Bharat R. Sarkar

Synthesis and evaluation of 99mTc-moxifloxacin, a potential infection specific imaging agent

To synthesize and evaluate a (99m)Tc labeled fluroquinolone, moxifloxacin as a potential bacteria specific infection imaging agent. A radiolabeling formulation including moxifloxacin, [Moxicip(TM) injection, Cipla] (4mg), sodium pertechnetate and stannous chloride (5microg) gave the best radiolabeling efficiency and moderately stable labeled (99m)Tc moxifloxacin. Quality control analysis was performed by ITLC. Rats and rabbit with infectious intramuscular lesions induced in either thigh with E. Colli were used for studying biodistribution and scintigraphic imaging of the labeled product. Imaging of an infected thigh of a rabbit was performed with a gamma-camera at various intervals. A good radiolabeling efficiency (90-95%) was obtained within 5min. No purification of the labeled product was done. Labeled product retained its radiochemical purity upto 85% even at 3h. Scintigraphy showed uptake in infectious lesions at 30min after injection, which remains constant upto 3h study. Abscess-to-muscle ratios were 1.60, 1.62, 1.74 and 1.75 at 30min, 1, 2 and 3h, respectively. Thus, (99m)Tc moxifloxacin, a new potential radiopharmaceutical has been developed for infection imaging agent.

Preparation, Characterization, and Biodistribution of Letrozole Loaded PLGA Nanoparticles in Ehrlich Ascites Tumor Bearing Mice

Letrozole (LTZ) incorporated PLGA nanoparticles were prepared by solvent displacement technique and characterized by transmission electron microscopy, poly-dispersity index and zeta potential measurement. Radiolabeling of free LTZ and LTZ-loaded PLGA NPs was performed with technetium-99m with high labeling efficiency. The labeled complex showed good in vitro stability as verified by DTPA challenge test. The labeled complexes also showed significant in vivo stability when incubated in rat serum for 24 h. Biodistribution studies of (99m)Tc-labeled complexes were performed after intravenous administration in normal mice and Ehrlich Ascites tumor bearing mice. Compared to free LTZ, LTZ-loaded PLGA NPs exhibited significantly lower uptake by the organs of RES. The tumor concentration of LTZ-loaded PLGA NPs was 4.65 times higher than that of free LTZ at 4 h post-injection. This study indicates the capability of PLGA nanopartcles in enhancing the tumor uptake of letrozole.

99mTc-labeling of ciprofloxacin and nitrofuryl thiosemicarbazone using fac-[99mTc(CO)3(H2O)3] core: evaluation of their efficacy as infection imaging agents

The aim of this study was to radiolabel ciprofloxacin (Cip) and nitrofuryl thiosemicarbazone (NFT) with the fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) core and to evaluate the ability of the radiopharmaceuticals as tracers in detecting sites of infection. Cip and NFT were radiolabeled with the fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) core and characterized by RHPLC. The stabilities of the preparations were evaluated in saline and rat serum. In vitro binding studies of the radiopharmaceuticals with S. aureus were performed. Biodistribution studies were conducted at different time points after injecting (i.v.) the radiopharmaceuticals in rats (intramuscularly infected with S. aureus) as well as in rats with sterile inflammation. To assess the infection targeting capacity of (99m)Tc-tricarbonyl ciprofloxacin and nitrofuryl thiosemicarbazone, (99m)Tc(v)O-Cip and (99m)Tc(v)O-NFT were used as control. Scintigraphic imaging studies of tricarbonyl compounds and (99m)Tc(v)O-Cip were performed at 4 h after injection. The radiochemical purities of (99m)Tc(CO)(3)-Cip and (99m)Tc(CO)(3)-NFT were between 97-98% as determined by thin layer chromatography (TLRC) and RHPLC; no further purification is necessary before injection. The radiopharmaceuticals exhibited substantial stability when incubated in isotonic saline and serum up to 24 h. Biodistribution studies showed maximum uptake in the infected rat thigh muscle at 4 h post injection and washing out at slower rate from the infected site than the oxo technetium chelate. The mean ratios of uptake in infected/non-infected thighs were 3.87:1, 3.41:1 and 3.17:1 for (99m)Tc(CO)(3)-Cip, (99m)Tc(CO)(3)-NFT and (99m)Tc(v)O-Cip respectively. During scintigraphic studies, infection sites appeared quite distinctly with (99m)Tc(CO)(3)-Cip and (99m)Tc(CO)(3)-NFT, comparable to the behaviour with (99m)Tc(v)O-Cip. These results encouraged us for further development of infection imaging radiopharmaceuticals based on the (99m)Tc-tricarbonyl core.

