Oral nanoparticles play an important role in improving the bioavailability of poorly water-soluble drug. It is necessary to investigate the interaction of nanoparticles with intestinal epithelial cells. In general, nano-carriers labeled with fluorescent probes are always chosen. However, fluorescent dye via physical loading may leak in complex biological environment and lose its function to trace the transport behavior ofnanoparticles. Fluorescent probes chemically coupled on the nanoparticles may alter the properties of nanoparticles. Therefore, a facile and exact detection method is required to trace intracellular and transcellular pathways of oral nano-medicines. In our study, gold nanoparticles were selected as nano-carriers owing to their unique characteristics of light scattering. The feasibility of gold nanoparticle detection through reflected light signal was tested in different situations, including gold nanoparticle solution, cell and animal level As a result, high resolution image of gold nanoparticles could be detected through reflection mode by confocal laser scanning microscope （CLSM） when excited at a wavelength of 633 nm. The reflected light signal of gold nanoparticles could be clearly shown in different intestinal epithelial cells no matter when they were in fixed or in living state, and the intracellular trafficking and distribution of gold nanoparticles were clearly shown in three-dimensional image. Meanwhile, this method was also applied to rat small intestine in vivo. In conclusion, we believed that this technique was a convenient and precise way to explore the transport behavior of gold nanoparticles via oral administration without fluorescent dye.
