177Lu‐labeled monomeric,dimeric and multimeric RGD peptides for the therapy of tumors expressing α(ν)β(3) integrins

The conjugation of peptides to gold nanoparticles (AuNPs) produces biocompatible and stable multimeric systems with target‐specific molecular recognition. Peptides based on the cyclic Arg‐Gly‐Asp (RGD) sequence have been reported as high‐affinity agents for the α(ν)β(3) integrin. The aim of this research was to prepare a multimeric system of ¹⁷⁷Lu‐labeled gold nanoparticles conjugated to c(RGDfK)C (cyclo(Arg‐Gly‐Asp‐Phe‐Lys)Cys) and to compare the radiation‐absorbed dose with that of ¹⁷⁷Lu‐labeled monomeric and dimeric RGD peptides to α(ν)β(3) integrin‐positive U87MG tumors in mice. DOTA‐GGC (1,4,7,10‐tetraazacyclododecane‐N‐N′,N″,N?‐tetraacetic acid‐Gly‐Gly‐Cys) and c(RGDfK)C peptides were synthesized and conjugated to AuNPs by a spontaneous reaction of the thiol groups. Transmission electron microscopy, ultraviolet–visible, X‐ray photoelectron spectroscopy, Raman and far‐infrared spectroscopy techniques demonstrated that AuNPs were functionalized with the peptides. For the ¹⁷⁷Lu‐AuNP‐c(RGDfK)C to be obtained, the ¹⁷⁷Lu‐DOTA‐GGC radiopeptide was first prepared and added to a solution of AuNPs followed by c(RGDfK)C (25 µl, 5 µ m ) at 18 °C for 15 min. ¹⁷⁷Lu‐DOTA‐GGC, ¹⁷⁷Lu‐DOTA‐cRGDfK and ¹⁷⁷Lu‐DOTA‐E‐c(RGDfK)₂ were prepared by adding ¹⁷⁷LuCl₃ (370 MBq) to 5 µl (1 mg/ml) of the DOTA derivative diluted with 50 µl of 1 m acetate buffer pH 5. The mixture was incubated at 90 °C in a block heater for 30 min. Radiochemical purity was determined by ultrafiltration and HPLC analyses. Biokinetic studies were accomplished in athymic mice with U87MG‐induced tumors. The radiochemical purity for all ¹⁷⁷Lu‐RGD derivatives was 96 ± 2%. ¹⁷⁷Lu‐absorbed doses per injected activity delivered to U87MG tumors were 0.357 ± 0.052 Gy/MBq (multimer), 0.252 ± 0.027 Gy/MBq (dimer) and 0.102 ± 0.018 Gy/MBq (monomer). ¹⁷⁷Lu‐labeled dimeric and multimeric RGD peptides demonstrated properties suitable for targeted radionuclide therapy of tumors expressing α(ν)β(3) integrins. Copyright © 2012 John Wiley & Sons, Ltd.     

Radiolabeling,quality control,biodistribution, and imaging studies of 177Lu‐ibandronate

The purposes of this study were as follows: (1) to radiolabel ibandronic acid (IBA, a third‐generation bisphosphonate) with ¹⁷⁷Lu, investigating optimal labeling conditions, and (2) to analyze biodistribution and imaging properties of intravenous ¹⁷⁷Lu‐ibandronate (¹⁷⁷Lu‐IBA) administered in animals. ¹⁷⁷Lu‐labeled methylene diphosphonate (¹⁷⁷Lu‐MDP) served as a comparator agent. Differing proportions of IBA solution and ¹⁷⁷LuCl₃ solution were combined to determine an optimal ratio for radiolabeling purposes, varying pH, temperature, and time to establish ideal reactivity conditions. Radiochemical purity of the labeled compounds was then assessed by paper chromatography. In vitro and in vivo stabilities were also measured at specific time intervals. In Kunming mice, biodistributions of ¹⁷⁷Lu‐IBA and ¹⁷⁷Lu‐MDP and respective agent activities in various organs were monitored by gamma counter, and we performed single photon computed tomography/computed tomography (SPECT/CT) imaging of ¹⁷⁷Lu‐IBA in normal New Zealand White rabbits. Radiolabeling yields for ¹⁷⁷Lu‐IBA proved to be >97% within 30 minutes at 90°C, and its radiochemical purity ensured stability in vitro and in vivo. Furthermore, we found that ¹⁷⁷Lu‐IBA is readily soluble in water, showing higher skeletal uptake than ¹⁷⁷Lu‐MDP but lower uptake by liver and spleen. The image quality of ¹⁷⁷Lu‐IBA was so clear that even after 6 days, analysis was still feasible.     

