A method of tracking growth and metastasis of specific cells in vivo is disclosed. The method of the disclosure includes culturing the specific cells in a medium containing 0.1 μM to 10 mM nanoparticles as a biomarker for X-rays, such that the specific cells carry the nanoparticles, administering the specific cells carrying the nanoparticles to a subject, irradiating the subject by an X-ray source, and determining the growth and metastasis of the specific cells by X-ray images of the nanoparticles in the subject.
