Synthesis of a new fluorine-18-labeled bexarotene analogue for PET imaging of retinoid X receptor

The reference standard 2-fluoro-4-(1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl)vinyl)benzoic acid was synthesized from 2,5-dimethyl-2,5-hexanediol and 2-fluoro-4-methylbenzoic acid in 10 steps with 3% overall chemical yield. The precursor 2-nitro-4-(1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl)vinyl)benzoic acid was synthesized from 2,5-dimethyl-2,5-hexanediol and dimethyl-2-nitroterephthalate in seven steps with 2% overall chemical yield. The target tracer 2-[¹⁸F]fluoro-4-(1-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl)vinyl)benzoic acid was synthesized from its nitro-precursor by the nucleophilic substitution with K[¹⁸F]F/Kryptofix 2.2.2 and isolated by HPLC combined with solid-phase extraction (SPE) purification in 20–30% radiochemical yield with 37–370 GBq/μmol specific activity at end of bombardment (EOB).     

Unusual inflammatory and fibrogenic pulmonary responses to single-walled carbon nanotubes in mice

Single-walled carbon nanotubes (SWCNT) are new materials of emerging technological importance. As SWCNT are introduced into the life cycle of commercial products, their effects on human health and environment should be addressed. We demonstrated that pharyngeal aspiration of SWCNT elicited unusual pulmonary effects in C57BL/6 mice that combined a robust but acute inflammation with early onset yet progressive fibrosis and granulomas. A dose-dependent increase in the protein, LDH, and gamma-glutamyl transferase activities in bronchoalveolar lavage were found along with accumulation of 4-hydroxynonenal (oxidative biomarker) and depletion of glutathione in lungs. An early neutrophils accumulation (day 1), followed by lymphocyte (day 3) and macrophage (day 7) influx, was accompanied by early elevation of proinflammatory cytokines (TNF-alpha, IL-1beta; day 1) followed by fibrogenic transforming growth factor (TGF)-beta1 (peaked on day 7). A rapid progressive fibrosis found in mice exhibited two distinct morphologies: 1) SWCNT-induced granulomas mainly associated with hypertrophied epithelial cells surrounding SWCNT aggregates and 2) diffuse interstitial fibrosis and alveolar wall thickening likely associated with dispersed SWCNT. In vitro exposure of murine RAW 264.7 macrophages to SWCNT triggered TGF-beta1 production similarly to zymosan but generated less TNF-alpha and IL-1beta. SWCNT did not cause superoxide or NO.production, active SWCNT engulfment, or apoptosis in RAW 264.7 macrophages. Functional respiratory deficiencies and decreased bacterial clearance (Listeria monocytogenes) were found in mice treated with SWCNT. Equal doses of ultrafine carbon black particles or fine crystalline silica (SiO2) did not induce granulomas or alveolar wall thickening and caused a significantly weaker pulmonary inflammation and damage.     

A Cy5.5-labeled phage-displayed peptide probe for near-infrared fluorescence imaging of tumor vasculature in living mice

Near-infrared (NIR) fluorescence optical imaging is an emerging imaging technique for studying diseases at the molecular level. Optical imaging with a NIR emitting fluorophore for targeting tumor vasculature offers a noninvasive method for early detection of tumor angiogenesis and efficient monitoring of response to anti-tumor vasculature therapy. The previous in vitro results demonstrated that the GX1 peptide, identified by phage-display technology, is a tumor vasculature endothelium-specific ligand. In this report, Cy5.5-conjugated GX1 peptide was evaluated in a subcutaneous U87MG glioblastoma xenograft model to investigate tumor-targeting efficacy. The in vitro flow cytometry results revealed dose-dependent binding of Cy5.5-GX1 peptide to U87MG glioma cells. In vivo optical imaging with the Cy5.5-GX1 probe exhibited rapid U87MG tumor targeting at 0.5 h p.i., and high tumor-to-background contrast at 4 h p.i. Tumor specificity of Cy5.5-GX1 was confirmed by effective blocking of tumor uptake in the presence of unlabeled GX1 peptide (20 mg/kg). Ex vivo imaging further confirmed in vivo imaging findings, and demonstrated that Cy5.5-GX1 has a tumor-to-muscle ratio (15.21 ± 0.84) at 24 h p.i. for the non-blocked group and significantly decreased ratio (6.95 ± 0.75) for the blocked group. In conclusion, our studies suggest that Cy5.5-GX1 is a promising molecular probe for optical imaging of tumor vasculature.     

