Non-Cytotoxic Dibenzyl and Difluoroborate Curcuminoid Fluorophores Allow Visualization of Nucleus or Cytoplasm in Bioimaging

Abstract

Curcumin, the most important secondary metabolite isolated from Curcuma longa, is known for its numerous purported therapeutic properties and as a natural dye. Herein, based on curcumin’s intrinsic fluorescence, a search for improved curcumin-based fluorophores was conducted. Within the set of semi-synthetic curcumin derivatives i.e. mono (1), di (2), tri (3), tetra (4) benzylated and dibenzyl-fluoroborate (5), the fluorescence properties of 2 and 5 in solution outstood with a two-fold quantum yield compared to curcumin. Furthermore, all benzylated derivatives showed a favorable minimal cytotoxic activity upon screening at 25 μM against human cancer and non-tumoral COS-7 cell lines, with a reduction of its cytotoxic effect related to the degree of substitution. Fluorophores 2 and 5 are versatile bioimaging tools, as revealed by Confocal Fluorescence Microscopy (CFM), and showed permeation of living cell membranes of astrocytes and astrocytomas. When 2 is excited with a 405- (blue) or 543-nm (green) laser, it is possible to exclusively and intensively visualize the nucleus. However, the fluorescence emission fades as the laser wavelength moves towards the red region. In comparison, 5 allows selective visualization of cytoplasm when a 560-nm laser is used, showing emission in the NIR region, while it is possible to exclusively observe the nucleus at the blue region with a 405-nm laser.

Synthesis, photophysical properties, bioimaging potential andin vitrotoxicity studies of naphthalimide imidazole boron complexes

“…An ideal fluorophore should exhibit a strong fluorescence with high quantum yield and bear a highly delocalized π-electron cloud but possess less or negligible cytotoxic properties. 46 As mentioned earlier, the complex 1 bears a moderate fluorescence quantum yield of 37–66%, which satisfied one of the criteria for being an ideal imaging probe. Hence, the cells were seeded on coverslips and treated with 25 μM of the complex 1 or the vehicle control (0.1% DMSO).…”

The Antitumoral Effect In Ovo of a New Inclusion Complex from Dimethoxycurcumin with Magnesium and Beta-Cyclodextrin

“…Mass spectra were obtained using a JEOL SX 102 A spectrometer (JEOL de México S.A. de C.V., Mexico City, Mexico) equipped with MALDI-Flight time technology or using MStation JMS-700 JEOL equipment (Electron Ionization, 70 eV, 250 • C, impact positive mode and calibration standard with perfluorokerosene) and AccuTOF JMS-T100LC JEOL equipment (DART + , 350 • C, positive ion mode and calibration standard with PEG 600) [21,77]. 1 H and 13 C NMR liquid spectra were acquired in dimethyl sulfoxide (DMSO-d 6 ) or deuterium oxide (D 2 O) on a Bruker Fourier 400 MHz (Billerica, MA, USA) spectrometer with TMS serving as the internal reference, and NMR spectra were processed with MestreNova software 12.0.3.3.…”

The Homoleptic Curcumin–Copper Single Crystal (ML2): A Long Awaited Breakthrough in the Field of Curcumin Metal Complexes

“…Partition coefficients were measured according to the shake–flask method previously reported [ 78 , 79 ], and the quantitation of the curcumin (8 μM) and Complex 1 (4 μM) was recorded by ultraviolet (UV) spectrophotometry. The experiments were conducted in triplicate and standard curves are found in the Supplementary Materials (Figures S18 and S19) .…”