Evaluation of 99mTc-sulfadiazine as Bacillus microorganisms infection imaging agent using animal model

Bacterial infection is one of the vital sources of morbidity and mortality. The development of single photon emission computed tomography [SPECT] radiotracer agents using antibiotics, for targeting in-vivo bacteria, helps in antibiotic dose calibration, targeted infection therapy and reduction in mortality rate. The aim of this study was to appraised [99m]Tc-labeling sulfadiazine as a radiopharmaceutical for bacillus infections imaging. Radiolabeling of sulfadiazine with technetium-99m was carried out by subsequent addition of 1.5 mL aqueous solution of sulfadiazine [1mg/mL], 120Mug stannous tartrate, gentistic acid as stabilizing agent and 185 MBq normal saline solution of 99mTcO4 -1 [pertechnetate] at pH = 5. The reaction mixture was incubated for 40 min at room temperature with light stirring. The quality control analysis [ITLC-SG and paper chromatography analysis] revealed 98% labeling yield. Biodistribution and scintigraphic study was carried using bacillus bacterial infection induced New Zealand white rabbits. Due to the ease of [99m]Tc-sulfadiazine conjugation method, high labeling efficiency, shelf stability [>95% up to 6h], blood serum stability [90% up to 6h] and high uptake in the infected muscle [T/NT =2.21 at 1h], [99m]Tc-SDZ could be used as radiopharmaceutical of choice for further pre-clinical and clinical studies

Enzymatic degradation study of 111In-labeled minigastrin peptides using cathepsin B enzyme and AR42J cancer cell line for the development of neuroendocrine tumor imaging radiopharmaceuticals

Neuroendocrine tumors [NET] are the rare tumors which often impose graveyard threat. These tumors are characterized by the overexpression of various G-protein coupled receptors including cholecystokinin [CCK] receptors-1 and 2 [A or B]. Minigastrin peptides are being investigated for theranostic purposes of CCK-2 receptor positive NET. The minigastrin analogue [APHO70] was modified by engineering enzyme susceptible tetrapeptide sequence into APHO70 peptide to reduce the random degradation by lysosome enzymes which pave the way to random trafficking in patient's body and dipeptide addition at c-terminus. All the four modified minigastrin peptides [MG-CL1-4] were investigated for lysosome cathepsin B [catB] enzyme susceptibility and fate into AR42J cancer cell line. The indium-111 labeled MG-CL1-4 peptides were also studied for target [tumor] and non-target saccumulation by using tumor induced mice. The RP-HPLC analysis result showed nonspecific cleavage of standard 111In-APH070 and 111In-MGCL1 while specific cleavage was noted in case of 111In-MGCL [2-4]. The effect of specific and non-specific cleavage on biodistribution in tumor induced nude mice model indicates the promising accumulation of 111In-MGCL2, 111In-MGCL3, and 111In-MGCL4 radiotracers while 111In-MGCL1 showed less accumulation. 111In-MGCL2 and 111In-MGCL3 showed highest target-to-kidney ratio [T/K] i.e. 1.71 and 1.72, respectively whereas standard compound showed T/K 1.13. In conclusion, the two indium-111 labeled analogues i.e. 111In-MGCL2 and 111In-MGCL3 showed promising sensitivity for tumor and could be tested for further investigation to reach pre-clinical studies