Facile synthesis of carbon-11-labeled cholesterol-based cationic lipids as new potential PET probes for imaging of gene delivery in cancer

Gene therapy based on gene delivery is a promising strategy for the treatment of various human diseases such as cancer. Cationic lipids represent one of the important synthetic gene delivery systems. There is a great interest in imaging of gene therapy using the biomedical imaging technique positron emission tomography (PET). Carbon-11-labeled cholesterol-based cationic lipids were first designed and synthesized as new potential PET probes for imaging of gene delivery in cancer. The [¹¹C-methyl]quaternary amine target tracers, N-[¹¹C]methyl-N-[4-(cholest-5-en-3β-yloxycarbonyl)butyl]pyrrolidinium iodide ([¹¹C]4a), N-[¹¹C]methyl-N′-[4-(cholest-5-en-3β-yloxycarbonyl)butyl]imidazolium iodide ([¹¹C]4b), N-[¹¹C]methyl-N-[4-(cholest-5-en-3β-yloxycarbonyl)butyl]piperidinium iodide ([¹¹C]4c), N-[¹¹C]methyl-N-[4-(cholest-5-en-3β-yloxycarbonyl)butyl]-4-methylpiperidinium iodide ([¹¹C]4d), and N-[¹¹C]methyl-N-[4-(cholest-5-en-3β-yloxycarbonyl)butyl]morpholinium iodide ([¹¹C]4e), were prepared from their corresponding tertiary amine precursors with [¹¹C]methyl iodide ([¹¹C]CH₃I) through N-[¹¹C]methylation and isolated by a simplified solid-phase extraction (SPE) method using a Silica Sep-Pak cartridge in 50-60% radiochemical yields decay corrected to end-of-bombardment (EOB), based on [¹¹C]CO₂, and 111-185 GBq/μmol specific activity at the end of synthesis (EOS).     

Initial evaluation of Cu-64 labeled PARPi-DOTA PET imaging in mice with mesothelioma

Poly(ADP-ribose) polymerase (PARP) has emerged as an important molecular target for the treatment of several oncological diseases. A couple of molecular probes based on Olaparib scaffold have been developed by incorporation of F-18 or fluorophore for positron emission tomography (PET) or optical imaging in several types of tumor. PARP has been reported overexpressed in mesothelioma. We hereby synthesized an analogue of Olaparib containing DOTA moiety and radiolabeled it with Cu-64 to evaluate its utility of PET tracer for mesothelioma. The Cu-64 labeling was conveniently achieved at 90% yield with final compound at >99% radiochemistry purity. The biodistribution and PET imaging were performed at 0.5, 1, 2 and 18 h to confirm the in vivo tumor targeting. The tumor uptake in study group was significant higher than that in control group (3.45 ± 0.47% ID/g vs 2.26 ± 0.30% ID/g) and tumor were clearly detected by PET imaging. These results suggest the feasibility to develop an Olaparib-based theranostic agent for mesothelioma.     

Synthesis of carbon-11-labeled aminoalkylindole derivatives as new candidates of cannabinoid receptor radioligands for PET imaging of alcohol abuse

Carbon-11-labeled aminoalkylindole derivatives (1-butyl-7-[¹¹C]methoxy-1H-indol-3-yl)(naphthalene-1-yl)methanone ([¹¹C]3), 1-butyl-7-[¹¹C]methoxy-3-(naphthalene-1-ylmethyl)-1H-indole ([¹¹C]5), and 1-butyl-7-[¹¹C]methoxy-3-(naphthalene-2-yl)-1H-indole ([¹¹C]8) were prepared by O-[¹¹C]methylation of their corresponding precursors with [¹¹C]CH₃OTf under basic condition (2 N NaOH) and isolated by a simplified solid-phase extraction (SPE) method in 50–60% radiochemical yields based on [¹¹C]CO₂ and decay corrected to end of bombardment (EOB). The overall synthesis time from EOB was 23 min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 185–555 GBq/μmol.     