Barium titanate microparticles as potential carrier platform for lanthanide radionuclides for their use in the treatment of arthritis

Since the inception of radiation synovectomy, a host of radioactive colloids and microparticles incorporating suitable therapeutic radionuclides have been proposed for the treatment of arthritis. The present article reports the synthesis and evaluation of barium titanate microparticles as an innovative and effective carrier platform for lanthanide radionuclides in the preparation of therapeutic agents for treatment of arthritis. The material was synthesized by mechanochemical route and characterized by X‐ray diffraction, scanning electron microscopy, surface area, and particle size distribution analyses. Loading of lanthanide radionuclides (¹⁶⁶Ho, ¹⁵³Sm, ¹⁷⁷Lu, and ¹⁶⁹Er) on the microparticles was achieved in high yield (> 95%) resulting in the formulation of loaded particulates with excellent radiochemical purities (> 99%). Radiolanthanide‐loaded microparticles exhibited excellent in vitro stability in human serum. In vitro diethylene triamine pentaacetic acid challenge study indicated fairly strong chemical association of lanthanides with barium titanate microparticles. Long‐term biodistribution studies carried out after administration of ¹⁷⁷Lu‐loaded microparticles into one of the knee joints of normal Wistar rats revealed near‐complete retention of the formulation (> 96% of the administered radioactivity) within the joint cavity even 14 days post‐administration. The excellent localization of the loaded microparticles was further confirmed by sequential whole‐body radio‐luminescence imaging studies carried out using ¹⁶⁶Ho‐loaded microparticles.     

177Lu‐5‐Fluorouracil a potential theranostic radiopharmaceutical: radiosynthesis,quality control,biodistribution, and scintigraphy

The aim of this study is to develop ¹⁷⁷Lu‐5‐Flourouracil as a potential cancer therapeutic radiopharmaceutical. 5‐Flourouracil (5‐FU) is widely accepted as an anticancer drug of broad spectrum fame. The labeling of 5‐FU was carried out at different set of experimental conditions using high specific activity of ¹⁷⁷LuCl₃. The optimum conditions for maximum radiochemical yield was set: 5‐FU (5 mg), ¹⁷⁷LuCl₃ (185 MBq), diethylenetriaminepentaacetic acid (10 µg), reaction volume (2 mL), pH (5.5), temperature (80°C), and reaction time (20 min). The radiochemical labeling was assessed with Whatman No. 2 paper, instant thin layer chromatographic, and radio‐HPLC, which revealed >94% labeling results with sufficient stability up to 6 h. Serum stability study also showed ¹⁷⁷Lu‐5‐FU promising stability. Biodistribution study in normal rats and rabbits showed liver, stomach, kidney, and heart as area of increased tracer accumulation just after injection, which decreased to 1.4%, 0.4%, 0.2%, and 0.39% ID/g, respectively, after 72 h. Glomerular filtration rate and cytotoxicity study results of ¹⁷⁷Lu‐5‐FU showed it had no adverse effect on renal function and nontoxic to blood cells. The promising characteristics of ¹⁷⁷Lu‐5‐FU, that is, clever elimination from kidney and nontoxic nature toward blood cells make it the radiopharmaceutical for further testing in patients for therapeutic purposes.     

Prospects of medium specific activity 177Lu in targeted therapy of prostate cancer using 177Lu‐labeled PSMA inhibitor

Targeted radionuclide therapy using ¹⁷⁷Lu‐labeled peptidomimetic inhibitor of prostate specific membrane antigen (PSMA) viz. PSMA‐617 is emerging as one the most effective strategies for management of metastatic prostate cancer, which is one of the leading causes of cancer related death. The aim of the present study is to develop a robust and easily adaptable protocol for formulation of therapeutic dose of ¹⁷⁷Lu‐PSMA‐617 at hospital radiopharmacy using moderate specific activity ¹⁷⁷Lu available at an affordable cost. Extensive radiochemical studies were performed to optimize the required [PSMA‐617] / [Lu] ratio and other parameters to formulate 7.4 GBq dose of ¹⁷⁷Lu‐PSMA‐617. Based on these, 7.4 GBq therapeutic dose of ¹⁷⁷Lu‐PSMA‐617 was formulated by incubating 160 µg of PSMA‐617 with indigenously produced ¹⁷⁷LuCl₃ (555 GBq/µg specific activity of ¹⁷⁷Lu) at 90 °C for 30 min. The radiochemical purity of the formulation was 98.3 ± 0.6% (n = 7) which was retained to the extent of >95% after 7 d in normal saline at room temperature and >96% after 2 d in human serum at 37 °C. Preliminary clinical studies showed specific targeting of the agent in the lesion sites and similar physiological distribution as in diagnostic ⁶⁸Ga‐PSMA‐11 PET scans performed earlier. The developed optimized protocol for formulating therapeutic dose of ¹⁷⁷Lu‐PSMA‐617 could be useful for large number of nuclear medicine therapy clinics across the world having access to moderate specific activity ¹⁷⁷Lu at an affordable cost.     

