ethidium-homodimer and fluorexon

Due to the unique physicochemical properties of nanomaterials (NM) and their unknown reactivity, the possibility of NM altering the optical properties of fluorometric/colorimetric probes that are used to measure their cyto- and genotoxicity may lead to inaccurate readings. This could have potential implications given that NM, such as ultrafine superparamagnetic iron oxide nanoparticles (USPION), are increasingly finding their use in nanomedicine and the absorbance/fluorescence based assays are used to assess their toxicity. This study looks at the potential of dextran-coated USPION (dUSPION) (maghemite and magnetite) to alter the background signal of common probes used for evaluating cytotoxicity (MTS, CyQUANT, Calcein, and EthD-1) and oxidative stress (DCFH-DA and APF). In the present study, both forms of dUSPION caused an increase in MTS signal but a decrease in background signal from calcein and 3'-(p-aminophenyl) fluorescein (APF) and no effect on CyQUANT and EthD-1 fluorescence responses. Magnetite caused a decrease in fluorescence signal of DCFH, but it did not decrease fluorescence signal in the presence of the reactive oxygen species-inducer tert-butyl hydroperoxide (TBHP). In contrast, maghemite caused an increase in fluorescence, which was substantially reduced in the presence of the antioxidant N-acetyl cysteine. This study emphasizes the importance of considering and controlling for possible interactions between NM and fluorometric/colorimetric dyes and, most importantly, the oxidation state of dUSPION that may confound their sensitivity and specificity.

Topics: Colorimetry; Coloring Agents; Dextrans; Ethidium; Ferric Compounds; Fluoresceins; Fluorescent Dyes; Fluorometry; Magnetite Nanoparticles; Reactive Oxygen Species; tert-Butylhydroperoxide

In vitro methods for measuring the adhesion and viability of lens epithelial cells on implant devices are needed to assess material biocompatibility. We investigated whether the use of confocal microscopy and spectrophotometric methods could determine the viability and adhesion of cells on a silicone biomaterial. Human lens epithelial cells adhered to silicone were treated with 0.01% benzalkonium chloride (cationic surfactant), 0.1% sodium dodecyl sulfate (anionic surfactant), and 10% Tween 20 (nonionic surfactant). Cell viability was then assessed using two fluorescent dyes (calcein and ethidium homodimer-1). Adhesion was determined directly by measuring the number of attached cells after surfactant treatment and by an indirect method that utilized the colorimetric agent crystal violet. The number of viable cells remaining on the biomaterial was determined both immediately after exposure and after the cells were allowed to grow for 1 day following surfactant exposure. The measurements for adhesion showed that the anionic surfactant weakened cell surface binding more than the cationic or nonionic surfactant. This study demonstrated that confocal microscopy in conjunction with crystal violet as an indirect colorimetric indicator can quantify the viability and adhesion of human lens epithelial cells attached to a material surface.

Topics: Benzalkonium Compounds; Cell Adhesion; Cell Proliferation; Cell Survival; Coated Materials, Biocompatible; Epithelial Cells; Ethidium; Fluoresceins; Fluorescent Dyes; Humans; Lens, Crystalline; Lenses, Intraocular; Microscopy, Confocal; Polysorbates; Silicones; Sodium Dodecyl Sulfate; Surface-Active Agents

Fluorescent viability probes have been used to visualise and investigate the viability, morphology and organisation of the keratocyte within the stroma of the intact living cornea. The live cell probe, calcien-AM, in combination with a dead cell probe, ethidium homodimer (Live/Dead Assay, Molecular Probes, U.S.A.) proved superior to earlier generation vital dyes such as fluorescein diacetate or 5,6-carboxyfluorescein diacetate, initially used in combination with ethidium bromide. The ubiquitous distribution of esterase enzymes that cleave calcien-AM within the keratocyte cytoplasm produced a high concentration of fluorescently active calcein throughout the cell, including fine cell processes. Epi-illuminated fluorescence microscopy on transparent corneal dissections subsequently revealed details of keratocyte microanatomy and three-dimensional network organisation in situ. Three morphologically discrete subpopulations of keratocytes were identified: two formed relatively small bands of cells, immediately subjacent to either Bowman's or Descemet's membranes, the third subpopulation constituting the majority of keratocytes typically located within the corneal stroma. The results indicate that calcein-AM is able to penetrate intact living cornea revealing cell viability, and it also has the capacity to 'trace' cellular elements and reveal fine structure within a dense connective tissue matrix.

Topics: Animals; Cattle; Cornea; Corneal Stroma; Descemet Membrane; Ethidium; Fluoresceins; Humans; Male; Microscopy, Fluorescence; Swine