Sensing and inhibition of amyloid-ß based on the simple luminescent aptamer-ruthenium complex system.

Aggregation of amyloid-ß (Aß) peptide has been known to be pathologically associated with Alzheimer and dementia diseases. Amyloid-ß fibrils serve as an important target for the drugs development and diagnosis of neurodegenerative diseases. Herein, we report a new [Ru(dmbpy)(dcbpy)dppz)] complex (dmbpy; 4,4'-dimethyl-2,2'-bipyridine, dcbpy; 4,4'-dicorboxy-2,2'-bipyridine, dppz; dipyridophenazine) intercalated aptamer based recognition of amyloid-ß. Interestingly, aforementioned Ru(II) complex shows weak luminescence intensity in the aqueous medium but it shows strong luminescence intensity in the presence of RNA aptamer. Upon addition of amyloid-ß monomers, the luminescence intensity of Ru(II) complex is reduced due to the strong interaction of aptamer with amyloid-ß monomer/small oligomers. Furthermore, present study implies that our system has ability to inhibit the formation of amyloid-ß fibrils, which is confirmed from the AFM morphological structures in the absence and presence of aptamer. This work may contribute the rapid diagnosis and inhibition of amyloid-ß aggregation in the clinical applications.

Alkoxy bridged binuclear rhenium (I) complexes as a potential sensor for ß-amyloid aggregation.

Alkoxy bridged binuclear rhenium(I) complexes are used as a probe for the selective and sensitive detection of aggregation of ß-amyloid fibrils that are consorted with Alzheimer's disease (AD). The strong binding of the complexes is affirmed by the fluorescence enhancement and calculated binding constant value in the order of 10(5)M(-1) is obtained from the Scatchard plots. The binding of ß-amyloid can be attributed to π-π stacking interaction of naphthalene moiety present in rhenium(I) complexes, and it is supported by docking studies. The selectivity is quite high towards other proteins and the formation of fibrils can be observed in the range of 30-40 nm through the AFM and TEM techniques.

A selective, long-lived deep-red emissive ruthenium(II) polypyridine complexes for the detection of BSA.

A selective, label free luminescence sensor for bovine serum albumin (BSA) is investigated using ruthenium(II) complexes over the other proteins. Interaction between BSA and ruthenium(II) complexes has been studied using absorption, emission, excited state lifetime and circular dichroism (CD) spectral techniques. The luminescence intensity of ruthenium(II) complexes (I and II), has enhanced at 602 and 613 nm with a large hypsochromic shift of 18 and 5 nm respectively upon addition of BSA. The mode of binding of ruthenium(II) complexes with BSA has analyzed using computational docking studies.

Sensitized near-infrared luminescence from Nd(III), Yb(III) and Er(III) complexes by energy-transfer from ruthenium 1,3-Bis([1,10]phenanthroline-[5,6-d]-imidazol-2 -yl)benzene.

The luminescent ruthenium 1,3 -bis([1,10]phenanthroline-[5,6 -d]- imidazol-2 -yl)benzene (bpibH2) complex, a potentially useful bridging ligand with a vacant diimine site, has been used as 'metallo ligand' to make heterodinuclear d-f complexes by attachment of a {Ln(dik)3} fragment (dik = 1,3-diketonate) at the vacant site. When Ln = Nd, Yb, or Er the lanthanide centre has low-energy f-f excited states capable of accepting energy from the (3)MLCT excited state of the Ru(II) centre, there is quenching in the (3)MLCT luminescence of the Ru(II) centre, that affords sensitized lanthanide(III) based luminescence in the near-IR region. Nd(III) was found to be the most effective at quenching the (3)MLCT luminescence of the ruthenium component because of the high density of f-f excited states of the appropriate energy which make it as effective energy-acceptor compared to Er and Yb complexes.

Optical recognition of anions by ruthenium(II)-bipyridine-calix[4]arene system.

The two t-butylcalix[4]arene attached ruthenium(II)-bipyridine complexes (Rubc2 and Rubc3) has been synthesized and the anion recognition studies have been carried out using emission techniques. The binding of anions, which are sensed by the complexes, are studied by UV-visible and emission techniques. The complex Rubc2 recognizes the Cl(-), H2PO4 (-) and AcO(-) anions. The complex Rubc3 recognizes the Br(-) and AcO(-) anions. The AcO(-) quenches the emission intensity of both two complexes but the other anion increases the emission intensity of the complexes. The excited state lifetime and transient absorption studies were carried out the AcO(-) facilitates non radiative pathway. The other anions stabilize the excited state and facilitate the radiative pathway.