F-18 labeled vasoactive intestinal peptide analogue in the PET imaging of colon carcinoma in nude mice.

As large amount of vasoactive intestinal peptide (VIP) receptors are expressed in various tumors and VIP-related diseases, radiolabeled VIP provides a potential PET imaging agent for VIP receptor. However, structural modification of VIP is required before being radiolabeled and used for VIP receptor imaging due to its poor in vivo stability. As a VIP analogue, [R(8, 15, 21), L(17)]-VIP exhibited improved stability and receptor specificity in preliminary studies. In this study, F-18 labeled [R(8,15,21), L(17)]-VIP was produced with the radiochemical yield being as high as 33.6% ± 3% (decay-for-corrected, n = 5) achieved within 100 min, a specific activity of 255 GBq/ µmol, and a radiochemical purity as high as 99% as characterized by radioactive HPLC, TLC, and SDS-Page radioautography. A biodistribution study in normal mice also demonstrated fast elimination of F-18 labeled [R(8,15,21), L(17)]-VIP in the blood, liver, and gastrointestinal tracts. A further micro-PET imaging study in C26 colon carcinoma bearing mice confirmed the high tumor specificity, with the tumor/muscle radioactivity uptake ratio being as high as 3.03 at 60 min following injection, and no apparent radioactivity concentration in the intestinal tracts. In addition, blocking experiment and Western Blot test further confirmed its potential in PET imaging of VIP receptor-positive tumor.

The tolerance and therapeutic efficacy of rhenium-188 hydroxyethylidene diphosphonate in advanced cancer patients with painful osseous metastases.

PURPOSE: This study evaluated the tolerance and therapeutic efficacy of rhenium-188 hydroxyethylidene diphosphonate ((188)Re-HEDP) in patients with different types of advanced cancer suffering from bone pain caused by osseous metastases. METHODS: Sixty-four patients received a single injection of escalating doses of (188)Re-HEDP with various dosages. Vital signs were observed before and after treatment for 8 weeks; adverse effects and rebound pain were recorded within 8 weeks after injection. Blood counts, biochemical parameters, and electrocardiogram were also measured over a period of 8 weeks. Clinical follow-up studies including the bone pain score and the Karnofsky performance score were performed. Pain response was scored by a four-point pain-rating scale as complete, marked, mild, and no response. RESULTS: No adverse effects or clinically significant changes in vital signs, electrocardiograms, and biochemical parameters in patients were observed, and there was no statistical change in alkaline phosphate levels in patients before or after treatment. The overall nadir of thrombopenia was at week 4, leucopoenia at week 3, and anemia at week 8. At week 8, the mean level of platelets and leukocytes returned to baseline levels. The pain score descended from 8.11 to 7.74 on the day of therapy, with a nadir of 4.89 at week 4, and up to 6.67 at week 8 after therapy (p < 0.05). The Karnofsky performance score continually increased from 74.81 before therapy to 82.31 at 8 weeks (p > 0.05 Pain palliation was reported by 73.33% of patients, with a mean duration of 6.85 weeks and a mean start time of 4.05 days. Of the specific tumor types, pain relief was achieved in 84.62% of patients with prostate cancer, 78.57% with breast cancer, 62.50% with lung cancer, and 55.56% with liver cancer. CONCLUSIONS: (188)Re-HEDP is a useful radiopharmaceutical agent for improving bone pain in patients with advanced cancer with painful bone metastases.

Modification of MR molecular imaging probes with cysteine-terminated peptides and their potential for in vivo tumour detection.

