Noncharged and Charged Monodendronised Perylene Bisimides as Highly Fluorescent Labels and their Bioconjugates.

A series of water-soluble, hydroxylated and sulphated, polyglycerol (PG) dendronised, monofunctional perylene bisimides (PBIs) were synthesised in three generations. Their photophysical properties were determined by absorption and emission spectroscopy and their suitability as potential biolabels examined by biological in vitro studies after bioconjugation. It could be shown that the photophysical properties of the PBI labels can be improved by increasing the sterical demand and ionic charge of the attached dendron. Thereby, charged labels show superior suppression of aggregation over charge neutral labels owing to electrostatic repulsion forces on the PG-dendron. The ionic charges also enabled a reduction in dendron generation while retaining the labels' outstanding fluorescence quantum yields (FQYs) up to 100 %. These core-unsubstituted perylene derivatives were successfully applied as fluorescent labels upon bioconjugation to the therapeutic antibody cetuximab. The dye-antibody conjugates showed a strongly enhanced aggregation tendency compared to the corresponding free dyes. Biological evaluation by receptor-binding, cellular uptake, and cytotoxicity studies revealed that labelling did not affect the antibody's function, which renders the noncharged and charged dendronised PBIs suitable candidates as fluorescent labels in biological imaging.

An amphiphilic perylene imido diester for selective cellular imaging.

A new amphiphilic membrane marker based on a water-soluble dendritic polyglycerol perylene imido dialkylester has been designed, synthesized, and its optical properties characterized. In water it forms fluorescently quenched micellar self-aggregates, but when incorporated into a lipophilic environment, it monomerizes, and the highly fluorescent properties of the perylene core are recovered. These properties make it an ideal candidate for the imaging of artificial and cellular membranes as demonstrated by biophysical studies.

Synthesis and optical properties of water-soluble polyglycerol-dendronized rylene bisimide dyes.

Four new water-soluble polyglycerol-dendronized perylene, terrylene, and quaterrylene bisimides have been synthesized and characterized with respect to their optical properties in polar organic solvents and water by using UV/Vis and fluorescence spectroscopy. All of these dyes were highly soluble in water, but the size of the chosen polyglycerol dendron was only sufficient to completely suppress dye aggregation for the core-unsubstituted perylene derivative. Their high solubility in water and their absorption and emission wavelengths up to the NIR region make the core-unsubstituted perylene and terrylene bisimides ideal candidates for applications in bioimaging, whilst the lack of fluorescence for quaterrylene bisimide in all polar solvents does not warrant further investigation of this chromophore in fluorescence and imaging applications. Likewise, tuning of the emission of rylene bisimides towards longer wavelengths by employing electron-donating bay substituents is not a promising strategy, owing to the lower fluorescence quantum yields in polar solvents and, in particular, in water.

Highly fluorescent water-soluble polyglycerol-dendronized perylene bisimide dyes.

Water-soluble perylene tetracarboxylic acid bisimides (PBIs) with terminally linked polyglycerol dendrons of four different generations have been synthesized. These PBI dyes reveal a strong dendritic effect, enabling outstanding fluorescence quantum yields in water up to almost 100% for the highest dendron generation.