High precision cell surgery with nanoparticles?

Irradiation of nanoabsorbers with pico- and nanosecond laser pulses could result in thermal effects with a spatial confinement of less than 50 nm. Therefore absorbing nanoparticles may be used for creating controlled intracellular effects. Conjugates of colloidal gold and alkaline phosphatase (aP) are presented as a model system for investigating protein inactivation in the vicinity of strongly absorbing nanoparticles. aP was coupled either directly or via antibodies to 15 nm gold particles. These conjugates were irradiated with picosecond pulses emitted by a frequency doubled Nd:YLF laser. Denaturation was detected as a loss of protein function with the help of a fluorescence assay. Irradiation with 10⁴ pulses resulted in the inactivation of aP at an irradiance of 50 mJ/cm² per pulse when the protein was coupled directly to the particles. With similar irradiation parameters a significant inactivation of aP which was coupled not directly but via two antibodies to the gold, was not observed. This shows that inactivating proteins with nanoabsorbers under irradiation with picosecond laser pulses is possible with a high spatial confinement. However, from these experiments it is difficult to determine whether the aP was destroyed thermally or whether it was inactivated by a photochemical reaction. Therefore, further experiments are needed to elucidate the damage mechanisms.