTs luminesce with large Stokes shifts in the near-infrared (900 to 1400 nm). This window is virtually free of autofluorescence in biological tissues. Fluorescence emission is highly stable with no blinking and negligible photobleaching (, allowing for long-term tracking. The fluorescence lifetime is short [~100 ps ] so that high excitation intensities allow millisecond time resolution.

Schematic of fluorescent probes. (A) Kinesin-1 Kif5c molecular motor construct. The motor was extended by a C-terminal HaloTag, binding to its counterpart linked to the DNA-wrapped SWNT. (B) SWNT bound to motor and MT track, drawn to scale. (C) SWNT-labeled kinesin motor moving along a MT embedded in an actin-myosin network.

Fakhri, Nikta, et al. “High-resolution mapping of intracellular fluctuations using carbon nanotubes.” Science 344.6187 (2014): 1031-1035.

Optical Trap

New experimental techniques are developed and further developed in our lab, with emphasis on high-resolution microscopy methods and single-molecule manipulation techniques (optical traps, atomic force microscopy), single-molecule fluorescence/spectroscopy techniques and microrheology. For example, we have explained how a first order interference effect makes it possible to detect motions of a particle trapped by an optical trap by monitoring the distribution of light intensity in the back-focal plane of the lens collecting the trapping laser light. Many subtle issues are furthermore involved in calibrating optical traps.


Mizuno, Daisuke, et al. “Nonequilibrium mechanics of active cytoskeletal networks.” Science 315.5810 (2007): 370-373.

Optical trap
Optical trap formed by a collimated laser beam focused to a diffraction-limited beam waist through a high-NA objective. To measure displacements and forces, the laser light can be collected by a condenser and directed onto a quadrant photo diode. The laser beam deflection resulting from lateral motions of the trapped bead can be understood as first-order interference effect