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. 2023;1(1):0006.
doi: 10.55092/bm20230006. Epub 2023 Jul 21.

FRET-based carbazole-fluorescein ionic nanoparticle for use as an effective bioimaging agent

Amanda Jalihal  1 , Hannah Krehbiel  1 , Samantha Macchi  1 , Mavis Forson  1 , Mujeebat Bashiru  1 , Thuy Le  1 , Caroline Kornelsen  1 , Noureen Siraj  1
Affiliations

FRET-based carbazole-fluorescein ionic nanoparticle for use as an effective bioimaging agent

Amanda Jalihal et al. Biofunctional Mater. 2023.

Abstract

Fӧrster resonance energy transfer (FRET)-based systems are widely applicable in many areas of interest. In this study, a novel FRET-based ionic material (IM) was synthesized by pairing carbazole imidazolium cation (CI+) with fluorescein anion (Fl2-) through a simple ion-exchange method. The resulting IM ([CI]2[Fl]) was converted into an ionic nanoparticle (INP) in aqueous media for practical use for bioimaging application. The photophysical properties of the parent dyes, [CI]2[Fl], and INP were studied in detail. All FRET parameters were calculated in the synthesized material. [CI]2[Fl] exhibited a significant spectral overlap integral and an ideal theoretical FRET distance. The presence of the FRET mechanism was verified by the observed decrease in donor fluorescence lifetime and a moderate FRET efficiency in [CI]2[Fl]. The INP formed from [CI]2[Fl] was evaluated for use as a fluorescent pH probe and bioimaging agent. FRET efficiency of INP is calculated in a series of pH studies which indicates the highest efficiency at physiological pH. Whereas no FRET phenomenon is observed in highly acidic and basic conditions. The pH-dependent photophysical properties of [CI]2[Fl] are monitored and allow for the potential application as a fluorescent probe for the detection of acidic tissues in biological systems. The FRET-capable INP showed superior bioimaging capability in vitro as compared to the parent dye.

Keywords: FRET; bioimaging; fluorescent probe; ionic material.

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Conflict of interest statement

Conflicts of Interests The authors declare no conflicts of interest.

Figures

Figure 1.
Figure 1.
Structure of parent compounds CII and Na2Fl.
Figure 2.
Figure 2.
Normalized absorbance spectra of Na2Fl (normalized to 493 nm, water), CII (normalized to 277 nm, ethanol), [CI]2[Fl] (ethanol), and INP (water) (A), normalized fluorescence emission spectra of CII (normalized to 378 nm, ethanol), [CI]2[Fl] (normalized to 378 nm, ethanol), and INP (normalized to 511 nm, water) excited at 277 nm (B), and normalized fluorescence emission spectra of Na2Fl (normalized to 511 nm, water), [CI]2[Fl] (normalized to 525 nm, ethanol), and INP (normalized to 511 nm, water) excited at 493 nm (C).
Figure 3.
Figure 3.
Absorbance (a) and fluorescence emission intensity excited at 277 nm (b) of INPs in various pH solutions.
Figure 4.
Figure 4.
Confocal images of MCF-7 cells were incubated in 5 μM samples for 1 hour, stained with MitoRed, and fixated with paraformaldehyde.
See this image and copyright information in PMC

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