Fate of GdF3 nanoparticles-loaded PEGylated carbon capsules inside mice model: a step toward clinical application.

The successful translation of nanostructure-based bioimaging and/or drug delivery system needs extensive in vitro and in vivo studies on biocompatibility, biodistribution, clearance, and toxicity for its diagnostic applications. Herein, we have investigated the in vitro cyto-hemocompatibility, in vivo biodistribution, clearance, and toxicity in mice after systemic administration of GdF3 nanoparticles loaded PEGylated mesoporous carbon capsule (GdF3-PMCC)-based theranostic system. In vitro cyto-hemocompatibility study showed a very good biocompatibility up to concentration of 500 µg/ml. Biodistribution studies carried out from 1 h to 8 days showed that GdF3-PMCC was found in major organs, such as liver, kidney, spleen, and muscle till 4th day and it was negligible in any tissue after 8th day. The clearance study was carried out for a period of 8 days and it was observed that the urinary system is the main route of excretion of GdF3-PMCC. The tissue toxicity study was done for 15 days and histopathological analysis indicated that the GdF3-PMCC based theranostic system does not have any adverse effect in tissues. Thus, PMCCs are nontoxic and can be applied as theranostic agents in contrast to the other carbon-based systems (PEGylated carbon nanotubes and PEGylated graphene oxide) which showed significant toxicity.

Fluorination Patterning: A Study of Structural Motifs That Impact Physicochemical Properties of Relevance to Drug Discovery.

The synthesis of a collection of 3-substituted indole derivatives incorporating partially fluorinated n-propyl and n-butyl groups is described along with an in-depth study of the effects of various fluorination patterns on their properties, such as lipophilicity, aqueous solubility, and metabolic stability. The experimental observations confirm predictions of a marked lipophilicity decrease imparted by a vic-difluoro unit when compared to the gem-difluoro counterparts. The data involving the comparison of the two substitution patterns is expected to benefit molecular design in medicinal chemistry and, more broadly, in life as well as materials sciences.

A reference agent model for DCE MRI can be used to quantify the relative vascular permeability of two MRI contrast agents.

Dynamic Contrast Enhancement (DCE) MRI has been used to measure the kinetic transport constant, K(trans), which is used to assess tumor angiogenesis and the effects of anti-angiogenic therapies. Standard DCE MRI methods must measure the pharmacokinetics of a contrast agent in the blood stream, known as the Arterial Input Function (AIF), which is then used as a reference for the pharmacokinetics of the agent in tumor tissue. However, the AIF is difficult to measure in pre-clinical tumor models and in patients. Moreover the AIF is dependent on the Fahraeus effect that causes a highly variable hematocrit (Hct) in tumor microvasculature, leading to erroneous estimates of K(trans). To overcome these problems, we have developed the Reference Agent Model (RAM) for DCE MRI analyses, which determines the relative K(trans) of two contrast agents that are simultaneously co-injected and detected in the same tissue during a single DCE-MRI session. The RAM obviates the need to monitor the AIF because one contrast agent effectively serves as an internal reference in the tumor tissue for the other agent, and it also eliminates the systematic errors in the estimated K(trans) caused by assuming an erroneous Hct. Simulations demonstrated that the RAM can accurately and precisely estimate the relative K(trans) (R(Ktrans)) of two agents. To experimentally evaluate the utility of RAM for analyzing DCE MRI results, we optimized a previously reported multiecho (19)F MRI method to detect two perfluorinated contrast agents that were co-injected during a single in vivo study and selectively detected in the same tumor location. The results demonstrated that RAM determined R(Ktrans) with excellent accuracy and precision.

Hydrothermal synthesis of NaLuF4:153Sm,Yb,Tm nanoparticles and their application in dual-modality upconversion luminescence and SPECT bioimaging.

