New fluorinated manganese carbonyl complexes for light controlled carbon monoxide (CO) release and the use of benchtop 19F-NMR spectroscopy

A comprehensive survey of Mn(I) carbonyls as CO-releasing molecules reported over the last two decades

Over the last two decades, manganese(I) carbonyl complexes have been widely investigated as carbon monoxide releasing molecules (CORMs) to transfer small quantities of CO to biological targets to have beneficial impacts such as preventing ischemia reperfusion injury and reducing organ transplant rejection. Furthermore, these complexes exhibit beneficial anti-coagulative, anti-apoptotic, anti-inflammatory, and anti-proliferative properties. Owing to their highly controlled substitution chemistry and oxidative durability, Mn(I) carbonyl moieties were combined with a wide range of auxiliary ligands, including biomolecules. This review focused on tri- and tetracarbonyl Mn(I) complexes that were exposed to light, changed the redox status, or underwent thermal activation to release carbon monoxide. Kinetic parameters, stability in the dark, number of CO release equivalents, CO detection tools, and the nature of solvents used in the studies are reported and tabulated. An overview of all the previously published Mn(I) CORMs is specifically provided to define the method of action of these promising biologically active compounds and discuss their possible therapeutic applications in relation to their CO-releasing and biocompatibility characteristics.

Naphthalimide-based light-induced nitric oxide-releasing nanoscale vesicles with visual detection and cytotoxicity studies

The therapeutic potential of nitric oxide (NO) has been receiving increasing interest, but achieving controlled release under physiological conditions remains challenging. Herein, we report a colorimetric and fluorescence responsive naphthalimide-based amphiphilic N-nitroso-based NO donor (Nap-NO) and its NO-releasing behavior. Nap-NO was incorporated into phospholipid nanovesicles to make it biocompatible and water-soluble. Light-induced NO-releasing behavior and emission changes were monitored via UV-vis, colorimetric detection, IR (Infrared) spectroscopy studies, and Griess assay. The Nap-NO donor within the 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)-cholesterol vesicles exhibited a slower release rate, with a significantly extended half-life as compared to the only DOPC vesicles. Incorporating the Nap-NO into alginate hydrogel beads enables a simple, visual detection of NO release through color and emission changes. Bioimaging experiments within the HCT cell line reveal the use of the new NO donor for fluorescent bio-imaging and clearly illustrate their proficiency in killing cancer cells upon NO delivery in the presence of light.

Quantifying CO-release from a photo-CORM using 19F NMR: An investigation into light-induced CO delivery

Carbon monoxide (CO) is an innate signaling molecule that can regulate immune responses and interact with crucial elements of the circadian clock. Moreover, pharmacologically, CO has been substantiated for its therapeutic advantages in animal models of diverse pathological conditions. Given that an excessive level of CO can be toxic, it is imperative to quantify the necessary amount for therapeutic use accurately. However, estimating gaseous CO is notably challenging. Therefore, novel techniques are essential to quantify CO in therapeutic applications and overcome this obstacle precisely. The classical Myoglobin (Mb) assay technique has been extensively used to determine the amount of CO-release from CO-releasing molecules (CORMs) within therapeutic contexts. Nevertheless, specific challenges arise when applying the Mb assay to evaluate CORMs featuring innovative molecular architectures. Here, we report a fluorinated photo-CORM (CORM-FBS) for the photo-induced CO-release. We employed the 19F NMR spectroscopy approach to monitor the release of CO as well as quantitative evaluation of CO release. This new 19F NMR approach opens immense opportunities for researchers to develop reliable techniques for identifying molecular structures, quantitative studies of drug metabolism, and monitoring the reaction process.

Multifunctional BODIPY embedded non-woven fabric for CO release and singlet oxygen generation

Materials that can simultaneously release CO and generate singlet oxygen upon visible light irradiation under ambient conditions are highly desirable for therapeutic applications. Furthermore, materials that can sequester the undesirable side products into the matrix without affecting the release of CO and singlet oxygen generation would allow them to be used for practical applications. Focussing on these aspects, we prepared two dipicolylamine appended BODIPY‑manganese(I) tricarbonyl complexes wherein the metal core was systematically tethered at 5- and 8- positions of the BODIPY core. The complexes were embedded into a polymer matrix via electrospinning and the resulting non-woven fabrics showed CO release as well as singlet oxygen generation upon irradiation. While the hybrid materials were non-toxic in dark, they were strongly photocytotoxic to c6 cancer cells when exposed to light. Rapid CO release alongside significant singlet oxygen generation, indefinite dark stability, good biocompatibility and negligible dark toxicity makes these fabrics a potent candidate for phototherapeutic applications.

Regulation of Nitric Oxide (NO) Release by Membrane Fluidity in Ruthenium Nitrosyl Complex-Embedded Phospholipid Vesicles

Incorporating water-insoluble nitric oxide (NO)-releasing molecules into biocompatible vesicles may allow for the tunable control of NO release on a specific target site. In vesicles, membrane fluidity plays an important role and influences the final therapeutic efficiency of drugs loaded into the vesicles. Hence, we aimed to investigate the effect of lipid fluidity on the NO release behavior of the photo-controllable ruthenium nitrosyl (Ru-NO) complex. In this regard, a new photoactive ruthenium nitrosyl complex (L.Ru-NO) with amphiphilic terpyridine ligand was synthesized and characterized in detail. L.Ru-NO was incorporated with commercial phospholipids to form nanoscale vesicles L.Ru-NO@Lip. The photoactive {Ru-NO}⁶ type complex released NO in the organic solvent CH₃CN and aqueous liposome solution by irradiating under low-intensity blue light (λ = 410 nm, 3 W). To demonstrate the effect of lipid structure and fluidity on NO release, four different liposome systems L.Ru-NO@Lip1-4 were prepared by using phospholipids such as DOPC, DSPC, DPPC, and DMPC having different chain lengths and saturation. The NO-releasing abilities of these liposomes in aqueous medium were studied by UV-vis spectrum, colorimetric Greiss, and fluorescent DAF assay. The results show that the rate of NO release could be easily tuned by varying the lipid fluidity. The effect of temperature and pH on NO release was also studied. Further, the complex L.Ru-NO and liposomes L.Ru-NO@Lip1 were assayed as an antibacterial agent against the strains of bacteria Escherichia coli and Staphylococcus aureus.

Recent Applications of Benchtop Nuclear Magnetic Resonance Spectroscopy

Benchtop nuclear magnetic resonance (NMR) spectroscopy uses small permanent magnets to generate magnetic fields and therefore offers the advantages of operational simplicity and reasonable cost, presenting a viable alternative to high-field NMR spectroscopy. In particular, the use of benchtop NMR spectroscopy for rapid in-field analysis, e.g., for quality control or forensic science purposes, has attracted considerable attention. As benchtop NMR spectrometers are sufficiently compact to be operated in a fume hood, they can be efficiently used for real-time reaction and process monitoring. This review introduces the recent applications of benchtop NMR spectroscopy in diverse fields, including food science, pharmaceuticals, process and reaction monitoring, metabolomics, and polymer materials.