Single vial kit formulation of DOTATATE for preparation of 177Lu‐labeled therapeutic radiopharmaceutical at hospital radiopharmacy

The clinical applications of radiolabeled somatostatin analogue ¹⁷⁷Lu‐DOTA‐Tyr³‐Thr⁸‐Octreotide (¹⁷⁷Lu‐DOTATATE) constitute a promising treatment option for patients with disseminated and inoperable neuroendocrine (NET) tumors. Formulation of ¹⁷⁷Lu‐DOTATATE in hospital radiopharmacy under aseptic conditions in a safe and reliable manner is a major constraint for its extensive use. The present work was intended to develop a kit for the safe preparation of the therapeutic radiopharmaceutical, viz. ¹⁷⁷Lu‐DOTATATE of high quality that can be easily adapted at conventional hospital radiopharmacies. Single vial kits of DOTATATE were formulated and evaluated for suitability for radiolabeling as well as stability on its storage. Patient dose of ¹⁷⁷Lu‐DOTATATE (7.4 GBq) could be successfully prepared using semi‐automated in‐house setup that assures safe handling and high yields of product of pharmaceutical purity suitable for clinical use. Fast clearance of activity via renal route was observed in preclinical biodistribution studies of ¹⁷⁷Lu‐DOTATATE carried out in normal Swiss mice. Deployment of in‐house produced ¹⁷⁷LuCl₃, cold kits and easy adaptability of synthesis setup at hospital radiopharmacy for preparation is likely to expand applications of peptide receptor radionuclide therapy.     

Preclinical evaluation of new GnRH‐I receptor radionuclide therapy with 177Lu‐peptide tracer

The purpose of this study was to develop preclinical evaluation of a novel radiolabeled gonadotropin‐releasing hormone (GnRH) receptor targeting peptide for prostate cancer therapy. The new antiproliferative agent of GnRH‐I analogue was developed on the basis of the D‐Trp⁶‐GnRH‐I scaffold, and in vivo pharmacokinetics and receptor binding affinity were enhanced by the substitution of Gly‐NHNH₂ for Gly‐NH₂ at position 10 in D‐Trp⁶‐GnRH‐I. To evaluate ¹⁷⁷Lu‐DOTA‐triptorelin‐hydrazide as radionuclide therapy of tumor, the quality control tests and preclinical stage assessment were carried out. Solid‐phase method was used to synthesize new peptide. Characterization and purity of peptide were done by mass spectroscopy and high‐performance liquid chromatography (HPLC). In order to be utilized in targeted therapy, the new GnRH‐I agonist was coupled with pSCN‐Bn‐DOTA. The precipitate crude of DOTA‐triptorelin‐hydrazide was then purified via preparative HPLC. At optimal conditions of time, temperature, ligand amount, and lutetium content, DOTA‐triptorelin‐hydrazide was labeled with ¹⁷⁷Lu (specific activity not less than 925 GBq/mg). Investigation of the in vivo biodistribution and in vitro studies for ¹⁷⁷Lu‐DOTA‐TRPHYD was performed in three different ways, and the binding of radiopeptide to GnRH receptors was expressed on the human cell lines using ¹²⁵I‐labeled D‐TRP⁶GnRH‐I as a tracer, respectively. Synthesized novel GnRH‐I was obtained with purity greater than 98%. Paper chromatography was found to be the most suitable with R_f of the complex and observed radiochemical purity of RTLC and HPLC greater than 97%. For in vivo studies, ¹⁷⁷Lu‐DOTA‐triptorelin‐hydrazide showed promising results with fast clearance from the blood and resulted in good T/NT ratios at 1, 4, and 24 hours postinjection and satisfactory biodistribution with no significant activity seen in normal tissue. The values of internalization efficiency and receptor affinity of new radiopeptide binding were IC₅₀ = 0.47 ± 0.06 vs 0.13 ± 0.01 nM for triptorelin and cellular uptake: 3.4 ± 0.7% at 1 hour and 6.8 ± 1.17% at 4 hours of the internal reference. The results showed a good stability and radiochemical purity of the obtained radioconjugate. For in vivo and in vitro studies, new radiopeptide showed a high uptake of ¹⁷⁷Lu conjugate in tumor and rapid clearance from the blood stream almost entirely via the renal/urinary pathway and binding to the GnRH receptors with high specificity and affinity, respectively.     

