A comparison study of detecting gold nanorods in living cells with confocal reflectance microscopy and two-photon fluorescence microscopy

Two-photon fluorescence microscopy and confocal reflectance microscopy were compared to detect intracellular gold nanorods in rat basophilic leukaemia cells. The two-photon photoluminescence images of gold nanorods were acquired by an 800 nm fs laser with the power of milliwatts. The advantages of the obtained two-photon photoluminescence images are high spatial resolution and reduced background. However, a remarkable photothermal effect on cells was seen after 30 times continuous scanning of the femto-second laser, potentially affecting the subcellular localization pattern of the nanorods. In the case of confocal reflectance microscopy the images of gold nanorods can be obtained with the power of light source as low as microwatts, thus avoiding the photothermal effect, but the resolution of such images is reduced. We have noted that confocal reflectance images of cellular gold nanorods achieved with 50 mu W 800 nm fs have a relatively poor resolution, whereas the 50 mu W 488 nm CW laser can acquire reasonably satisfactory 3D reflectance images with improved resolution because of its shorter wavelength. Therefore, confocal reflectance microscopy may also be a suitable means to image intracellular gold nanorods with the advantage of reduced photothermal effect.