Recent advances in Gd-chelate based bimodal optical/MRI contrast agents.

Research on bimodal contrast agents in general and optical/MRI contrast agents in particular has attracted increased attention from the scientific community in recent years. Whereas optical contrast agents reveal pathologies at the cellular or sub-cellular level, MRI contrast agents generally report physiological differences at the level of tissues and organs. The complementary information obtained from these two techniques allows for a more precise diagnosis. Furthermore the emergence of near-infrared luminophores accommodates the simultaneous detection of optical and MRI signals. The current multitude and diversity in molecular architectures mirrors the ever increasing interest in the field. In this review the developments between 2010 and mid-2014 are highlighted.

In vivo imaging of ß-galactosidase stimulated activity in hepatocellular carcinoma using ligand-targeted fluorescent probe.

Development of targeted, selective, and noninvasive fluorescent probes for in vivo visualization of tumor-associated overexpressed enzymes are highly anticipated for cancer diagnosis and therapy. Herein, we developed a noninvasive fluorescent probe (DCDHF-ßgal) for the sensitive detection, and in vivo visualization of ß-galactosidase in hepatocyte HepG2 cells and its xenograft model. As a model system for in vivo targeted imaging, DCDHF-ßgal possessing galactose unit selectively target hepatocyte and monitor the ß-galactosidase activity with deep tissue penetration, and low background interference. DCDHF-ßgal was activated by intracellular ß-galactosidases as the driving force for the release of NIR fluorophore, thereby exhibiting ratiometric optical response. Initial fluorescence emission measured at 615 nm was changed to fluorescence at 665 nm upon activation of DCDHF-ßgal with ß-galactosidase. Ratiometric fluorescence detection of ß-galactosidase was also observed in hepatocellular carcinoma cells and tumor xenograft. The noninvasive in vivo optical imaging facilitated by targeted and enzyme-activated imaging agent would be useful in various biomedical and diagnostic applications.

Blood-brain barrier-permeable fluorone-labeled dieckols acting as neuronal ER stress signaling inhibitors.

We studied the blood-brain barrier (BBB) permeability and intracellular localization of a fluorescein isothiocyanate (FITC)-labeled dieckol (1) and a rhodamine B-labeled dieckol (7), for exploring the possible therapeutic application of fluorone-labeled dieckols in neurodegenerative diseases. Both compounds (1 &7) were synthesized through a click reaction and were found to be localized in the endoplasmic reticulum (ER) of the two types of brain cell lines (SH-SY5Y and BV-2 cells) tested; they also reduced ER stress in the SH-SY5Y human neuroblastoma cells. In addition, 1 and 7 were shown to pass the BBB in rats upon intravenous administration. Altogether, our study demonstrates, for the first time, that targeted ER-stress reduction in brain cells can be achieved by introducing fluorone-dieckol conjugates into systemic circulation. Therefore, 1 and 7 provide a novel and promising ER-targeting therapeutic strategy for neurodegenerative diseases.

Synthesis of rhodamine-labelled dieckol: its unique intracellular localization and potent anti-inflammatory activity.

Rhodamine-labelled dieckol (1) synthesized through a click reaction was found to be localized in the endoplasmic reticulum (ER) of RAW 264.7 cells. Anti-inflammatory activity of compound was considerably greater than that of dieckol itself.