Local Radiation Treatment of HER2-Positive Breast Cancer Using Trastuzumab-Modified Gold Nanoparticles Labeled with <Superscript>177</Superscript>Lu

Purpose

To compare the effectiveness of trastuzumab-modified gold nanoparticles (AuNP) labeled with ¹⁷⁷Lu (trastuzumab-AuNP-¹⁷⁷Lu) targeted to HER2 with non-targeted AuNP-¹⁷⁷Lu for killing HER2-overexpressing breast cancer (BC) cells in vitro and inhibiting tumor growth in vivo following intratumoral (i.t.) injection.

Methods

AuNP (30 nm) were modified with polyethylene glycol (PEG) polymers linked to trastuzumab or to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelators to complex ¹⁷⁷Lu. The binding and internalization of trastuzumab-AuNP-¹⁷⁷Lu in HER2-positive SK-BR-3, BT-474 and MDA-MB-361 human BC cells were studied. Clonogenic survival and DNA double-strand breaks (DSBs) were measured after exposure of SK-BR-3 or MDA-MB-361 cells to trastuzumab-AuNP-¹⁷⁷Lu or AuNP-¹⁷⁷Lu. NOD/SCID mice with s.c. MDA-MB-361 tumor xenografts were treated by i.t. injection of 3 MBq (0.15 mg) of trastuzumab-AuNP-¹⁷⁷Lu, AuNP-¹⁷⁷Lu or normal saline. Tumor growth was measured over 16 days and normal tissue toxicity evaluated.

Results

Trastuzumab-AuNP-¹⁷⁷Lu was bound and internalized by HER2 positive BC cells (K_D?=?7.6?±?2.0 nM). Trastuzumab-AuNP-¹⁷⁷Lu was 42.9 and 2.6-fold more effective than AuNP-¹⁷⁷Lu at decreasing the clonogenic survival of SK-BR-3 (1.3?×?10⁶ HER2/cell) and MDA-MB-361 (5.1?×?10⁵ HER2/cell) cells, respectively, exposed overnight to these agents (1.5 nM; 20 MBq/mg Au). Under the same treatment conditions, 10-fold and 2.8-fold more DNA DSBs were observed in SK-BR-3 and MDA-MB-361 cells, respectively, exposed to trastuzumab-AuNP-¹⁷⁷Lu than AuNP-¹⁷⁷Lu. Trastuzumab-AuNP-¹⁷⁷Lu was 1.8-fold more effective at inhibiting tumor growth than AuNP-¹⁷⁷Lu. No or minimal normal tissue toxicity was observed for trastuzumab-AuNP-¹⁷⁷Lu or AuNP-¹⁷⁷Lu treatments.

Conclusion

Trastuzumab-AuNP-¹⁷⁷Lu enables an efficient local radiation treatment of HER2-positive BC.

     

Automated cGMP‐compliant radiosynthesis of [18F]‐(E)‐PSS232 for brain PET imaging of metabotropic glutamate receptor subtype 5

(E)‐3‐(Pyridin‐2‐yl ethynyl)cyclohex‐2‐enone O‐(3‐(2‐[¹⁸F]‐fluoroethoxy)propyl) oxime ([¹⁸F]‐(E)‐PSS232, [¹⁸F] 2a ) is a recently developed radiotracer that can be used to visualize metabotropic glutamate receptor subtype 5 (mGlu₅) in vivo. The mGlu₅ has become an attractive therapeutic and diagnostic target owing to its role in many neuropsychiatric disorders. Several carbon‐11‐labeled and fluorine‐18‐labeled radiotracers have been developed to measure mGlu₅ receptor occupancy in the human brain. The radiotracer [¹⁸F] 2a , which is used as an analogue for [¹¹C]ABP688 ([¹¹C] 1 ) and has a longer physical half‐life, is a selective radiotracer that exhibits high binding affinity for mGlu₅. Herein, we report the fully automated radiosynthesis of [¹⁸F] 2a using a commercial GE TRACERlab? FX‐_FN synthesizer for routine production and distribution to nearby satellite clinics. Nucleophilic substitution of the corresponding mesylate precursor with cyclotron‐produced [¹⁸F]fluoride ion at 100°C in dimethyl sulfoxide (DMSO), followed by high‐performance liquid chromatography (HPLC) purification and formulation, readily provided [¹⁸F] 2a with a radiochemical yield of 40 ± 2% (decay corrected, n = 5) at the end of synthesis. Radiochemical purity for the [¹⁸F]‐(E)‐conformer was greater than 95%. Molar activity was determined to be 63.6 ± 9.6 GBq/μmol (n = 5), and the overall synthesis time was 70 minutes.     

