Synthesis, quality control and biodistribution of 99mTc-Kanamycin

Summary Kanamycin is an antibiotic used for treatment of infections when penicillin or other less toxic drugs cannot be used. Kanamycin was labeled with technetium-99m pertechnetate using SnCl₂^. 2H₂O as reducing agent. The labeling efficiency depends on the ligand/reductant ratio, pH, and volume of reaction mixture. Radiochemical purity and stability of ^99mTc-Kanamycin was determined by thin layer chromatography. Biodistribution studies of ^99mTc-Kanamycin were performed in rats and rabbits. A significantly higher accumulation of ^99mTc-Kanamycin was seen at sites of S. aureusinfected animals (rat/rabbit).     

99mTc-glucoheptonate-guanine: Synthesis, biodistribution and imaging in animals

The aim of the current study was to design a nucleotide-based radiopharmaceutical which could be labeled with ^99mTc and to investigate its radiopharmaceutical efficiency and stability. GHA (glucoheptonate) was used as bifunctional chelate. GHA was labeled with ^99mTc by SnCl₂ reduction method first, and then G (guanine) was conjugated with ^99mTc-GHA at 90 °C. In order to determine its radiopharmaceutical stability, thin layer radio chromatography (TLRC) and electrophoresis were employed. In addition, the results were confirmed using high performance liquid radio chromatography (HPLRC). Scintigraphic imaging was performed on rats with mammary tumors, while tissue distribution was determined on Albino Wistar rats. Labeling yield was found to be over 95% and the labeled complex maintained its stability during the study period. The lipophilicity of the ^99mTc-GHG was measured and the partition coefficient (logP) of the labeled compound calculated. The results demonstrated that the uptake of ^99mTc-GHG (^99mTc-glucoheptonate-guanine) reached its maximum at 3 hours p.i. in stomach and intestines. Main way of excretion was renal. Hepatobiliary excretion was also observed. In conclusion, ^99mTc-GHG may be useful as a nucleotide-based radiopharmaceutical for in vivo applications.     

Effect of gamma-radiation on the Sn(II) content,radiochemical purity,in-vitro stability and biological distribution of some99mTc-labelled freeze dried kits

Gamma-irradiation can be used for the sterilization of some^99mTc-labelled freeze dried kits. In connection with this the effect of -radiation on Sn(II) content, radiochemical purity,in-vitro stability and biological distribution of some currently used^99mTc-labelled kits has been investigated. For irradiation the certain radiation sterilization doses (25 and 50 kGy) were used. A variable decrease of Sn(II) content was observed in all -irradiated kits. The losses are in the order of 10–25% compared with the Sn(II) content of original ones. The colour of the irradiated kits did not changed except DTPA which developed yellow colour after irradiation. For the irradiated and original kits nearly the same pH were found. The irradiated kits seemed to undergo partial decomposition or chemical alteration which led to some deviation of the biological distribution of them.     

Synthesis,radiochromatography and biodistribution of99mTc-dimethylphosphinoethane (DMPE) complexes

The title complexes were prepared from no-carrier-added^99mTc–TcO ₄ ^– and the air-sensitive reducing ligand DMPE under argon in ethanol-water. At acidic pH [Tc(III)Cl₂ dmpe₂]⁺ was formed, while alkaline pH led to the formation of [Tc(I)dmpe₃]⁺. About 150°C and at least 10^–3M DMPE was needed to achieve over 95% yield in less than 1 hour, otherwise the [Tc(V)O₂dmpe₂]⁺ intermediate was present. Electrophoresis demonstrated the unit positive charge and reversed-phase ion-pair HPLC provided separation and identification of^99mTc-products by direct comparison with known⁹⁹Tc-complexes. In rats the^99mTc-complexes were excreted by kidneys and liver and reached high heart/blood but only low heart/lung and heart/liver ratios. In dogs satisfactory myocardial scintigrams were obtained in spite of high liver activity.     