A cation exchange method for separation of 111In from inactive silver, copper, traces of iron and radioactive gallium and zinc isotopes

Abstract 111 In was produced by the 109 Ag(α, 2n) 111 In reaction. A simple radiochemical separation technique, using Dowex-50 cation exchange resin (with prior removal of copper bulk, if present), has been employed to separate radioindium from inactive contaminants like Ag, Cu, Fe and active contaminant like 67 Ga and 65 Zn. The radiochemical separation yield was 90–99%. The radionuclidic purity of 111 In was >99% at 60 h after EOB. The level of all the inactive contaminants was μ g/mL in the final product.

Preparation and evaluation of 99mTc-cefuroxime, a potential infection specific imaging agent: a reliable thin layer chromatographic system to delineate impurities from the 99mTc-antibiotic.

Technetium-99m labelled cefuroxime, a second-generation cephalosporin antibiotic and potential bacteria specific infection imaging agent was evaluated. A good radiochemical purity (95%) of the labelled product was obtained after filtering the reaction mixture through a 0.22 μm filter. Scintigraphy study of the purified product showed uptake in infectious lesions 45 min after injection and abscess-to-muscle ratios were found to be 1.80, 1.85 and 1.88 at 45 min, 1.5 hr and 3 hr, respectively. A versatile and reliable chromatographic technique to assess the radiochemical purity of (99m)Tc-cefuroxime has also been described.

Radiochemical separation of high purity 111In from cadmium, copper, aluminium and traces of iron: Use of a cation exchange resin with hydrobromic acid and hydrochloric acid

Abstract 111In was obtained by a two-step separation procedure from an irradiated cadmium target, extending the method developed earlier by the authors for silver targets. The overall yield was 90–95% and the purity of the 111In was compatible with medical applications.

Synthesis and evaluation of technetium-99m-labeled bioreductive pharmacophores conjugated with amino acids and peptides for tumor imaging.

Development of molecular imaging agents to target tumor has become a major trend in nuclear medicine. With the aim to develop new potential 99mTc‐radiopharmaceuticals for targeting tumor, we have synthesized 5‐nitroimidazolyl amino acids and RGD‐coupled 2‐nitroimidazoles. Technetium‐99m radiolabeling with high radiochemical purity (>90%) was achieved for all the compounds. The radiolabeled complexes exhibited substantial in vitro stability in saline, serum, and histidine solution (10−2 m). Cell binding studies in EAC and B16F10 cell lines also revealed rapid and comparatively high cellular internalization. Among all the compounds studied, the binding of 99mTc(CO)3‐5 to B16F10 cells was moderately inhibited by the competitive peptide c[RGDfV], suggesting specificity of the radioligand toward αvβ3 receptor. However, no significant displacement of bound radioligand was observed when the binding of the 99mTc‐labeled complexes to above cells was challenged with excess competitive peptide. Fluorescent microscopy study provided direct evidence of intracellular localization of 5(6)‐carboxyfluorescein‐labeled 2‐nitroimidazolyl‐RGD‐peptide in αvβ3‐positive B16F10 mouse melanoma cell line. The ligands caused only 8–13% of hemolysis toward rat erythrocytes at concentrations as high as 100 μm. Imaging and biodistribution studies were performed in Swiss albino mice bearing induced tumor. 99mTc‐1 and 99mTc(CO)3‐5 demonstrated a very favorable in vivo profile. Selective uptake and retention in tumor with encouraging tumor/muscle and tumor/blood ratio and significant cellular uptake of fluorescence‐labeled‐2‐nitroimidazolyl RGD indicate the great potentiality of the pharmacophore for further evaluation as potential molecular imaging agent in cancer diagnosis.

