Radioiodination, purification and bioevaluation of Piroxicam in comparison with Meloxicam for imaging of inflammation

The present study is performed to compare the electrophilic substitution radioiodination reaction of two non-steroidal anti-inflammatory drugs namely, Piroxicam (Pirox) and Meloxicam (Melox) with ¹²⁵I where both chloramine-T (CAT) and iodogen were used as oxidizing agents. The factors affecting the percent of radiochemical yields such as drug concentration, pH of the reaction mixtures, different oxidizing agents, reaction time, temperature and different organic media were studied to optimize the conditions for labeling of Pirox and Melox and to obtain high radiochemical yields. The maximum radiochemical yield of ¹²⁵I-Piroxicam (¹²⁵I-Pirox) was 94% using 3.7 MBq of Na¹²⁵I, 0.4 mM of Pirox as substrate, 3.6 mM of chloramine-T (CAT) as oxidizing agent in acetone at neutral pH = 7 and at 60 °C within 20 min where the maximum radiochemical yield of ¹²⁵I-Melox was 92% using 0.7 mM of Melox as substrate, 0.62 mM of iodogen as oxidizing agent in acetone at neutral pH = 7 and at 25 °C within 30 min. The radiochemical yields were determined by TLC and high-pressure liquid chromatography (HPLC). Tracers showed good localization in inflamed muscle either septic or sterile. The collected data indicates that Pirox and Melox can be used as antiinflammatory imaging agents at 24 and 2 h post injection, respectively.     

Preparation of <Superscript>125</Superscript>I-celecoxib with high purity as a possible tumor agent

A preparation of ¹²⁵I-celecoxib is carried out via an electrophilic substitution reaction. The reaction parameters studied were celecoxib concentration, reaction temperature, pH of the reaction mixture and kinds of oxidizing agents in order to obtain a high radiochemical yield of the ¹²⁵I-celecoxib. Using 3.7 MBq of Na¹²⁵I, 150 μg (3.9 mM (mmol/L)) of celecoxib, and 1.6 mM (mmol/L) of chloramine-T (CAT) as oxidant at pH 4 and 60 °C for 15 min a maximum radiochemical yield of ¹²⁵I-celecoxib (65%) was obtained. The labeled compound was separated and purified by means of high pressure liquid chromatography (HPLC). The biological distribution in infected mice indicates the suitability of radioiodinated celecoxib as imaging of tumor.     

Radioiodination of 4-benzyl-1-(3-iodobenzylsulfonyl)piperidine, 4-(3-iodobenzyl)-1-(benzylsulfonyl)piperazine and their derivatives via isotopic and non-isotopic exchange reactions

A mild and simple technique for preparing of 4-benzyl-1-(3-[¹²⁵I]iodobenzylsulfonyl)piperidine, 4-(3-[¹²⁵I]iodobenzyl)-1-(benzylsulfonyl)piperazine and their derivatives, as sigma-1 receptor ligands, with relatively high radiochemical yields via nucleophilic substitution reaction by means of isotopic and non-isotopic exchange reactions is described. Some factors affecting the radiochemical yield were commonly studied in presence of acidic medium at elevated temperature. Unfortunately, the radiochemical yields were weak. Some attempts were carried out in presence of polar aprotic solvents to enhance the radiochemical yield. N,N-Dimethylformamide was proved highly efficient for preparing of radioiodinated 4-benzyl-1-(3-iodobenzylsulfonyl)piperidine (4-B-[¹²⁵I]-IBSP, 70 ± 5.7 %) and 4-(3-iodobenzyl)-1-(benzylsulfonyl)piperazine (4-[¹²⁵I]-IBBSPz, 72 ± 6.0 %) at moderate temperature (100–105 °C) within 8 h. The specific activities of 4-B-[¹²⁵I]-IBSP and 4-[¹²⁵I]-IBBSPz (6,534.2 and 5,927.4 MBq/mmol) were obtained respectively.     

