Design and synthesis of a multivalent fluorescent folate–calix[4]arene conjugate: cancer cell penetration and intracellular localization

The design and optimization of fluorescent molecules has driven the ability to interrogate complex biological events in real time. Notably, most advances in bioimaging fluorophores are based on optimization of core structures that have been known for over a century. Recently, new synthetic methods have resulted in an explosion of nonplanar conjugated macrocyclic molecules with unique optical properties yet to be harnessed in a biological context. Herein we report the synthesis of the first aqueous-soluble carbon nanohoop (i.e., a macrocyclic slice of a carbon nanotube prepared via organic synthesis) and demonstrate its bioimaging capabilities in live cells. Moreover, we illustrate that these scaffolds can be easily modified by well-established “click” chemistry to enable targeted live cell imaging. This work establishes the nanohoops as an exciting new class of macrocyclic fluorophores poised for further development as novel bioimaging tools.

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“…Folic acid ( K D = 0.1 nM) therefore can be an effective targeting group for imaging of cancer cells and even selective drug delivery. 47 , 48 …”

Section: Resultsmentioning

confidence: 99%

Expanding the Chemical Space of Biocompatible Fluorophores: Nanohoops in Cells

et al. 2018

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“…45 Several fluorescent compounds have been designed as tools for monitoring the cellu-lar entry of e.g. 56 7-Nitro-2,1,3benzoxadiazole (NBD) and dansyl served as particularly used fluorophores, 46,[49][50][51]54,57 but also fluorescein, 48,52 indocarbocyanines, 53 rhenium(I) complexes, 56 or BODIPYs have been applied. 56 7-Nitro-2,1,3benzoxadiazole (NBD) and dansyl served as particularly used fluorophores, 46,[49][50][51]54,57 but also fluorescein, 48,52 indocarbocyanines, 53 rhenium(I) complexes, 56 or BODIPYs have been applied.…”

Section: Resultsmentioning

confidence: 99%

Design, characterization and cellular uptake studies of fluorescence-labeled prototypic cathepsin inhibitors

et al. 2015

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Besides their extracellular activity crucial for several pathophysiological conditions, human cysteine cathepsins, in particular cathepsins K and S, represent important intracellular targets for drug development. In the present study, a prototypic dipeptide nitrile inhibitor structure was equipped with a coumarin moiety to function as a fluorescent reporter group. In a second inhibitor, a PEG linker was introduced between the dipeptide nitrile and the fluorophore. These tool compounds 6 and 7 were characterized by kinetic investigations as covalent reversible inhibitors of human cathepsins L, S, K and B. Probe 6 showed a pronounced inhibitory activity against cathepsins K and S, which was corroborated by modeling of inhibition modes. Probe 7 was highly potent (Ki = 93 nM) and selective for cathepsin S. To examine the ability of both probes to enter living cells, human embryonic kidney 293 cells were targeted. At a concentration of 10 μM, cellular uptake of probe 6 was demonstrated by fluorescence measurement after an incubation time of 30 min and 3 h, respectively. The probe's concentration in cell lysates was ascertained on the basis of the emission at 492 nm upon excitation at 450 nm, and the results were expressed as concentrations of probe 6 relative to the protein concentration originating from the lysate. After incubation of 10 μM of probe 6 for 3 h, the cellular uptake was confirmed by fluorescence microscopy. HPLC was used to assess the probes’ lipophilicity, and the obtained

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“…Currently, some groups have reported success of the CuAAC reaction between folate-propargyl and polymers containing an azido group [30,31,32,33,34]. However, their folate-propargyl conjugates were a mixture of propargyl groups bound to the C α and C γ of the glutamic acid part of folate.…”

Section: Resultsmentioning

confidence: 99%

Enhancement of Binding Affinity of Folate to Its Receptor by Peptide Conjugation

Dharmatti

Miyatake

Nandakumar

et al. 2019

IJMS

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(1) Background: The folate receptor (FR) is a target for cancer treatment and detection. Expression of the FR is restricted in normal cells but overexpressed in many types of tumors. Folate was conjugated with peptides for enhancing binding affinity to the FR. (2) Materials and Methods: For conjugation, folate was coupled with propargyl or dibenzocyclooctyne, and 4-azidophenylalanine was introduced in peptides for “click” reactions. We measured binding kinetics including the rate constants of association (ka) and dissociation (kd) of folate-peptide conjugates with purified FR by biolayer interferometry. After optimization of the conditions for the click reaction, we successfully conjugated folate with designed peptides. (3) Results: The binding affinity, indicated by the equilibrium dissociation constant (KD), of folate toward the FR was enhanced by peptide conjugation. The enhanced FR binding affinity by peptide conjugation is a result of an increase in the number of interaction sites. (4) Conclusion: Such peptide-ligand conjugates will be important in the design of ligands with higher affinity. These high affinity ligands can be useful for targeted drug delivery system.

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Design and synthesis of a multivalent fluorescent folate–calix[4]arene conjugate: cancer cell penetration and intracellular localization

Cited by 35 publications

References 49 publications

Expanding the Chemical Space of Biocompatible Fluorophores: Nanohoops in Cells

Expanding the Chemical Space of Biocompatible Fluorophores: Nanohoops in Cells

Design, characterization and cellular uptake studies of fluorescence-labeled prototypic cathepsin inhibitors

Enhancement of Binding Affinity of Folate to Its Receptor by Peptide Conjugation

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