Density-Dependence of Surface Transport in Tellurium-Enriched Nanograined Bulk Bi2 Te3.

Three-dimensional topological insulators (3D TI) exhibit conventional parabolic bulk bands and protected Dirac surface states. A thorough investigation of the different transport channels provided by the bulk and surface carriers using macroscopic samples may provide a path toward accessing superior surface transport properties. Bi2 Te3 materials make promising 3D TI models; however, due to their complicated defect chemistry, these materials have a high number of charge carriers in the bulk that dominate the transport, even as nanograined structures. To partially control the bulk charge carrier density, herein the synthesis of Te-enriched Bi2 Te3 nanoparticles is reported. The resulting nanoparticles are compacted into nanograined pellets of varying porosity to tailor the surface-to-volume ratio, thereby emphasizing the surface transport channels. The nanograined pellets are characterized by a combination of resistivity, Hall- and magneto-conductance measurements together with (THz) time-domain reflectivity measurements. Using the Hikami-Larkin-Nagaoka (HLN) model, a characteristic coherence length of ≈200 nm is reported that is considerably larger than the diameter of the nanograins. The different contributions from the bulk and surface carriers are disentangled by THz spectroscopy, thus emphasizing the dominant role of the surface carriers. The results strongly suggest that the surface transport carriers have overcome the hindrance imposed by nanoparticle boundaries.

Synthetic methodologies and PET imaging applications of fluorine-18 radiotracers: a patent review.

INTRODUCTION: Fluorine-18 is a promising radionuclide for developing novel PET radiotracers due to its characteristic features such as convenient half-life, metabolic stability, good imaging properties, and easy access to various clinical PET centers. Currently, many 18F-radiotracers are available to study disease status in the fields of oncology, cardiology, and neurology. AREAS COVERED: In this review, the authors have covered patents and research papers of 18F-radiotracers with clinical applications in various diseases using PET modality since 2015 until the present through SciFinder database. EXPERT OPINION: Despite other PET radionuclides 11C, 13N, and 15O, the 18F is widely used for radiotracer development because of maximum half-life of 109.8 min. The major limitations of PET radiotracer development include low radiochemical yields and less regioselectivity of the radiofluorination reactions. Therefore, various synthetic methodologies were developed for radiofluorination via nucleophilic, electrophilic with specific precursors, transition metal mediated, and prosthetic groups mediated radiofluorination. Automated radiosynthesis methods have been adapted for easy and convenient synthesis of various 18F-radiotracers, whereas the PET provides functional information about a disease condition through its pharmacology and physiological processes in vivo, and it is also an essential tool in drug discovery to study therapeutic drug development, and pharmacokinetic profiles.

Human Galectin-1 in Multiple Cancers: A Privileged Molecular Target in Oncology.

Galectin-1 (Gal-1), a 14kDa carbohydrate-binding protein of the galectin family found in humans, affects intracellular signaling pathways upon interaction with ß-galactosides on cell-surface, cytosol, and nucleus. The structural information reveals that it consists of a monovalent dimer composed of subunits with one Carbohydrate Recognition Domain (CRD), which is the main active site to interact with various glycoproteins, and carbohydrates in the body to regulate cellular functions. Gal-1 contributes towards different events associated with cancer biology, including tumor transformation, cell cycle regulation, apoptosis, cell adhesion, migration, and inflammation. The extracellular existence and function of Gal-1 have been well-established, and it is known to express in many tumor types, including astrocytoma, melanoma, prostate, colon, bladder, and ovarian carcinomas, etc. Several studies suggested the upregulation of Gal-1 levels in multiple cancer cells. Thus, Gal-1 is a promising molecular target for the development of new therapeutic tools. The present review focuses on the functions of Gal-1 in tumor progression in multiple cancers and its structural insights.

Carbon-11: Radiochemistry and Target-Based PET Molecular Imaging Applications in Oncology, Cardiology, and Neurology.

The positron emission tomography (PET) molecular imaging technique has gained its universal value as a remarkable tool for medical diagnosis and biomedical research. Carbon-11 is one of the promising radiotracers that can report target-specific information related to its pharmacology and physiology to understand the disease status. Currently, many of the available carbon-11 (t1/2 = 20.4 min) PET radiotracers are heterocyclic derivatives that have been synthesized using carbon-11 inserted different functional groups obtained from primary and secondary carbon-11 precursors. A spectrum of carbon-11 PET radiotracers has been developed against many of the upregulated and emerging targets for the diagnosis, prognosis, prediction, and therapy in the fields of oncology, cardiology, and neurology. This review focuses on the carbon-11 radiochemistry and various target-specific PET molecular imaging agents used in tumor, heart, brain, and neuroinflammatory disease imaging along with its associated pathology.

Radiosynthesis challenges of 11C and 18F-labeled radiotracers in the FX2C/N tracerlab and their validation through PET-MR imaging.

Glucose is the renowned source of the energy for the cancer growth, that's the reason for [18F]FDG success and make it widely used radiotracer. Though [18F]FDG has its own inherent limitations therefore many tracers have been developed to target specific receptors, and other metabolic routes. We have used FX2C and FX2N Tracerlab modules for the synthesis of the [11C]methionine, [18F]choline and [18F]fluorodopa via nucleophilic pathway in FX2C/N module. [11C]methionine was standardized in FX2C module using two different precursors, and purified using C18 cartridge based technique. [18F]methylcholine was synthesized using dimethylaminoethanol precursor and purified using cartridge-based method. [18F]fluorodopa was synthesized using nucleophilic precursor and purified using in-built preparative HPLC on FX2N module. All radioactive intermediates and chemical impurities were evaluated by analytical HPLC. The radiochemical purity of D and L-[11C]methionine were 4.6 ± 3.2% and 95.4 ± 3.6% while other chemical impurities were less than prescribed limits with yield of 20 ± 5%. [18F]fluoromethylcholine was prepared with high radiochemical purity of 97.3 ± 2.6% with yield of 8 ± 3%. [18F]fluorodopa was synthesized with high radiochemical purity of 95.8 ± 1.4% with 15 ± 3% yield. The adaptation of [18F]fluorodopa synthesis to FX2N module via designing synthesis sequence and purified through on-line HPLC has provided high radiochemical purity. PET-MR imaging was done using these tracers which have validated the synthesis and their availability for future clinical applications.