Characterization and bioevaluation of radioiodinated oseltamivir phosphate for inflammation imaging as a new perspective

This study explores the dual antibacterial and imaging capabilities of radioiodinated Oseltamivir phosphate [¹³¹I]IodoTam for distinguishing infection from sterile inflammation. Oseltamivir phosphate (Tamiflu) was successfully labeled with iodine-131 via electrophilic substitution, achieving a high radiochemical yield (96.5 ± 1.2 %) under optimal conditions: 100 μg Tam, 100 μg chloramine-T, pH 4, 30-min incubation at room temperature, 25 °C. Quality control confirmed tracer purity through TLC and HPLC techniques. The in vitro antibacterial activity of Tamiflu was evaluated using a standard agar disk diffusion test against Staphylococcus aureus. A clear dose-dependent inhibition was observed, with zones measuring 10–24 mm in diameter at increasing Tamiflu doses (5–50 μg), exceeding the positive control (vancomycin 50 μg, 16 mm zone). Additionally, bacterial binding tests showed substantial uptake of [¹³¹I]IodoTam by S. aureus (56 ± 0.32 %), highlighting its potential targeting ability. In vivo, bioevaluation revealed that the [¹³¹I]IodoTam tracer accumulated more in infected tissue (T/NT = 6.6 at 2 h post-injection) compared to sterile inflamed tissue (T/NT = 2.71 at 2 h post-injection). It was also significantly higher than the ratio of commercially available ^99mTc-ciprofloxacin (T/NT = 3.18 at 1 h post-injection). These findings suggest that [¹³¹I]IodoTam could be a valuable tool for differentiating bacterial infections from sterile inflammation, demonstrating its potential as a dual-action antiviral and antibacterial agent for imaging and therapy in infectious diseases.