Pulmonary biocompatibility assessment of inhaled single-wall and multiwall carbon nanotubes in BALB/c mice

With the widespread application of carbon nanotubes (CNTs) in diverse commercial processes, scientists are now concerned about the potential health risk of occupational exposures. In this study, CNT-induced pulmonary toxicity was investigated by exposing BALB/c mice to aerosolized single-wall (SW) CNT and multiwall (MW) CNT (5 μg/g of mice) for 7 consecutive days in a nose-only exposure system. Microscopic studies showed that inhaled CNTs were homogeneously distributed in the mouse lung. The total number of bronchoalveolar lavage polymorphonuclear leukocytes recovered from the mice exposed to SWCNT and MWCNT (1.2 × 10(6) ± 0.52 and 9.87 × 10(5) ± 1.45; respectively) was significantly greater than control mice (5.46 × 10(5) ± 0.78). Rapid development of pulmonary fibrosis in mice that inhaled CNT was also confirmed by significant increases in the collagen level. The lactate dehydrogenase levels were increased nearly 2- and 2.4-fold in mice that inhaled SWCNT and MWCNT, respectively, as compared with control mice. In addition, exposure of CNTs to mice showed a significant (p < 0.05) reduction of antioxidants (glutathione, superoxide dismutase, and catalase) and induction of oxidants (myloperoxidase, oxidative stress, and lipid peroxidation) compared with control. Apoptosis-related proteins such as caspase-3 and -8 activities were also significantly increased in mice that inhaled CNT than in control mice. Together, this study shows that inhaled CNTs induce inflammation, fibrosis, alteration of oxidant and antioxidant levels, and induction of apoptosis-related proteins in the lung tissues to trigger cell death.     

X线、CT、SPECT、PET在评估小鼠的骨成像中的作用

目的利用各种影像诊断设备对正常小鼠的骨进行成像,观察其在小鼠骨成像中最佳成像参数。方法分别使用X线、CT、SPECT、PET对小鼠的骨进行拍摄成像。结果X线和CT均可以清楚地对小鼠的骨组织成像,而SPECT、PET由于其分辨率和特异性不高,成像较模糊。结论X线和CT检查对小鼠的骨成像明显,对小鼠疾病的观察有重要意义。而SPECT、PET对诊断小鼠的骨疾病意义不是很大。     

Synthesis and in vitro biological evaluation of carbon-11-labeled quinoline derivatives as new candidate PET radioligands for cannabinoid CB2 receptor imaging

Cannabinoids have been recently proposed as a new family of potential antitumor agents, and cannabinoid receptor 2 (CB2) is believed to be over-expressed in tumor cells. This study was designed to develop new radioligands for imaging of CB2 receptor in cancer using biomedical imaging technique positron emission tomography (PET). Carbon-11-labeled 2-oxoquinoline and 2-chloroquinoline derivatives, [¹¹C]6a–d and [¹¹C]9a–d, were prepared by O-[¹¹C]methylation of their corresponding precursors using [¹¹C]CH₃OTf under basic conditions and isolated by a simplified solid-phase extraction (SPE) method in 40–50% radiochemical yields based on [¹¹C]CO₂ and decay corrected to end of bombardment (EOB). The overall synthesis time from EOB was 15–20 min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 111–185 GBq/μmol. Radioligand binding assays indicated compounds 6f, 6b, and 9f display potent in vitro binding affinities with nanomolar K_i values and at least 100–2000-fold selectivity for CB2.     

Synthesis of carbon-11-labeled casimiroin analogues as new potential PET agents for imaging of quinone reductase 2 and aromatase expression in breast cancer

Carbon-11-labeled casimiroin analogues were first designed and synthesized as new potential PET agents for imaging of quinone reductase (QR) 2 and aromatase expression in breast cancer. [¹¹C]casimiroin (6-[¹¹C]methoxy-9-methyl-[1,3]dioxolo[4,5-h]quinolin-8(9H)-one, [¹¹C]11) and its carbon-11-labeled analogues 5,6,8-trimethoxy-1-[¹¹C]methyl-4-methylquinolin-2(1H)-one ([¹¹C]17), 8-methoxy-1-[¹¹C]methyl-4-methylquinolin-2(1H)-one ([¹¹C]21a), 6,8-dimethoxy-1-[¹¹C]methyl-4-methylquinolin-2(1H)-one ([¹¹C]21b), and 5,8-dimethoxy-1-[¹¹C]methyl-4-methylquinolin-2(1H)-one ([¹¹C]21c), were prepared from their corresponding precursors with [¹¹C]methyl triflate ([¹¹C]CH₃OTf) under basic conditions (NaH) through either O- or N-[¹¹C]methylation and isolated by semi-preparative HPLC method in 40-50% radiochemical yields decay corrected to end of bombardment (EOB), based on [¹¹C]CO₂, and 111-185 GBq/μmol specific activity at the end of synthesis (EOS).     

