For in vivo trafficking and analysis of excretion levels, biotinylated GQDs were intraperitoneally infused. To determine the remaining amounts of GQDs, mesentery tissue was collected after mice were sacrificed. After the tissue was minced and homogenized, it was incubated with FITC-conjugated anti-biotin antibody (BD Biosciences). Fluorescence was assessed using flow cytometric analysis. In addition, urine samples were also collected at designated time points to investigate excretion as described in a previous report (14 (link)). The concentrations of the GQDs in urine samples were measured by the Quant*Tag Biotin Kit (Vector Laboratories Inc., Burlingame, CA, USA).