Shantanu Ganguly

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.

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.

Polymers derived from Xanthomonas campesteris and Cyamopsis tetragonolobus used as retardant materials for the formulation of sustained release floating matrix tablet of atenolol

The objective of the present study was to develop, optimize, in vitro, and in vivo evaluation of floating matrix tablet of atenolol using polymer blend derived from Xanthomonas campesteris and Cyamopsis tetragonolobus that are characterized by release requirements of sustained-release product and to improve the oral bioavailability of the drug. A 3(2) full factorial design was employed to optimize the tablets, where content of polymer blend (X1) and ratio of xanthan gum-to-guar gum (X2) were considered as independent variables. The effects of independent variables on dependent variables, i.e. floating time, diffusion exponent, and time to release 50% of atenolol were evaluated. The in vivo pharmacokinetic parameters of the optimized formulation were compared with the marketed sustained release formulation of atenolol (Aten(®)). The optimized formulation containing 20% (w/w) of polymer blend and 50:50 ratio of xanthan gum-to-guar gum was able to float more than 12h and showed the desired sustained drug release from the tablets. In vivo retention studies in rabbit stomach showed the gastric residence of tablet up to 6h. The in vivo study of optimized tablets illustrated significant improvement in the oral bioavailability of atenolol in rabbits. It can be concluded that floating matrix tablet of atenolol prepared by using xanthan gum and guar gum has potential for sustained release of the drug as well as improved oral bioavailability through enhanced gastric residence time of formulation in stomach.

Garcinol loaded vitamin E TPGS emulsified PLGA nanoparticles: preparation, physicochemical characterization, in vitro and in vivo studies

Garcinol (GAR) is a naturally occurring polyisoprenylated phenolic compound. It has been recently investigated for its biological activities such as antioxidant, anti-inflammatory, anti ulcer, and antiproliferative effect on a wide range of human cancer cell lines. Though the outcomes are very promising, its extreme insolubility in water remains the main obstacle for its clinical application. Herein we report the formulation of GAR entrapped PLGA nanoparticles by nanoprecipitation method using vitamin E TPGS as an emulsifier. The nanoparticles were characterized for size, surface morphology, surface charge, encapsulation efficiency and in vitro drug release kinetics. The MTT assay depicted a high amount of cytotoxicity of GAR-NPs in B16F10, HepG2 and KB cells. A considerable amount of cell apoptosis was observed in B16f10 and KB cell lines. In vivo cellular uptake of fluorescent NPs on B16F10 cells was also investigated. Finally the GAR loaded NPs were radiolabeled with technetium-99m with >95% labeling efficiency and administered to B16F10 melanoma tumor bearing mice to investigate the in vivo deposition at the tumor site by biodistribution and scintigraphic imaging study. In vitro cellular uptake studies and biological evaluation confirm the efficacy of the formulation for cancer treatment.

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.

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.

Technetium-99m radiolabeled ouabagenin-cysteine conjugate: Biological evaluation in animal models

Two ouabagenin-cysteine conjugates were synthesized by condensing 3-beta monochloroacetyl and 3-beta, 11-alpha dichloroacetyl ouabagenin with cysteine. The resulting ligands were radiolabeled with technetium-99m (99mTc) to furnish a single homogenous 99mTc chelate in each case with good stability. The animal experiments with these 99mTc-labeled conjugates established the superiority of guinea pig over rat and rabbit as an animal model, as previously observed for other tritiated or radioidinated cardiac glycosides or aglycones. In biodistribution experiments in guinea pig, these 99mTc chelates showed a favorable heart to liver (and other nontarget organ) uptake ratio, comparable to that of recently reported 125I-digoxigenin iodohistamine-3-oxime. The low heart to blood ratio in animal experiments with ouabagenin derivatives could be attributed to the absence of 3-beta sugar residues in these molecules, which is in agreement with the previous observation reported in connection with radioiodinated digoxin and digoxigenin derivatives.

Iodoacetylated ouabagenins: Their syntheses, spectroscopic characterizations, and stability studies

Ouabain shows high binding ability to myocardial Na+,K(+)-ATPase and, therefore, a suitably radiolabeled derivative of this compound may find use in myocardial imaging. In this pilot experiment we report the preparation of several chloroacetylated and iodoacetylated ouabagenins. These intermediates may possess the potential for conversion to 99mTc-labeled tracer by a reported procedure with which the imaging of myocardial Na+,K(+)-ATPase may be possible. Appropriate analytical and spectroscopic data for these intermediates are reported for the first time. To determine the stability of the iodoacetylated ouabagenins, corresponding 131I derivatives were synthesized which showed sufficient stability for incorporating a suitable radiometal-binding chelating moiety to these steroid molecules.