Rhodamine 800

Excitation of rhodamine 800 in aqueous media: a theoretical investigation

The main goal of this work was to obtain a calculated absorption spectrum of rhodamine 800 in an aqueous solution, which most accurately reproduces the experimental one. To achieve this result, I used the hybrid functionals supported by Gaussian 16 software package. In this case, the basis set (6-31++G(d,p)) and the solvent model (IEFPCM) were not varied. The B3PW91 functional gave the best agreement with the experimental absorption spectrum of the dye in an aqueous medium. B3P86, B971, B972, B98, X3LYP, APF, HSE06, and N12SX functionals also give good absorption energy coincidence. The B3PW91/6-31++G(d,p)/IEFPCM theory level chosen in this way made it possible to calculate the various characteristics of rhodamine 800 in the ground and excited states. An important result of this work was the establishment of the vibronic nature of the short-wavelength smaller maximum of the absorption spectrum. The influence of the strong H-bond of the exocyclic nitrogen atom with the water molecule on the dye excitation was analyzed.

Rhodamine 800 as a probe of energization of cells and tissues in the near-infrared region: a study with isolated rat liver mitochondria and hepatocytes

To examine the feasibility of optical monitoring of cellular energy states with tissue-transparent near-infrared (NIR) light, the absorption and fluorescence characteristics of Rhodamine 800 in isolated rat liver mitochondria and hepatocytes were investigated. When the dye was incubated with isolated mitochondria, a large red shift of the absorption spectra and quenching of the fluorescence intensity were observed. The absorbance difference at 730 minus 685 nm, or at 730 minus 800 nm, and the fluorescence intensity measured at 692 nm varied linearly with the mitochondrial membrane potential. The spectral changes observed could be explained in terms of the potential-dependent uptake of the dye from the buffer solution into the mitochondrial matrix. The respiration control ratio and oxygen consumption rate were not affected by the addition of Rhodamine 800 at concentrations lower than 5 microM, which was the concentration range mostly employed throughout the present study. In a suspension of hepatocytes, the red shift and fluorescence quenching of Rhodamine 800 characteristic of energized mitochondria were also observed, and these changed to those of the buffer solution with the addition of an uncoupler under normoxia. At the early stage of anoxia, within about 5 min, when cytochrome oxidase was completely reduced, hepatocytes were concluded to be in the fully energized state, since the optical characteristics of Rhodamine 800 were the same as those of energized mitochondria. On the basis of these in vitro data, Rhodamine 800 is concluded to be a possible NIR-active contrast agent, that can be used to monitor the energy states of living tissues, in addition to the tissue oxygenation states, by the use of near-infrared spectrophotometry (NIRS) without harmful effects.

Rhodamine 800 as a near-infrared fluorescent deposition flow tracer in rodent hearts

We investigated the use of a near-infrared (NIR) fluorescent dye, Rhodamine 800 (Rhod800, λ(exc) = 693 nm, λ(em) > 720 nm) as a flow-dependent molecular tracer for NIR spectroscopy and high-resolution cardiac imaging. Rhod800 accumulates in isolated mitochondria in proportion to the mitochondrial membrane potential (ΔΨ). However, in the intact myocardium, Rhod800 binding is ΔΨ-independent. Rat hearts were perfused in a Langendorff mode with Krebs-Henseleit buffer containing 45-nM Rhod800 at normal (100%), increased (150%), or reduced (50%) baseline coronary flow (CF) per gram, for 30 to 60 min. In a different group of hearts, the left anterior descending artery (LAD) was occluded prior to Rhod800 infusion to create a flow deficit area. Rhod800 deposition was analyzed by: 1. absorbance spectroscopy kinetics in the Rhod800-perfused hearts, 2. Rhod800 absorbance and fluorescence imaging in the short-axis heart slices, and 3. dynamic epicardial/subepicardial fluorescence imaging of Rhod800 in KCl-arrested hearts, with a spatial resolution of ? 200 μm. Rhod800 deposition was proportional to the perfusate volume (CF and perfusion time) and there was no Rhod800 loss during the washout period. In the LAD-ligated hearts, Rhod800 fluorescence was missing from the no-flow, LAD-dependent endocardial and epicardial/subepicardial area. We concluded that Rhod800 can be used as a deposition flow tracer for dynamic cardiac imaging.

Rhodamine 6G and 800 J-heteroaggregates with enhanced acceptor luminescence (HEAL) adsorbed in transparent SiO2 GLAD thin films

An enhanced fluorescent emission in the near infrared is observed when the Rhodamine 800 (Rh800) and 6G (Rh6G) dyes are coadsorbed in porous SiO(2) optical thin films prepared by glancing angle deposition (GLAD). This unusual behavior is not observed in solution and it has been ascribed to the formation of a new type of J-heteroaggregates with enhanced acceptor luminescence (HEAL). This article describes in detail and explains the main features of this new phenomenology previously referred in a short communication [J. R. Sánchez-Valencia, J. Toudert, L. González-García, A. R. González-Elipe and A. Barranco, Chem. Commun., 2010, 46, 4372-4374]. It is found that the efficiency and characteristics of the energy transfer process are dependent on the Rh6G/Rh800 concentration ratio which can be easily controlled by varying the pH of the solutions used for the infiltration of the molecules or by thermal treatments. A simple model has been proposed to account for the observed enhanced acceptor luminescence in which the heteroaggregates order themselves according to a "head to tail" configuration due to the geometrical constrains imposed by the SiO(2) porous matrix thin film. The thermal stability of the dye molecules within the films and basic optical (absorption and fluorescence) principles of the HEAL process are also described.

Rhodamine dye transfer from hydrogel to nanospheres for the chemical detection of potassium ions

Smart hydrogels incorporating various functional nanomaterials are becoming popular tools for chemical sensing. Here, ion-exchange nanospheres composed of the block copolymer Pluronic F-127 played the role of a scavenger for a signal transducer dye (Rhodamine 800) in a three-phase based optical detection system for potassium ions. Rhodamine 800, a positively charged dye, was incorporated into a hydrogel together with the potassium ionophore valinomycin and an ion-exchanger (Na⁺R^-). The concentration of Rhodamine 800 in the aqueous sample was kept low by the nanospheres containing Na⁺R^-. Consequently, the detection limit (0.3 μM) of the three-phase based system was shifted 2 orders of magnitude lower compared with those of previously reported two-phase based sensing systems. The concept of controlling the dye transfer among the three phases provided a new train of thought for the design of ionophore-based chemical sensors.