Optimization of the preparation conditions of radioiodoepidepride: A dopamine D<Subscript>2</Subscript>receptor antagonist radioligand

Summary [¹²⁵I]iodepidepride, (s)-(-)-[(1-ethyl-2-pyrrolidinyl)methyl]-5-[¹²⁵I]-iodo-2,3-dimethoxybenzamide is the iodine substituted analogue of isoremoxipride, both of which are very potent dopamine D₂-antagonists. Epidepride was radioiodinated using different oxidizing agents such as chloramine-T, iodogen, iodogen glass frit and hydrogen peroxide. Chloramine-T is a powerful oxidizing agent compared to both iodogen and hydrogen peroxide so that the side products, especially the chlorinated epidepride, decreases the radiochemical yield. This chlorinated epidepride is minimized in the case of iodogen and iodogen glass frit and are not observed in case of the non-chlorinated oxidizing agent hydrogen peroxide. TLC and HPLC were used to analyze the reaction components and to estimate both the radiochemical yield and purity. The reaction parameters such as reaction time, pH, epidepride and oxidizing agent concentrations and the stabilty of the final product were studied to optimize the radiochemical yield and purity. The optimized radiochemical yield was about 90% and the radiochemical purity of the final product was 99.9%.     

Labeling of atenolol with radioactive iodine-125 using <Emphasis Type="Italic">N</Emphasis>-bromosuccinimide and hydrogen peroxide as oxidizing agents

An adopted method for the preparation of high radiochemical purity ¹²⁵I-atenolol was investigated. Direct radioiodination of atenolol was carried out using N-bromosuccinamide or hydrogen peroxide as an oxidizing agent. The reaction proceeds well within 30 min at room temperature (25 ± 1 °C) and afforded a radiochemical yield up to 97% as pure as ¹²⁵I-atenolol. Different chromatographic techniques (electrophoresis, TLC and HPLC) were used to determine the radiochemical yield and purity of the labeled product. Biodistribution studies were carried out in normal Albino Swiss mice and the results indicate that ¹²⁵I-atenolol can be used safely as myocardial imaging agent.     

Synthesis,bioevaluation and gamma scintigraphy of <Superscript>99m</Superscript>Tc-N-2-(furylmethyl iminodiacetic acid) complex as a new renal radiopharmaceutical

A ligand of N-2-(furylmethyl iminodiacetic acid) (FMIDA) has been easily labeled by a tetradentate chelating agent of [^99mTc]. Factors like a stannous chloride solution as a reducing agent (100 μg), substrate amount (100 μg), pH (7), in vitro stability (8 h) and temperature (37 °C) have been systematically studied to optimize high radiochemical yield (98.0%). The radiochemical conversion was calculated on thin-layer chromatography, paper electrophoresis, and high performance liquid chromatography. Biodistribution study showed that this complex was removed from the kidneys and bladder path way during 1 h post injection. Therefore, [^99mTc]FMIDA may be used as renal function radiotracer.     

Radiolabeling of EGCG with 125I and its biodistribution in mice

The aim of the present study was to label EGCG with ¹²⁵I and to determine its radiopharmaceutical potential in mice. EGCG was labeled with ¹²⁵I using the iodogen method. The labeling yield and the radiochemical purity of ¹²⁵I–EGCG were determined by radio thin-layer chromatography (RTLC). The Labeling yield was approximately 89.4 %. The radiochemical purity was approximately 96.4 %. The biodistribution studies of the labeled compound (specific activity; 0.47 TBq/μg) were performed in male Kunming mice. The uptakes of ¹²⁵I–EGCG in some organs were determined at different time after injection to the mice. The radioactivity in each organ was counted and the percentage of injected activity per gram of tissue weight (%ID/g) for each organ and blood was calculated. Incorporation of radioactivity in the various tissue/organ was confirmed by microautoradiography. ¹²⁵I–EGCG uptake in the stomach and salivary gland was higher than other organ/tissue. The black silver grains was concentrated in the nucleus, cytoplasm, intercellular substance and capillaries of that various organs, and its unevenly distributed. Thus, ¹²⁵I–EGCG may be radiopharmaceutical for the imaging of the stomach and salivary gland.     

Comparative study between chloramine-T and iodogen to prepare radioiodinated etodolac for inflammation imaging

This study describes a fast and efficient method for radiolabeling of etodolac with iodine-125 [¹²⁵I], where both chloramine-T and iodogen were used as oxidizing agents. The labeling reaction was carried out via electrophilic substitution of hydrogen atom with the iodonium cation I⁺. The labeling yield was found to be influenced by different factors such as drug concentration, pH of the reaction mixtures, different oxidizing agents, reaction time, temperature and different organic media. The radiochemical yield (RCY) was determined by TLC system using methylene chloride:ethyl acetate (3:7 v/v) as a developing solvent and by electrophoresis using cellulose acetate moistened with 0.02 M phosphate buffer pH 7. The maximum radiochemical yield of [¹²⁵I]Etodolac (87.7%) was obtained. Labeled etodolac shows a good localization in inflamed muscle. It excretes mainly via kidney and to some via liver.     

