Synthesis and biodistribution of a novel 99mTc complex of HYNIC-conjugated metronidazole as a potential tumor hypoxia imaging agent

Abstract

A conjugate of 6-hydrazinopyridine-3-carboxylic acid (HYNIC) with the amino analogue of metronidazole (MN) was synthesized through a multiple-step reaction. HYNIC-MN could be labeled easily and efficiently with 99mTc using N-(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)glycine (tricine) and ethylenediamine -N,N′-diacetic acid (EDDA) as coligands to form the 99mTc–HYNIC–MN complex in high yield (>95%). Its partition coefficient indicated that it was a good hydrophilic complex. The tumor cell experiment showed that the 99mTc–HYNIC–MN complex had a certain hypoxic selectivity. The biodistribution studies of 99mTc–HYNIC–MN in Kunming mice bearing S180 tumor showed a favorable tissue distribution profile with high tumor uptake, and low or negligible accumulation in non-target organs, suggesting 99mTc–HYNIC–MN would be a novel potential tumor hypoxia imaging agent.