  Tracking individual nano-objets in live cells during arbitrary long times is
an ubiquitous need in modern biology. We present here a method for tracking
individual 5 nm gold nanoparticles on live cells. It relies on the photothermal
effect and the detection of the Laser Induced Scattering around a NanoAbsorber
(LISNA). The key point for recording trajectories at video rate is the use of a
triangulation procedure. The effectiveness of the method is tested against
Single fluorescent Molecule Tracking in live COS7 cells on subsecond time
scales. We further demonstrate recordings for several minutes of AMPA receptors
trajectories on the plasma membrane of live neurons. SNaPT has the unique
potential to record arbitrary long trajectory of membrane proteins using
non-fluorescent nanometer sized labels.
