Tricarbonyl (99m)Tc(i) and Re(i)-thiosemicarbazone complexes: synthesis, characterization and biological evaluation for targeting bacterial infection.

Methyl, ethyl and phenyl nitrofuryl thiosemicarbazone ligands (, and respectively) were radiolabeled with freshly prepared aqueous solution of a fac[(99m)Tc(CO)3(H2O)3](+) precursor. The radiochemical yield was around 98% as determined by thin layer chromatography and HPLC. The complexes exhibited substantial stability. The corresponding Re(i) complexes were prepared from a Re(CO)5Br precursor to understand the coordination behavior of the ligands against a tricarbonyl rhenium(i) precursor. The rhenium(i) complexes were characterized by means of IR, NMR and mass spectroscopic studies as well as by X-ray crystallography, and correlated with the technetium complexes by means of HPLC studies. Electrochemical reduction of monomeric Re(CO)3-complexes of nitrofuryl ethyl thiosemicarbazone was also studied using cyclic voltammetry. Biodistribution studies of (99m)Tc(CO)3-labeled thiosemicarbazones in rats intramuscularly infected with S. aureus exhibited substantial in vivo stability of the complex and moderate accumulation at the site of focal infection.

[Diagnosis of sphincter of Oddi dysfunction in patients with postcholecystectomy syndrome from hepatobiliary scintigraphic findings].

OBJECTIVE: to diagnose and estimate the clinical value of postcholecystectomy sphincter of Oddi dysfunction in patients. MATERIAL AND METHODS: Examinations were made in 100 postcholecystectomy patients without signs of cholestasis; of them 14 postpapillotomy patients formed a comparison group. Hepatobiliary scintigraphy using the radiotracer 99mTC-bromeside was performed for 90 minutes with cholagogue breakfast at 45 minutes. Common bile duct and duodenal functions and duodenogastric reflux (DGR) were evaluated comparing them with clinical, laboratory, and instrumental findings. RESULTS: Two patient groups were identified according to bile outflow changes. In Group I consisting of 20 (23.2%) patients, the time of maximum accumulation (Tmax) of the radiopharmaceutical in the projection of the choledochus coincided with that in the cholagogue test (46.0 1.8 min) and in Group 2 including 66 (76.8%) patients that was shorter than in the cholagogue test (32.9 +/- 6.8 min) (p<0.05). In Group 2, Tmax was similar to that in the comparison group (30.9 +/- 7.5 min; p > 0.05) and there was no significant difference in intestinal imaging time (18.6 +/- 6.0 min versus 17.6 +/- 0.8) either, which could be indicative of sphincter of Oddi dysfunction. Diarrhea was observed in 73% of the patients with sphincter of Oddi dysfunction and in 86% of the patients in the comparison group versus 10% of the patients with normal bile passage (p<0.01). Statistical data processing showed a correlation of the indicators of sphincter of Oddi dysfunction with those of duodenal evacuator function (r = 0.57; p < 0.0005) and DGR (r = 0.74; p < 0.009). CONCLUSION: Postcholecystectomy sphincter of Oddi dysfunction assumes the greatest clinical value in patients with duodenal motor-evacuator dysfunction, which should be hepatobiliamy scintigraphic, kept in mind when choossphincter of Oddi dysfunction ing a treatment policy.

Direct 99m Tc labeling of Herceptin (trastuzumab) by 99m Tc(I) tricarbonyl ion.

By simply incubating Herceptin (trastuzumab) with [99m Tc(CO)3(OH2)3]+ ion in saline, a significant yield of 99m Tc-labeled trastuzumab was found to be achievable. The effective labeling may be based on that trastuzumab is inherent with endogenous histidine group to which 99m Tc(I) tricarbonyl ion can be strongly bound. For practical 99m Tc labeling processing, trastuzumab was purified beforehand from the commercial product, Herceptin (Genentech) via size exclusion chromatography to remove the excipient, alpha-histidine and a high-labeled yield could be obtained by incubating the purified trastuzumab with [99m Tc(CO)3(OH2)3]+. Retention of bioactivity of the 99m Tc(I)-labeled trastuzumab was validated using a cell binding test.

Molecular modeling of hexakis(areneisonitrile)technetium(I), tricarbonyl eta5 cyclopentadienyl technetium and technetium(V)-oxo complexes: MM3 parameter development and prediction of biological properties.

Genetic algorithms (GA) were used to develop specific technetium metal-ligand force field parameters for the MM3 force field. These parameters were developed using automated procedures within the program FFGenerAtor from a combination of crystallographic structures and ab initio calculations. These new parameters produced results in good agreement with experiment when tested against a blind validation set. To illustrate the utility of these new force field parameters, quantitative structure-activity relationship (QSAR) models were developed to predict the P-glycoprotein uptake (log10 VI) of a series of hexakis(areneisonitrile)technetium(I) complexes and to predict their biodistribution. The log10 VI QSAR model, built using a training set of 16 Tc(I) isonitrile complexes, exhibited a correlation between the experimental log10 VI and 5 simple descriptors as follows: r2 = 0.94, q2 = 0.93. When applied to an external test set of six Tc(I) isonitrile complexes, the QSAR preformed with great accuracy q2 = 0.78 based on a leave-one-out cross-validation analysis. Further QSAR models were developed to predict the biodistribution of the same set of Tc(I) isonitrile complexes; a QSAR model to predict hepatic uptake exhibited a correlation between the experimental log10(Blood/Liver) with six simple descriptors as follows: r2 = 0.97, q2 = 0.96. A QSAR model to predict renal uptake exhibited a correlation between the experimental log10(Blood/Kidney) and six simple descriptors as follows: r2 = 0.85, q2 = 0.82. When applied to the external test set the QSAR models preformed with great accuracy, q2 = 0.78 and 0.56, respectively.