One of the challenges facing superparamagnetic iron oxide (SPIO) nanoparticles is to improve their biological compatibility. While highly uniform SPIOs can be manufactured, the surfaces are hydrophobic as a result of the surfactants used in their fabrication. In this study, we developed a general strategy to fabricate an MR molecular imaging probe in one step by replacing hydrophobic surfactants with small peptides terminated with cysteine. The hydrophobic SPIO surface was transformed into a hydrophilic one by exchanging surface oleic acids with the peptides RGD-Cys or RGD-PEG-Cys. After the RGD-Cys and RGD-PEG-Cys peptide exchange, both RGD-Cys-SPIO and RGD-PEG-Cys-SPIO specifically targeted α(v)ß(3)-expressing cells (A549) in vitro, with RGD-Cys-SPIO achieving this more efficiently. Furthermore, MR imaging of A549 tumors receiving RGD-Cys-SPIO or RGD-PEG-Cys-SPIO demonstrated that both the targeted particles could reach and label the α(v)ß(3)-expressing tumor, much more efficiently than the non-targeted particles (Cys-SPIO). Histology showed that the probes not only target the tumor neovasculature but also extravasate from vessels and address the tumor cells. Our study shows that directly replacing oleic acid with cysteine or cysteine-terminated small peptides is a general strategy to transforming the hydrophobic surface of SPIO into a hydrophilic one, as well as providing targeting ligands. Such SPIOs are of interest as MR molecular imaging probes to detect for cancer in vivo.

Radiolabeling RGD peptide and preliminary biodistribution evaluation in mice bearing S180 tumors.

OBJECTIVE: To prepare the rhenium-188 (188Re)-arginine-glycine-aspartic acid (RGD) peptide in a convenient manner and to evaluate its potential as an agent for alphavbeta3 integrin receptor-positive tumors. METHODS: Radiolabeled RGD was obtained by conjugating the His group at the end of peptide with fac-[188Re(H2O)3(CO)3]+. Chelating efficiency of fac-[188Re(H2O)3(CO)3]+ and radiolabeling efficiency of radiolabeled peptide were measured by thin-layer chromatography and high-performance liquid chromatography. In-vitro stability of the radio-complex was determined in phosphate-buffered saline (0.05 mol/l, pH 7.4), new-born calf serum, His or Cys solution at 37 degrees C or room temperature and analyzed by thin-layer chromatography. A biodistribution study was carried out in mice bearing S180 tumors. RESULTS: 188Re-RGD was obtained with a more than 95% of radiolabeling efficiency, and showed high stability in phosphate-buffered saline, new-born calf serum, His and Cys solution. Furthermore, this radio-complex was cleared rapidly from the blood and showed specific tumor uptake in mice bearing S180 tumors. CONCLUSION: 188Re-RGD was prepared by a simple method. Preliminary biodistribution results showed its potential as an agent for cancer therapy and encouraged further investigation.

Superparamagnetic magnetite nanocrystal clusters: a sensitive tool for MR cellular imaging.

Silica coated, PEI and citric acid hybrid superparamagnetic magnetite nanocrystal clusters (SMNC) were synthesized using either a mini-emulsion/sol-gel method or a polyol technique. After careful characterization of the size, structure, composition, and magnetic properties, the as-synthesized SMNC were used for cell labeling while the MR detection sensitivity of cells labeled with silica SMNC was performed with a 3 T whole body MR scanner. TEM investigations revealed that the sizes of the SMNC were about 200 nm and the SMNC mainly consisted of magnetite nanoparticles imbedded in a PEI, citric acid or polystyrene scaffold. Silica and citric acid SMNC were highly negatively charged and PEI SMNC were positively charged. Relaxometry measurements revealed that these SMNC possessed a very high MR sensitivity (silica SMNC: r(2) = 299 s(-1) mM(-1), PEI SMNC: r(2) = 124 s(-1) mM(-1)), especially for the citric acid SMNC (r(2) = 360 s(-1) mM(-1)). Furthermore, when used for cell (RAW264.7 cells) labeling, the SMNC had no adverse effect on cell viability, and the cell uptake of the SMNC show a dose- and time-dependent feature. MR imaging of cells labeled with silica SMNC indicated that cells with a concentration as low as 10 x 10(3) cells ml(-1) could be detected with a 3 T MRI scanner. Our study demonstrated that superparamagnetic magnetite nanocrystal clusters are a sensitive tool for cell imaging.

Biological characters of [18F]O-FEt-PIB in a rat model of Alzheimer's disease using micro-PET imaging.

