Speaker
Description
Background/goal/objective of the study
This study aimed to synthesize and characterize of N-(2,4,6-trimethylphenylcarbamoylmethyl)iminodiacetic acid (TMIDA) and then radiolabel it with technetium-99m by direct technique using sodium didithionite as reducing agent. The labeling parameters including TMIDA concentration, sodium didithionite concentration, pH of the reaction mixture, reaction temperature and reaction time were optimized.
Methodology
Synthesis
N-(2,4,6-trimethylphenylcarbamoylmethyl)iminodiacetic acid (TMIDA) was prepared in two steps. The first one involves the synthesis of ω-chloro-2,4,6-trimethylacetanilide and the second step involves the synthesis of TMIDA by reaction of ω-chloro-2,4,6-trimethylacetanilide (10 mmol) and iminodiacetic acid (10 mmol) in 50% aqueous ethanol was refluxed for 5 h at 85°C and adjusted to pH 11-12 with 10% NaOH every hour. The mixture was cooled to room temperature and the ethanol was removed using rotary evaporated. The mixture was extracted three times with diethyl ether. The aqueous layer was then adjusted to pH 2-3 with HCl and the precipitate was formed on cooling. The pecipitate was filtered off, dried and recrystallized with ethanol to give TMIDA (Yield: 23.5 % and Mp: 218-221 °C).
Labeling procedure study
TMIDA was labeled with technetium-99m by the direct technique using sodium dithionite (Na2S2O4) as a reducing agent as shown in scheme 2. To 100 μl of freshly eluted 99mTcO4- (400 MBq), the required concentration of solid sodium dithionite was added directly with continuous stirring followed by immediate addition of the required TMIDA concentration, which dissolved in 0.1 M NaOH. The pH of the preparation was adjusted followed by incubation at room temperature at specific reaction time. TMIDA concentration, Na2S2O4 concentration pH, reaction time and temperature were studied as factors affecting labeling efficiency. Each factor studying experiment was repeated three times.
Results and discussion
Synthesis of N-(2,4,6-trimethylphenylcarbamoylmethyl)iminodiacetic acid (TMIDA)
Synthesis of TMIDA was accomplished according to the reaction sequence in two steps. The first one involves the reaction between 2,4,6-trimethylaniline derivative and chloroacetyl chloride to give ω-chloro-2,4,6-trimethylacetanilide.
The second step involves condensation reaction between ω-chloro-2,4,6-trimethylacetanilide and iminodiacetic acid at alkaline pH in ethanol for 5 h to give TMIDA.
Characterization of TMIDA
The synthesized compound, TMIDA, was confirmed by IR, mass and 1H-NMR spectra
IR spectrum of TMIDA
Radiolabeling of TMIDA
Factors affecting the percent radiochemical yield of 99mTc–TMIDA complex
Biodistribution of 99mTc–TMIDA complex
Table 1. In-vivo biodistribution study of 99mTc-TMIDA complex in mice at different time intervals p.i., (% ID/g organ ± S.E., n = 3)
Conclusion
TMIDA can be synthesized and radiolabeled using an easy and cheap method, considering the biodistribution data results, 99mTc-TMIDA can be used as a hepatobiliary imaging agent for an evaluation of the functional status of the hepatocytes and the patency of the biliary duct.
