Metal Based Imaging Probes of DO3A-Act-Met for LAT1 Mediated Methionine Specific Tumors : Synthesis and Preclinical Evaluation

99mTc-Methionine Gold Nanoparticles as a Promising Biomaterial for Enhanced Tumor Imaging

Methionine-gold nanoparticles (MGNs) was synthesized by conjugating methionine via dithiocarbamate linkage to gold nanoparticles (GNPs), prepared simultaneously by one pot modified Burst method. Formation of MGNs was confirmed by UV-visible spectroscopy and appearance of new IR bands in the range of 934 cm^-1 to 1086 cm^-1 and shifting of N-C,S-S and S-C-S stretching, confirms the involvement of '-S-C-S-' group of methionine dithiocarbamate with GNPs. The presence of Au in MGNs was confirmed by EDXA spectrum, whereas TEM, SAED and XRD revealed that MGNs are nanocrystalline (~13 nm) and have face-centered cubic structure. MGNs was labeled with ^99mTc (TMGNs) with radiolabeling efficiency greater than 99% using 300 μg of stannous chloride, pH 7 and 90.6 MBq of ^99mTcO₄. The stability data showed that the conjugate will remain infrangible in systemic circulation and in acidic microenvironment of tumor. The blood kinetic profile of TMGN in rabbits and biodistribution studies in EAT tumor bearing balb/c mice showed longer in vivo circulation and slow clearance compared to radiolabeled methionine (TM). TMGN demonstrated nearly three-fold higher tumor accumulation (3.9 ± 0.35% ID/g), 2-fold lower tumor saturation dose (1.0 μg/kg) and higher tumor retention compared with TM. Data showed that the TMGN tumor: blood ratio (1.05) is nearly 2.5-fold higher than TM (0.44), whereas TMGN tumor: muscle ratio (97.5) is nearly 8-fold higher than TM (11.6). In conclusion, TMGN showed excellent tumor targeting and has promising prospects as a SPECT-radiopharmaceutical for imaging tumors.

Picolinic acid based acyclic bifunctional chelating agent and its methionine conjugate as potential SPECT imaging agents: syntheses and preclinical evaluation

Syntheses and preclinical evaluation of picolinic acid based acyclic bifunctional chelating agent and its methionine conjugate as SPECT imaging agents.

Evaluation of methionine and tryptophan derivatised vehicles: Met-ac-TE3A/Trp-ac-TE3A for tumor imaging

Two novel amino acid (methionine and tryptophan) appended 1,4,8,11-tetraazacyclotetradecane triacetate (TE3A) compounds Met-ac-TE3A and Trp-ac-TE3A were synthesized and evaluated for imaging applications.