Metal-ion speciation in blood plasma incorporating the water-soluble polymer, polyethyleneimine functionalised with methylenephosphonate groups, in therapeutic radiopharmaceuticals

摘要

A water-soluble polymer, polyethyleneimine functionalised with methylene phosphonate groups (PEI-MP) and labelled with Tc-99m, has shown selective uptake into bone tumours. Apparent formation constants for the complexation of important blood plasma metal-ions and metal-ions of radionuclides used in therapeutic radiopharmaceuticals (excluding Tc) with PEI-MP were measured potentiometrically. These were added to the ECCLES data base in order to construct a blood plasma model for PEI-MP. From this model it could be predicted that the polymer would not deliver the therapeutic radionuclides Sm-153, Ho-166, Pb-212, Pb-213 and Sr-89 to bone. This was clinically verified for Sm-153. However good uptake of Tc-99m-PEI-MP could be demonstrated in dogs. Due to the similar chemistry of Re as compared to Tc, it can be expected that PEI-MP labelled with Re-186 or Re-188 could result in effective therapeutic radiopharmaceuticals for bone cancer. [References: 28]