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Effect of lanthanide complex structure on cell viability and association.

Peterson KL, Dang JV, Weitz EA, Lewandowski C, Pierre VC - Inorg Chem (2014)

Bottom Line: A systematic study of the effect of hydrophobicity and charge on the cell viability and cell association of lanthanide metal complexes is presented.Only the hexyl-substituted complex reduced cell viability to 60% in the presence of 100 μM complex.Surprisingly, the hydrophobic moieties did not increase cell association in comparison to the hydrophilic amino acid derivatives.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.

ABSTRACT
A systematic study of the effect of hydrophobicity and charge on the cell viability and cell association of lanthanide metal complexes is presented. The terbium luminescent probes feature a macrocyclic polyaminocarboxylate ligand (DOTA) in which the hydrophobicity of the antenna and that of the carboxyamide pendant arms are independently varied. Three sensitizing antennas were investigated in terms of their function in vitro: 2-methoxyisophthalamide (IAM(OMe)), 2-hydroxyisophthalamide (IAM), and 6-methylphenanthridine (Phen). Of these complexes, Tb-DOTA-IAM exhibited the highest quantum yield, although the higher cell viability and more facile synthesis of the structurally related Tb-DOTA-IAM(OMe) platform renders it more attractive. Further modification of this latter core structure with carboxyamide arms featuring hydrophobic benzyl, hexyl, and trifluoro groups as well as hydrophilic amino acid based moieties generated a family of complexes that exhibit high cell viability (ED50 > 300 μM) regardless of the lipophilicity or the overall complex charge. Only the hexyl-substituted complex reduced cell viability to 60% in the presence of 100 μM complex. Additionally, cellular association was investigated by ICP-MS and fluorescence microscopy. Surprisingly, the hydrophobic moieties did not increase cell association in comparison to the hydrophilic amino acid derivatives. It is thus postulated that the hydrophilic nature of the 2-methoxyisophthalamide antenna (IAM(OMe)) disfavors the cellular association of these complexes. As such, responsive luminescent probes based on this scaffold would be appropriate for the detection of extracellular species.

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Fluorescence microscopy images of representative L6 myoblaststreated with 200 μM [Tb-3] and [Tb-6] for 4 h at 37 °C: (a) fluorescence images, 60× objective,325–375 nm excitation filter, 470–750 nm emission filter,0.4 s exposure time; (b) bright field images, 0.04 s exposure time.Cells were rinsed with PBS and fixed with formaldehyde prior to imaging.Scale bars represent 10 μm.
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fig3: Fluorescence microscopy images of representative L6 myoblaststreated with 200 μM [Tb-3] and [Tb-6] for 4 h at 37 °C: (a) fluorescence images, 60× objective,325–375 nm excitation filter, 470–750 nm emission filter,0.4 s exposure time; (b) bright field images, 0.04 s exposure time.Cells were rinsed with PBS and fixed with formaldehyde prior to imaging.Scale bars represent 10 μm.

Mentions: The cellularassociation of the Tb complexes was also investigated with epifluorescencemicroscopy. L6 myoblasts were treated with Tb complex (200 μMfor 4 h), washed with PBS at room temperature, and fixed with formaldehydeprior to imaging. Results of representative cells indicate the presenceof weak cellular association for the trifluoro-substituted [Tb-6]3+, while the fluorescence intensity of phenanthridine-containing[Tb-3] is comparable to that of the control cells (Figure 3). The remaining Tb complexes exhibit similar weakcellular fluorescence (Figure S3 (Supporting Information)). Due to reports that different staining patterns can be observedin experiments that differ only in whether cells were imaged in alive or fixed state,41 the cellular associationof [Tb-6]3+ was also examined in live cellsvia fluorescence microscopy (Figure S4 (SupportingInformation)). In these images, an overall decrease in thefluorescence to levels comparable to those for the untreated controlcells was observed.