Impaired clearance and enhanced pulmonary inflammatory/fibrotic response to carbon nanotubes in myeloperoxidase-deficient mice

Advancement of biomedical applications of carbonaceous nanomaterials is hampered by their biopersistence and pro-inflammatory action in vivo. Here, we used myeloperoxidase knockout B6.129X1-MPO (MPO k/o) mice and showed that oxidation and clearance of single walled carbon nanotubes (SWCNT) from the lungs of these animals after pharyngeal aspiration was markedly less effective whereas the inflammatory response was more robust than in wild-type C57Bl/6 mice. Our results provide direct evidence for the participation of MPO - one of the key-orchestrators of inflammatory response - in the in vivo pulmonary oxidative biodegradation of SWCNT and suggest new ways to control the biopersistence of nanomaterials through genetic or pharmacological manipulations.     

Study of hepatotoxicity and oxidative stress in male Swiss-Webster mice exposed to functionalized multi-walled carbon nanotubes

Carbon nanotubes (CNTs), the most promising material with unique characteristics, find its application in different fields ranging from composite materials to medicine and from electronics to energy storage. However, little is known about the mechanisms behind the interaction of these particles with cells and their toxicity. The aim of this study was to assess the effects, after intraperitoneal (ip) injection, of functionalized multi-walled carbon nanotubes (MWCNT) (carboxyl groups) on various hepatotoxicity and oxidative stress biomarkers (ROS, LHP, ALT, AST, ALP, and morphology of liver) in the mouse model. The mice were dosed ip at 0.25, 0.5, and 0.75 mg/kg/day for 5 days of purified/functionalized MWCNTs and two controls (negative; saline and positive; carbon black 0.75 mg/kg) as appropriate. Samples were collected 24 h after the fifth day treatment following standard protocols. Exposure to carboxylated functionalized MWCNT; the body-weight gain of the mice decreased, induced reactive oxygen species (ROS), and enhanced the activities of serum amino-transferases (ALT/AST), alkaline phosphatases (ALP), and concentration of lipid hydro peroxide compared to control. Histopathology of exposed liver showed a statistically significant effect in the morphological alterations of the tissue compared to controls. The cellular findings reported here do suggest that purified carboxylated functionalized MWCNT has the potential to induce hepatotoxicity in Swiss-Webster mice through activation of the mechanisms of oxidative stress, which warrant in vivo animal exposure studies. However, more studies of functionalization in the in vivo toxicity of MWCNTs are required and parallel comparison is preferred.     

Applications of carbon nanotubes in drug delivery

The development of new and efficient drug delivery systems is of fundamental importance to improve the pharmacological profiles of many classes of therapeutic molecules. Many different types of drug delivery systems are currently available. Within the family of nanomaterials, carbon nanotubes (CNT) have emerged as a new alternative and efficient tool for transporting and translocating therapeutic molecules. CNT can be functionalised with bioactive peptides, proteins, nucleic acids and drugs, and used to deliver their cargos to cells and organs. Because functionalised CNT display low toxicity and are not immunogenic, such systems hold great potential in the field of nanobiotechnology and nanomedicine.     

Single-walled carbon nanotubes modulate pulmonary immune responses and increase pandemic influenza a virus titers in mice

Background

Numerous toxicological studies have focused on injury caused by exposure to single types of nanoparticles, but few have investigated how such exposures impact a host’s immune response to pathogen challenge. Few studies have shown that nanoparticles can alter a host’s response to pathogens (chiefly bacteria) but there is even less knowledge of the impact of such particles on viral infections. In this study, we performed experiments to investigate if exposure of mice to single-walled carbon nanotubes (SWCNT) alters immune mechanisms and viral titers following subsequent influenza A virus (IAV) infection.

Methods

Male C57BL/6 mice were exposed to 20 μg of SWCNT or control vehicle by intratracheal instillation followed by intranasal exposure to 3.2?×?10⁴ TCID₅₀ IAV or PBS after 3 days. On day 7 mice were euthanized and near-infrared fluorescence (NIRF) imaging was used to track SWCNT in lung tissues. Viral titers, histopathology, and mRNA expression of antiviral and inflammatory genes were measured in lung tissue. Differential cell counts and cytokine levels were quantified in bronchoalveolar lavage fluid (BALF).

Results

Viral titers showed a 63-fold increase in IAV in SWCNT + IAV exposed lungs compared to the IAV only exposure. Quantitation of immune cells in BALF indicated an increase of neutrophils in the IAV group and a mixed profile of lymphocytes and neutrophils in SWCNT + IAV treated mice. NIRF indicated SWCNT remained in the lung throughout the experiment and localized in the junctions of terminal bronchioles, alveolar ducts, and surrounding alveoli. The dual exposure exacerbated pulmonary inflammation and tissue lesions compared to SWCNT or IAV single exposures. IAV exposure increased several cytokine and chemokine levels in BALF, but greater levels of IL-4, IL-12 (P70), IP-10, MIP-1, MIP-1α, MIP-1β, and RANTES were evident in the SWCNT?+?IAV group. The expression of tlr3, ifnβ1, rantes, ifit2, ifit3, and il8 was induced by IAV alone but several anti-viral targets showed a repressed trend (ifits) with pre-exposure to SWCNT.

