Recent Development of Radiofluorination of Boron Agents for Boron Neutron Capture Therapy of Tumor: Creation of 18F-Labeled C-F and B-F Linkages

Boron neutron capture therapy (BNCT) is a binary therapeutic technique employing a boron agent to be delivered to the tumor site followed by the irradiation of neutrons. Biofunctional molecules/nanoparticles labeled with F-18 can provide an initial pharmacokinetic profile of patients to guide the subsequent treatment planning procedure of BNCT. Borono phenylalanine (BPA), recognized by the l-type amino acid transporter, can cross the blood-brain barrier and be accumulated in gliomas. The radiofluoro BNCT agents are reviewed by considering (1) less cytotoxicity, (2) diagnosing and therapeutic purposes, (3) aqueous solubility and extraction route, as well as (4), the trifluoroborate effect. A trifluoroborate-containing amino acid such as fluoroboronotyrosine (FBY) represents an example with both functionalities of imaging and therapeutics. Comparing with the insignificant cytotoxicity of clinical BPA with IC50 > 500 μM, FBY also shows minute toxicity with IC50 > 500 μM. [18F]FBY is a potential diagnostic agent for its tumor to normal accumulation (T/N) ratio, which ranges from 2.3 to 24.5 from positron emission tomography, whereas the T/N ratio of FBPA is greater than 2.5. Additionally, in serving as a BNCT therapeutic agent, the boron concentration of FBY accumulated in gliomas remains uncertain. The solubility of 3-BPA is better than that of BPA, as evidenced by the cerebral dose of 3.4%ID/g vs. 2.2%ID/g, respectively. While the extraction route of d-BPA differs from that of BPA, an impressive T/N ratio of 6.9 vs. 1.5 is noted. [18F]FBPA, the most common clinical boron agent, facilitates the application of BPA in clinical BNCT. In addition to [18F]FBY, [18F] trifluoroborated nucleoside analog obtained through 1,3-dipolar cycloaddition shows marked tumoral uptake of 1.5%ID/g. Other examples using electrophilic and nucleophilic fluorination on the boron compounds are also reviewed, including diboronopinacolone phenylalanine and nonsteroidal anti-inflammatory agents.

Molecular Immobilization and Resonant Raman Amplification by Complex-Loaded Enhancers (MIRRACLE) on copper (II)-chitosan-modified SERS-active metallic nanostructured substrates for multiplex determination of dopamine, norepinephrine, and epinephrine

A unique approach based on Molecular Immobilization and Resonant Raman Amplification by Complex-Loaded Enhancers (MIRRACLE) on copper (II)-chitosan-modified SERS-active metallic nanostructured substrates is proposed for sensitive and rapid determination of the catecholamines (CA) dopamine, norepinephrine, and epinephrine. The ternary (CA)₂Cu(4AAP)₂ complexes were characterized by the appearance of new absorbance bands at 555, 600, and 500 nm for dopamine, norepinephrine, and epinephrine, respectively. The new absorbance band matched with a broad surface plasmon resonance band of utilized silver nanoparticles: 450-600 nm, and 633 excitation wavelength. We observed enhancement factors up to 3.6·10⁶ due to the additional resonant enhancement. The multiplexing capabilities of quantitative spectral unmixing for Raman spectra of a group of CAs, which differ by only either hydroxy or methyl group, at the fingerprint region were successfully demonstrated with the direct classic least squares model. The achieved nM limits of detection with only 1.5 mW laser power and analysis of spiked human blood plasma samples proved the possibility of the multiplex determination of the catecholamines at the level of reference concentrations in the blood of healthy people as well as promise for the future facilitation in the precision diagnosis of neuroendocrine tumors and neurodegenerative diseases.

Nanotechnology as a Versatile Tool for 19F-MRI Agent’s Formulation: A Glimpse into the Use of Perfluorinated and Fluorinated Compounds in Nanoparticles

Simultaneously being a non-radiative and non-invasive technique makes magnetic resonance imaging (MRI) one of the highly sought imaging techniques for the early diagnosis and treatment of diseases. Despite more than four decades of research on finding a suitable imaging agent from fluorine for clinical applications, it still lingers as a challenge to get the regulatory approval compared to its hydrogen counterpart. The pertinent hurdle is the simultaneous intrinsic hydrophobicity and lipophobicity of fluorine and its derivatives that make them insoluble in any liquids, strongly limiting their application in areas such as targeted delivery. A blossoming technique to circumvent the unfavorable physicochemical characteristics of perfluorocarbon compounds (PFCs) and guarantee a high local concentration of fluorine in the desired body part is to encapsulate them in nanosystems. In this review, we will be emphasizing different types of nanocarrier systems studied to encapsulate various PFCs and fluorinated compounds, headway to be applied as a contrast agent (CA) in fluorine-19 MRI (¹⁹F MRI). We would also scrutinize, especially from studies over the last decade, the different types of PFCs and their specific applications and limitations concerning the nanoparticle (NP) system used to encapsulate them. A critical evaluation for future opportunities would be speculated.

