Effect of morpholine and charge distribution of cyanine dyes on cell internalization and cytotoxicity

Abstract

To improve the potency of Heptamethine cyanines (Hcyanines) in cancer research, we designed and synthesized two novel Hcyanines based theranostic probes, IR794-Morph and IR794-Morph-Mpip, to enhance cancer cell internalization and targeting. In acidic conditions that resemble to tumour environment, both IR794 derivatives exhibited broad NIR absorption band (704‒794 nm) and fluorescence emission (798‒828 nm) that is suitable for deep seated tumour imaging. Moreover, in vitro study revealed that IR794-Morph-Mpip exhibited better cancer targetability towards various cancer cell lines under physiological and slightly acidic conditions compared to normal cells. IR794-Morph-Mpip was fast internalized into the cancer cells within the first 5 min and mostly localized in lysosomes and mitochondria. In addition, the internalized signal was brighter when the cells were in the hypoxic environment. Furthermore, cellular uptake mechanism of both IR794 dyes, investigated via flow cytometry, revealed that endocytosis through OATPs receptors and clathrin-mediated endocytosis were the main routes. Moreover, IR794-Morph-Mpip, displayed anti-cancer activity towards all tested cancer cell types with IC50 below 7 μM (at 6 h incubation), which is approximately three times lower than that of the normal cells. Therefore, increasing protonated cites in tumour environment of Hcyanines together with incorporating morpholine in the molecule can enhance structure-inherent targeting of these dyes.

Optimizing the SYBR green related cyanine dye structure to aim for brighter nucleic acid visualization

“…Cyanine dye studies are nowadays widely focused on biological and medicinal research. New potential uses for cyanine dyes are for example cancer treatment [1][2][3], nanofibers mimicking tissues [4], detecting cysteine, which is linked to many illnesses, such as Alzheimer's disease [5], turn-on probes for redox reactions in cells [6] and using cyanine dyes as selective fluorescent probes for RNA [7]. Cyanine dyes are already a popular choice as fluorescent probes to image nucleic acids in many cell and molecular biology laboratories [8].…”

Mitochondrial Targeting and Imaging with Small Organic Conjugated Fluorophores: A Review

“…Compound 75 and 76 both bear central cyclohexene and morpholine substitution linked to the indolium nitrogen atom through a long alkyl chain. In line with concerns associated to single indolium targeting units, both probes exhibited poor mitochondrial accumulation [129] . While 75 , encompassing chlorine substitution on the central cyclohexene was observed to accumulate in the lysosomes, replacing it for piperazine allowed for mitochondrial accumulation, albeit not selective nor preferential.…”

“…In line with concerns associated to single indolium targeting units, both probes exhibited poor mitochondrial accumulation. [129] While 75 , encompassing chlorine substitution on the central cyclohexene was observed to accumulate in the lysosomes, replacing it for piperazine allowed for mitochondrial accumulation, albeit not selective nor preferential. Their analogues, 77 , [130] 78 [131] and 79 [132] bearing substitution on both indole and indolium nitrogen atoms exhibited superior mitochondrial accumulation.…”

Morpholinyl silicon phthalocyanine nanoparticles with lysosome cell death and two-photon imaging functions for in vitro photodynamic therapy of cancer cells

“…Morpholine and its substituted derivatives are widely employed pharmaceuticals and are biologically active molecules because of their special physicochemical, biological, and metabolic properties (Dwivedi et al, 2022;Wangngae et al, 2022). Moreover, since the morpholinyl moiety has a pKa of 5-6 and can be protonated in an acidic environment (pH 4.5-5.0), it is a suitable lysosome-targeting unit (Jiang et al, 2017).…”