Photodegradation of Lipofuscin in Suspension and in ARPE-19 Cells and the Similarity of Fluorescence of the Photodegradation Product with Oxidized Docosahexaenoate

Retinal lipofuscin accumulates with age in the retinal pigment epithelium (RPE), where its fluorescence properties are used to assess retinal health. It was observed that there is a decrease in lipofuscin fluorescence above the age of 75 years and in the early stages of age-related macular degeneration (AMD). The purpose of this study was to investigate the response of lipofuscin isolated from human RPE and lipofuscin-laden cells to visible light, and to determine whether an abundant component of lipofuscin, docosahexaenoate (DHA), can contribute to lipofuscin fluorescence upon oxidation. Exposure of lipofuscin to visible light leads to a decrease in its long-wavelength fluorescence at about 610 nm, with a concomitant increase in the short-wavelength fluorescence. The emission spectrum of photodegraded lipofuscin exhibits similarity with that of oxidized DHA. Exposure of lipofuscin-laden cells to light leads to a loss of lipofuscin granules from cells, while retaining cell viability. The spectral changes in fluorescence in lipofuscin-laden cells resemble those seen during photodegradation of isolated lipofuscin. Our results demonstrate that fluorescence emission spectra, together with quantitation of the intensity of long-wavelength fluorescence, can serve as a marker useful for lipofuscin quantification and for monitoring its oxidation, and hence useful for screening the retina for increased oxidative damage and early AMD-related changes.

Photodegradation of Lipofuscin in Suspension and in ARPE-19 cells and the Similarity of Fluorescence of the Photodegradation Product with Oxidized Docosahexaenoate

Retinal lipofuscin accumulates with age in the retinal pigment epithelium (RPE) where its fluorescence properties are used to assess the retinal health. It was observed that there is a decrease in lipofuscin fluorescence above the age of 75 years and in early stages of age-related macular degeneration (AMD). The purpose of this study was to investigate the response of lipofuscin isolated from human RPE, and lipofuscin-laden-cells to visible light, and determine whether an abundant component of lipofuscin, docosahexaenoate (DHA) can contribute to lipofuscin fluorescence upon oxidation. Exposure of lipofuscin to visible leads to a decrease of its long-wavelength fluorescence at about 610 nm with concomitant growth of the short-wavelength fluorescence. The emission spectrum of photodegraded lipofuscin exhibits similarity with that of oxidized DHA. Exposure to light of lipofuscin-laden cells leads to loss of lipofuscin granules from cells, while retaining cell viability. The spectral changes of fluorescence in lipofuscin-laden cells resemble those seen during photodegradation of isolated lipofuscin. Our results demonstrate that fluorescence emission spectra together with quantitation of intensity of long-wavelength fluorescence can serve as a marker useful for lipofuscin quantification and for monitoring its oxidation, thereby useful for screening the retina for increased oxidative damage and early AMD-related changes.

Solvatochromic and pH Switch Properties of a D–π–A Dye with benzo[b]thiophene as Donor Moiety

A charge transfer dye with the D–[Formula: see text]–A structure was synthesized by Pd catalyzed Hartwig–Buchwald coupling and Knoevenagel condensation reaction, using N, N-dihexylbenzo[b]thiophen-6-amine as donor and 2-(3-cyano-4, 5, 5-trimethylfuran-2 (5H)-ylidene)malononitrile (TCF) as acceptor. The solvatochromic and pH switch properties of the as-synthesized dye were investigated through UV-vis absorption and fluorescence emission spectra. A positive solvatochromism of the dye in different polar solvents was observed along with a visible color change of the solution. By adding acid/base into the DMSO solution of the dye, the color as well as the absorption and emission spectra of the solution exhibited outstanding characteristics of pH switch.

Microencapsulated Caraway Essential Oil Affects Initial Growth of Maize Cultivars

Caraway (Carum carvi L.) essential oil is a candidate for botanical herbicides. A hypothesis was formulated that the sand-applied maltodextrin-coated caraway oil (MCEO) does not affect the growth of maize (Zea mays L.). In the pot experiment, pre-emergence application of five doses of MCEO was tested on four maize cultivars up to the three-leaf growth stage. The morphological analyses were supported by the measurements of relative chlorophyll content (SPAD), two parameters of chlorophyll a fluorescence, e.g., Fv/Fm and Fv/F0, and fluorescence emission spectra. The analyzed MCEO contained 6.5% caraway EO with carvone and limonene as the main compounds, constituting 95% of the oil. The MCEO caused 7-day delays in maize emergence from the dose of 0.9 g per pot (equal to 96 g m−2). Maize development at the three-leaf growth stage, i.e., length of roots, length of leaves, and biomass of shoots and leaves, was significantly impaired already at the lowest dose of MCEO: 0.4 g per pot, equal to 44 g m−2. A significant drop of both chlorophyll a fluorescence parameters was noted, on average, from the dose of 0.7 g per pot, equal to 69 g m−2. Among the tested cultivars, cv. Rywal and Pomerania were less susceptible to the MCEO compared to the cv. Kurant and Podole. In summary, maize is susceptible to the pre-emergence, sand-applied MCEO from the dose of 44 g m−2.