Synthesis,characterization and biodistribution of 99mTc-Bioquin-HMPAO (99mTc-BH) as a novel brain imaging agent

Recently, the development of novel brain imaging agents has aroused much interest thanks to limited number of brain cancer or diseases diagnosis agents. It is aimed to synthesize a novel brain imaging agent including a promise for further studies on AD diagnosis potential and investigate its bioaffinity with biodistribution studies on healthy Balb/c mice. A novel radiolabeled agent was synthesized and characterized. Quality control of ^99mTc-BH was performed utilizing solvent extraction and chromatographic (Radio TLC and Radio HPLC) methods. Bioaffinity of the ^99mTc-BH was investigated on male Balb/c mice at various time points (5, 30, 60, 120 min post-injection). Paper electrophoresis showed that ^99mTc-BH has a neutral structure. Radiochemical purity of ^99mTc-BH was over 95 % with appropriate stability for imaging period. Selected brain regions have uptakes over 4 % ID/g following intravenous injection. Hippocampus has uptake approximately 10 % ID/g. ^99mTc-BH has shown brain uptake, so it may prove to be valuable for brain imaging as a novel technetium-labeled agent. Further investigations with AD animal model are our on going effort to show that this agent has AD diagnosis potential.     

Synthesis of 99m TcN(IPDTC)2 and its biodistribution in mice

In order to seek a new class of brain perfusion imaging agent containing[ ^99m TcN]²+ core, the bis(N-isopropyl dithiocarbamato)nitrido technetium-99m complex [ ^99m TcN(IPDTC)₂ ] (IPDTC:N-isopropyldithiocarbamato) has been synthesized through a simple and efficient method,which can be utilized for the preparation of a radiopharmaceutical througha lyophilized formulation. The radiochemical purity of the complex was over90% determined by thin layer chromatography. No decomposition of the complexwas observed at room temperature over a period of 12 hours. Its partitioncoefficient indicated that it was a good lipophilic complex. Biodistributionin mice demonstrated that the complex was significantly retained into thebrain. The brain uptake (ID%/g) was 3.90, 2.67 and 1.54 and the brain/bloodratios were 1.26, 1.06 and 0.85 at 5, 30 and 60-minute post-injection, respectively.The results showed that the complex may lead to a further development of theradiopharmaceutical as a brain perfusion tracer.     

Biosynthesis,Characterization and Antibacterial Application of Novel Silver Nanoparticles against Drug Resistant Pathogenic Klebsiella pneumoniae and Salmonella Enteritidis

The present study highlights the biosynthesis of silver nanoparticles (AgNPs) using culture supernatant of Massilia sp. MAHUQ-52 as well as the antimicrobial application of synthesized AgNPs against multi-drug resistant pathogenic Klebsiella pneumoniae and Salmonella Enteritidis. Well-defined AgNPs formation occurred from the reaction mixture of cell-free supernatant and silver nitrate (AgNO₃) solution within 48 h of incubation. UV-visible spectroscopy analysis showed a strong peak at 435 nm, which corresponds to the surface plasmon resonance of AgNPs. The synthesized AgNPs were characterized by FE-TEM, EDX, XRD, DLS and FT-IR. From FE-TEM analysis, it was found that most of the particles were spherical shape, and the size of synthesized nanoparticles (NPs) was 15–55 nm. EDX spectrum revealed a strong silver signal at 3 keV. XRD analysis determined the crystalline, pure, face-centered cubic AgNPs. FT-IR analysis identified various functional molecules that may be involved with the synthesis and stabilization of AgNPs. The antimicrobial activity of Massilia sp. MAHUQ-52 mediated synthesized AgNPs was determined using the disk diffusion method against K. pneumoniae and S. Enteritidis. Biosynthesized AgNPs showed strong antimicrobial activity against both K. pneumoniae and S. Enteritidis. The MICs of synthesized AgNPs against K. pneumoniae and S. Enteritidis were 12.5 and 25.0 μg/mL, respectively. The MBC of biosynthesized AgNPs against both pathogens was 50.0 μg/mL. From FE-SEM analysis, it was found that the AgNPs-treated cells showed morphological changes with irregular and damaged cell walls that culminated in cell death.     

