Fast Ion-Chelate Dissociation Rate for In Vivo MRI of Labile Zinc with Frequency-Specific Encodability

Labile Coordination Interphase for Regulating Lean Ion Dynamics in Reversible Zn Batteries

Rechargeability in zinc (Zn) batteries is limited by anode irreversibility. The practical lean electrolytes exacerbate the issue, compromising the cost benefits of zinc batteries for large-scale energy storage. In this study, a zinc-coordinated interphase is developed to avoid chemical corrosion and stabilize zinc anodes. The interphase promotes Zn2+ ions to selectively bind with histidine and carboxylate ligands, creating a coordination environment with high affinity and fast diffusion due to thermodynamic stability and kinetic lability. Experiments and simulations indicate that interphase regulates dendrite-free electrodeposition and reduces side reactions. Implementing such labile coordination interphase results in increased cycling at 20 mA cm-2 and high reversibility of dendrite-free zinc plating/stripping for over 200 hours. A Zn||LiMn2 O4 cell with 74.7 mWh g-1 energy density and 99.7% Coulombic efficiency after 500 cycles realized enhanced reversibility using the labile coordination interphase. A lean-electrolyte full cell using only 10 µL mAh-1 electrolyte is also demonstrated with an elongated lifespan of 100 cycles, five times longer than bare Zn anodes. The cell offers a higher energy density than most existing aqueous batteries. This study presents a proof-of-concept design for low-electrolyte, high-energy-density batteries by modulating coordination interphases on Zn anodes.

Recent Research Progress of 19 F Magnetic Resonance Imaging Probes: Principle, Design, and Their Application

Visualization of biomolecules, cells, and tissues, as well as metabolic processes in vivo is significant for studying the associated biological activities. Fluorine magnetic resonance imaging (19 F MRI) holds potential among various imaging technologies thanks to its negligible background signal and deep tissue penetration in vivo. To achieve detection on the targets with high resolution and accuracy, requirements of high-performance 19 F MRI probes are demanding. An ideal 19 F MRI probe is thought to have, first, fluorine tags with magnetically equivalent 19 F nuclei, second, high fluorine content, third, adequate fluorine nuclei mobility, as well as excellent water solubility or dispersity, but not limited to. This review summarizes the research progresses of 19 F MRI probes and mainly discusses the impacts of structures on in vitro and in vivo imaging performances. Additionally, the applications of 19 F MRI probes in ions sensing, molecular structures analysis, cells tracking, and in vivo diagnosis of disease lesions are also covered in this article. From authors' perspectives, this review is able to provide inspirations for relevant researchers on designing and synthesizing advanced 19 F MRI probes.

A snapshot of the vast array of diamagnetic CEST MRI contrast agents

Since the inception of CEST MRI in the 1990s, a number of compounds have been identified as suitable for generating contrast, including paramagnetic lanthanide complexes, hyperpolarized atom cages and, most interesting, diamagnetic compounds. In the past two decades, there has been a major emphasis in this field on the identification and application of diamagnetic compounds that have suitable biosafety profiles for usage in medical applications. Even in the past five years there has been a tremendous growth in their numbers, with more and more emphasis being placed on finding those that can be ultimately used for patient studies on clinical 3 T scanners. At this point, a number of endogenous compounds present in tissue have been identified, and also natural and synthetic organic compounds that can be administered to highlight pathology via CEST imaging. Here we will provide a very extensive snapshot of the types of diamagnetic compound that can generate CEST MRI contrast, together with guidance on their utility on typical preclinical and clinical scanners and a review of the applications that might benefit the most from this new technology.

Self-assembly of an MRI responsive agent under physiological conditions provides an extended time window for in vivo imaging

An MRI-responsive agent that spontaneously self-assembles to a large supramolecular structure under physiological conditions was designed. The obtained assembly provides an extended time window for in vivo studies, as demonstrated for a fluorine-19 probe constructed to sense Zn²⁺ with ¹⁹F-iCEST MRI, in the future.

Insights into the Responding Modes of Highly Potent Gadolinium-Based Magnetic Resonance Imaging Probes Sensitive to Zinc Ions

Zn ions (Zn²⁺) play an important biological role in many diseases; hence, an imaging method for monitoring the Zn²⁺ distribution in tissues could provide important clinical insights. Recently, we reported a potent Zn-sensitive probe based on the Gd-DO3A (DO3A = 1,4,7,10-tetraazacyclododecane-1,4,7-tricarboxylic acid), modified tyrosine. and di(2-picolyl)amine chelator for this metal cation, which generates an outstanding magnetic resonance imaging (MRI) response. Here we further explored the origin of this unprecedented response and expanded the choice of potential MRI probes by preparing the free acid version of the initial MRI sensor. We report a detailed investigation of the ¹H NMR dispersion, ¹⁷O NMR, and isothermal titration calorimetry properties of these two MRI probes upon interaction with Zn²⁺. The performed experiments confirm selective interaction of the MRI probes and target metal cation, which causes substantial changes in the coordination sphere of the paramagnetic center. It also evidenced some aggregation, which enhances the relaxivity response. Interestingly, conversion of the methyl ester to the free carboxylic acid of the tyrosine moiety changes the nature of the aggregates and leads to a smaller relaxivity response. The probes interact with human serum albumin (HSA) in the absence of Zn²⁺, which leads to a possible modification of the coordination sphere of Gd³⁺ or a substantial change in the exchange rate of second-sphere water molecules. In the presence of Zn²⁺, the interaction with HSA is very weak, demonstrating the importance of the Zn²⁺ coordination sphere in the behavior of these systems.

Highlight selection of radiochemistry and radiopharmacy developments by editorial board

Background

The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biyearly highlight commentary to update the readership on trends in the field of radiopharmaceutical development.

Results

This commentary of highlights has resulted in 23 different topics selected by each member of the Editorial Board addressing a variety of aspects ranging from novel radiochemistry to first in man application of novel radiopharmaceuticals and also a contribution in relation to MRI-agents is included.

Conclusion

Trends in (radio)chemistry and radiopharmacy are highlighted demonstrating the progress in the research field being the scope of EJNMMI Radiopharmacy and Chemistry.

Solution NMR of synthetic cavity containing supramolecular systems: what have we learned on and from?

NMR has been instrumental in studies of both the structure and dynamics of molecular systems for decades, so it is not surprising that NMR has played a pivotal role in the study of host-guest complexes and supramolecular systems. In this mini-review, selected examples will be used to demonstrate the added value of using (multiparametric) NMR for studying macrocycle-based host-guest and supramolecular systems. We will restrict the discussion to synthetic host systems having a cavity that can engulf their guests thus restricting them into confined spaces. So discussion of selected examples of cavitands, cages, capsules and their complexes, aggregates and polymers as well as organic cages and porous liquids and other porous materials will be used to demonstrate the insights that have been gathered from the extracted NMR parameters when studying such systems emphasizing the information obtained from somewhat less routine NMR methods such as diffusion NMR, diffusion ordered spectroscopy (DOSY) and chemical exchange saturation transfer (CEST) and their variants. These selected examples demonstrate the impact that the results and findings from these NMR studies have had on our understanding of such systems and on the developments in various research fields.