The purpose of this study was to investigate the usefulness of radiolabelled polyethylene glycol (PEG) I in reticuloendothelial scintigraphy as a better agent than existing radiopharmaceuticals, Tc-99m Sulfur-M-colloid and Tc-99m Phytate. The properties and characterization of polyethylene glycol for protein conjugation and encapsulation of liposomes are well established. The pharmacological benefits of PEG modification are also extended to other compounds. PEG adriamycin has a high anticancer activity and reduced toxicity when compared with unmodified adriamycin. Various problems posed by liposomes are also alleviated by PEG modification. PEG was labeled with Tc-99m by simple reduction method using stannous chloride dihydrate as a pertechnetate reductant whereas sulfur colloid and phytate were labeled as reported earlier. The labeling achieved was consistently more than 98%. Biokinetic behavior of the tracers was defined in animals after the radioligand had been evaluated for various in vitro and in vivo quality control parameters. Scintigraphy of Tc-99m-PEG was carried out at different time intervals under planar Gamma camera. Significant accumulation of the tracer, as early as 10 min post administration suggests the utility ofTc-99m-PEG for RE scintigraphy. After critical evaluation of various parameters data suggest its comparativity with Tc-99m sulfur colloid and Tc-99m phytate in all aspects.
Tc-99m-PEG, RES Scintigraphy, Biokinetics