Preparation of clinical‐scale 177Lu‐Rituximab: Optimization of protocols for conjugation,radiolabeling, and freeze‐dried kit formulation

Rituximab is a monoclonal chimeric antibody, which has been approved by the US Food and Drug Administration for immunotherapy of non–Hodgkin lymphoma. Bexxar and Zevalin are the two other approved radiolabeled antibodies for radioimmunotherapy of non–Hodgkin lymphoma; however, they are of murine origin that reduces their treatment efficacy. So as to circumvent this, efforts have been made to radiolabel Rituximab with various therapeutic radioisotopes. In the present study, an effort has been made to optimize the conjugation (bifunctional chelating agent and antibody) and radiolabeling procedures for the preparation of clinical‐scale ¹⁷⁷Lu‐labeled Rituximab. An attempt was also made to prepare the freeze‐dried Rituximab kit for the easy and convenient clinical translation of the agent. Clinical‐scale ¹⁷⁷Lu‐Rituximab (40 mCi, 1.48 GBq) was prepared with >95% radiochemical purity using the kit. Biological evaluation of ¹⁷⁷Lu‐Rituximab was performed by in vitro cell binding studies in Raji cell lines, which showed satisfactory binding at 4°C and 37°C. Pharmacokinetic behavior of the agent, evaluated by biodistribution studies in normal Swiss mice, revealed high blood and liver uptake at the initial time points, although it exhibited slow and gradual clearance with time. The study indicates that clinical‐scale ¹⁷⁷Lu‐Rituximab could be conveniently formulated using the methodology described in the present article.     

Ce‐141‐labeled DOTMP: A theranostic option in management of pain due to skeletal metastases

Owing to its favorable radioactive decay characteristics (T_1/2 = 32.51 d, E_β [max] = 434.6 keV [70.5%] and 580.0 keV [29.5%], E_γ = 145.4 keV [48.5%]), ¹⁴¹Ce could be envisaged as a theranostic radionuclide for use in nuclear medicine. The present article reports synthesis and evaluation of ¹⁴¹Ce complex of 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetramethylenephosphonic acid (DOTMP) as a potent theranostic agent targeting metastatic skeletal lesions. Ce‐141 was produced with 314 ± 29 MBq/mg (n = 6) specific activity and >99.9% radionuclidic purity (n = 6). Around 185 MBq dose of [¹⁴¹Ce]Ce‐DOTMP was synthesized with 98.6 ± 0.5% (n = 4) radiochemical yield under optimized conditions of reaction, and the preparation showed adequately high in vitro stability. Biodistribution studies in normal Wistar rats demonstrated significant skeletal localization and retention of injected activity (2.73 ± 0.28% and 2.63 ± 0.22% of injected activity per gram in femur at 3 hours and 14 days post‐injection, respectively) with rapid clearance from non‐target organs. The results of biodistribution studies were corroborated by serial scintigraphic imaging studies. These results demonstrate the potential utility of ¹⁴¹Ce‐DOTMP as a theranostic molecule for personalized patient care of cancer patients suffering from painful metastatic skeletal lesions.     

Preparation and preliminary biological evaluation of 177Lu‐labeled GluDTPA‐cyclo(RGDfK) for integrin ανβ3 receptor‐positive tumor targeting