Upconversion luminescence (UCL) properties and radioactivity have been integrated into NaLuF(4):(153)Sm,Yb,Tm nanoparticles by a facile one-step hydrothermal method, making these nanoparticles potential candidates for UCL and single-photon emission computed tomography (SPECT) dual-modal bioimaging in vivo. The introduction of small amount of radioactive (153)Sm(3+) can hardly vary the upconversion luminescence properties of the nanoparticles. The as-designed nanoparticles showed very low cytotoxicity, no obvious tissue damage in 7 days, and excellent in vitro and in vivo performances in dual-modal bioimaging. By means of a combination of UCL and SPECT imaging in vivo, the distribution of the nanoparticles in living animals has been studied, and the results indicated that these particles were mainly accumulated in the liver and spleen. Therefore, the concept of (153)Sm(3+)/Yb(3+)/Tm(3+) co-doped NaLuF(4) nanoparticles for UCL and SPECT dual-modality imaging in vivo of whole-body animals may serve as a platform for next-generation probes for ultra-sensitive molecular imaging from the cellular scale to whole-body evaluation. It also introduces an easy methodology to quantify in vivo biodistribution of nanomaterials which still needs further understanding as a community.

Alternate strategies to obtain mass balance without the use of radiolabeled compounds: application of quantitative fluorine (19F) nuclear magnetic resonance (NMR) spectroscopy in metabolism studies.

Nuclear magnetic resonance (NMR) spectroscopy is playing an increasingly important role in the quantitation of small and large molecules. Recently, we demonstrated that (1)H NMR could be used to quantitate drug metabolites isolated in submilligram quantities from biological sources. It was shown that these metabolites, once quantitated by NMR, were suitable to be used as reference standards in quantitative LC/MS-based assays, hence circumventing the need for radiolabeled material or synthetic standards to obtain plasma exposure estimates in humans and preclinical species. The quantitative capabilities of high-field NMR is further demonstrated in the current study by obtaining the mass balance of fluorinated compounds using (19)F-NMR. Two fluorinated compounds which were radio-labeled with carbon-14 on metabolically stable positions were dosed in rats and urine and feces collected. The mass balance of the compounds was obtained initially by counting the radioactivity present in each sample. Subsequently, the same sets of samples were analyzed by (19)F-NMR, and the concentrations determined by this method were compared with data obtained using radioactivity counting. It was shown that the two methods produced comparable values. To demonstrate the value of this analytical technique in drug discovery, a fluorinated compound was dosed intravenously in dogs and feces and urine collected. Initial profiling of samples showed that this compound was excreted mainly unchanged in feces, and hence, an estimate of mass balance was obtained using (19)F-NMR. The data obtained by this method was confirmed by additional quantitative studies using mass spectrometry. Hence cross-validations of the quantitative (19)F-NMR method by radioactivity counting and mass spectrometric analysis were demonstrated in this study. A strategy outlining the use of fluorinated compounds in conjunction with (19)F-NMR to understand their routes of excretion or mass balance in animals is proposed. These studies demonstrate that quantitative (19)F-NMR could be used as an alternate technique to obtain an estimate of the mass balance of fluorinated compounds, especially in early drug development where attrition of the compounds is high, and cost savings could be realized through the use of such a technique rather than employing radioactive compounds. The potential application of qNMR in conducting early human ADME studies with fluorinated compounds is also discussed.

[Biologic markers of exposure to and effects of fluorine compounds in workers engaged into aluminum industry].

The study in 727 workers exposed to inorganic fluorine compounds revealed through ultrasound densitometry changes in fluorine excretion and bone tissue density in accordance with the length of service, through markers of bone destruction and synthesis features of bone remodelling were specified.

Trifluoromethoxy-benzylated ligands improve amyloid detection in the brain using (19)F magnetic resonance imaging.

The chemical properties of probes that improve amyloid detection by non-invasive (19)F magnetic resonance imaging (MRI) are of interest. We synthesized benzoxazole compounds with trifluoromethoxy groups, and found that these compounds displayed sharp (19)F nuclear magnetic resonance (NMR) signals in an assay buffer. However, the intensities of the (19)F NMR signals were dramatically reduced in mouse brain lysates. Our results indicate that the inhibitory effect of brain tissue on the (19)F NMR signals from these probes can be attributed to the hydrophobicity of the tissue. These results highlight the importance of using hydrophilic (19)F-MRI agents to avoid the inhibitory effects of brain tissues on (19)F NMR signals.

The tissue distribution of fluoride in a fatal case of self-poisoning.

