Localization-controlled two-color luminescence imaging via environmental modulation of energy transfer in a multichromophoric species

Abstract

We prepared a bichromophoric species 1, made of two different bodipy dyes bridged by a d-galactose unit. 1 exhibits different emission spectra when located in different compartments of biological systems, independently of its concentration. This is an unprecedented feature for a single multicomponent molecule and is due to the dependence on the environment of the photoinduced energy transfer process occurring between its bodipy subunits. Therefore, 1 can give useful information about cell composition and ultimately anomalies without requiring the simultaneous use of several different compounds, paving the way for the use of environment-controlled inter-component energy transfer to gain cell information based on luminescence imaging.

BODIPY on Board of Sugars: A Short Enlightened Journey up to the Cells

“…[41] Distyryl BODIPY G (Green colored) was obtained from BODIPY O in one step [42] and led to tetraalkylammonium BODIPY B (Blue colored) through reaction with methyl iodide. [43] Monochromophoric and multichromophoric near-IR BODI-PY-based fluorescent probes were synthesized from gluco and galacto mono-bis-and tetra-alkynyl derivatives. From a synthetic point of view, the galactose moiety allowed an easier use of the protecting groups with respect to the glucose.…”

“…[18] For this reason, copper-free Sonogashira crosscouplings were always used in the synthesis of such BODIPYcarbohydrates dyes. [18,19,38,43] In Scheme 4 a general representation of the synthesis of monochromophoric carbohydrate-based BODIPY fluorescent probes is reported, [19,43] with the conditions used for the copper-free Sonogashira and the glycosyl alkynes employed in reaction with BODIPY O or BODIPY G, respectively. Conversion of carbohydrate-BODIPY G probes into the analogous with BODIPY B led to probes with a marked water solubility.…”

“…Conversion of carbohydrate-BODIPY G probes into the analogous with BODIPY B led to probes with a marked water solubility. [19] The schematic representation of the synthesis of multichromophoric fluorescent probes [18,38,43] from the coupling of alkynyl carbohydrates with BODIPY O and/or BODIPY G, is shown in Scheme 5. In any case two consecutive copper-free Sonogashira reactions have been performed for their obtainment.…”

“…Schematic representation of the procedure to multichromophoric species. [18,38,43] DYAD 1 and MULTI 1), and assuming 10 Å as the donoracceptor distance in DYAD 1, an energy transfer rate constant of 200 fs was calculated for this species, according to the experimental results obtained by pump-probe spectroscopy. For MULTI 1, assuming an average donor-acceptor distance relative to the two most distant BODIPY donors and the acceptor distance of 19.5 Å, the speed constant for the Förster Energy Transfer process is 13 ps, also in impressive agreement with the experimental results (12 ps).…”

“…BODIPY B exhibits a structured absorption spectrum profile and an emission band that are both blue shifted with respect to the ones of BODIPY G. Moreover, the excited state lifetime and luminescence quantum yield are relatively high (see Table 1). [43] This behavior has been rationalized taking into account the charge transfer character present in the former species. This CT contribution in BODIPY G, essentially due to the amino groups that play the role of donors, disappear upon amino quaternarization (BODIPY B), so the pure singlet S2 excited state is populated at higher energy.…”