Cyclodextrin Encapsulated pH Sensitive Dyes as Fluorescent Cellular Probes: Self-Aggregation and In Vitro Assessments

Abstract

We have designed and synthesized a series of novel, supramolecular, long-lived fluorescent probes based on the host-guest inclusion complexes formation between fluorescent indolizinyl-pyridinium salts and β-cyclodextrin. Fluorescence and electrospray ionisation mass spectrometry experiments, supported by theoretical molecular docking studies, were utilized in the monitoring of the inclusion complexes formation, evidencing the appearance of corresponding 1:1 and 1:2 species. Additionally, the influence of the guest molecule over the aggregation processes of the cyclodextrin inclusion complexes was investigated by transmission electron microscopy. The absence of cytotoxicity, cellular permeability, long-lived intracellular fluorescence, and in time specific accumulation within acidic organelles identified the investigated supramolecular entities as remarkable candidates for intracellular fluorescence probes. Co-staining experiments using specific organelle markers revealed the fact that, after a 24-h incubation period, the inclusion complexes accumulate predominantly in lysosomes rather than in mitochondria. This study opens new possibilities for a broad range of fluorescent dyes with solubility and high toxicity issues, able to form inclusion complexes with β-cyclodextrin, to be tested as intracellular fluorescence probes.

Facilitating Nitrification Inhibition through Green, Mechanochemical Synthesis of a Novel Nitrapyrin Complex

“…Crystalline powder of β-CD·NP, as obtained by mechanochemical synthesis, was then suspended in water and analyzed through a combination of TEM/EDX techniques for its morphological characterization. As shown in Figure , β-CD·NP crystals are characterized by a rhombic shape, already observed in TEM mode for crystals of β-CD and β-CD inclusion compounds. − An EDX analysis was performed on a single crystal: the elemental analysis confirmed the presence of the expected chemical elements (Figure S4).…”

Ultrasound-Assisted Synthesis of Fluorescent Azatetracyclic Derivatives: An Energy-Efficient Approach

“…The fluorescence quantum yields of these compounds show their ability to serve as long-term monitoring fluorescent probes. This aspect is particularly important due to the continuous high demand in photostable fluorophores, especially for in vivo microscopy, to obtain high-quality images and to allow prolonged monitoring of same cells over time [ 32 , 40 ].…”

“…Our group focused on the dipolar cycloaddition reactions of azinium ylides with various dipolarophiles in order to obtain new compounds with fluorescent properties and biological activities [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. We also added additional contributions in the field of using US irradiation in organic synthesis [ 1 , 2 , 3 , 4 , 5 , 37 ].…”

Novel Dual-Organelle-Targeting Probe (RCPP) for Simultaneous Measurement of Organellar Acidity and Alkalinity in Living Cells

“…We ,, and others − ,− have previously developed a series of lysosome-targeting fluorescent probes for the study of lysosomal activity. In our present study, two fluorophores (rhodamine and coumarin) were selected to construct a broad pH probe.…”

“…For the determination of the lysosomal pH, two types of lysosomal markers are employed, including weak basic amines (e.g., neutral red, acridine orange) and LysoTracker probes, the latter demonstrating the capacity to selectively accumulate in the lysosome. , Nonetheless, all of the previously reported probes, for both lysosomes − and mitochondria, − have limitations primarily associated with fluorescence intensity alterations in the respective organelle. Recently, we reported a series of novel fluorescent probes (LysoProbes and Superior LysoProbes) with the capacity for monitoring lysosomal pH, which are an improvement over commercially available lysosomal markers (e.g., LysoTracker) as fluorescent signals are both stable and highly selective.…”