Biodistribution and acute toxicity of cadmium-free quantum dots with different surface functional groups in mice following intratracheal inhalation.

Indium phosphide/zinc sulfate (InP/ZnS) quantum dots (QDs) are presumed to be less hazardous than those that contain cadmium. However, the toxicological profile has not been established. The present study investigated the acute toxicity of InP/ZnS QDs with different surface modifications (COOH, NH2, and OH) in mice after pulmonary aerosol inhalation. InP/ZnS QDs were able to pass through the blood-gas barrier and enter the circulation, and subsequently accumulated in major organs. No obvious changes were observed in the body weight or major organ coefficients. Red blood cell counts and platelet-related indicators were in the normal range, but the proportion of white blood cells was altered. The InP/ZnS QDs caused varying degrees of changes in some serum markers, but no histopathological abnormalities related to InP/ZnS QDs treatment was observed in major organs except that hyperemia in alveolar septa was found in lung sections. These results suggested that the effects of respiratory exposure to InP/ZnS QDs on the lungs need to be fully considered in future biomedical application although the overall toxicity of quantum dots is relatively low.

Pharmacokinetics and Tissue Distribution of a Novel Bis-Chelated Gold(I) Diphosphine Compound, Bis(2,3-bis(tert-butylmethylphosphino)Quinoxaline)Aurate(I), in Rats.

GC20, a novel soluble bis-chelated gold(I)-diphosphine compound, has been reported as a promising anticancer candidate. Assessing the pharmacokinetic properties of GC20 is critical for its medicinal evaluation. First, a sensitive and specific liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed and well validated to determine GC20 in rat plasma and rat tissue homogenate after one step protein precipitation. Chromatographic separation was achieved on an Angilent ZORBAX-C18 column (3.5 µm, 2.1 × 50 mm) with gradient elution and mass spectrometry was performed on a triple quadrupole in positive ion mode using an electrospray ionization source. This method was then applied to investigate the pharmacokinetics and tissue distribution of GC20 in rats after intravenous administration. The results showed that the plasma exposure of GC20 in vivo increased with increasing doses after a single dose. However, after multiple doses, a significant accumulation and a saturation at elimination were observed for GC20 in rats. Moreover, after intravenous administration, GC20 was widely distributed in various tissues, with the highest levels in the lung, spleen, liver, and pancreas, followed by the kidney and heart, while the lowest level was found in the brain. This is the first report on the pharmacokinetic properties of GC20.

A luminescent and biocompatible photoCORM.

The water-soluble rhenium(I) complex fac-[Re(bpy)(CO)(3)(thp)](+) (1) [CF(3)SO(3)(-) salt; bpy = 2,2'-bipyridine, thp = tris(hydroxymethyl)phosphine] is both strongly luminescent and photoactive toward carbon monoxide release. It is stable in aerated aqueous media, is incorporated into cells from the human prostatic carcinoma cell line PPC-1, and shows no apparent cytotoxicity. Furthermore, the solvated Re(I) photoproduct of CO release (2) is also luminescent, a feature that allows one to track the transformation of 1 to 2 inside such cells using confocal fluorescence microscopy. In this context, 1 is a very promising candidate as a photoactivated CO releasing moiety (photoCORM) with potential therapeutic applications.

Synthesis of phosphine and antibody-azide probes for in vivo Staudinger ligation in a pretargeted imaging and therapy approach.

The application of intact monoclonal antibodies (mAbs) as targeting agents in nuclear imaging and radioimmunotherapy is hampered by the slow pharmacokinetics of these molecules. Pretargeting with mAbs could be beneficial to reduce the radiation burden to the patient, while using the excellent targeting capacity of the mAbs. In this study, we evaluated the applicability of the Staudinger ligation as pretargeting strategy using an antibody-azide conjugate as tumor-targeting molecule in combination with a small phosphine-containing imaging/therapeutic probe. Up to 8 triazide molecules were attached to the antibody without seriously affecting its immunoreactivity, pharmacokinetics, and tumor uptake in tumor bearing nude mice. In addition, two (89)Zr- and (67/68)Ga-labeled desferrioxamine (DFO)-phosphines, a (177)Lu-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-phosphine and a (123)I-cubyl phosphine probe were synthesized and characterized for their pharmacokinetic behavior in nude mice. With respect to the phosphine probes, blood levels at 30 min after injection were <5% injected dose per gram tissue, indicating rapid blood clearance. In vitro Staudinger ligation of 3.33 µM antibody-azide conjugate with 1 equiv of radiolabeled phosphine, relative to the azide, in aqueous solution resulted in 20-25% efficiency after 2 h. The presence of 37% human serum resulted in a reduced ligation efficiency (reduction max. 30% at 2 h), while the phosphines were still >80% intact. No in vivo Staudinger ligation was observed in a mouse model after injection of 500 µg antibody-azide, followed by 68 µg DFO-phosphine at t = 2 h, and evaluation in blood at t = 7 h. To explain negative results in mice, Staudinger ligation was performed in vitro in mouse serum. Under these conditions, a side product with the phosphine was formed and ligation efficiency was severely reduced. It is concluded that in vivo application of the Staudinger ligation in a pretargeting approach in mice is not feasible, since this ligation reaction is not bioorthogonal and efficient enough. Slow reaction kinetics will also severely restrict the applicability of Staudinger ligation in humans.

