Limitation of Q dot as an in vivo cell tracer

Cell viability and survival are the most important factors in tissue engineering because cells that are transplanted in vivo reconstruct the injured or diseased site. Estimation of cell survival after transplantation and reconstruction is important for the confirmation of efficiency and of the need for cell transplantation, and in understanding the roles of the transplanted cells during tissue reconstruction. Therefore, several methods to trace transplanted cells such as radiolabeling, fluorescence labeling, and gene transfection, have been developed. However these techniques have short half-lives, weak fluorescence intensity or low efficiency, and they are expensive or hard to be used. Quantum dot(Q dot) is a highly stable inorganic fluorophore with remarkable resistance to photobleaching. It is easy to be used, has long-lived intense and unchanged fluorescence emission, and is photostable for prolonged periods after tissue fixation. However, it is unclear how long Q dot labeled cells can be traced in vivo. In this study, we transplanted Q dot labeled cells into canine trachea and used PKH26 fluorescence labeling for comparison. After three months, we compared the fluorescence of Q dot and PKH26 labeled cells in the reconstructed tissue. We found that the Q dot was not suitable for long term tracing in vivo.