Evaluation of 99mTc labelled monodisperse polystyrene/polyacrylate latex particles for the study of colon transit and morphology.

A new radiopharmaceutical for the study of colon transit time and morphology is proposed. Polymeric latexes, as monodisperse polymeric spheres (1-10 microns in diameter), were prepared by a coaxial dispersion polymerization of styrene and dimethylaminoethyl-methacrylate (DMAEA). They were labelled with 99mTc by the tin reduction method with high efficiency (greater than 99%). The label was stable up to 48 h at pH values of 1-8 at room temperature. Scintigrams obtained in rabbits after oral administration of 37 MBq of 99mTc-latex particles showed that greater than 90% of the dose remained in the gastrointestinal tract. The cumulative faecal excretion was 8.6 +/- 6.7 in 24 h and 21.3 +/- 13.8% in 48 h. In human studies the colon was well visualized at 4 h. The thyroid and the urinary bladder were not detected on scintigrams, indicating the stability of the label in vivo. Our results demonstrated that the radiopharmaceutical developed in the present study was ideal for the intended purpose.