AIM: To evaluate whether the newly-synthesized positron emission tomography (PET) tracer, [18F]2-(4'-(methylamino)phenyl)-6-fluoroethoxy- benzothiazole ([18F] O-FEt-PIB), could bind to beta-amyloid aggregates in a rat model of Alzheimer's disease (AD) using micro-PET. METHOD: [18F]O-FEt-PIB was synthesized and purified by radio HPLC. PET imaging was performed with a R4 rodent model scanner in 3 model and 3 control rats. Dynamic PET scans were performed for 40 min in each rat following an injection of approximately 37 MBq of [18F]O-FEt-PIB. Static scans were also performed for 15 min in each rat. PET data were reconstructed by a maximum posteriori probability algorithm. On the coronal PET images, regions of interest were respectively placed on the cortex, hemicerebrum [including the hippocampus and thalamus (HT)], and were guided by a 3-D digital map of the rat brain or the brain images of [18F]2-Deoxy-2-fluoro-D-glucose ([18F]FDG) in normal rats. Time-activity curves (TAC) were obtained for the cerebrum and cerebellum. The activity difference value (ADV) between 2 hemicerebrums was also calculated. RESULTS: The TAC for [18F]O-FEt-PIB in the cerebrum or cerebellum peaked early (at approximately 2 min), but washed out a little slowly. In the dynamic and static micro-PET images, increased radioactivity was found in the area of the right HT in the model rats where infused with beta-amyloid (1-40). No distinct difference of radioactivity was found between the right and left HT areas in the control rats. The ADV(HT) was approximately 14.6% in the AD model rats and approximately 4 times greater than that of the control rats (3.9%). CONCLUSION: To our knowledge, this study is the first to evaluate a small molecular PET probe for the beta-amyloid deposits in vivo using micro-PET imaging in an AD-injected rat model. The suitable biological characters showed that the tracer had potential to be developed as a probe for detecting beta-amyloid plaques in AD.

Preparation and biological evaluation of 2-amino-6-[18F]fluoro-9-(4-hydroxy-3-hydroxy-methylbutyl) purine (6-[18F]FPCV) as a novel PET probe for imaging HSV1-tk reporter gene expression.

INTRODUCTION: 2-Amino-6-[(18)F]fluoro-9-(4-hydroxy-3-hydroxy-methylbutyl) purine (6-[(18)F]FPCV) was prepared via a one-step nucleophilic substitution and evaluated as a novel probe for imaging the expression of herpes simplex virus type 1 thymidine kinase (HSV1-tk) reporter gene. METHODS: Log P of 6-[(18)F]FPCV was calculated in octanol/phosphate-buffered saline (PBS). Stability studies were performed in PBS and bovine serum albumin (BSA). Cell uptake was performed at various time points in wild-type cells and transduced cells. For in vivo studies, tumors were grown in nude mice by inoculation with C6 cells, wild type and tk positive. The radiotracer was intravenously injected to animals, and micro-PET imaging was performed. Biodistribution of 6-[(18)F]FPCV was performed on another group of animals at different time points. RESULTS: Log P of 6-[(18)F]FPCV was -0.517. 6-[(18)F]FPCV was fairly stable in PBS and BSA at 6 h. The tracer uptake in C6-tk cells was 5.5-18.8 times higher than that in wild-type cells. The plasma half-life of 6-[(18)F]FPCV was as follows: alpha t(1/2)=1.2 min and beta t(1/2)=73.7 min. The average ratio of tumor uptake between the transduced tumor and the wild-type tumor was 1.69 at 15 min. CONCLUSION: Biological evaluation showed that 6-[(18)F]FPCV is a potential probe for imaging HSV1-tk gene expression. However, its in vivo defluorination may limit its application in PET imaging of gene expression.

Surface modified superparamagnetic iron oxide nanoparticles: as a new carrier for bio-magnetically targeted therapy.

