internal charge transfer

Biotin-V is a fluorescent probe targeting the biotin receptor (BiR), which can be used to detect changes in intracellular viscosity in cancer cells and tumor tissues. Biotin-V consists of a viscosity-responsive TICT (twisted internal charge transfer) fluorophore and a biotin-targeting moiety. In a high-viscosity environment, intramolecular rotation is restricted, which reduces non-radiative transitions and enhances fluorescence intensity and fluorescence lifetime. Biotin-V enters BiR-positive cancer cells via biotin receptor-mediated uptake, and mainly localizes to mitochondria, enabling dual-modal viscosity imaging (fluorescence intensity imaging and fluorescence lifetime imaging) (Ex/Em = 540/608 nm; cell imaging Ex/Em = 561/570-620 nm) .

DCA-Mln is a Fluorescent probe for ferric iron (Fe³⁺) detection. The probe works via an internal charge transfer (ICT) process from its diethylamino group to its dicyano group, which produces bright pink fluorescence in its unbound state; when Fe³⁺ is present, two molecules of DCA-Mln chelate with one Fe³⁺ ion, with one cyano group of each DCA-Mln participating in the complexation, and this binding triggers a photoinduced electron transfer (PET) process that provides a nonradiative deactivation pathway, resulting in fluorescence quenching; additionally, the probe exhibits a visible color change from purple to peach pink upon Fe³⁺ binding, enabling dual-channel detection. The probe has an excitation wavelength of 570 nm and an emission wavelength of 670 nm, and it shows a rapid response, with fluorescence stabilizing within 15 seconds of Fe³⁺ addition. DCA-Mln is cell-membrane-permeable, nontoxic at the imaging concentration of 10 μM, and can be used for Fe³⁺ detection in actual water samples, Fe³⁺ imaging in living cells, and as an anti-counterfeiting ink[1].