A new family of robust, non‐toxic, water‐compatible ruthenium(II) vinyl probes allows the rapid, selective and sensitive detection of endogenous carbon monoxide (CO) in live mammalian cells under ...normoxic and hypoxic conditions. Uniquely, these probes incorporate a viscosity‐sensitive BODIPY fluorophore that allows the measurement of microscopic viscosity in live cells via fluorescence lifetime imaging microscopy (FLIM) while also monitoring CO levels. This is the first example of a probe that can simultaneously detect CO alongside small viscosity changes in organelles of live cells.
Carbon monoxide (CO) is produced in mammals and regulates many critical cellular functions, including the response to disease. A ruthenium(II) vinyl probe is presented that allows rapid, selective and sensitive detection of endogenous CO in live mammalian cells under normoxic and hypoxic conditions. By exploiting fluorescence lifetime imaging microscopy, the probe can also measure microscopic viscosity in live cells at the same time.
The noncoordinating ionic liquid bmimOTf (bmim=1‐butyl‐3‐methylimidazolium) is an effective and versatile solvent for the high‐yield dehydration of fructose to the platform chemical ...5‐hydroxymethylfurfural (HMF) over short reaction times. In contrast to prior studies in which low yields were obtained for this transformation in ionic liquids (ILs) with noncoordinating anions, this contribution reveals that the water content is an essential parameter for an efficient reaction in ILs. Achieving the optimum amount of water can increase the yield dramatically by regulating the acidity of the catalyst and partially suppressing the side reaction caused by self‐condensation of HMF. Using acid catalysis in bmimOTf with 3.5 % water content, yields above 80 % can be achieved at 100 °C in only 10 min, even at high (14 %) fructose loading. These results also suggest that bmimOTf represents a superior medium for solvent extraction of HMF compared to halide‐based ILs, allowing the option of isolation or further valorization of the HMF formed.
Just add (a little) water: The noncoordinating ionic liquid bmimOTf is an effective and versatile solvent for the high‐yield dehydration of fructose to the platform chemical 5‐hydroxymethylfurfural over short reaction times. This study reveals that water content is an essential parameter and that judicious addition of water can increase the yield dramatically.
The sensing of carbon monoxide (CO) using electrochemical cells or semiconducting metal oxides has led to inexpensive alarms for the home and workplace. It is now recognised that chronic exposure to ...low levels of CO also poses a significant health risk. It is perhaps surprising therefore that the CO is used in cell-signalling pathways and plays a growing role in therapy. However, the selective monitoring of low levels of CO remains challenging, and it is this area that has benefited from the development of probes which give a colour or fluorescence response. This feature article covers the design of chromo-fluorogenic probes and their application to CO sensing in air, solution and in cells.
A series of new ruthenium(II) vinyl complexes has been prepared incorporating perylenemonoimide (PMI) units. This fluorogenic moiety was functionalised with terminal alkyne or pyridyl groups, ...allowing attachment to the metal either as a vinyl ligand or through the pyridyl nitrogen. The inherent low solubility of the perylene compounds was improved through the design of poly‐PEGylated (PEG=polyethylene glycol) units bearing a terminal alkyne or a pyridyl group. By absorbing the compounds on silica, vapours and gases could be detected in the solid state. The reaction of the complexes Ru(CH=CH‐PerIm)Cl(CO)(py‐3PEG)(PPh3)2 and Ru(CH=CH‐3PEG)Cl(CO)(py‐PerIm)(PPh3)2 with carbon monoxide, isonitrile or cyanide was found to result in modulation of the fluorescence behaviour. The complexes were observed to display solvatochromic effects and the interaction of the complexes with a wide range of other species was also studied. The study suggests that such complexes have potential for the detection of gases or vapours that are toxic to humans.
Sensors: The first reported examples of ruthenium(II) vinyl complexes bearing perylenemonoimide units are able to detect carbon monoxide, isonitriles or cyanide through fluorescence changes (see figure).
Optical sensing offers a low‐cost and effective means to sense carbon monoxide in air and in solution. This contribution reports the synthesis of a new series of vinyl complexes ...Ru(CH=CHR)Cl(CO)(TBTD)(PPh3)2 (R=aryl, TBTD=5‐(3‐thienyl)‐2,1,3‐benzothiadiazole) and shows them to be highly sensitive and selective probes for carbon monoxide in both solution and air. Depending on the vinyl substituent, chromogenic and fluorogenic responses signalled the presence of this invisible, odourless, tasteless and toxic gas. Adsorbing the complexes on silica produced colorimetric probes for the ′naked eye′ detection of CO in the gas phase with a limit of detection as low as 8 ppm in some cases, while the release of the TBTD fluorophore allowed detection at much lower concentrations through the fluorescence response. Structural data were obtained by single‐crystal X‐ray diffraction techniques, while the photophysical behaviour was explored computationally using TD‐DFT experiments. The systems were also shown to be selective for CO over all other gases tested, including water vapour and common organic solvents. By introducing a poly(ethylene)glycol chain to the vinyl functionality, water compatibility was achieved and these non‐cytotoxic complexes were employed in the sensing of CO in HeLa cells, offering a simple and rapid system for sensing this gasotransmitter in this challenging medium.