Synthesis and in vitro/in vivo evaluation of novel 99mTc(CO)3-folates.

Novel organometallic 99mTc(I)-folate derivatives have been synthesized and evaluated in vitro and in vivo in order to assess the influence of the overall charge of the radioconjugates and the spacer entity on the affinity and pharmacokinetic profile. Folic acid has been functionalized at the gamma-carboxylate group of the glutamate moiety with (i) a hydrophilic diethoxyethyl spacer bearing a picolylamine monoacetic acid chelate, (ii) a hexyl spacer bearing an iminodiacetic acid chelate, and (iii) a hexyl spacer with a bis(pyridylmethyl)amine chelating system. Coordination of the 99mTc(CO)3-core resulted in neutral complex 21, anionic complex 22, and cationic complex 23 in excellent yields (>90%) at ligand concentrations of 10(-4) M. Complexes 21-23 were HPLC purified for in vitro and in vivo experiments. In the case of 23, separation from the unlabeled folate analogue was incomplete, leading to low specific activity and, hence, significantly inferior in vivo uptake in folate-receptor-positive (FR-positive) organs and tissues (tumors and kidneys). Time dependent in vivo studies were performed in female, athymic nude mice bearing subcutaneous FR-positive human KB cell xenografts at 1, 4, and 24 h post injection (p.i.) of the radiotracers. Tumor uptake ranged between 1.9-2.7% ID/g, 4 h p.i. and 1.6-2.2% ID/g, 24 h p.i. for 21 and 22, and 0.9% ID/g, 4 h p.i. and 1.1% ID/g, 24 h p.i. for 23. Blood clearance was fast for all derivatives (< or =0.2% ID/g 1 h p.i.). Significant fractions of radioactivity were found in nontargeted and FR-negative organs and tissues (particularly in the liver and the intestines/intestinal contents) at early time points p.i. Coadministration of folic acid reduced radioactivity in FR-positive tissues and organs to background levels. In conclusion, overall charge and the nature of the spacer entity seemed to have a relatively minor influence on receptor affinity and the in vivo pharmacokinetic profile of the tested radiofolates.

99mTc-SnF2 colloid "LLK": particle size, morphology and leucocyte labelling behaviour.

99mTc-SnF2 colloid (Radpharm LLK) leucocyte labelling agent is used in whole blood, exploiting phagocytosis. The objectives of this work were to optimize leucocyte labelling in leucocyte-enriched plasma, and to investigate: (i) the effect of temperature and other factors on labelling efficiency; (ii) the selectivity for different leucocyte types; (iii) the viability of the labelled cells and efflux of the radiolabel; and (iv) the physical characteristics of the colloid. Density gradient centrifugation was used to investigate the labelling efficiency, cell selectivity and efflux, Trypan blue to study the viability, and laser scattering, electron microscopy and membrane filtration to investigate particle size and morphology. Particles appeared as loose, coiled, chain-like aggregates of much smaller particles (<0.05 microm). The aggregate diameter ranged from <0.1 to >5 microm and increased with time. The distribution of radioactivity amongst the particle sizes varied widely. The labelling efficiency in leucocyte-rich plasma was enhanced at 37 degrees C compared to room temperature, and by centrifuging during labelling. The selectivity for different leucocyte types varied markedly between batches and blood samples, in some cases showing preference for mononuclear cells and in others for granulocytes. Viability was excellent and comparable with 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO)-labelled cells. A significant fraction of radiolabel, comparable to that observed with 99mTc-HMPAO, was lost from leucocytes during incubation in vitro over 4 h. Thus, 99mTc-SnF2 is a convenient, efficient labelling agent for leucocytes, but shows variable cell selectivity which may be linked to particle size variability, and there is significant efflux of radioactivity from labelled cells.

Thrombus imaging using technetium-99m-labeled high-potency GPIIb/IIIa receptor antagonists. Chemistry and initial biological studies.

Platelet-specific compounds which are radiolabeled with gamma-emitting radionuclides may be particularly useful for the noninvasive in vivo detection of thrombi. The synthesis of peptides which are potent inhibitors of platelet aggregation and which contain a chelator for the radionuclide technetium-99m are described. The target compounds were designed such that stable, oxotechnetium(V) species could be prepared where the site of metal coordination was well defined. A strategy was employed where the pharmacophore-Arg-Gly-Asp-(RGD), or RGD mimetic, was constrained in a ring which was formed by the S-alkylation of a cysteine residue with an N-terminal chloroacetyl group. Binding affinities were enhanced by the replacement of arginine with the arginine mimetics S-(3-aminopropyl)cysteine and 4-amidinophenylalanine. Further enhancements could be obtained by the synthesis of oligomers which contained two or more rings containing receptor binding regions. The increase in binding affinity seen was more than that expected from a simple stoichiometric increase of pharmacophore. The most potent compounds described had IC50s of approximately 0.03 microM for the inhibition of human platelet aggregation. Two of the more potent peptides (P280 and P748) were labeled with technetium-99m and assessed in a canine thrombosis model. The 99m Tc complexes of the peptides prepared in this work hold promise as thrombus imaging agents due to their high receptor binding affinity, ease of preparation, and expected rapid pharmacokinetics.