Amino-functionalized superparamagnetic iron oxide nanoparticles (SPION) were synthesized by coprecipitation method. The particles were characterized by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron micrographs (SEM), transmission electron micrographs (TEM) and atomic force micrographs (AFM). The size of the modified particles varied in the range 10-15 nm and did not change significantly after modification. Hepama-1, an excellent humanized monoclonal antibody directed against liver cancer, was conjugated to the SPION to prepare immuno-magnetic nanoparticles (IMN). A direct labeling method was employed to radiolabel IMN with rhenium-188. The radiolabeling efficiency was about 90% with good in vitro stability. (188)Re labeled IMN could markedly kill SMMC-7721 liver cancer cells. Such SPION might be very useful for bio-magnetically targeted radiotherapy in liver cancer treatment.

Radiosynthesis of 18F-(R8,15,21, L17)-vasoactive intestinal peptide and preliminary evaluation in mice bearing C26 colorectal tumours.

BACKGROUND: Radiolabelled vasoactive intestinal peptide (VIP) and its analogues have shown their potential as imaging agents for diagnosing tumours expressing VIP receptor. However, the fast proteolytic degradation in vivo has limited their clinical use. AIM: To prepare the 18F-labelled (R8,15,21, L17)-VIP analogue in a convenient way and to evaluate its potential as an imaging agent for VIP receptor-positive tumours. METHODS: Radiolabelled (R8,15,21, L17)-VIP was obtained by conjugation with N-succinimidyl 4-([18F]fluoromethyl) benzoate and purified by HPLC. Radiochemical purity and specific radioactivity were measured by analytical HPLC. In-vitro stability of the product was carried out in HSA solution and analysed by HPLC. Biodistribution study was carried out in mice bearing C26 colorectal tumours. RESULTS: 18F-(R8,15,21, L17)-VIP was obtained in greater than 99% radiochemical purity within 60 min in decay-for-corrected radiochemical yields of 21.8+/-4.7% (n=5) and a specific activity of 17.76 GBq x mumol(-1) at the end of synthesis (EOS). Results of in-vitro studies demonstrated a high stability in human serum albumin (HSA) solution. Biodistribution data showed a rapid blood clearance and specific binding towards receptor-positive tumours. CONCLUSION: 18F-(R8,15,21, L17)-VIP was prepared by a convenient method. Preliminary biodistribution results showed its potential for imaging tumours over-expressing VIP receptors and encouraged further investigation.

Radiolabeling and in vitro and in vivo characterization of [18F]FB-[R(8,15,21), L17]-VIP as a PET imaging agent for tumor overexpressed VIP receptors.

In an effort to develop a peptide-based radiopharmaceutical for the detection of tumors overexpressed vasoactive intestinal peptide receptors with positron emission tomography, we have prepared a novel [R(8,15,21), L17]-VIP peptide for 18F-labeling. This peptide inhibited 125I-VIP binding to rats lung membranes with high affinity [half-maximal inhibitory concentrations (IC50) of 0.12 nm]. Additionally, [R(8,15,21), L17]-VIP showed higher stability than native vasoactive intestinal peptide in vivo of mice. With N-succinimidyl 4-[18F] fluorobenzoate as labeling prosthetic group, [18F]FB-[R(8,15,21), L17]-VIP was obtained in >99% radiochemical purity within 100 min in decay-for-corrected radiochemical yield of 33.6 +/- 3% (n = 5) and a specific radioactivity 255 GBq/micromol at the end of synthesis. Stability of [18F]FB-[R(8,15,21), L17]-VIP in vitro and in vivo were investigated. Biodistribution of this trace was carried out in mice with induced C26 colorectal tumor. Fast clearance of [18F]FB-[R(8,15,21), L17]-VIP from non-target tissues and specific uptakes by tumors realized higher tumor-to-muscle ratio (3.55) and tumor-to-blood ratio (2.37) 60 min postinjection. Clear difference was observed between the blocking and unblocking experiments in biodistribution and whole body radioautography. [18F]FB-[R(8,15,21), L17]-VIP has demonstrated its potential for diagnosing tumors overexpressed vasoactive intestinal peptide receptors both in vitro and in vivo.

Applied radioactivity in radiation synovectomy with [188Re]rhenium sulfide suspension.