Synthesis, biodistribution and evaluation of 99mTc-sitafloxacin kit: a novel infection imaging agent

Radiosynthesis of ^99mTc-sitafloxacin (^99mTc-STF) complex and its efficacy as a potential infection imaging agent was evaluated. Effect of sitafloxacin (STF) concentration, sodium pertechnetate (Na^99mTcO₄), stannous chloride dihydrate (SnCl₂·2H₂O), and pH on the % radiochemical purity yield (RCP) of ^99mTc-STF complex was studied. A stable ^99mTc-STF complex up to 120 min with maximum %RCP yield was observed by mixing 2 mg of STF with 3 mCi of Na^99mTcO₄ and 150 μL of SnCl₂·2H₂O (1 μg/μL in 0.01 N HCl) at a pH 5.5. Artificially infected rats with Staphylococcus aureus were used for studying the biodistribution behavior of the ^99mTc-STF complex. After 30 min of the intravenous (I.V.) administration of the ^99mTc-STF complex, 7.50 ± 0.10% was absorbed in the infected thigh of the rats and the uptake gradually increased to 18.50 ± 0.20% within 90 min. Rabbits with artificially induced infection were used for evaluating the scintigraphic accuracy. Higher uptake in the infected thigh was observed after 2 h of I.V. administration of the ^99mTc-STF complex. Target to non-target organ ratio of the % absorbed dose incase of infected/normal muscle was 6.82 ± 0.40, 17.11 ± 0.60, and 23.13 ± 1.00% at 30, 60 and 90 min of administration. Stable and higher %RCP, higher uptake in the infected thigh, and spectral studies, recommend the ^99mTc-STF for routine infection imaging.     

Synthesis, radiolabeling and biodistribution studies of [99mTc(CO)3(MN-TZ-BPA)]+ in tumor-bearing mice

This study reports the synthesis, radiolabeling and preliminary biodistribution results of [^99mTc(CO)₃(MN-TZ-BPA)]⁺ in tumor-bearing mice. The novel nitroimidazole derivative was successfully synthesized by conjugation of bis(pyridin-2-ylmethyl)amine (BPA) to 2-methyl-5-niroimidazole via “click” reaction. The ligand could be labeled by [^99mTc(CO)₃]⁺ core in high yield to get [^99mTc(CO)₃(MN-TZ-BPA)]⁺, which was very hydrophilic and was stable at room temperature. Biodistribution studies in tumor-bearing mice showed that [^99mTc(CO)₃(MN-TZ-BPA)]⁺ accumulated in the tumor with certain initial uptake while poor retention. The rapid clearance from normal organs with favorable tumor/muscle ratios warrants further research to improve tumor targeting efficacy and pharmacokinetic profile of radiolabeled nitroimidazoles by structural modification.     

Microcalorimetric study of the growth of Enterococcus faecalis, Klebsiella pneumoniae and their mixtures in an enriched culture medium

In the last few years there has been a growing interest in microcalorimetric investigations of microbial processes. Microcalorimetry is a technique based on heat output of bacterial metabolism which can be applied to detect bacterial growth in a few hours. However, there are few studies that attempt to investigate the interactions between two or more bacteria. In this study, we researched the interaction relationship of Enterococcus faecalis and Klebsiella pneumoniae, which are important pathogens responsible for infections in humans. The measures were carried out using a Calvet microcalorimeter, that contains two stainless steel cells of approximately 10 cm³ (reference and experimental). Experiments were carried out at concentration of 10³ CFU mL^?1 and a constant temperature of 309.65 K. The differences in shape of the heat flow-time curves of E. faecalis and K. pneumoniae and their mixtures were compared. Curves of E. faecalis and K. pneumoniae and their mixtures were analyzed mathematically allowing to calculate thermokinetic parameters such as growth constant (k), generation time (G), detection time (t _d) and the amount of heat released (Q). The results revealed that when E. faecalis and K. pneumoniae were put together in the same proportion, the growth character of E. faecalis was not present, due to the inhibitory effects of K. pneumoniae on E. faecalis. Microcalorimetric investigations of microbial interactions is possible and promising.     