Integrin α_νβ₃ is a receptor and is highly expressed on activated and proliferating endothelial cells during the growth and metastasis of solid tumors but not on resting endothelial cells and normal organs. Because RGD peptide binds to integrin α_νβ₃ receptor, a variety of radiolabeled RGD peptides have been evaluated for non‐invasive imaging of integrin α_νβ₃‐positive tumors. In an attempt to develop RGD‐based radiopharmaceuticals, a novel GluDTPA‐cyclo arginine‐glycine‐aspartic acid‐d ‐phenylalanine‐lysine (GluDTPA‐cycloRGDfK) was simply synthesized and radiolabeled with ¹⁷⁷Lu. Also, tumor targeting and retention of the radiolabeled complex were evaluated in U87MG glioma‐bearing mice. The ¹⁷⁷Lu‐labeled GluDTPA‐cyclo(RGDfK) was formulated with a high radiolabeling yield (>98%) under mild condition, and the radiochemical purity was sustained in both saline and serum for over 4 days at 37°C. The radiolabeled compounds were rapidly cleared from the blood pool and non‐target tissue. Tumor‐to‐blood ratio was 12.09 at 2 h post injection and increased to 134.67 at 24 h, while tumor to liver ratio was 2.01 at 24 h similar to that of 2 h. Though it is inappropriate for targeted therapy due to its low uptake in tumor (~ 1 %ID/g), the acceptable results on radiochemistry and biodistribution propose to take a further assessment for non‐invasive imaging and detection of integrin α_νβ₃‐positive tumors by applying diagnostic radionuclides. Copyright © 2011 John Wiley & Sons, Ltd.     

The influence of humic acid on the toxicity of nano‐ZnO and Zn2+ to the Anabaena sp.

This study explored the effects of humic acid (HA) on the toxicity of ZnO nanoparticles (nano‐ZnO) and Zn²⁺ to Anabaena sp. Typical chlorophyll fluorescence parameters, including effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse‐amplitude modulated fluorometer. Results showed that nano‐ZnO and Zn²⁺ could inhibit Anabaena sp. growth with the EC₅₀ (concentration for 50% of maximal effect) of 0.74 ± 0.01 and 0.3 ± 0.01 mg/L, respectively. In the presence of 3.0 mg/L of HA, EC₅₀ of nano‐ZnO increased to 1.15 ± 0.04 mg/L and EC₅₀ of Zn²⁺ was still 0.3 ± 0.01 mg/L. Scanning electron microscopy observation revealed that HA prevented the adhesion of nano‐ZnO on the algae cells due to the increased electrostatic repulsion. The generation of intracellular reactive oxygen species and cellular lipid peroxidation were significantly limited by HA. Nano‐ZnO had more damage to the cell membrane than Zn²⁺ did, which could be proven by the malondialdehyde content in Anabaena sp. cells. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 895–903, 2015.     

Production,quality control,and determination of human absorbed dose of no carrier added 177Lu‐risedronate for bone pain palliation therapy

In this study, the radiocomplexation of risedronic acid, a potent bisphosphonate with a no carrier added (NCA) ¹⁷⁷Lu, was investigated and followed by quality control studies, biodistribution evaluation, and dosimetry study for human based on biodistribution data in Wistar rats. The moderate energy β⁻ emitter, ¹⁷⁷Lu (T _½ = 6.7 days, E _βmax = 497 keV), has been considered as a potential agent for development of bone‐seeking radiopharmaceuticals. Because the specific activity of the radiolabeled carrier molecules should be high, the NCA radionuclides have an effective role in nuclear medicine. Many researchers illustrated an NCA ¹⁷⁷Lu production; among these separation techniques, extraction chromatography has been considered more capable than other methods. The NCA ¹⁷⁷Lu was produced with specific activity of 48 Ci/mg and radionuclidic purity of 99.99% by the irradiation of enriched ¹⁷⁶Yb target in thermal neutron flux of 4 × 10¹³ n·cm⁻²·s⁻¹ for 14 days. The NCA ¹⁷⁷Lu was mixed to a desired amount of sodium risedronate (15 mg/mL, 200 μL) and incubated with stirring at 95°C for 30 minutes. The radiochemical purity of ¹⁷⁷Lu‐risedronate was determined by radio thin‐layer chromatography, and high radiochemical purities (>97%) were obtained under optimized reaction conditions . The complex was injected to Wistar rats, and complex biodistribution was performed 4 hours to 7 days postinjections showing high bone uptake (9.8% ± 0.24% ID/g at 48 hours postinjection). Also, modeling the radiation dose delivery by RADAR software for the absorbed dose evaluation of each human organ showed a major accumulation of the radiocomplex in bone tissue.     

