Introduction: Constipation is affecting a quarter of human population at any one time in all age groups. However, a proper gamma scintigraphic study of whole GI transit is rarely performed in Malaysia due to the lack of suitable radiopharmaceutical. Hence, this study was taken to develop a suitable radiotracer formulation for gamma scintigraphy study of whole gastric-intestinal transit. Methods: The biocompatible polystyrene (PS) incorporated with 152Sm2O3 (5%, w/v) will be used to synthesize the radiotracer. The 152Sm-labelled PS particles was neutron activated to 153Sm in a nuclear reactor for 5 minutes. Characterization of the physicochemical properties, gamma spectrometry and in-vitro radiolabeling studies in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were carried out to study the properties and stability of the radiotracer before and after neutron activation. Results: Scanning electron microscope (SEM) and particle size analysis showed that size, shape and surface morphology of the particles remained after neutron activation. The synthesized 153Sm-labelled PS radiotracer (100 mg) particles achieved an activity of 3.7 MBq after 46 hrs. As indicated by the gamma spectrometry result, there is no long half-life radioimpuirties present in the samples. The 153Sm-labelled PS particles achieved radiolabeling efficiency of more than 95% in both SGF and SIF over 72 hrs. Conclusions: A 153Sm-labelled radiotracer particles formulation has been successfully developed from biocompatible PS. The proposed formulation has the advantage of cheaper, easier to be produced and reduced radiation exposure to staff. Further studies are required to validate the in-vivo performance of 153Sm-labelled formulation for assessing GI motility and transit in clinical use.