Importance of Fluorine in Benzazole Compounds

Fluorine-containing heterocycles continue to receive considerable attention due to their unique properties. In medicinal chemistry, the incorporation of fluorine in small molecules imparts a significant enhancement their biological activities compared to non-fluorinated molecules. In this short review, we will highlight the importance of incorporating fluorine as a basic appendage in benzothiazole and benzimidazole skeletons. The chemistry and pharmacological activities of heterocycles containing fluorine during the past years are compiled and discussed.

Cationic radionuclides and ligands for targeted therapeutic radiopharmaceuticals

This review considers the already used and potential α- and β-emitting cationic radionuclides for targeted radionuclide therapy. Recent results of laboratory, preclinical and clinical applications of these radionuclides are discussed. As opposed to β-emitters, which are already used in nuclear medicine, α-emitters involved in targeted radiopharmaceuticals were subjected to clinical trials only recently and were found to be therapeutically effective. The review summarizes recent trends in the development of ligands as components of radiopharmaceuticals addressing specific features of short-lived cationic radionuclides applied in medicine. Despite a steadily growing number of chelating ligands, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and diethylenetriaminepentaacetic acid (DTPA) remain the most widely used agents in nuclear medicine. The drawbacks of these compounds restrict the application of radionuclides in medicine. Variations in the macrocycle size, the introduction and modification of substituents can significantly improve the chelating ability of ligands, enhance stability of radionuclide complexes with these ligands and eliminate the influence of ligands on the affinity of biological targeting vectors.

The bibliography includes 189 references.

Supramolecular Organogels Based on N-Benzyl, N'-Acylbispidinols

The acylation of unsymmetrical N-benzylbispidinols in aromatic solvents without an external base led to the formation of supramolecular gels, which possess different thicknesses and degrees of stability depending on the substituents in para-positions of the benzylic group as well as on the nature of the acylating agent and of the solvent used. Structural features of the native gels as well as of their dried forms were studied by complementary techniques including Fourier-transform infrared (FTIR) and attenuated total reflection (ATR) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and small-angle X-ray scattering and diffraction (SAXS). Structures of the key crystalline compounds were established by X-ray diffraction. An analysis of the obtained data allowed speculation on the crucial structural and condition factors that governed the gel formation. The most important factors were as follows: (i) absence of base, either external or internal; (ii) presence of HCl; (iii) presence of carbonyl and hydroxyl groups to allow hydrogen bonding; and (iv) presence of two (hetero)aromatic rings at both sides of the molecule. The hydrogen bonding involving amide carbonyl, hydroxyl at position 9, and, very probably, ammonium N-H⁺ and Cl- anion appears to be responsible for the formation of infinite molecular chains required for the first step of gel formation. Subsequent lateral cooperation of molecular chains into fibers occurred, presumably, due to the aromatic π-π-stacking interactions. Supercritical carbon dioxide drying of the organogels gave rise to aerogels with morphologies different from that of air-dried samples.

Promising methods for noninvasive medical diagnosis based on the use of nanoparticles: surface-enhanced raman spectroscopy in the study of cells, cell organelles and neurotransmitter metabolism markers

Application of advances in nanomedicine and materials science to medical diagnostics is a promising area of research. Surface-enhanced Raman spectroscopy (SERS) is an innovative analytical method that exploits noble metal nanoparticles to noninvasively study cells, cell organelles and protein molecules. Below, we summarize the literature on the methods for early clinical diagnosis of some neurodegenerative and neuroendocrine diseases. We discuss the specifics, advantages and limitations of different diagnostic techniques based on the use of low- and high molecular weight biomarkers. We talk about the prospects of optical methods for rapid diagnosis of neurotransmitter metabolism disorders. Special attention is paid to new approaches to devising optical systems that expand the analytical potential of SERS, the tool that demonstrates remarkable sensitivity, selectivity and reproducibility of the results in determining target analytes in complex biological matrices.