The purpose of this paper is to report a case of fluoride poisoning along with a discussion of poisoning characteristics, analytical procedures, and a review of previous reports of fatal intoxications with analytical data. A case of suicidal ingestion of 40 mL of a rust removal agent containing hydrofluoric acid and ammonium fluoride by a 33-year-old white male is presented. He had an organic personality disorder with residual schizophrenia and previous suicide attempts with therapeutic drugs and cleaning products. At admission, he presented with a Glasgow coma score of 3, third degree atrioventricular block, and asystole. Resuscitation efforts were performed during which the patient suffered two episodes of ventricular fibrillation followed by asystole. In spite of advanced resuscitation efforts and the administration of calcium chloride, he died 2.5 h after the ingestion. Analytical data in the hospital showed calcium levels of 3.1 mg/dL and metabolic acidosis. Internal findings were erosive gastritis, brain edema, and pulmonary and hepatic congestion. Quantitation of fluoride was performed using an ion-selective electrode for the anion. Disposition of fluoride in the different tissues was as follows: peripheral blood, 19.4 mg/L; urine, 670 mg/L; vitreous humor, 2.5 mg/L; liver, 40.0 mg/kg; kidney, 60.0 mg/kg; lung, 17.5 mg/kg; brain, 2.5 mg/kg; spleen, 30.0 mg/kg; bone, 0.5 mg/ kg; and gastric content, 1120 mg/L (67 mg total). Validation of the analytical method was performed using different spiked tissues, in a range of concentrations from 2.4 to 475 mg/L or mg/kg, and submitting them to dilution (1:25) to avoid the matrix effect and to bring these concentrations to the range of the aqueous calibration curve (0.19-19 mg/L). Limits of detection and quantitation were 0.02 and 0.1 mg/L, respectively. The linearity of the method, for all studies tissues, was excellent, with r(2) values of 0.999. Accuracy and precision were within 10.5% and 5.7%, respectively. Fluoride analyses using the ion selective electrode are simple, sensitive, and rapid. This report provides an extensive tissue distribution study of fluoride after a well documented case of acute poisoning. Based on the autopsy findings, patient history, toxicology results, and previously reported data the forensic pathologists ruled that the cause of death was due to a fluoride poisoning, and the manner of death was listed as suicide.

Magnetic resonance spectroscopy for measuring the biodistribution and in situ in vivo pharmacokinetics of fluorinated compounds: validation using an investigation of liver and heart disposition of tecastemizole.

BACKGROUND AND OBJECTIVE: The study of biodistribution and in situ pharmacokinetics is a challenging, but sometimes very important, aspect of premarketing characterization of drugs. We aimed to develop a non-invasive fluorine magnetic resonance (MR) spectroscopic method for the absolute quantitation of a mono-fluorinated compound and of its metabolites in the heart and liver of healthy subjects for this purpose. METHOD: We used fluorine MR spectroscopy (MRS) at 4 T (Tesla) and external standardization in an open label multiple-dose study. Twenty-three healthy adult subjects were enrolled in the study. The surface coil localized fluorine MR spectrum was monitored in the heart and liver at baseline and after oral administration of multiple doses of tecastemizole. Steady-state measurements were made at set time points that depended upon dose, and washout measurements were made only on subjects in which in vivo fluorine signal was observed. RESULTS AND DISCUSSION: At 4 T, under the given experimental conditions, the method had a lower limit of quantitation (LLOQ) of about 2.6 microm and a limit of detection (LOD) of about 0.3 microm for solution state samples (linewidth approximately 15 Hz). The measurement reproducibility was 6.4% using a 50 microm phantom. The effect of MR operator and spectral analyst on the calculated calibration curve slope was small, with inter-rater correlation coefficients of 0.999 and 0.998 respectively. MR signal from fluorine-containing tecastemizole-related moieties was observed in situ only at day 8 in the liver of three of five subjects dosed at 270 mg/day. The average in situ concentration was estimated to be 58+/-22 microm, with an average test-retest reproducibility of 216%. Extrapolating the in vitro results to human measurements, with an approximate linewidth of 250 Hz, predicts in situ LOD and LLOQ values of approximately 6 and 44 microm respectively. However, the human study had a fluorine MRS LOD of approximately 20 microm. The decrease in sensitivity and the increase in variability of the in vivo, in situ measurements compared with the validation study most likely arose from coil placement and incomplete rephasing of the MR signal by the respiratory phase compensation method. CONCLUSION: The measured concentrations were the lowest ever recorded for a multi-dose exogenous mono-fluorinated compound in the human liver using a validated fluorine MR quantitation method. The proposed non-invasive MR method for studying the biodistribution and in situ pharmacokinetics of mono-fluorinated compounds in the liver and heart should have broader application to the development of non-invasive biomarkers.

