Acetaminosalol labeling reaction with technetium-99m was optimized, and the radiocomplex was obtained in a high radiochemical yield of 98.9 +/- 0.6% and high stability (>30 h). The tracer was characterized, and its binding to the PPARgamma receptor was assessed in silico. To reduce radiation exposure to non-target organs and increase accumulation in the colon, the tracer was formulated as pH-sensitive microspheres with a mean particle size of 201 +/- 2.1 mum, a polydispersity index of 0.18, a 25.3 +/- 3.6 zeta potential, and 98.6 +/- 0.33% entrapment efficiency. The system suitability was assessed in vivo in normal and ulcerative rats, and the biodistribution profile in the colon showed 56.5 +/- 1.4% localization within 4 h. Blocking study suggested the selectivity of the tracer to the target receptor. Overall, the reported data encouraged the potential use of the labeled microspheres to target ulcerative colitis.