Synthesis, characterization and biological evaluation of [188Re(N)(cys ∼)(PNP)]+/0 mixed-ligand complexes as prototypes for the development of 188Re(N)-based target-specific radiopharmaceuticals.

We report on an efficient procedure for the preparation of [(188)Re(N)(PNP)]-based complexes (where PNP is diphosphinoamine) useful in the development of target-specific radiopharmaceuticals. The radiochemical yield of the compounds was optimized considering such reaction parameters as nature of the nitrido nitrogen donor, reaction times and pH level. The chemical identity of the (188)Re agents was determined by high-performance liquid chromatography comparison with the corresponding well-characterized cold Re compounds. (188)Re(N) mixed compounds have been evaluated with regard to stability toward transchelation with GSH and degradation by serum enzymes. The clearance of selected radiocompounds from normal tissues and their in vivo stability were evaluated in rats by biodistribution and imaging studies. [(188)Re(N)(cys ∼)(PNP)](+/0) mixed-ligand compounds were efficiently prepared in aqueous solution from perrhenate using a multistep procedure based on the preliminary formation of the labile (188)Re(III)-EDTA species, which easily undergo oxidation/ligand exchange reaction to afford the [(188)Re(V) ≡ N](2+) core in the presence of dithiocarbazate. The final mixed-ligand compounds were obtained, at 100 °C, by adding the two bidentate ligands to the buffered [(188)Re(V) ≡ N](2+) solution (pH 3.2-3.6). However, a relatively high amount of cys ∼ ligand was required to obtain a quantitative radiochemical yield. The complexes were stable toward reoxidation to perrhenate and ligand exchange reactions. In vivo studies showed rapid distribution and elimination of the complexes from the body. No specific uptakes in sensitive tissues/organs were detected. A positive correlation of the distribution of the complexes estimated with biodistribution studies (%ID) and with micro-SPECT semiquantification imaging analysis (standard uptake values) was observed. These results support the possibility of applying [(188)Re(N)(PNP)] technology to the preparation of target-specific agents.

Radiolabeled bombesin analogs for prostate cancer diagnosis: preclinical studies.

INTRODUCTION: Radionuclide imaging can be a useful tool for the diagnosis of prostate cancer. Bombesin (BBN) is a molecule with high affinity for gastrin releasing peptide (GRP) receptors which are over-expressed in that tumor. This report compares (99m)Tc-HYNIC-betaAla-BBN(7-14)NH2 [(99m)Tc-HYNIC-BBN] and (99m)Tc identical withN(PNP6)-Cys-betaAla-BBN(7-14)NH2 [(99m)TcN(PNP6)-Cys-BBN] with regard to labeling procedures as well as in vitro and in vivo evaluation (biodistribution and scintigraphic imaging). METHODS: Peptide synthesis was performed in an automated peptide synthesizer. HYNIC-BBN was radiolabeled with pertechnetate using tricine and ethylenediamine diacetic acid (EDDA) as coligands. Cys- BBN was radiolabeled in a two-step procedure with the preparation of the precursor (99m)Tc-Nitrido first and then introducing diphosphine (PNP6). Radiochemical evaluation of conjugates, as well as studies of stability, transchelation toward cysteine, and partition coefficient were done. Biological studies included internalization, biodistribution in healthy animals and in animals bearing PC3 cancer cells with acquisition of images from the tumor-bearing animals. RESULTS: Both complexes showed a high radiochemical yield along with good stability. Biodistribution studies pointed out strong renal excretion for the former complex due to its hydrophilic profile and marked hepatobiliary excretion for the latter, corresponding to observed lipophilicity. Tumor uptake was higher for (99m)Tc-HYNIC-BBN and the same occurred with internalization findings, which exceeded those of (99m)TcN(PNP6)-BBN. Blocking studies in mice bearing PC-3 tumor cells revealed significantly reduced pancreas and tumor uptake, demonstrating receptor specificity of the conjugates. CONCLUSION: The best radiotracer was (99m)Tc-HYNIC-BBN on the basis of high radiochemical yield, fast radiolabeling procedure without need for a purification step, and more consistent tumor uptake.

