BODIPY Conjugates as Functional Compounds for Medical Diagnostics and Treatment

Abstract

Fluorescent dyes absorbing and emitting in the visible and near-IR regions are promising for the development of fluorescent probes for labeling and bio-visualization of body cells. The ability to absorb and emit in the long-wavelength region increases the efficiency of recording the spectral signals of the probes due to the higher permeability of the skin layers. Compared to other fluorescent dyes, BODIPYs are attractive due to their excellent photophysical properties-narrow absorption and emission, intense fluorescence, simple signal modulation for the practical applications. As part of conjugates with biomolecules, BODIPY could act as a biomarker, but as therapeutic agent, which allows solving several problems at once-labeling or bioimaging and treatment based on the suppression of pathogenic microflora and cancer cells, which provides a huge potential for practical application of BODIPY conjugates in medicine. The review is devoted to the discussion of the recent, promising directions of BODIPY application in the field of conjugation with biomolecules. The first direction is associated with the development of BODIPY conjugates with drugs, including compounds of platinum, paclitaxel, chlorambucil, isoxazole, capsaicin, etc. The second direction is devoted to the labeling of vitamins, hormones, lipids, and other biomolecules to control the processes of their transport, localization in target cells, and metabolism. Within the framework of the third direction, the problem of obtaining functional optically active materials by conjugating BODIPY with other colored and fluorescent particles, in particular, phthalocyanines, is being solved.

Keywords: BODIPY; biomarker; conjugate; drug delivery; fluorescent label; luminophore.

Figure 1

Structures of organic dyes.

Figure 2

The absorption ranges.

Scheme 1

Structures of compounds 1 and 2.

Scheme 2

Structure of compound 3.

Scheme 3

Structures of compounds 4 and 5.

Scheme 4

Structures of compounds 6 and 7.

Scheme 5

Structures of compounds 8, 9 and 10.

Scheme 6

Structure of compound 11.

Scheme 7

Structure of compound 12.

Scheme 8

Structure of compound 13.

Scheme 9

Structures of compounds 14 and 15.

Figure 3

Fluorescence spectra of metallocycles 14 and 15 in different solvents (λ_ex = 556 nm, c = 1.00 μM). Photographs of 14 and 15 under UV lamp at 365 nm in different solvents. Adapted from [14].

Scheme 10

Structures of compounds 16–19.

Figure 4

Confocal microscopic images of MCF-7 cells after 4 h of incubation with 17: (a) bright field, (b) fluorescence of Mito Tracker Deep Red, (c) fluorescence of 17, and (d) merged image of (b,c). Scale bar = 10 μm. Adapted from [15].

Scheme 11

Structure of compound 20.

Figure 5

UV–Vis absorption (a) and fluorescence (b) spectra of nanoparticles 20 (NPs) in aqueous solution and free 20 in DMF/H₂O 9:1. (c) Fluorescent photos 20 and NPs 20 in water and in DMF/H₂O 9:1. Adapted from [16].

Scheme 12

Structure of compound 21.

Scheme 13

Structure of compound 22.

Scheme 14

Structure of compound 23.

Figure 6

CLSM images of live/dead assay (Calcein-AM/PI) on co-stained MDAMB-231 cells after incubation with (a) PEGylated BODIPY without lighting, (b) PEGylated BODIPY with lighting, (c) Dox@PEGylated BODIPY with lighting. The Calcein-AM has green fluorescence and the PI has red fluorescence. Scale bar was 100 μm. Adapted from [19].

Scheme 15

Structures of compounds 24 and 25.

Figure 7

CLSM images of MCF-7 cells with BODIPY-PEG 24 or Et-BODIPY-PEG 25 at various concentrations, with the nucleus labeled with 4′,6-diamidino-2-phenylindole (DAPI). Top: DAPI images; middle: BODIPY-PEG/Et-BODIPY-PEG dye images; bottom: merged images of both (10.0 μM). Adapted from [20].

Scheme 16

Structure of compound 26.

Scheme 17

Conversion of meso-ester-BODIPY into meso-carboxylate-BODIPY.

Scheme 18

Structure of compound 27 and release process of drug molecule and fluorescent dye upon light activation.

Scheme 19

Structures of compounds 28–31.

Scheme 20

Structure of compound 32.

Scheme 21

Structure of compound 33.

Figure 8

Cellular fluorescence images of prodrug 33 treated MCF-7 cells. The cells were incubated with 33 (1 mM) for 2 h and then irradiated with a blue LED for: (a) 0 min, (b) 10 min, (c) 30 min, and (d) 60 min. (e) Relative pixel intensity (n = 3) from the images. The pixel intensity from the images. The pixel of (d) is defined as 1.0. Scale bar 10 μm. λ_ex 650 nm; λ_Mon window of 530–710 nm. Adapted from [25].