<Superscript>99m</Superscript>Tc-roxifiban: a potential molecular imaging agent for the detection and localization of acute venous thrombosis

^99mTc-roxifiban was obtained in a high radiochemical yield (98.4%) by complexing ~750 MBq ^99mTc with 2.5 mg roxifiban in the presence of 150 µg SnCl₂·2H₂O. Factors affecting the labelling yield were investigated and optimized. The complex was lipophilic and stable in saline and serum for more than 8 h. The complex structure prediction and molecular docking to its target activated GPIIb/IIIa receptor were performed. The tracer in vitro binding to activated platelets was high (27–32%). In vivo evaluation was performed through clearance, biodistribution and imaging studies in rats. All results supported the usefulness of the tracer as thrombus imaging agent.     

Preparation of radioiodinated L-α-methyl tyrosine, a tumour brain imaging agent

Preparation of radioidinated L-α-methyl tyrosine by the oxidative radioiodination using chloramine-T (CAT) and iodogen (1,3,4,6-tetrachloro,-3α, 6α-diphenyl glycoluril) to generate electrophilic radioiodine has been carried out. The factors affecting the labeling yield such as pH of the medium, reaction time, substrate and oxidizing agent concentrations have been investigated to optimize the conditions for the preparation of radioiodinated L-α-methyl tyrosine in high radiochemical yields. Side product impurities were observed at long reaction times and high oxidizing agent concentrations. Maximum radiochemical yields of 89.7±1.5% and 87.8±1.6% were obtained in case of CAT and iodogen, respectively. Separation and purification by high pressure liquid chromatography (HPLC) resulted in radiochemically pure products. Using high specific activity¹²³I, the SPECT brain imaging agent can be prepared.     

Determination of arsenic in food and dietary supplement standard reference materials by neutron activation analysis

Arsenic was measured in food and dietary supplement standard reference materials by neutron activation analysis for the purpose of assigning certified or reference As mass fractions and to assess material homogeneity. Instrumental neutron activation analysis was used to value assign As in candidate SRM 3532 Calcium Dietary Supplement and candidate SRM 3262 Hypericum perforatum (St. John’s Wort) Aerial Parts down to about 100 μg/kg. Values were also determined for two additional candidate St. John’s Wort SRMs with As mass fractions <100 μg/kg. The presence of significant amounts of ²⁴Na and ⁸²Br limited the reproducibility of the method below 100 μg/kg. For measurement of lower As mass fractions, a radiochemical neutron activation analysis method with extraction of As³⁺ into diethyl-dithiocarbamate in chloroform and detection limits down to 0.1 μg/kg. As was used to value-assign As mass fractions for SRM 3280 Multivitamin/Multielement Tablets and for candidate SRM 3233 Fortified Breakfast Cereal, and at <10 μg/kg in candidate SRM 1845a Whole Egg Powder.     

Labeling of ursodeoxycholic acid with technetium-99m for hepatobiliary imaging

An adopted method for the preparation of high radiochemical purity ^99mTc-ursodeoxycholic acid (UDCA) was conducted with a high radiochemical yield up to 97.5 %. The reaction proceeds well using 2 mg UDCA, 50 μg tin chloride in solution of pH 8 at room temperature for 30 min. The radiochemical yield was up to 97.5 % as pure as ^99mTc-UDCA. Different chromatographic techniques (paper chromatography and electrophoresis) were used to evaluate the radiochemical yield and purity of the labeled product. Biodistribution studies were carried out in Albino Swiss mice at different time intervals after administration of ^99mTc-UDCA. The uptake of ^99mTc-UDCA in the liver gave the chance to diagnose it. The results indicate that the labeled compound cleared from the systematic circulation within 2 h after administration and majority of organs showed significant decrease in uptake of ^99mTc-UDCA. Finally, the liver uptake was high and the results indicate the possibility of using ^99mTc-UDCA for hepatobiliary imaging.     