Synthesis, in vitro and in vivo characterization of (64)Cu(I) complexes derived from hydrophilic tris(hydroxymethyl)phosphane and 1,3,5-triaza-7-phosphaadamantane ligands.

Four novel (64)Cu complexes ([(64)Cu(thp)(4)](+) (1), [(64)Cu(TPA)(4)](+) (2), [HC(CO(2))(pz(Me2))(2) (64)Cu(thp)(2)] (3) and [HC(CO(2))(tz)(2) (64)Cu(thp)(2)] (4), [where thp is tris(hydroxymethyl)phosphine, TPA is 1,3,5-triaza-7-phosphaadamantane, pz(Me2) is 3,5-dimethylpyrazole and tz is 1,2,4-triazole] were successfully synthesized and characterized. The complexes were produced in high radiochemical purity and yield (more than 98%) without the need for further purification. Their logP values and serum stabilities were measured and in vitro behavior was observed in cultured EMT-6 cells. The logP values (+/- standard deviation) obtained were -2.26 +/- 0.04 (1), 0.01 +/- 0.01 (2), -1.24 +/- 0.03 (3) and -2.06 +/- 0.03 (4). Complex 3 demonstrated the highest serum stability, with approximately 33% of the complex still intact after 1-h incubation. Complex 2 showed a rapid cell-association with EMT-6 cells, with more than 8.5% association at 2 h. This association was significantly higher (P < 0.001) than for the other three compounds after a 2-h incubation (1, 1.21%; 3, 0.63%; 4, 2.75%). Biodistribution and small-animal positron emission tomography/computed tomography was undertaken with 1 in mice bearing EMT-6 tumors. EMT-6 tumor uptake was high at 1 h (7.71 +/- 2.17 %ID/g) and decreased slowly over 24 h (4 h, 4.90 +/- 0.78 %ID/g; 24 h, 3.74 +/- 0.73 %ID/g). The PET/CT images show that the EMT-6 tumors can be visualized at all time points. In this proof-of-concept study, we have successfully synthesized and characterized a novel series of versatile water-soluble Cu(I) complexes containing monophosphine ligands. We also report the use of 1 as a building block for new radiopharmaceuticals, perhaps the first time such a method has been used in the production of copper radiopharmaceuticals.

Versatile PEG-derivatized phosphine oxide ligands for water-dispersible metal oxide nanocrystals.

We report the simple synthesis of poly(ethylene glycol)(PEG)-derivatized phosphine oxide ligands for water-dispersible metal oxide nanocrystals.

Role of lipophilicity in determining cellular uptake and antitumour activity of gold phosphine complexes.

PURPOSE: The lipophilic cation [Au(I)(dppe)2]+ [where dppe is 1,2-bis(diphenylphosphino)ethane] has previously demonstrated potent in vitro antitumour activity. We wished to determine the physicochemical basis for the cellular uptake of this drug, as well as of analogues including the 1:2 adducts of Au(I) with 1,2-bis(di-n-pyridylphosphino)ethane (dnpype; n = 2, 3 and 4), and to compare in vitro and in vivo antitumour activity. METHODS AND RESULTS: Logarithmic IC50 values for the CH-1 cell line bore a parabolic dependence on drug lipophilicity, as measured either by high-performance liquid chromatography or by n-octanol-water partition. Cellular uptake of drug, as measured by inductively coupled plasma mass spectrometry, varied by over three orders of magnitude over the series. Logarithmic uptake had a parabolic dependence on drug lipophilicity but a linear relationship to logarithmic IC50 values. Free drug concentrations were determined under the culture conditions and logarithmic free drug IC50 values and uptake rates were linearly related to lipophilicity. Uptake of drug in vivo in tissue from murine colon 38 tumours was approximately proportional to the dose administered. Host toxicity varied according to lipophilicity with the most selective compound having an intermediate value. This compound was also the most active of those tested in vivo, giving a growth delay of 9 days following daily intraperitoneal dosing (10 days) at 4 micromol kg(-1) day(-1). It was also significantly more active than another lipophilic cation, MKT-077. CONCLUSIONS: Alteration of lipophilicity of aromatic cationic antitumour drugs greatly affects cellular uptake and binding to plasma proteins. Changes in lipophilicity also affect host toxicity, and optimal lipophilicity may be a critical factor in the design of analogues with high antitumour activity.