Synthesis, radiolabeling and biological evaluation of a neutral tripeptide and its derivatives for potential nuclear medicine applications

Peptides are important regulators of growth and cellular functions not only in normal tissue but also in tumors. So they are becoming radioligands of increasing interest in nuclear oncology for targeted tumor diagnosis and therapy. So development of new peptide radiopharmaceuticals is becoming one of the most important areas in nuclear medicine research. A small tripeptide derivative NH(2)PhePheCys was synthesized by Fmoc solid phase peptide synthesis using an automated synthesizer. The oxidized form, i.e. NH(2)PhePheCysCysPhePheNH(2,) was also prepared by iodine oxidation method from NH(2)PhePheCys(ACM). The ligands were analyzed by HPLC and mass spectroscopy. They were radiolabeled with (99m)Tc using SnCl(2). In vitro analytical studies and biological characterizations were performed using the peptide radiopharmaceuticals. Images taken under gamma camera showed very high uptake in the liver, lung and spleen. Significant uptake was also observed in bone marrow and brain for (99m)Tc-NH(2)PhePheCys. Metabolites were produced in vivo when the radiopharmaceuticals were injected intravenously and were identified from rat brain and liver homogenate studies. Clearance through kidney did not show any evidence of breaking of the labeled compounds and formation of free (99m)Tc. Radiopharmaceuticals prepared using tripeptide and hexapeptide ligands were transported into the brain through blood brain barrier depending on the size and sequence characteristics. Using this property of peptide new derivatives can be prepared to develop (99m)Tc radiopharmaceuticals for imaging normal brain tissues as well as for diagnosing various brain disorders.

Single Vial Kit Formulation of Technetium-99m-L,L -Ethylene Dicysteine: Its Characterisation, Biodistribution and Comparison with Commercially Available 99mTc-L, L-EC Kits

Protection of the thiol function of L,L-EC by S-thiomethylation allowed automatic deprotection during 99mTc – chelation without the use of any additional reagents. After radiolabeling (either at pH 8.5 or > 8.5), this precursor of L,L- EC produced the desired chelate that was compared to 99mTc L,L-EC, the standard chelate, by HPLC, biodistribution and scintigraphic studies. This led to the development of a single vial kit for 99mTc L,L-EC. The chromatographic and biological properties of this kit were comparable to those of the commercially available EC kits, e.g. TCK-43 and TC-IK-25. This method of chelation from S-thiomethylated precursor has been extended to prepare the corresponding technetium-99 and rhenium chelates. These chelates of the protected ligands were chromatographically (HPLC) and spectroscopically comparable to the corresponding Tc and Re chelates obtained from the unprotected precursor. The results suggest that 99mTc L,L-EC could be prepared from S-thiomethyl EC at pH 8.5 or higher, and this method of chelation could be used for the development of single vial EC kit.

Radiometric studies on adsorption of iron on cation exchange resin and also of indium and gallium in Presence of Iron: Applicability to Prepare 67Ga with Low Iron Content

Abstract The retention and elution of Fe(III) on Dowex-50 cation exchange column in conc. HCl medium was studied using 59 Fe as a tracer. Details of the retention/elution behaviour of trace quantities of 114m In and 67 Ga on Dowex-50 resin in the presence of various iron concentrations were also studied since the iron content altered the adsorption behaviour of 67 Ga and 111 In during chemical separation of these isotopes from irradiated target solutions. A method is reported to remove iron from the column by reduction of Fe(III) to Fe(II) on the Dowex-50 column itself with 1% NaI in conc. HCl or 0.1 N HCl and subsequent elution of the Fe(II) with conc. HCl.