Scheme 22

Structure of compound 34.

Scheme 23

Structure of compound 35.

Figure 9

The normalized absorption (purple) and emission spectra (green) of BODIPYmyrt in 1-octanol.

Figure 10

CLSM of bacterial cells (a) and fungal cells (b) stained by BODIPYmyrt and calcofluor-white (CFW). Scale bar is 10 μm. Adapted from [40].

Scheme 24

Structures of compounds 36–38.

Scheme 25

Structures of compounds 39–42.

Scheme 26

The oxidized and reduced forms of compound 43.

Scheme 27

Structure of compound 44.

Scheme 28

Structures of compounds 45–47.

Scheme 29

Structure of compound 48.

Figure 11

Flow cytometric analysis of human fibroblasts cells incubated for 4, 24, or 48 h with 20 μM BODIPY-labeled vitamin B₁₂ (a) or free BODIPY (b). Fluorescence microscopy images of human fibroblasts cells incubated 24 h with free BODIPY (c). Adapted from [47].

Scheme 30

Structures of compounds 49–53.

Figure 12

Confocal microscopic images of A549 cells after 4 h of incubation with 51 and 53. The top panels: (a) bright field, (b) fluorescence of 51, (c) fluorescence of Mitotracker deep red (MTR), (d) merged image of 51, Mitotracker deep red and Hoechst. The bottom panels: (e) bright field, (f) fluorescence of Mitotracker green (MTG), (g) fluorescence of 53, and (h) merged image of 53 and Mitotracker green. The overlap coefficient of 51 with Mitotracker red is ∼0.65, and that for 53 and Mitotracker green is ∼0.6. Scale bar represents 10 μm. Adapted from [48].

Scheme 31

Structure of compound 54.

Figure 13

Changes in the absorption (a) and fluorescence (b) spectra of 54 (0.34 μM) upon addition of insulin fibrils (0–30 μM). Inset: Bar diagram for the change in emission intensity of 54 in water and different forms of insulin protein: W—water, NP—native protein, AA—amorphous aggregates, AF—amyloid fibrillar aggregates. Adapted from [49].

Scheme 32

Structures of compounds 55 and 56.

Scheme 33

Structure of compound 57.

Scheme 34

Structures of compounds 58–62.

Scheme 35

Structures of compounds 63 and 64.

Scheme 36

Structures of compounds 65 and 66.

Scheme 37

Structure of compound 67.

Figure 14

Self-assembly 67 into a BODIPYsome nanoparticle (phospholipid head group in brown and aza-BODIPY in blue). Adapted from [55].

Scheme 38

Structures of compounds 68–72.

Scheme 38

Structures of compounds 68–72.

Scheme 39

Structure of compound 73.

Figure 15

Subcellular localization of E2-BODIPY 73 in uteri of non-ovariectomized mice. The first image in each row is the emission fluorescence at 488 nm. The second image in each row is the image of the Hoechst 33,342 nuclear stain that has excitation/emission maxima at 350/461 nm when bound to DNA. The third image is a merged photo of the first two images. Row B shows intranuclear localization of E2-BODIPY. Adapted from [57].

Scheme 40

Structure of compound 74.

Scheme 41

Structures of compounds 75 and 76.

Scheme 42

Structures of compounds 77–83.

Scheme 43

Structure of compound 84.

Scheme 44

Structures and synthetic route for compounds 85 and 86.

Scheme 44

Structures and synthetic route for compounds 85 and 86.

Scheme 45

Structures and synthetic route for compounds 87 and 88.

Figure 16

Emission spectra of compounds (2), 88 and unsubstituted silicon(IV) phthalocyanine in toluene. Adapted from [63].

Scheme 46

Structure and synthetic route for compound 89.

Scheme 47

Structures of compounds 90 and 91.

Scheme 48

Structures and synthetic route for the hybrid material of DND with BODIPY (a) and combined with ZnTPPcQ (b).

Figure 17

UV–Vis spectra of DNDs, ZnTPPcQ, BODIPY, DNDs-BODIPY and ZnTPPcQ-DND, and ZnTPPcQ-DNDs-BODIPY in (a) DMSO and (b) water (containing 1% DMSO) for all samples. Adapted from [66].

Scheme 49

Structures and synthetic route for compounds 92 and 93.

Scheme 50

Structures and synthetic route for compounds 94 and 95.

Scheme 51

Structure and synthetic route for compound 96.

Scheme 52

Structure and synthetic route for compound 97.

Scheme 53

Structures of compounds 98, 99, 100, 101.

Scheme 53

Structures of compounds 98, 99, 100, 101.

Scheme 54

Structures and synthetic route for compounds 102, 103, 104.

Scheme 55

Structure of compound 105.

Scheme 56

Structure of compound 106.