Technetium‐99m radiolabeling and biological study of epirubicin for in vivo imaging of multi‐drug‐resistant Staphylococcus aureus infections via single photon emission computed tomography

The development of functional imaging is a promising strategy for diagnosis and treatment of infectious and cancerous diseases. In this study, epirubicin was developed as a [^99mTc]‐labeled radiopharmaceutical for the imaging of multi‐drug‐resistant Staphylococcus aureus infections. The labeling was carried out using sodium pertechnetate (Na^99mTcO₄; ~370 MBq). The other parameters such as amount of ligand, reducing agent (SnCl₂.2H₂O), and pH were optimized. The highest labeling yield ≥96.98% was achieved when 0.3 mg epirubicin, 13 μg SnCl₂.2H₂O, and ~370 MBq Na^99mTcO₄ were incubated at pH 7 for 15 min in the presence of ascorbic acid at room temperature. Radiochemical purity, stability, charge, and glomerular filtration rate were studied to evaluate the biological compatibility for in vivo administration. Biodistribution investigations showed radiotracer uptake (13.89 ± 1.56% ID/gm organ) by liver and 7.79 ± 0.38% ID/gm organ by kidneys at 30 min post‐injection which promisingly wash out at 24 hr post‐injection. Scintigraphy study showed selective uptake in S. aureus‐infected tissues in contrast to turpentine oil‐induced inflamed tissues. Target‐to‐non‐target ratio (6.7 ± 0.05) was calculated at 1 hr post‐injection using SPECT gamma camera. The results of this study reveal that the [^99mTc]‐epirubicin can be a choice of imaging and monitoring the treatment process of multi‐drug resistant S. aureus bacterial infections.     

Radiosynthesis of 13N‐labeled thalidomide using no‐carrier‐added [13N]NH3

Recent studies revealed that thalidomide (1) has unique and broad pharmacological effects on multi‐targets although the application of 1 in therapy is still controversial. In this study, we synthesized nitrogen‐13‐labeled thalidomide ([¹³N]1) as a potential positron emission tomography (PET) probe using no‐carrier‐added [¹³N]NH₃ as a labeling agent. By use of an automated system, [¹³N]1 was prepared by reacting N‐phthaloylglutamic anhydride (2) with [¹³N]NH₃, following by cyclization with carbonyldiimidazole in a radiochemical yield of 56±12% (based on [¹¹N]NH₃, corrected for decay) and specific activity of 49±24 GBq/µmol at the end of synthesis (EOS). At EOS, 570–780 MBq (n=7) of [¹³N]1 was obtained at a beam current of 15 µA after 15 min proton bombardment with a synthesis time of 14 min from the end of bombardment. Using a small animal PET scanner, preliminary biodistribution of [¹³N]1 in mice was examined. Copyright © 2010 John Wiley & Sons, Ltd.     

Multifunctional targeted therapy system based on 99mTc/177Lu‐labeled gold nanoparticles‐Tat(49–57)‐Lys3‐bombesin internalized in nuclei of prostate cancer cells

Radiolabeled gold nanoparticles may function simultaneously as radiotherapy and thermal ablation systems. The gastrin‐releasing peptide receptor (GRP‐r) is overexpressed in prostate cancer, and Lys³‐bombesin is a peptide that binds with high affinity to the GRP‐r. HIV Tat(49–57) is a cell‐penetrating peptide that reaches the DNA. In cancer cells, ¹⁷⁷Lu shows efficient crossfire effect, whereas ^99mTc that is internalized in the cancer cell nuclei acts as an effective system of targeted radiotherapy because of the biological Auger effect. The aim of this research was to evaluate the in vitro potential of ^99mTc‐labeled and ¹⁷⁷Lu‐labeled gold nanoparticles conjugated to Tat(49–57)‐Lys³‐bombesin peptides (^99mTc/¹⁷⁷Lu‐AuNP‐Tat‐BN) as a plasmonic photothermal therapy and targeted radiotherapy system in PC3 prostate cancer cells. Peptides were conjugated to AuNPs (5 nm) by spontaneous reaction with the thiol group of cysteine (Cys). The effect on PC3 cell viability after laser heating of the AuNP‐Tat‐BN incubated with the cancer cells was conducted using an Nd:YAG laser pulsed for 5 ns at 532 nm (0.65 W/cm²). For the ^99mTc/¹⁷⁷Lu‐AuNP‐Tat‐BN to be obtained, the ¹⁷⁷Lu‐DOTA‐Gly‐Gly‐Cys and ^99mTc‐HYNIC‐octreotide radiopeptides were first prepared and added simultaneously to a solution of AuNP‐Tat‐BN. ^99mTc/¹⁷⁷Lu‐AuNP‐Tat‐BN (20 Bq/cell) was incubated with PC3 cells, and the effect on the cell proliferation was evaluated after 3 days. Fluorescence images of ^99mTc/¹⁷⁷Lu‐AuNP‐Tat‐BN internalized in nuclei of PC3 were also obtained. After laser irradiation, the presence of AuNP‐Tat‐BN caused a significant increase in the temperature of the medium (46.4 vs 39.5 °C of that without AuNP) resulting in a significant decrease in PC3 cell viability down to 1.3%. After treatment with ^99mTc/¹⁷⁷Lu‐AuNP‐Tat‐BN, the PC3 cell proliferation was inhibited. The nanosystem exhibited properties suitable for plasmonic photothermal therapy and targeted radiotherapy in the treatment of prostate cancer.     