Effect of lanthanide complex structure on cell viability and association.

Peterson KL, Dang JV, Weitz EA, Lewandowski C, Pierre VC - Inorg Chem (2014)

Fluorescence microscopy images of representative L6 myoblaststreated with 200 μM [Tb-3] and [Tb-6] for 4 h at 37 °C: (a) fluorescence images, 60× objective,325–375 nm excitation filter, 470–750 nm emission filter,0.4 s exposure time; (b) bright field images, 0.04 s exposure time.Cells were rinsed with PBS and fixed with formaldehyde prior to imaging.Scale bars represent 10 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4060611&req=5

fig3: Fluorescence microscopy images of representative L6 myoblaststreated with 200 μM [Tb-3] and [Tb-6] for 4 h at 37 °C: (a) fluorescence images, 60× objective,325–375 nm excitation filter, 470–750 nm emission filter,0.4 s exposure time; (b) bright field images, 0.04 s exposure time.Cells were rinsed with PBS and fixed with formaldehyde prior to imaging.Scale bars represent 10 μm.
Mentions: The cellularassociation of the Tb complexes was also investigated with epifluorescencemicroscopy. L6 myoblasts were treated with Tb complex (200 μMfor 4 h), washed with PBS at room temperature, and fixed with formaldehydeprior to imaging. Results of representative cells indicate the presenceof weak cellular association for the trifluoro-substituted [Tb-6]3+, while the fluorescence intensity of phenanthridine-containing[Tb-3] is comparable to that of the control cells (Figure 3). The remaining Tb complexes exhibit similar weakcellular fluorescence (Figure S3 (Supporting Information)). Due to reports that different staining patterns can be observedin experiments that differ only in whether cells were imaged in alive or fixed state,41 the cellular associationof [Tb-6]3+ was also examined in live cellsvia fluorescence microscopy (Figure S4 (SupportingInformation)). In these images, an overall decrease in thefluorescence to levels comparable to those for the untreated controlcells was observed.

Bottom Line: A systematic study of the effect of hydrophobicity and charge on the cell viability and cell association of lanthanide metal complexes is presented.Only the hexyl-substituted complex reduced cell viability to 60% in the presence of 100 μM complex.Surprisingly, the hydrophobic moieties did not increase cell association in comparison to the hydrophilic amino acid derivatives.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States.

ABSTRACT
A systematic study of the effect of hydrophobicity and charge on the cell viability and cell association of lanthanide metal complexes is presented. The terbium luminescent probes feature a macrocyclic polyaminocarboxylate ligand (DOTA) in which the hydrophobicity of the antenna and that of the carboxyamide pendant arms are independently varied. Three sensitizing antennas were investigated in terms of their function in vitro: 2-methoxyisophthalamide (IAM(OMe)), 2-hydroxyisophthalamide (IAM), and 6-methylphenanthridine (Phen). Of these complexes, Tb-DOTA-IAM exhibited the highest quantum yield, although the higher cell viability and more facile synthesis of the structurally related Tb-DOTA-IAM(OMe) platform renders it more attractive. Further modification of this latter core structure with carboxyamide arms featuring hydrophobic benzyl, hexyl, and trifluoro groups as well as hydrophilic amino acid based moieties generated a family of complexes that exhibit high cell viability (ED50 > 300 μM) regardless of the lipophilicity or the overall complex charge. Only the hexyl-substituted complex reduced cell viability to 60% in the presence of 100 μM complex. Additionally, cellular association was investigated by ICP-MS and fluorescence microscopy. Surprisingly, the hydrophobic moieties did not increase cell association in comparison to the hydrophilic amino acid derivatives. It is thus postulated that the hydrophilic nature of the 2-methoxyisophthalamide antenna (IAM(OMe)) disfavors the cellular association of these complexes. As such, responsive luminescent probes based on this scaffold would be appropriate for the detection of extracellular species.

Show MeSH
Related in: MedlinePlus