Synthesis and biodistribution of 99mTc(CO)3-DMSA-MIBI in mice

Mixed ligand fac-tricarbonyl complex of [^99mTc(CO)₃-DMSA-MIBI] has been prepared starting from the precursor [^99mTc(OH₂)₃(CO)₃]⁺. The complex can be obtained in good yield and purity in a two-step procedure by first attaching meso-2,3-dimercaptosuccinic acid (DMSA, HOOCCH(SH)CH(SH)COOH) with [^99mTc(OH₂)₃(CO)₃]⁺, followed by addition of MIBI [tetrakis-2-methoxyisobutylisonitrile (CH₃OC(CH₃)₂CH₂-N≡C) copper(I) tetrafluoroborate] solution. The complex was characterized by TLC and HPLC and was studied by means of octanol-water partition coefficient, electrophoresis, stability in vitro, and normal mice experiment. Biodistribution in mice demonstrated that the complex showed higher myocardial uptake after 0.5-hour p.i. The ratios of heart/liver (%ID/g) in the case of ^99mTc(CO)₃-DMSA-MIBI was higher (1.88) than that observed in case of ^99mTc-MIBI¹ (0.93) after 0.5-hour p.i. (P<0.05). Results showed that the complex may be developed to a novel myocardial perfusion-imaging agent.     

Synthesis,labeling and biodistribution of <Superscript>99m</Superscript>Tc-3-amino-2-quinoxalin-carbonitrile 1,4-dioxide in tumor bearing mice

3-Amino-2-quinoxalincarbonitrile 1,4-dioxide (AQCD) is a quinoxaline derivative, which was synthesized by condensation method. AQCD was labeled with ^99mTc with labeling yield above 90% investigated by paper chromatography. ^99mTc-AQCD was prepared using stannous chloride as reducing agent at pH 7 and 10 min reaction time. ^99mTc-AQCD should be freshly prepared, otherwise the yield significantly decreased after 15 min post labeling. Stability study of ^99mTc-AQCD reflected the short time stability of Biodistribution study of ^99 mTc-AQCD in tumor bearing mice reflected that its uptake in tumor sites in both ascites and solid tumor sites. This uptake of ^99mTc-AQCD in tumor sites was sufficient to radioimage the inoculated sites.     

Synthesis, radiolabeling and in vivo biodistribution of diethylstilbestrol phosphate derivative (DES-P)

Diethylstilbestrol (DES) is a well known, nonsteroidal estrogen with high affinity for the estrogen receptor (ER). Today DES is used to treat breast and prostate cancers. A phosphate derivative of DES [Diethylstilbestrol diphosphate (DES-P)] which is specific to tumor cells consisting alkaline phosphatase enzyme was synthesized and labeled with ^99mTc using tin chloride as reducing agent. In vivo biological activity of ^99mTc labeled diethylstilbestrol phosphate compound (^99mTc-DES-P) was examined by biodistribution studies on Wistar Albino rats. Statistical evaluation was performed using SPSS 13 program. The percentage (%) radiolabeling yield of ^99mTc-DES-P and quality control studies were done by Thin Layer Radio Chromatography (TLRC). Results showed that, ^99mTc-DES-P may be proposed as an imaging agent for ER enriched tumors such as uterus and prostate and their metastases in bones.     

Design, synthesis and biological evaluation of non-natural modulators of quorum sensing in Pseudomonas aeruginosa

Many species of bacteria employ a mechanism of intercellular communication known as quorum sensing which is mediated by small diffusible signalling molecules termed autoinducers. The most common class of autoinducer used by Gram-negative bacteria are N-acylated-L-homoserine lactones (AHLs). Pseudomonas aeruginosa is a clinically important bacterium which is known to use AHL-mediated quorum sensing systems to regulate a variety of processes associated with virulence. Thus the selective disruption of AHL-based quorum sensing represents a strategy to attenuate the pathogenicity of this bacterium. Herein we describe the design, synthesis and biological evaluation of a collection of structurally novel AHL mimics. A number of new compounds capable of modulating the LasR-dependent quorum sensing system of P. aeruginosa were identified, which could have value as molecular tools to study and manipulate this signalling pathway. Worthy of particular note, this research has delivered novel potent quorum sensing antagonists, which strongly inhibit the production of virulence factors in a wild type strain of this pathogenic bacterium.     