High-performance liquid chromatography/inductively coupled plasma mass spectrometry with iodine-specific detection for profiling the metabolites produced in the earthworm Eisenia veneta by exposure to 2-fluoro-4-iodoaniline.

High-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICPMS) provided a rapid and specific means for profiling the iodine-containing metabolites produced by the earthworm Eisenia veneta following exposure to 2-fluoro-4-iodoaniline. Profiles were obtained, using gradient reversed-phase HPLC, from extracts of whole earthworms and from coleomic fluid with as little as 25 ng/peak of iodine detected. The use of ICPMS in this way provides a convenient means of determining the metabolic fate of iodinated compounds without the need for radiolabelled compounds.

Comparison of [18 F]fluorocholine and [18 F]fluorodeoxyglucose for positron emission tomography of androgen dependent and androgen independent prostate cancer.

PURPOSE: Positron emission tomography (PET) imaging is used for the metabolic evaluation of cancer. [18F]fluorodeoxyglucose (FDG) is commonly used as a radiotracer but its low cellular uptake rate in prostate cancer limits its usefulness. We evaluated the novel choline analog [18F]fluorocholine (FCH) for detecting androgen dependent and androgen independent prostate cancer, and its metastases. MATERIALS AND METHODS: The cellular uptake of FCH and FDG was compared in cultured prostate cancer cells (LNCaP and PC-3). FCH and FDG were injected into nude mice xenografts (CWR-22 and PC-3) and radiotracer uptake in various organs were evaluated. Patients with androgen dependent (9) and independent (9) prostate cancer were studied by FCH and FDG PET. RESULTS: FCH uptake was 849% and 60% greater than FDG uptake in androgen dependent (LNCaP) and independent (PC-3) cells, respectively. The addition of hemicholinium-3 (5 mM.) 30 minutes before radiotracer administration inhibited FCH uptake by 79% and 70% in LNCaP and PC-3 cells, respectively, whereas FDG uptake was not significantly affected. Although nude mice xenografts showed that FDG uptake was equal to or greater than FCH uptake, clinical imaging in patients demonstrated 2 to 4-fold higher uptake of FCH in those with androgen and androgen independent prostate carcinoma (p <0.001). More lesions were detected by FCH than by FDG in primary tumors, osseous metastases and soft tissue metastases. CONCLUSIONS: In vitro data demonstrated greater FCH than FDG uptake in androgen dependent (LNCaP) and androgen independent (PC-3) prostate cancer cells. Although the murine xenograft data showed greater accumulation of FDG than FCH in PC-3 tumors, PET in humans showed that FCH was better than FDG for detecting primary and metastatic prostate cancer. Overall the data from this study suggest that FCH is preferable to FDG for PET of prostate carcinoma and support the need for future validation studies in a larger number of subjects.

Metabolism of fluorine-containing drugs.

This article reviews current knowledge of the metabolism of drugs that contain fluorine. The strategic value of fluorine substitution in drug design is discussed in terms of chemical structure and basic concepts in drug metabolism and drug toxicity.

Fluorination of 3-(3-(piperidin-1-yl)propyl)indoles and 3-(3-(piperazin-1-yl)propyl)indoles gives selective human 5-HT1D receptor ligands with improved pharmacokinetic profiles.

It has previously been reported that a 3-(3-(piperazin-1-yl)propyl)indole series of 5-HT1D receptor ligands have pharmacokinetic advantages over the corresponding 3-(3-(piperidin-1-yl)propyl)indole series and that the reduced pKa of the piperazines compared to the piperidines may be one possible explanation for these differences. To investigate this proposal we have developed versatile synthetic strategies for the incorporation of fluorine into these ligands, producing novel series of 4-fluoropiperidines, 3-fluoro-4-aminopiperidines, and both piperazine and piperidine derivatives with one or two fluorines in the propyl linker. Ligands were identified which maintained high affinity and selectivity for the 5-HT1D receptor and showed agonist efficacy in vitro. The incorporation of fluorine was found to significantly reduce the pKa of the compounds, and this reduction of basicity was shown to have a dramatic, beneficial influence on oral absorption, although the effect on oral bioavailability could not always be accurately predicted.