Naringenin Enhances Anti-Proliferation Effect of FMSP On K562 Human Chronic Myelogenous Leukemia Cells Via Targeting Calmodulin Signaling Pathway

Background: FMSP is a synthesized ferrocene derivative which possesses strong anti-proliferative and apoptosis inducing characteristics on tumor cells. Naringenin as a polyphenolic flavonoid is also able to reduce cell viability in tumors.Methods: Cell viability and proliferation of cancer cells after treatment with these agents were determined with MTT assay. To predict the possible interaction between calmodulin (CaM) and FMSP and naringenin, docking stuies were performed. By using fluorescence emission spectra, effects of FMSP and naringenin on CaM structure and activity were studied. CaM-dependent activation of phosphodiesterase 1 (PDE1) by FMSP in relation to naringenin and their combination were compared. Effects of these compounds on PDE1 inhibition, cAMP accumulation, and cAMP-dependent protein kinase A (PKA) activation were assayed. Results: Our results showed that combination of FMSP and naringenin had more inhibitory effects on CaM structure than FMSP and naringenin alone. Results of docking analyses also confirmed efficient intraction of the two compunds with hydrophobic pocket of calmodulin active site. Kinetic analyses of these agents interaction with CaM showed FMSP and naringenin both competitively inhibited PDE1 activation without changing Vmax parameter. FMSP and naringenin synergistically increased Km values in a higher level compared to FMSP or naringenin alone. Combination of these two agents also had more cytotoxic effects on K562 cells than FMSP alone. Conclusions: It was shown that mechanism of K562 cell proliferation inhibition by these compounds is based on CaM and consequent PDE inhibition followed by intracellular cAMP level elevation and increased PKA activity in a dose-dependent manner.

One-Pot Hydrothermal Synthesis of Carbon Dots as Fluorescent Probes for the Determination of Mercuric and Hypochlorite Ions

Nitrogen and sulfur codoped carbon dots (NSCDs) were synthesized via a one-pot hydrothermal method, and citric acid, ethylenediamine, and methyl blue were used as precursors. The obtained NSCDs were spherical with an average size of 1.86 nm. The fluorescence emission spectra of the NSCDs were excitation independent and emitted blue fluorescence at 440 nm with an excitation wavelength at 350 nm. The quantum yield of the NSCDs was calculated to be 68.0%. The NSCDs could be constructed as fluorescent probes for highly selective and sensitive sensing mercuric (Hg2+) and hypochlorite (ClO−) ions. As the addition of Hg2+ or ClO− ions to the NSCDs, the fluorescence intensity was effectively quenched due to dynamic quenching. Under the optimal conditions, the linear response of the fluorescence intensity ranged from 0.7 μM to 15 μM with a detection limit of 0.54 μM and from 0.3 μM to 5.0 μM with a limit of detection of 0.29 μM for Hg2+ and ClO− ions, respectively. Finally, the proposed method was successfully used for quantifying Hg2+ and ClO− ions in spiked tap water samples.

Abstract P-39: Fluorescent Silver Nanoclusters with Immunoglobulins and Albumins

Background: Multiplex biomedical assays including molecular genetic tests and immunoanalysis require multiple fluorophores with a wide excitation range and different emission spectra. In comparison with organic fluorophores and quantum dots, the metal nanoclusters (NC) consisting of a few to hundred atoms have the following advantages: small size, large Stokes shift, prolonged fluorescence lifetime and biocompatibility. Our research was aimed at construction of fluorescent AgNC with the main blood proteins and transmission electron microscopy (TEM). Methods: AgNC were synthesized from AgNO3 in the presence of albumins and immunoglobulins (Ig) of different classes and origin at pH 9-11 with NaBH4 recovery. The resulting AgNC with proteins were loaded to "Formvar/Carbon 200 Mesh Copper" copper grids (Ted Pella, USA) and examined using TEM system JEM 2100 Plus (JEOL, Japan) without contrast. Fluorescence excitation/emission spectra were measured in quartz cuvette using the FluoroMax + spectrofluorometer (Horiba Scientific, Japan). Results: Recovery of Ag+ ions did not occur in the presence of IgG and albumins without NaBH4 at different temperatures, pH, and incubation time. Broad excitation spectra of AgNC were in a range 340-540 nm. Their emission spectra correlated with the original AgNO3 concentration and did not depend on protein and pH. NC stabilized with IgG or albumin with blue fluorescence and emission maximum at 420 nm contained NC from 0.6 nm and higher. Green AgNC with proteins had bright fluorescence at 430-470 nm and red NC showed emission maximum at 650 nm. TEM revealed discrete AgNC and their numerous aggregates in each sample of fluorescent NC in spite of different fluorescent emission spectra. According to the MTT test, AgNC with human IgG and BSA with protein concentrations up to 3 mg/ml were not toxic for human larynx carcinoma HEp-2 cells despite cytotoxicity of silver nanoparticles covered with IgG or albumin envelopes as well as Cd and AuNC with BSA. Conclusion: AgNC with antibodies and albumin with a broad size range and aggregation possess tunable fluorescence emission spectra with broad excitation at 340-540 nm. Different emission spectra permit AgNC to be used in multiplex assays. AgNC were not toxic for human tissue culture and may be applied for bioimaging.