Detection of Salmonella in fresh cheese,poultry products,and dried egg products by the ISO 6579 Salmonella culture procedure and the AOAC official method: collaborative study

Three food types were analyzed for the presence of Salmonella by the AOAC culture method and by the International Organization for Standardization (ISO 6579:2002) culture method. Paired test portions of each food type were simultaneously analyzed by both methods. A total of 21 laboratories representing federal government agencies and private industry, in the United States and Europe, participated in this interlaboratory study. Foods were artificially contaminated with Salmonella and competing microflora if naturally contaminated sources were not available. No statistical differences (p < 0.05) were observed between the AOAC and ISO culture methods for fresh cheese and dried egg products. A statistically significant difference was observed for one of the 2 lots of poultry from the first trial. The poultry meat used in this run was radiation sterilized, artificially contaminated with Salmonella and competitive flora, and then lyophilized. A second trial was conducted with 2 separate lots of raw ground chicken that were naturally contaminated. The results from the second trial showed no statistical difference between the 2 culture methods. A third trial involving 4 laboratories was conducted on 2 separate lots of naturally contaminated raw poultry. Again, no statistically significant differences occurred. It is recommended that ISO 6579:2002 culture method for Salmonella be adopted Official First Action for the analysis of fresh cheese, fresh chilled and frozen poultry, and dried egg products.     

Juglone Inactivates Pseudomonas aeruginosa through Cell Membrane Damage,Biofilm Blockage,and Inhibition of Gene Expression

Due to the strong drug resistance of Pseudomonas aeruginosa (P. aeruginosa), the inhibition effects of conventional disinfectants and antibiotics are not obvious. Juglone extracted from discarded walnut husk, as a kind of plant-derived antimicrobial agent, has the advantages of naturalness, high efficiency, and low residue, with a potential role in the inhibition of P. aeruginosa. This study elucidated the inhibitory effect of juglone on the growth of plankton and the formation of P. aeruginosa biofilm. The results showed that juglone (35 μg/mL) had an irreversible inhibitory effect on P. aeruginosa colony formation (about 10⁷ CFU/mL). The integrity and permeability of the cell membrane were effectively destroyed, accompanied by disorder of the membrane permeability, mass leakage of the cytoplasm, and ATP consumption. Further studies manifested that juglone could induce the abnormal accumulation of ROS in cells and block the formation of the cell membrane. In addition, RT-qPCR showed that juglone could effectively block the expression of five virulence genes and two genes involved in the production of extracellular polymers, thereby reducing the toxicity and infection of P. aeruginosa and preventing the production of extracellular polymers. This study can provide support for the innovation of antibacterial technology toward P. aeruginosa in food.     

Muropeptides in Pseudomonas aeruginosa and their Role as Elicitors of β‐Lactam‐Antibiotic Resistance

Muropeptides are a group of bacterial natural products generated from the cell wall in the course of its turnover. These compounds are cell‐wall recycling intermediates and are also involved in signaling within the bacterium. However, the identity of these signaling molecules remains elusive. The identification and characterization of 20 muropeptides from Pseudomonas aeruginosa is described. The least abundant of these metabolites is present at 100 and the most abundant at 55,000 molecules per bacterium. Analysis of these muropeptides under conditions of induction of resistance to a β‐lactam antibiotic identified two signaling muropeptides (N‐acetylglucosamine‐1,6‐anhydro‐N‐acetylmuramyl pentapeptide and 1,6‐anhydro‐N‐acetylmuramyl pentapeptide). Authentic synthetic samples of these metabolites were shown to activate expression of β‐lactamase in the absence of any β‐lactam antibiotic, thus indicating that they serve as chemical signals in this complex biochemical pathway.     

Synthesis of [125I]iodoclorgyline, a selective monoamine oxidase A inhibitor, and its biodistribution in mice.

A new radioiodinated monoamine oxidase A (MAO-A) specific inhibitor, [125I]iodoclorgyline, was synthesized from its tin precursor by iododestannylation reaction using sodium [125I]iodide and hydrogen peroxide with high yield and site specificity. The product possessed a high radiochemical purity as well as high specific activity. The method can be readily applicable for labeling with 123I, a very suitable radioisotope for in vivo imaging with single photon emission computer tomography (SPECT). Biodistribution studies of the [125I]iodoclorgyline in mice showed high initial uptake in the brain, and brain radioactivity reached a constant level at 60 min after intravenous injection. The results suggested that [125I]iodoclorgyline might have potential as a radiopharmaceutical for MAO-A studies in the brain with SPECT.