BACKGROUND: Early experience demonstrated absorbed dose in radiation synovectomy is about 100 Gy. For reaching this dose, the applied radioactivity should be calculated. METHOD: Twenty-nine synovitic models of rabbit were treated by intra-articular injection of [(188)Re]rhenium sulfide and histological changes of synovium and cartilage were examined. The applied radioactivity was calculated by method of absorbed dose factor. In clinical, eleven haemophilic patients with haemarthrosis were performed radiation synovectomy with treated [(188)Re]rhenium sulfide. The synovial thickness was evaluated by MR and its value was used to calculate the applied radioactivity. After radiation synovectomy, all patients were followed up by synovial thickness, regional inflammation, and clinical course including bleeding frequency. RESULTS: In rabbit models, the synovitic membrane can be eliminated by calculated radioactivity as planed without damaging the joint cartilage. In patients study, all patients exhibited significant reductions in synovial thickness and inflammation after radiation synovectomy with the planed radioactivities of [(188)Re]rhenium sulfide. Post-procedure bleeding frequency reduction in excellent and good reached to 63.6% by 18 months. In the cases of joint bleeding, the need for antihaemophilic factor treatment decreased immensely. Most of the recurrent episodes of bleeding were mild, subsiding with local means. CONCLUSION: The applied radioactivity in radiation synovectomy could be calculated according to thickness of inflamed synovium. Further study including comparison therapeutic results from calculated individual activities with results from fixed activities and long-term follow-up is warranted.

Radiolabelling of poly(histidine) derivatized biodegradable microspheres with the 188Re tricarbonyl complex [188Re(CO)3(H2O)3]+.

OBJECTIVES: Many radiopharmaceuticals have been studied as radiation synovectomy agents. In this study, we developed a new potential agent for radiation synovectomy: poly(lactic acid)-histidine (PLA-his) microspheres radiolabelled with [188Re(CO)3(H2O)3]+. METHODS: The reaction conditions for the chelation of [188Re(CO)3(H2O)3]+ and the radiolabelling of PLA microspheres were optimized and the stabilities for both steps tested in vitro. RESULTS: The chelation efficiency of [188Re(CO)3(H2O)3]+ reached 93.12 +/- 1.82% with >95% radiochemical purity once the colloidal and free 188Re were removed by a small Sep-Pak column (Plus QMA). More than 90% of radioactivity stayed in the [188Re(CO)3(H2O)3]+ form over 5 h. The radiolabelling efficiency of PLA-his microspheres with [188Re(CO)3(H2O)3]+ was above 92%. After 3 days incubation at 37 degrees C in calf serum, more than 80% of the radioactivity was still bound to the microspheres. CONCLUSION: Such microspheres are potentially useful as a radiation synovectomy agent for the treatment of chronically inflamed arthritic joints. Furthermore, they might be valuable in cancer brachytherapy.

Preparation of 103Pd seed-molecular plating of 103Pd onto silver rod.

A method for 103Pd "molecular plating" onto the surface of a silver rod is reported. The optimal composition of the plating bath is as follows: palladium chloride 0.1 mol/l, formaldehyde 2 mol/l, nitric acid 1 mol/l, and formic acid 0.4 mol/l. The 103Pd molecular plating procedure will last 25 min at 30 degrees C. This article provides a valuable experience for the preparation of 103Pd brachytherapy seed.

Enantioselective synthesis of no-carrier-added (NCA) 6-[18F]fluoro-L-DOPA.

The application of a chiral phase-transfer-catalyst (PTC) in the synthesis of N.C.A. 6-[18F]fluoro-L-DOPA has been recently developed. The 6-trimethylammoniumveratraldehyde triflate precursor and PTC (O-allyl-N-(9)-anthracenylcinchonidinium bromide) were synthesized and successful synthesis route was developed for the preparation of 6-[18F]fluoro-L-DOPA with high radiochemical yields (4-9%, decay uncorrected) and short synthesis time (80min). The radiochemical purity was over 99% and no D-isomer was detected by HPLC analysis using a chiral mobile phase.