Crown Ether-Capped Gold Nanoclusters as a Multimodal Platform for Bioimaging

The distinct polarity of biomolecule surfaces plays a pivotal role in their biochemistry and functions as it is involved in numerous processes, such as folding, aggregation, or denaturation. Therefore, there is a need to image both hydrophilic and hydrophobic bio-interfaces with markers of distinct responses to hydrophobic and hydrophilic environments. In this work, we present a synthesis, characterization, and application of ultrasmall gold nanoclusters capped with a 12-crown-4 ligand. The nanoclusters present an amphiphilic character and can be successfully transferred between aqueous and organic solvents and have their physicochemical integrity retained. They can serve as probes for multimodal bioimaging with light (as they emit near-infrared luminescence) and electron microscopy (due to the high electron density of gold). In this work, we used protein superstructures, namely, amyloid spherulites, as a hydrophobic surface model and individual amyloid fibrils with a mixed hydrophobicity profile. Our nanoclusters spontaneously stained densely packed amyloid spherulites as observed under fluorescence microscopy, which is limited for hydrophilic markers. Moreover, our clusters revealed structural features of individual amyloid fibrils at a nanoscale as observed under a transmission electron microscope. We show the potential of crown ether-capped gold nanoclusters in multimodal structural characterization of bio-interfaces where the amphiphilic character of the supramolecular ligand is required.publishedVersionPeer reviewe

Corneal biomechanical changes and intraocular pressure in patients with thyroid orbitopathy

AIM: To determine the relevance of the objective parameters addressing the altered biomechanical properties of cornea for glaucoma monitoring in patients with mild or moderate thyroid associated orbitopathy (TAO), and in healthy individuals. METHODS: Twenty-five patients with TAO (group 1) and 25 healthy adults (group 2) were included to the study. Both groups were of a similar age and the ratio women:man. For each patient, the following parameters of both eyes were measured with ocular response analyzer (ORA): corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc). In both groups participating in our study, all measurements were performed within minutes to reduce the diurnal effects. RESULTS: The mean age in group 1 was 56±11y and 76% were women, 24% were men. The mean age in group 2 was 64±11y and 68% were women, 32% were men. CH correlated negatively with IOPg in group 1 (r2=0.10, P<0.05). IOPg strongly correlated with IOPcc in both groups (group 1: r2=0.79, P<0.0001; group 2: r2=0.85, P<0.0001). There was positive correlation between CRF and IOPg in group 1 (r2=0.12, P<0.05) and in group 2 (r2=0.31, P<0.0001). Statistical analysis revealed no significant correlation between CRF and IOPcc in group 1 (r2=0.009, P>0.05) and also no significant correlation in group 2 (r2=0.04, P>0.05). CRF mean value in group 2 (11.51±1.72 mm Hg) was higher than in group 1 (10.85±1.45 mm Hg) (P<0.05). IOPg strongly correlated with IOPcc in both groups (group 1: r2=0.79, P<0.0001; group 2: r2=0.85, P<0.0001). There was also strong correlation between CRF and CH in both populations: group 1: (r2=0.58, P<0.0001), group 2: (r2=0.41, P<0.0001). CONCLUSION: Biomechanical parameters of cornea, as quantified by CH and CRF, and measured together with IOPcc, precisely reveal glaucoma staging in TAO and thus are reliable for diagnosing and follow-up in clinical practice

Synthesis, structure, photophysical and chiroptical properties of dinuclear rhenium complexes with a bridging helicene‐bis‐bipyridine ligand

By attaching pyridine groups to a diaza[6]helicene, a helical, bis‐ditopic, bis‐N^N‐coordinating ligand can be accessed. Dinuclear rhenium complexes featuring this bridging ligand, of the form [{Re(CO)3Cl}2(N^N–N^N)], have been prepared and resolved to give enantiopure complexes. They are phosphorescent in solution at room temperature under one‐ and two‐photon excitation. Their experimental chiroptical properties (optical rotation, electronic circular dichroism and circularly polarized emission) have been measured. They show, for instance, emission dissymmetry factors of c.a. ±3.10‐3. Quantum‐chemical calculations indicate the importance of stereochemistry on the optical activity, pointing towards further design improvements in such types of complexes