Effect of methoxy group position on biological properties of 18 F–labeled benzyl triphenylphosphonium cations

A Novel Method of Self-Cross-Linking of Syringaldehyde with Activated Methoxy Groups via Cross-Coupling for Lignin-Based Wood Adhesives

As steric hindrance, methoxy groups are limiting the valorization of hardwood lignin. This paper reports a novel method of self-cross-linking of the syringaldehyde with activated methoxy groups (-OCH3) via cross-coupling reaction to obtain thermosetting polymers for lignin-based wood adhesives. The methoxy groups of syringaldehyde have been activated via cross-coupling reaction by substituting Ar-OCH3 with Ar-CH2-SiMe3, and dichloromethane, leading to cross-linking via methylene bridges to build a thermosetting polymer. FTIR spectra showed a decrease in the intensity of a -CH3 and -OH group, owing to the substitution of the methoxy group. 13C NMR spectra also supported these results with the -SiMe3 signal that disappeared after the cross-linking reaction. Furthermore, cross-linking between the activated methoxy groups was confirmed with a strong exothermic peak at 130 °C, resulting in an increase in the adhesion strength as hot-pressing temperature increased from 160 to 180 °C. These results suggest that the cross-linking between the activated methoxy groups of syringaldehyde is an important understanding of valorizing hardwood lignin via building thermosetting polymers for lignin-based adhesives.

Development of Mitochondria-Targeted Small-Molecule Dyes for Myocardial PET and Fluorescence Bimodal Imaging

Mitochondria-targeting positron emission tomography (PET) and fluorescent dual-modal probes are rarely reported. As one of the most promising lipophilic cations, F16 and its derivatives (F16s) have never been used for myocardial imaging. In this work, 14 F16s are synthesized and evaluated for cardiac imaging. In vitro cell fluorescence imaging revealed that the lead probe 5MEF is precisely localized in the mitochondria of cardiomyocytes. In addition, it shows excellent ex vivo fluorescence imaging quality with the heart-to-muscle and heart-to-liver ratios up to ∼2. Furthermore, the radiofluorinated probe ¹⁸F-5MEF is successfully prepared and shows a high initial heart uptake of 8.66 ± 0.34 % ID/g at 5 min post injection. It displays a high heart imaging performance, a long retention time in the heart, and a low background in the most normal tissues as revealed by PET. To our knowledge, this is the first time novel F16 analogues are designed and developed for myocardial dual-modal imaging.

Preparation and biological evaluation of radioiodine-labeled triphenylphosphine derivatives as mitochondrial targeting probes

The positive-charged lipophilic triphenylphosphonium cations (TPPs+ ) have been served as mitochondrial targeting vehicles for the delivery of various probes. In this study, we developed a new method for the preparation of radioiodine-labeled TPPs+ . Four 125 I-labeled TPPs+ , [125 I] 9-[125 I] 12, were prepared from the corresponding triphenylphosphine phenylborate precursors of B 5-B 8 via an optimized copper-catalyzed one-step procedure in high radiochemical yield (>95%). After radio-HPLC purification, the final products could be obtained with high specific activity. Their physicochemical properties, in vitro cellular uptake, and ex vivo mice biodistribution were investigated. The results suggested the 125 I-labeled TPPs+ were lipophilic and could specifically accumulate in the mitochondrial-rich myocardial cells through the mitochondrial membrane potential.

A Novel Triphenylphosphonium Carrier to Target Mitochondria without Uncoupling Oxidative Phosphorylation

Mitochondrial dysfunction is an underlying pathology in numerous diseases. Delivery of diagnostic and therapeutic cargo directly into mitochondria is a powerful approach to study and treat these diseases. The triphenylphosphonium (TPP⁺) moiety is the most widely used mitochondriotropic carrier. However, studies have shown that TPP⁺ is not inert; TPP⁺ conjugates uncouple mitochondrial oxidative phosphorylation. To date, all efforts toward addressing this problem have focused on modifying lipophilicity of TPP⁺-linker-cargo conjugates to alter mitochondrial uptake, albeit with limited success. We show that structural modifications to the TPP⁺ phenyl rings that decrease electron density on the phosphorus atom can abrogate uncoupling activity as compared to the parent TPP⁺ moiety and prevent dissipation of mitochondrial membrane potential. These alterations of the TPP⁺ structure do not negatively affect the delivery of cargo to mitochondria. Results here identify the 4-CF₃-phenyl TPP⁺ moiety as an inert mitochondria-targeting carrier to safely target pharmacophores and probes to mitochondria.

Emerging Tracers for Nuclear Cardiac PET Imaging

Myocardial perfusion imaging using positron emission tomography (PET) has several advantages over single photon emission computed tomography (SPECT). The recent advances in SPECT technology have shown promise, but there is still a large need for PET in the clinical management of coronary artery disease (CAD). Especially, absolute quantification of myocardial blood flow (MBF) using PET is extremely important. In spite of considerable advances in the diagnosis of CAD, novel PET radiopharmaceuticals remain necessary for the diagnosis of CAD because clinical use of current cardiac radiotracers is limited by their physical characteristics, such as decay mode, emission energy, and half-life. Thus, the use of a radioisotope that has proper characteristics and a proper half-life to develop myocardial perfusion agents could overcome these limitations. In this review, the current state of cardiac PET and a general overview of novel 18F or 68Ga-labeled radiotracers, including their radiosynthesis, in vivo characterization, and evaluation, are provided. The future perspectives are discussed in terms of their potential usefulness based on new image analysis methods and hybrid imaging.