Samarendu Sinha

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.

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 Exploration of Novel Radiolabeled Bombesin Peptides for Targeting Receptor Positive Tumor.

Graphical abstract Figure. No Caption available. HighlightsSynthesis and biological interpretation of two new bombesin analogs HYNIC‐Asp[Phe13]BBN(7–13)‐NH‐CH2‐CH2‐CH3 (BA1) and HYNIC‐Pro[Tyr13,Met14]BBN‐ (7–14)‐NH2 (BA2) were synthesized and compared to BBN(7–14)‐NH2 (BS) with the goal of improving GRP receptor specific cellular internalization and retention of radioactivity in cancer cells for targeting molecular imaging.These BBN peptides could efficiently be radiolabeled with 99mTc via the ligand exchange method which exhibited improved radiochemical and in vitro metabolic stability compared to the previously reported analogs BS.Binding assay of radioconjugates confirmed its high binding affinity (affinity sequences were BA1 > BA2 > BS) towards GRP receptor specific breast cancer cell line MDA‐MB‐231. Potential usefulness of these analogs as diagnostic imaging agents was assessed by biodistribution and imaging studies and compare with 99mTc‐BS.In view of these results, 99mTc‐BA1 and 99mTc‐BA2 were efficient radiotracer for targeting GRP receptor positive tumor than 99mTc‐BS. The 99mTc‐BA1 exhibited two different entities: specific for extra and an intracellular target in the same radioconjugate which seems to be a promising candidate for detection and therapy of GRP receptor positive lesions in the clinical phase. However, during scintigraphic studies 99mTC‐BA1 showed improved and distinct delineation of the tumor than 99mTC‐BA2 and 99mTC‐BS.These studies demonstrate the potential of using the bombesin analog, BA1 possessing antagonist C‐terminal vectors as a potential diagnostic as well as antagonistic agent for specific targeting of GRP‐receptors over‐expressing tumors. Abstract Increasing evidence of peptide receptor overexpression in various cancer cells, warrant the development of receptor specific radiolabeled peptides for molecular imaging and therapy in nuclear medicine. Gastrin‐releasing‐peptide (GRP) receptor, are overexpressed in a variety of human cancer cells. The present study report the synthesis and biological evaluation of new bombesin (BBN) analogs, HYNIC‐Asp‐[Phe13]BBN(7–13)‐NH‐CH2‐CH2‐CH3:BA1, HYNIC‐Pro‐[Tyr13Met14]BBN(7–14)NH2:BA2 as prospective tumor imaging agent with compare to BBN(7–14)NH2:BS as standard. The pharmacophores were radiolabeled in high yields with 99mTc, characterized for their stability in serum and saline, cysteine/histidine and were found to be substantially stable. Internalization/externalization and receptor binding studies were assessed using MDA‐MB‐231 cells and showed high receptor binding‐affinity and favourable internalization. Fluorescence studies revealed that BA1 changed the morphology of the cells and could localize in the nucleus more effectively than BA2/BS. Cell‐viability studies displayed substantial antagonistic and nuclear‐internalization effect of BA1. BA1 also exhibited antiproliferative effect on MDA‐MB‐231 cell by inducing apoptosis. In vivo behaviour of the radiopeptides was evaluated in GRP receptor positive tumor bearing mice. The 99mTc‐BA1/99mTc‐BA2 demonstrated rapid blood/urinary clearance through the renal pathway and comparatively more significant tumor uptake image and favourable tumor‐to‐non‐target ratios provided by 99mTc‐BA1. The specificity of the in vivo uptake was confirmed by co‐injection with BS. Moreover, 99mTc‐BA1 provided a much clearer tumor image in scintigraphic studies than others. Thus the combination of favourable in vitro and in vivo properties renders BA1 as more potential antagonist bombesin‐peptide for targeting GRP‐receptor positive tumor. These properties are encouraging to carry out further experiments for non‐invasive receptor targeting potential diagnostinc and therapeutic agent for tumors.

Technetium-99m Cysteine; A Novel Radiopharmaceutical for Detection of Experimental Myocardial Infarction in Rats

Infarct avid radiopharmaceuticals are necessary for rapid and timely diagnosis of acute myocardial infarction. None of the infarct avid radiopharmaceuticals so far developed fulfill all the required criteria like rapid localization at the infarct, high avidity and specificity, and reasonable duration of scan positivity. 99mTc Cysteine was already reported from this laboratory as a suitable radiopharmaceutical to determine both morphology and function of kidney. The chemical structure of this radiopharmaceutical was also established. The present study demonstrates the affinity of the same chelate for damaged myocardial mass. 99mTc-cysteine was first tested on isoproterenol induced damaged rat myocardium, when ECG and histological studies demonstrated significant damage of the heart muscle following isoproterenol injection. The results were compared to that of 99mTc-glucarate. The uptake of 99mTc-cysteine in damaged rat myocardium was maximum (0.45% ID/g) when the animals were treated with isoproterenol 18 hrs before radiopharmaceutical injection; under the same experimental protocol 99mTc glucarate exhibited maximum heart uptake (0.263% ID/g) when injected 8 hrs after isoproterenol treatment. Evaluation was also performed on rat models of reperfused and non reperfused acute myocardial infarction. Animals were sacrificed after radiopharmaceutical injection and the excised hearts were subjected to radionuclide imaging, TTC and H-E staining. 99mTc-Cysteine chelate localized predominantly in the damaged portion. The highest infarct/viable tissue activity ratio (12/1) was obtained in 90 min occlusion model (protocol-2).