No abstract

D-Serine is a physiological coagonist of the N-methyl D-aspartate (NMDA) type of glutamate receptor-a key excitatory neurotransmitter receptor in the brain. D-Serine appears to be a part of the synapse through a variety of transporters located on both neurons and astrocytes. The development of 99mTc radiolabeled amino acid based radiopharmaceuticals for imaging a variety of tumors has found to be useful in diagnostic imaging. Diethylene triamine penta acetic acid (DTPA) is one of the most well-known chelating reagent for the production of stable complexes with various heavy metal ions. We have synthesized [DTPA-bis(D-ser)] in 90% yield and analyzed the chelate by spectroscopic techniques. The DBDSC chelate binds to 99mTc with high efficiency at ambient temperature. The resulting chelate is stable under physiological conditions (37oC, pH=7.4) for at least 24 h after radiocomplexation. The receptor binding studies of 99mTc-[DTPA-bis(D-ser)] in established lung adeno carcinoma A549 exhibited Kd value to be 26nM. A549 Tumor in athymic mice was accumulated in the γ-images. The major accumulation of the radiotracer was observed in tumor, followed by kidneys. 99mTc-[DTPA-bis(D-ser)] has promising utility as SPECT-radiopharmaceutical.

Novel and facile synthesis of a triazole based bisconjugated triazaspirodecanone as a potential MRI contrast agent.

Rational design of a new class of MR (magnetic resonance) contrast agent for enhance relaxivity has been described. The click chemistry was employed to incorporate two moieties of 1‐(2‐methoxyphenyl)piperazine and serinol as a linker to enhance the affinity at the recognition sites. The designed ligand was attached to DO3A to synthesize DO3A‐serinol‐bis‐MPP (SBMPP) in 89 % yield. Gd‐DO3A‐SBMPP showed enhanced relaxivity r1 of 10.85±0.04 mM−1s−1 as compare to known gadolinium based contrast agents in clinics. The potentiometric titration of gadolinium loaded SBMPP exhibited strong selectivity for Gd3+ over physiological metal ions such as Zn2+ and Cu2+. Thus, the synthesis of bis‐conjugate could be observed as novel, instructive and initial proof of concept for the synthesis of MR contrast agent with enhanced relaxivity. The preliminary findings show the good biocompatibility and potential functionalities of MPP analogue to target brain regions through MRI.