Preparation and biological distribution of 99mTc-cefazolin complex, a novel agent for detecting sites of infection

The optimization of the radiolabeling yield of cefazolin with ^99mTc was described. Dependence of the labeling yield of ^99mTc-cefazolin complex on the amounts of cefazolin and SnCl₂·2H₂O, pH and reaction time was studied. Cefazolin was labeled with ^99mTc with a labeling yield of 89.5 % by using 1 mg cefazolin, 5 μg SnCl₂·2H₂O at pH 4 and 30 min reaction time. The radiochemical purity of ^99mTc-cefazolin was evaluated with ITLC. The formed ^99mTc-cefazolin complex was stable for a time up to 3 h, after that the labeling yield decreased 64.0 % at 8 h. Biological distribution of ^99mTc-cefazolin complex was investigated in experimentally induced inflammation mice, in the left thigh, using Staphylococcus aureus (bacterial infection model) and turpentine oil (sterile inflammation model). Both thighs of the mice were dissected and counted and the ratio of bacterial infected thigh/contralateral thigh was then evaluated. In case of bacterial infection, T/NT for ^99mTc-cefazolin complex was 8.57 ± 0.4 after 0.5 h, which was higher than that of the commercially available ^99mTc-ciprofloxacin under the same experimental conditions. The ability of ^99mTc-cefazolin to differentiate between septic and aseptic inflammation indicates that ^99mTc-cefazolin could undergo further clinical trials to be used for imaging sites of infection.     

Synthesis and preliminary evaluation of a novel 125I-labeled T140 analog for quantitation of CXCR4 expression

The aim of this study was to develop a radiopharmaceutical for the imaging of CXCR4-expressing tumors in vivo. For ¹²⁵I-labeling, ¹²⁵I-SIB was synthesized and conjugated with the ε-NH₂ group of Ac-TZ14011, a specific CXCR4 antagonist. The specific radioactivity of the product was 5 GBq/μmol and the radiochemical purity (RCP) was 96% (n = 3). After 6 h, the RCP of the product in PBS was 93%. The MCF-7 cell uptake of Ac-TZ14011 was rapid and high. Primary biodistribution studies indicated that ¹²⁵I-IB-Ac-TZ14011 was mainly excreted via the kidney, and further evaluation in mice with induced tumors was necessary.     

Separation of <Superscript>125</Superscript>IBZM and <Superscript>125</Superscript>ILIS using polyacrylamide-acrylic acid resin

Radioiodination of both S(−)BZM and LIS was carried out using n-bromosuccimide(NBS) as a mild oxidizing agent. The factors affecting on the radiochemical yield such as pH, reaction time, substrate concentration and oxidizing agent have been studied. The chromatographic separation of both ¹²⁵IBZM and ¹²⁵ILIS was carried out using HPLC and poly(acrylamide-acrylic acid) resin P(AAm-AA). The copolymer was prepared by a template polymerization of AA in aqueous solution on PAAm as a template polymer and in the presence of N,N-methylenebisacrylamide (NMBA) as a crosslinker using gamma rays as initiator. The purifications of tracers were carried out using prepared resin compared with TLC and HPLC. The effects of pH buffer, variable elution volumes, flow rate and temperature on the separation process of the resin efficiency have been studied.     

Biosynthesis of Ethyl (S)-4-Chloro-3-Hydroxybutanoate by NADH-Dependent Reductase from E. coli CCZU-Y10 Discovered by Genome Data Mining Using Mannitol as Cosubstrate

The reductase (PgCR) from recombinant Escherichia coli CCZU-Y10 displayed high reductase activity and excellent stereoselectivity for the reduction of ethyl 4-chloro-3-oxobutanoate (COBE) into ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE). To efficiently synthesize (S)-CHBE (>99 % enantiomeric excess (ee)), the highly stereoselective bioreduction of COBE into (S)-CHBE with the whole cells of E. coli CCZU-Y10 was successfully demonstrated in a dibutyl phthalate-water biphasic system. The appropriate ratio of the organic phase to water phase was 1:1 (v/v). The optimum reaction temperature, reaction pH, cosubstrate, NAD⁺, and cell dosage of the biotransformation of 100 mM COBE in this biphasic system were 30 °C, 7.0, mannitol (2.5 mmol/mmol COBE), 0.1 μmol/(mmol COBE), and 0.1 g (wet weight)/mL, respectively. Moreover, COBE at a high concentration of (1,000 mM) could be asymmetrically reduced to (S)-CHBE in a high yield (99.0 %) and high enantiometric excess value (>99 % ee). Significantly, E. coli CCZU-Y10 shows high potential in the industrial production of (S)-CHBE (>99 % ee).     

