18F-labeled somatostatin analogs for somatostatin receptors (SSTRs) targeted PET imaging of neuroendocrine tumors (NETs).

PURPOSE: A novel 18F-radiolabeled somatostatin analogue, [Al18F]NODA-MPAA-HTA, was synthesized and evaluated for positron emission tomography (PET) imaging of Neuroendocrine tumors (NETs). [Al18F]NODA-MPAA-HTA was designed and synthesized by conjugating 18F nuclide with a modified KE108 peptide, a somatostatin analog with high affinity for all five subtypes of somatostatin receptors (SSTR 1-5), through coupling a bifunctional chelator (NODA) to target somatostatin receptor (SSTR) positive tumors. METHODS: The amino group of KE108 peptide, a SSTRs-targeting pharmacophore, was conjugated with the carboxyl group of NODA by a condensation reaction to obtain the labeling precursor of [Al18F]NODA-MPAA-HTA, in which its precursor was obtained through Fmoc solid-phase methods. A novel methodology for Al18F labeling of chelating agent-biomolecule conjugates was used to synthesize [Al18F]NODA-MPAA-HTA. In vitro stabilities of [Al18F]NODA-MPAA-HTA were evaluated by incubating it in saline or bovine serum for 2 h. Ex vivo biodistribution and in vivo imaging of [Al18F]NODA-MPAA-HTA were further investigated to evaluate its SSTRs targeting ability and feasibility for the diagnosis of NETs using PET imaging. RESULTS: [Al18F]NODA-MPAA-HTA was synthesized using a one-step 18F-AlF labeling procedure resulting in moderate radiochemical yield (60-80 %, non-decay corrected) and high radiochemical purity (>95 %). It exhibited good hydrophilicity and excellent stability in vitro, with a molar activity of 122 GBq/µmol. At 30 min and 60 min, the uptake of [Al18F] NODA-MPAA-HTA by HEK293-SSTR2 cells was 5.47 ± 0.97 %/105 cells and 12.11 ± 0.32 %/105 cells, respectively. The affinity of [Al18F]NODA-MPAA-HTA for SSTR2 was determined to be 8.77 ± 1.14 nM. In micro-PET imaging of HEK293-SSTR2 tumor-bearing mice, [Al18F]NODA-MPAA-HTA showed high tumor uptake of radioactivity and a high tumor-to-muscle ratio. Biodistribution results confirmed that radioactivity uptake in the tumor was significantly higher than that in the muscle by more than five-fold (P<0.001). Furthermore, the relatively low bone uptake of [Al18F]NODA-MPAA-HTA suggested that defluorination did not occur in vivo. These preliminary results provide experimental evidence for further study of Al18F-labeled somatostatin analogues as tumor probes for PET imaging of NETs. CONCLUSION: Fluorine-18 is widely used as a radionuclide for the production of radiopharmaceuticals for positron emission tomography (PET). Due to its short half-life (T1/2,109.8 min), its ease of production will facilitate the widespread dissemination of this radiopharmaceutical. A high-quality [Al18F]NODA-MPAA-HTA was synthesized with satisfactory yield. This radiopharmaceutical demonstrated higher tumor uptake and better tumor-to-muscle contrast, resulting to excellent image quality. These findings suggest that the novel 18F-labeled somatostatin analogue, [Al18F]NODA-MPAA-HTA, is a promising tool for PET imaging of NETs.

Fluorine-18-Labeled Diaryl-azines as Improved ß-Amyloid Imaging Tracers: From Bench to First-in-Human Studies.

The deposition of ß-amyloid (Aß) in the brain is a pathologic hallmark of Alzheimer's disease (AD), appearing years before the onset of symptoms, and its detection is incorporated into clinical diagnosis. Here, we have discovered and developed a class of diaryl-azine derivatives for detecting Aß plaques in the AD brain using PET imaging. After a set of comprehensive preclinical assessments, we screened out a promising Aß-PET tracer, [18F]92, with a high binding affinity to the Aß aggregates, significant binding ability with the AD brain sections, and optimal brain pharmacokinetic properties in rodents and non-human primates. The first-in-human PET study declared that [18F]92 displayed low white matter uptake and could bind to Aß pathology for distinguishing AD from healthy control subjects. All these results support that [18F]92 might become a promising PET tracer for visualizing Aß pathology in AD patients.

Dynamic Porous Pattern through Controlling Noncovalent Interactions in Polyelectrolyte Film for Sequential and Regional Encapsulation.

Inspired by nature, many functional surfaces have been developed with special structures in biology, chemistry, and materials. Many research studies have been focused on the preparation of surfaces with static structure. Achieving dynamical manipulation of surface structure is desired but still a great challenge. Herein, a polyelectrolyte film capable of regional and reversible changes in the microporous structure is presented. Our proposal is based on the combination of azobenzene (Azo) π-π stacking and electrostatic interaction, which could be affected respectively by ultraviolet (UV) irradiation and water plasticization, to tune the mobility of polyelectrolyte chains. The porous patterns can be obtained after regional ultraviolet irradiation and acid treatment. Owing to the reversibility of Azo π-π stacking and electrostatic interaction, the patterns can be repeatedly created and erased in the polyelectrolyte film made by layer-by-layer (LbL) self-assembly of poly(ethyleneimine)-azo and poly(acrylic acid). Furthermore, through two rounds of porous pattern formation and erasure, different functional species can be loaded separately and confined regionally within the film, showing potential applications in the functional surface. This work highlights the coordination of two noncovalent interactions in thin films for regional and reversible controlling its structure, opening a window for more in-depth development of functional surfaces.

[High-resolution THz spectra of six biological and pharmaceutical materials].

The temperature dependent vibrational spectra of,three biological and pharmaceutical sets, genistein and biochanin A, clenbuterol hydrochloride and salbutamol, as well as ginseng R2 and R3, in the range of 0.2-4.5 THz (6.6-150.0 cm(-)) are presented over the temperature range from 295 to 77 K Although there are only some minor difference in their molecular structures, the spectra of two samples in every group are quite differences in both absorption band positions and their relative intensities, and display strong linewidth narrowing and frequency blue-shift with cooling. Au 77 K, 13 highly resolved spectral features for biochanin A were obtained and the sensitivity of the experiment allows detection of amounts as small as 1.9 x 10(-5) mol of ginseng R3. Such high-resolution THz fingerprint spectra provide a rapid, nondestructive and reliable method for the identification of these pharmaceutical settings molecules.