Lanthanide luminescent logic gate mimics in soft matter: [H(+)] and [F(-)] dual-input device in a polymer gel with potential for selective component release

Non-covalent incorporation of responsive luminescent lanthanide into a polymer gel produces three-output logic circuit with significant naked-eye colour changes.</p

Quantifying the formation of chiral luminescent lanthanide assemblies in an aqueous medium through chiroptical spectroscopy and generation of luminescent hydrogels

Herein we present the synthesis and the photophysical evaluation of water-soluble chiral ligands (2·(R,R) and 2·(S,S)) and their application in the formation of lanthanide directed self-assembled structures. These pyridine-2,6-dicarboxylic amide based ligands, possessing two naphthalene moieties as sensitising antennae, that can be used to populate the excited state of lanthanide ions, were structurally modified using 3-propanesultone and caesium carbonate, allowing for the incorporation of a water-solubilising sulfonate motif. We show, using microwave synthesis, that Eu(III) forms chiral complexes in 1 : 3 (M : L) stoichiometries (Eu·[2·(R,R)]3 and Eu·[2·(S,S)]3) with these ligands, and that the red Eu(III)-centred emission arising from these complexes has quantum yields (Φtot) of 12% in water. Both circular dichroism (CD) and circular polarised luminescence (CPL) analysis show that the complexes are chiral; giving rise to characteristic CD and CPL signatures for both the Λ and the Δ complexes, which both possess characteristic luminescence dissymmetry factors (glum), describing the structure in solution. The self-assembly process was also monitored in situ by observing the changes in the ligand absorption and fluorescence emission, as well as in the Eu(III) luminescence. The change, fitted using non-linear regression analysis, demonstrated high binding affinity for Eu(III) which in part can be assigned to being driven by additional hydrophobic effects. Moreover, using CD spectroscopy, the changes in the chiroptical properties of both (2·(R,R) and 2·(S,S)) were monitored in real time. Fitting the changes in the CD spectra allowed for the step-wise binding constants to be determined for these assemblies; these matched well with those determined from both the ground and the excited state changes. Both the ligands and the Eu(III) complexes were then used in the formation of hydrogels; the Eu(III)-metallogels were luminescent to the naked-eye

Luminescent lanthanide cyclen-based enzymatic assay capable of diagnosing the onset of catheter-associated urinary tract infections both in solution and within polymeric hydrogels

Herein we present a supramolecular (delayed luminescent) Eu­(III)-based pH-responsive probe/sensor with the ability to detect the urease-mediated hydrolysis of urea in aqueous solution. A series of photophysical titrations show this Eu­(III) chelate behaves as an “<i>on–off</i>” luminescent switching probe, with its luminescence being quenched upon urea being enzymatically converted into ammonia and carbon dioxide. Calculation of the rate constant (<i>k</i>) and activation energy (<i>E</i>_a) for this hydrolysis reaction are detailed; the results demonstrate a direct observation of enzymatic activity in solution by the sensor. The potential application of this probe in detecting the onset of catheter-associated urinary tract infections (CAUTIs) is also demonstrated by incorporating <b>1.Eu</b> into water-permeable hydrogels that can be utilized as an alternative coating for catheters

Towards “drug-like” indole-based transmembrane anion transporters

A series of mono-ureas and mono-thioureas, some incorporating a trifluoromethyl group, have been synthesised and their ability to facilitate ion transport assessed using a combination of ion selective electrode and fluorescence techniques. Chloride/nitrate and chloride/bicarbonate antiport and HCl symport processes were examined using phospholipid vesicles as a model system. In general, the trifluoromethyl functionalised receptors showed greater transport activity than unfluorinated analogous systems, corresponding with increased clogP. The most active transporter facilitated chloride efflux from phospholipid vesicles at receptor to lipid ratios as low as 1:20,000. In addition, in vitro fluorescence and viability assays indicated that the most potent anion transporters induced apoptosis in human cancer cell lines.<br/

A positron emission tomography study of nigro-striatal dopaminergic mechanisms underlying attention: implications for ADHD and its treatment

Through the combined use of (18)F-fallypride positron emission tomography and magnetic resonance imaging this study examined the neural mechanisms underlying the attentional deficits associated with attention deficit/hyperactivity disorder and their potential reversal with a single therapeutic dose of methylphenidate. Sixteen adult patients with attention deficit/hyperactivity disorder and 16 matched healthy control subjects were positron emission tomography and magnetic resonance imaging scanned and tested on a computerized sustained attention task after oral methylphenidate (0.5 mg/kg) and placebo administration in a within-subject, double-blind, cross-over design. Although patients with attention deficit/hyperactivity disorder as a group showed significant attentional deficits and reduced grey matter volume in fronto-striato-cerebellar and limbic networks, they had equivalent D(2)/D(3) receptor availability and equivalent increases in endogenous dopamine after methylphenidate treatment to that observed in healthy control subjects. However, poor attentional performers drawn from both the attention deficit/hyperactivity disorder and the control groups had significantly reduced left caudate dopamine activity. Methylphenidate significantly increased dopamine levels in all nigro-striatal regions, thereby normalizing dopamine levels in the left caudate in low performers. Behaviourally, methylphenidate improved sustained attention in a baseline performance-dependent manner, irrespective of diagnosis. This finding was accompanied by an equally performance-dependent effect of the drug on dopamine release in the midbrain, whereby low performers showed reduced dopamine release in this region. Collectively, these findings support a dimensional model of attentional deficits and underlying nigro-striatal dopaminergic mechanisms of attention deficit/hyperactivity disorder that extends into the healthy population. Moreover, they confer midbrain dopamine autoreceptors a hitherto neglected role in the therapeutic effects of oral methylphenidate in attention deficit/hyperactivity disorder. The absence of significant case–control differences in D(2)/D(3) receptor availability (despite the observed relationships between dopamine activity and attention) suggests that dopamine dysregulation per se is unlikely to be the primary cause underlying attention deficit/hyperactivity disorder pathology in adults. This conclusion is reinforced by evidence of neuroanatomical changes in the same set of patients with attention deficit/hyperactivity disorder