Development of 170Tm‐DOTA‐cetuximab for radioimmunotherapy

Thulium‐170 [T_1/2 = 128.4 days, E_β(max) = 968 keV, E_γ = 84 keV (3.26%)] has radionuclidic properties suitable for use in therapy. ¹⁷⁰Tm can be produced by a relatively feasible route involving thermal neutron bombardment on natural Tm(NO₃)₃ (100% ¹⁶⁹Tm) in medium flux research reactors. The combination of beta‐particle emission of Tm‐170 with therapeutic properties of C225 monoclonal antibody (cetuximab) as well as optimization studies for future Tm‐167 labeling was targeted in this study. Conjugated cetuximab was obtained by the addition of 0.5 ml of a cetuximab pharmaceutical solution (1 mg, in phosphate buffer, pH 7.8) to a glass tube pre‐coated with in situ prepared 1,4,7,10‐tetraazacyclododecane‐N,N,N,N‐tetraacetic acid mono‐(N‐hydroxysuccinimidyl) ester (DOTA‐NHS) (~5 mg) at 25°C. Cetuximab was labeled with ¹⁷⁰Tm‐Thulium chloride (100 MBq) after conjugation with DOTA‐NHS in 2–3 h (radiochemical purity >99%, instant thin‐layer chromatography, specific activity = 77–385 TBq/mmol). Biodistribution studies in wild‐type rats for free Tm‐170 and the radioimmunoconjugate were performed to determine the distribution up to 72 h. A comparative time‐frame study was performed for critical organs for both radiochemical species. The major organs of accumulation were shown to be the lung, liver, and spleen, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Development of a novel,fibrin‐specific PET tracer

Fibrin deposition is observed in several diseases such as atherosclerosis, deep vein thrombosis, and also tumors, where it contributes to the formation of mature tumor stroma. The aim of this study was to develop a gallium‐labeled peptide tracer on the basis of the fibrin‐targeting peptide Epep for PET imaging of fibrin deposition. For this purpose, the peptide Epep was modified with a NOTA moiety for radiolabeling with ⁶⁷Ga and ⁶⁸Ga and compared with the earlier validated ¹¹¹In‐DOTA‐Epep tracer. In vitro binding assays of ⁶⁷Ga‐NOTA‐Epep displayed an enhanced retention as compared to previously published data showing binding of ¹¹¹In‐DOTA‐Epep to human (84.0 ± 0.6 vs 66.6 ± 1.4 %Dose) and mouse derived fibrin clots (83.5 ± 1.7 vs 74.2 ± 2.4% Dose). In vivo blood kinetics displayed a bi‐phasic elimination profile (t_1/2,_α = 2.6 ± 1.0 minutes and t_1/2,_β = 15.8 ± 1.3 minutes) and ex vivo biodistribution showed low blood values at 4 hours post injection and a low uptake in nontarget tissue (<0.2 %ID/g; kidneys, 1.9%ID/g). In conclusion, taking into account the ease of radiolabeling and the promising in vitro and in vivo studies, gallium‐labeled Epep displays the potential for further development towards a PET tracer for fibrin deposition.     

Synthesis of carbon‐14 labeled ZJ0712, a novel strobilurin fungicide

ZJ0712, a broad‐spectrum fungicidal ingredient of strobilurin, exhibits a high protective and curative activity against plant pathogenic fungi. To support the study on its metabolism, residue, environmental behavior, and fate for safety evaluation, two versions of carbon‐14 labeled ZJ0712, methyl (E)‐2‐(2‐((2,5‐dimethylphenoxy)methyl)phenyl)‐3‐methoxy[2‐¹⁴C]acrylate ( 2 ) and methyl (E)‐2‐(2‐((2,5‐dimethyl[phenyl‐U‐¹⁴C₆]phenoxy)methyl)phenyl)‐3‐methoxyacrylate ( 3 ), were synthesized from barium [¹⁴C]carbonate in 6‐step yield of 47% and from 2,5‐dimethyl[phenyl‐U‐¹⁴C₆]phenol in the yield of 91%, respectively.