99mTc-glycopeptide: Synthesis, biodistribution and imaging in breast tumor-bearing rodents

This study was aimed to develop a glycopeptide (GP) to be used as a carrier for anti-cancer drug delivery. GP was synthesized by conjugating glutamate peptide and chitosan using carbodiimide as a coupling agent. Elemental analysis and capillary electrophoresis confirmed the purity was >95%. GP was labeled with sodium pertechnetate (Na99mTcO4) for in vitro and in vivo studies. Rhenium-GP was synthesized to support the binding site of 99mTc at the glutamate positions 3–5. In vitro cellular uptake of 99mTc-GP was performed in breast cancer cells. Cytosol had 60% whereas nucleus had 40% uptake of 99mTc-GP. When cancer cells were incubated with glutamate or aspartate, followed by 99mTc-GP, there was decreased uptake in cells treated with glutamate but not aspartate. The findings indicated that cellular uptake of 99mTc-GP was via glutamate transporters. In addition, 99mTc-GP was able to measure uptake differences after cells treated with paclitaxel. Biodistribution and planar imaging were conducted in breast tumor-bearing rats. Biodistribution of 99mTc-GP showed increased tumor-to-tissue ratios as a function of time. Planar images confirmed that 99mTc-GP could assess tumor uptake changes after paclitaxel treatment. In vitro and in vivo studies indicated that GP could target tumor cells, thus, GP may be a useful carrier for anti-cancer drug delivery.