Preparation,molecular modeling and biodistribution of 99mTc-phytochlorin complex

Phytochlorin [21H, 23H-Porphine-7-propanoicacid, 3-carboxy-5-(carboxymethyl)13-ethenyl-18-ethyl-7,8-dihydro-2,8,12,17-tetramethyl-,(7S,8S)] was labeled with ^99mTc and the factors affecting the labeling yield of ^99mTc-phytochlorin complex were studied in details. At pH 10, ^99mTc-phytochlorin complex was obtained with a high radiochemical yield of 98.4 ± 0.6 % by adding ^99mTc to 100 mg phytochlorin in the presence of 75 μg SnCl₂·2H₂O after 30 min reaction time. The molecular modeling study showed that the structure of ^99mTc-phytochlorin complex presents nearly linear HO–Tc–OH unit with an angle of 179.27° and a coplanar Tc(N1N2N3N4) unit. Biodistribution of ^99mTc-phytochlorin complex in tumor bearing mice showed high T/NT ratio (T/NT = 3.65 at 90 min post injection). This preclinical study showed that ^99mTc-phytochlorin complex is a potential selective radiotracer for solid tumor imaging and afford it as a new radiopharmaceutical suitable to proceed through the clinical trials for tumor imaging.     

Preparation of 186Re-MIBI complex for myocardial perfusion imaging as potential replacement of analogues 99mTc-MIBI complex

The optimum conditions to label 2-methoxyisobutyl-isonitrile (MIBI) compound with pure ¹⁸⁶Re as a stable contrast agent for myocardial perfusion imaging were investigated. Complexation of MIBI with ¹⁸⁶Re was carried out using anhydrous stannous chloride, gentisic acid and 1 ml of 37 MBq ¹⁸⁶ReO₄ ^? at pH 2 in a boiling water bath for 30 min. The corresponding radiochemical yield was ≈95.5 %. The biodistribution studies in mice indicated that, the complex was cleared from the body by kidneys to urinary bladder and finally into urine. ¹⁸⁶Re-MIBI demonstrated satisfactory heart uptake like to ^99mTc- MIBI (8.94 % dose/organ at 5 min). The obtained data showed that ¹⁸⁶Re-MIBI is a potential replacement of ^99mTc-MIBI for myocardial perfusion imaging.     

Biosynthesis of Benzoylformic Acid from Benzoyl Cyanide with a New Bacterial Isolate of Brevibacterium sp. CCZU12-1

Brevibacterium sp. CCZU12-1 with high nitrilase activity could effectively hydrolyze benzoyl cyanide into benzoylformic acid. After the culture optimization, the preferred carbon sources, nitrogen sources, and inducer were glucose (10 g/L), a composite of peptone (10 g/L) plus yeast extract (2.5 g/L), and ε-caprolactam (2.0 mM), respectively. After the reaction optimization, the optimum reaction temperature, reaction pH, organic cosolvent, and metal ion were 30 °C, 7.0, ethanol (2 %, v/v), and Ca²⁺ (0.1 mM), respectively. At biotransformation of 120-mM benzoyl cyanide for 24 h, the yield of benzoylformic acid reached 91.8 %. Moreover, the microbial nitrilase from Brevibacterium sp. CCZU12-1 could hydrolyze various nitriles, and it significantly exhibited high nitrilase activity against benzoyl cyanide, 3-cyanopyridine, and α-cyclohexyl-mandelonitrile.     

Radiosynthesis of 10-(2-[18F]fluoroethoxy)-20(S)-camptothecin as a potential positron emission tomography tracer for the imaging of topoisomerase I in cancers

The preparation of 10-(2-[¹⁸F]fluoroethoxy)-20(S)-camptothecin, a potential positron emission tomography tracer for the imaging of topoisomerase I in cancers, is described. 10-(2-[¹⁸F]Fluoroethoxy)-20(S)-camptothecin was synthesized by the [¹⁸F]fluoroalkylation of the corresponding hydroxy precursor molecule with 2-[¹⁸F]fluoroethyl bromide ([¹⁸F]FEtBr) in dimethylsulfoxide (DMSO) at 55 °C for 20 min; this was followed by purification using high performance liquid chromatography (HPLC) with a total preparation time of 60 min. The overall radiochemical yield was approximately 5.4–12 % (uncorrected), and the radiochemical purity was above 96 %.