Chromo‐fluorogenic ruthenium and osmium compounds: TBTD (5‐(3‐thienyl)‐2,1,3‐benzothiadiazole) complexes can be used to detect carbon monoxide in solution, in air and in cells (see figure).
The detection of carbon monoxide in solution and air has been achieved using simple, inexpensive systems based on the vinyl complexes M(CHCHR)Cl(CO)(BTD)(PPh3)2 (R=aryl, BTD=2,1,3‐benzothiadiazole). ...Depending on the nature of the vinyl group, chromogenic and fluorogenic responses signalled the presence of this odourless, tasteless, invisible, and toxic gas. Solutions of the complexes in CHCl3 underwent rapid change between easily differentiated colours when exposed to air samples containing CO. More significantly, the adsorption of the complexes on silica produced colorimetric probes for the naked‐eye detection of CO in the gas phase. Structural data for key species before and after the addition of CO were obtained by means of single X‐ray diffraction studies. In all cases, the ruthenium and osmium vinyl complexes studied showed a highly selective response to CO with exceptionally low detection limits. Naked‐eye detection of CO at concentrations as low as 5 ppb in air was achieved with the onset of toxic levels (i.e., 100 ppm), thus resulting in a remarkably clear colour change. Moreover, complexes bearing pyrenyl, naphthyl, and phenanthrenyl moieties were fluorescent, and greater sensitivities were achieved (through turn‐on emission fluorescence) in the presence of CO both in solution and air. This behaviour was explored computationally using time‐dependent density functional theory (TDDFT) experiments. In addition, the systems were shown to be selective for CO over all other gases tested, including water vapour and common organic solvents. Supporting the metal complexes on cellulose strips for use in an existing optoelectronic device allows numerical readings for the CO concentration to be obtained and provision of an alarm system.
Naked‐eye detection of carbon monoxide in solution and air is achieved using simple inexpensive ruthenium and osmium complexes M(CHCHR)Cl(CO)(BTD)(PPh3)2 (BTD=2,1,3‐benzothiadiazole). The chromogenic and fluorogenic responses signal the presence of CO depending on the nature of the vinyl group. Furthermore, the adsorption of the complexes on silica produced colorimetric probes for the naked‐eye detection of carbon monoxide in the gas phase (see figure).
A robust dithiocarbamate tether allows novel gadolinium units based on DOTAGA (q=1) to be attached to the surface of gold nanoparticles (2.6–4.1 nm diameter) along with functional units offering ...biocompatibility, targeting and photodynamic therapy. A dramatic increase in relaxivity (r1) per Gd unit from 5.01 mm−1 s−1 in unbound form to 31.68 mm−1 s−1 (10 MHz, 37 °C) is observed when immobilised on the surface due to restricted rotation and enhanced rigidity of the Gd complex on the nanoparticle surface. The single‐step synthetic route provides a straightforward and versatile way of preparing multifunctional gold nanoparticles, including examples with conjugated zinc–tetraphenylporphyrin photosensitizers. The lack of toxicity of these materials (MTT assays) is transformed on irradiation of HeLa cells for 30 minutes (PDT), leading to 75 % cell death. In addition to passive targeting, the inclusion of units capable of actively targeting overexpressed folate receptors illustrates the potential of these assemblies as targeted theranostic agents.
Enhancing contrast: The straightforward synthesis of multifunctional nanoparticles combines the robust attachment of gadolinium units for enhanced MRI contrast with photodynamic therapy.
The first example of an octadentate gadolinium unit based on DO3A (hydration number q=1) with a dithiocarbamate tether has been designed and attached to the surface of gold nanoparticles (around 4.4 ...nm in diameter). In addition to the superior robustness of this attachment, the restricted rotation of the Gd complex on the nanoparticle surface leads to a dramatic increase in relaxivity (r1) from 4.0 mm−1 s−1 in unbound form to 34.3 mm−1 s−1 (at 10 MHz, 37 °C) and 22±2 mm−1 s−1 (at 63.87 MHz, 25 °C) when immobilised on the surface. The one‐pot synthetic route provides a straightforward and versatile way of preparing a range of multifunctional gold nanoparticles. The incorporation of additional surface units for biocompatibility (PEG and thioglucose units) and targeting (folic acid) leads to little detrimental effect on the high relaxivity observed for these non‐toxic multifunctional materials. In addition to the passive targeting attributed to gold nanoparticles, the inclusion of a unit capable of targeting the folate receptors overexpressed by cancer cells, such as HeLa cells, illustrates the potential of these assemblies.
A simple orthogonal strategy based on dithiocarbamate and thiolate tethers allows gold nanoparticles to be functionalised with five different surface units for targeted MRI enhancement.
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