Amino-isocyanoacridines: Novel, Tunable Solvatochromic Fluorophores as Physiological pH Probes

Abstract

Amino-isocyanoacridines ( ICAAc s), as first members of their class, turned out to be a novel, multifunctional acridine orange (AO) type dye family with a number of additional favorable properties. They have enhanced solvatochromic emission range, low quantum yields (Φ F = 2.9–0.4%) in water, reduced basicity (pK a = 7.05–7.58), and their optical behavior could be fine-tuned by complexation with Ag(I) ions, too. Based on both their vibronic absorption and the charge transfer bands, ICAAc s can be applied as stable pH-probes with great precision (2–3% error) in the physiological pH range of 6–8 using UV-vis and fluorescence detection. The dyes are also able to sense pH change in different microenvironments, such as the Stern layer, as it was demonstrated on sodium lauryl sulfate micelles. The optical behavior of the ICAAc derivatives is discussed based on high-level quantum chemical calculations. All three dyes are well-applicable with conventional epifluorescence imaging. Furthermore, at the blue excitation, diMICAAc is optimally suited as a whole-cell probe for both the conventional microscopic and the laser-illumination studies, like flow- and imaging cytometric, or confocal laser-scanning microscopic examinations.

Evaluating the cytotoxicity of Ge–Sb–Se chalcogenide glass optical fibres on 3T3 mouse fibroblasts

“…This must be kept within strict boundaries (between 6 and 8 according to ref. 23) to facilitate correct cellular function and prevent cell death. 25,26 Pathologies associated with an acidic extracellular environment include ischemia (pH <6.…”

Isocyanide Substitution in Acridine Orange Shifts DNA Damage-Mediated Phototoxicity to Permeabilization of the Lysosomal Membrane in Cancer Cells

“…The pure dimethylamino derivative (DM) was obtained after purification by column chromatography. The detailed synthetic procedures and characterization of DM and the intermediates are found in the Supporting Information of [15]. All chemicals were from (Sigma Aldrich, Budapest, Hungary) unless otherwise stated.…”

“…Molecular weight of AO: 265.35 g/mol, molecular formula: C17H19N3, and chemical name: N,N,N′,N′-tetramethylacridine-3,6-diamine [14]. DM molecular weight: 247.29 g/mol and molecular formula: C16H13N3 [15].…”

“…Recently, we reported the synthesis and characterization of a novel fluorescent dye family called amino-isocyanoacridines for pH sensing in the physiological range and live-cell imaging [15]. These acridine derivatives showed altered properties compared to AO, such as reduced basicity, enhanced solvatochromic emission range, low quantum yield in water, and easy tuning of their fluorescent behavior by complexation with metal ions.…”

“…The basis of the high polarity is the internal charge transfer (ICT) between the two different groups (D-A) through the aromatic acridine ring, which results in an enhanced dipole moment change (∆µ = µ e − µ g ) between the excited and ground state (∆µ = 2 and ∆µ = 8 calculated in debye for AO and DM, respectively). The more considerable dipole moment change in DM is the reason for its enhanced solvatochromic range compared to that of AO and its potential application as pH probes for lysosomes at physiologic cellular conditions [15]. Thus, we wondered whether DM could be an efficient lysosomal probe of human cells.…”