Exploring the Impact of Phenanthroline-Based Glycoconjugated Ru(II) Polypyridyl Photosensitizers on Metastasis-Related Processes

Abstract

Novel water-soluble, phosphorescent ruthenium(II) polypyridyl-glycoconjugates of general formula [Ru{N-(1,10-phenanthroline)}₂{N-(1,10-phenanthrolin-5-yl)-β-glycopyranosylamine}][Cl]₂ (glycopyranosyl = D-glucopyranosyl (1), D-mannopyranosyl (2), L-rhamnopyranosyl (3), L-xylopyranosyl (4), and 2,3,4-tri-O-acetyl-L-xylopyranosyl (5)) and corresponding aglycone [Ru{N-(1,10-phenanthroline)}₂{N-(1,10-phenanthrolin-5-amine)}][Cl]₂ (6) have been synthesized and fully characterized. Their stability and behavior in physiological media have been assessed using ultraviolet visible spectroscopy (UV-Vis) and ¹H nuclear magnetic resonance (¹H-NMR), revealing minor N-glycosidic cleavage and high photostability. The photocytotoxicity of the complexes has been evaluated in two different cancer (PC-3 and MCF-7) and one nontumorigenic (HFF-1) cell lines. While exhibiting no toxicity in the dark, some glycoconjugates achieve photoselectivity indexes of up to 40 upon blue-light irradiation. Remarkably, complexes 1-6 potently affect the metastatic phenotype of PC-3 cells, evidenced by the inhibition of migration in the wound healing assay and the increased resistance to trypsin detachment following photoactivation.

Keywords: antimetastatic; glycoconjugates; photodynamic therapy; photosensitizer; ruthenium(II) polypyridyl.

Figure 1

Selected examples of reported Ru(II) polypyridyl glycoconjugates.

Figure 2

Synthesis of novel Ru(II) polypyridyl compounds 1–6.

Figure 3

Atom numbering of Ru(II) polypyridyl compounds.

Figure 4

UV‐Vis absorption spectra of compounds 4, 5, and 6, in water (10 µM).

Figure 5

A) Selected simulated absorption spectra of compounds 4, 5, and 6, showing the electronic nature of the most optically brilliant transitions. B) Natural transition orbitals (NTOs) describing the electronic nature of selected transitions of compounds 4, 5, and 6.

Figure 6

UV‐Vis spectra recorded at different irradiation times (blue LED) of compounds 4, 5, and aglycone 6 in A) PBS and B) ACN.

Figure 7

Confocal microscopy images of PC‐3 cells incubated with compounds A) 1, B) 5, and c) 6 (10 µM, 48 hours at 37 °C). Scale bar: 25 µm.

Figure 8

Effect of complexes 1–6 (10 µM) on cell resistance to trypsin A) before, and B) after 30 minutes of irradiation (see protocol details in Experimental section, Trypsin resistance assay). Percentages of adherent cells are normalized to nonirradiated control cells (a, black bar) or irradiated control cells (b, gray bar). The values are expressed as the percentage of viable cells adhered to the well ± S.E.M of at least three independent experiments (**P < 0.01, ***P < 0.001). P values < 0.05 were considered statistically significant based on the two‐way ANOVA, and Bonferroni's multiple comparison test.

Figure 9

Effect of metal polypyridyl glycoconjugates 1, 3–6 (IC_{50,light(48 hours)}/2) on wound area closure of irradiated (1 hour) PC‐3 cells relative to irradiated untreated cells, after A) 24 hours or B) 48 hours of incubation with the cells (see protocol details in Experimental section). The values are expressed as the ± S.E.M of at least five independent experiments (*P < 0.05, **P < 0.01, ***P < 0.001). P values < 0.05 were considered statistically significant based on the two‐way ANOVA, and Bonferroni's multiple comparison test.