Conclusions

These findings reveal a pronounced effect of SWCNT on IAV infection in vivo as evidenced by exacerbated lung injury, increased viral titers and several cytokines/chemokines levels, and reduction of anti-viral gene expression. These results imply that SWCNT can increase susceptibility to respiratory viral infections as a novel mechanism of toxicity.

     

Development of immunosensors using carbon nanotubes

With increasing reports on bioterrorism, avian flu, and other bio-threats, rapid and real time detection methods are highly warranted. Studies on developing highly sensitive immunosensors aiming at the early detection and clinical diagnoses of various diseases including cancer are undertaken all over the globe. Carbon nanotubes (CNTs) have been widely discussed as materials with enormous potential for a wide range of in vivo and in vitro bioapplications, ranging from drug delivery to highly sensitive biosensors, owing to their superior electronic and mechanical properties along with nanoscale dimensions. Though a lot of attention has been drawn toward carbon nanotubes for the past 15 years in academia and to a certain extent in industry, CNT-based immunosensors and other applications are still in the nascent stage, and there are many challenges to be overcome for the successful commercialization of the concepts. This article highlights on the recent developments and the possible impacts of carbon nanotube based immunosensors.     

(18)F]-labeled isoindol-1-one and isoindol-1,3-dione derivatives as potential PET imaging agents for detection of beta-amyloid fibrils

In this study a novel series of isoindol-1-one and isoindol-1,3-dione derivatives for beta-amyloid-specific binding agents is described. Twelve compounds were synthesized and evaluated via a competitive binding assay with [(125)I]TZDM against beta-amyloid 1-42 (Abeta42) aggregates. Two new [(18)F]-labeled isoindole derivatives were synthesized and evaluated as potential beta-amyloid imaging probes based on the in vivo pharmacokinetic profiles. The preliminary results suggest that these [(18)F]18b and [(18)F]18c are promising positron emission tomography (PET) imaging probes for studying accumulation of Abeta fibrils in the brains of Alzheimer's disease (AD) patients.     

Activity and stability comparison of immobilized NADH oxidase on multi-walled carbon nanotubes,carbon nanospheres,and single-walled carbon nanotubes

Nanomaterials have been studied widely as the supporting materials for enzyme immobilization because in theory, they can provide low diffusion resistance and high surface/volume ratio. Common immobilization methods, such as physical adsorption, covalent binding, crosslinking, and encapsulation, often cause problems in enzyme leaching, 3D structure change and strong mass transfer resistance. We have previously demonstrated a site-specific enzyme immobilization method, which is based on the specific interaction between a His-tagged enzyme and functionalized single-walled carbon nanotubes (SWCNTs), that can overcome the foresaid constraints. In this work, we broadened the use of this immobilization approach by applying it on other nanomaterials, including multi-walled carbon nanotubes and carbon nanospheres. Both supporting materials were modified with N_α,N_α-bis(carboxymethyl)-l-lysine hydrate prior to enzyme immobilization. The resulting nanomaterial–enzyme conjugates could maintain 78–87% of the native enzyme activity and showed significantly better stability than the free enzyme. When compared with the SWCNT–enzyme conjugate, we found that the size variance among these supporting nanomaterials may affect factors such as surface curvature, surface coverage and particle mobility, which in turn results in differences in the activity and stability among these immobilized biocatalysts.     

Enzymatic determination of carbon (14C)-labeled glycerol in biological samples

A method for determination of glycerol-specific-radioactivity in biological samples is presented. It is based on the following steps: (a) enzymatic conversion of glycerol to dihydroxyacetone-phosphate, (b) quantitative trapping of dihydroxyacetone-phosphate in SPE amino (NH₂) columns, (c) eluation with HCl 0.5 N of dihydroxyacetone-phosphate followed by radioactivity counting and (d) estimation of the radioactivity thus trapped compared with that of enzymatically untreated aliquots of the same samples. No interferences from other ¹⁴C-labeled materials tested such as d-glucose, l-alanine, l-glutamine and d-β-hydroxybutyrate were observed. This inexpensive and high-speed method can be applied in routine multiple estimations of glycerol-specific-radioactivity in biological samples in tracer metabolic studies.