Direct Fluorescent Detection of a Polymethoxyflavone in Cell Culture and Mouse Tissue

Apolipoprotein E3 Containing Nanodiscs as Vehicles for Transport and Targeted Delivery of Flavonoid Luteolin

Luteolin is a flavonoid that possesses multiple beneficial biological properties, such as anticancer, antioxidant, and anti-inflammatory effects. The objective of this study is to test the hypothesis that luteolin can be transported across a cell via a nanodisc delivery system and delivered to intracellular sites. Luteolin was incorporated into reconstituted high-density lipoprotein complexes made up of apolipoprotein E3 (apoE3) N-terminal domain (apoE3NT) and 1,2-dimystrioyl-sn-glycero-3-phosphocholine. ApoE3NT confers the ability on nanodiscs to traverse the plasma membrane via low-density lipoprotein receptor or scavenger receptor-B1. Physicochemical characterization revealed that the nanodiscs were 17-22 nm in diameter as demonstrated by native polyacrylamide gel electrophoresis and dynamic lightering analysis and ∼660 kDa in size, with a luteolin content of ∼4 luteolin molecules/nanodisc. Luteolin appeared to be embedded in the nonpolar core of nanodiscs, as revealed by fluorescence quenching and polarization analysis and spectroscopic characterization. The presence of luteolin did not affect the ability of apoE3NT to mediate binding and cellular uptake of luteolin containing nanodiscs in macrophages, as inferred from immunofluorescence analysis that revealed apoE- and lipid-related fluorescence as punctate perinuclear vesicles and from flow cytometry studies. Lastly, luteolin appeared to be localized in the nucleus, having escaped the lysosomes following disassembly of the nanodiscs as suggested by fluorescence spectroscopy and microscopy analyses. Taken together, nanodiscs offer the potential to effectively transport luteolin and potentially therapeutic drugs into perinuclear sites in cells, where they can be available to enter the nucleus.

Effect of squalane-based emulsion on polyphenols skin penetration: Ex vivo skin study

Polyphenols have gained attractiveness as ingredients in cosmetic formulations as result of their ability to delay the aging process. However, different factors limit their use, including low solubility and poor skin permeability. In this sense, this study describes the potential of squalane to increase the polyphenols ex vivo skin penetration, incorporated into a water-in-oil emulsion. Polyphenols skin permeation followed the Fick's first law and, p-coumaric acid, vitexin, schaftoside and ferulic acid had the higher permeability coefficients (Kp = 6.0-8.0 × 10^-3 cm^-2 h^-1). Addition of squalane to phenolic compounds decreased the permeability coefficients (Kp = 4.1-5.9 × 10^-3 cm^-2 h^-1), indicating that squalane increased the retention of polyphenols in the skin. Gentisic acid, ferulic acid, and p-coumaric acid were the only compounds permeating from water-in-oil emulsion, in the first 8 h of study and, according Krosmeyer-Peppas model, its n value was > 1 indicating a high transport resistance from the formulation and throughout the skin. Results suggest squalane as an efficient vehicle to increase the dermal availability increasing phenolic compounds physiological functions, by enhancing the skin retention time where they should exert antiaging effect.

New Horizons in Microbiological Food Safety: Ultraefficient Photodynamic Inactivation Based on a Gallic Acid Derivative and UV-A Light and Its Application with Electrospun Cyclodextrin Nanofibers

An excellent bactericidal effect of octyl gallate (OG)-mediated photodynamic inactivation (PDI) against foodborne pathogens (Escherichia coli and Staphylococcus aureus) was evaluated in relation to the mode of action. UV-A irradiation (wavelength, 365 nm; irradiance, 8.254 ± 0.18 mW/cm²) of the bacterial suspension containing 0.15 mM OG could lead to a >5-log reduction of viable cell counts within 30 min for E. coli and only 5 min for S. aureus. Reactive oxygen species (ROS) formation was considered the main reason for the bactericidal effect of OG + UV-A light treatment because toxic ROS induced by OG-mediated PDI could attack the cellular wall, proteins, and DNA of microbes. Moreover, the bactericidal effect, as well as the yields of ROS, depended on OG concentrations, irradiation time, and laser output power. Furthermore, we prepared an edible photodynamic antimicrobial membrane comprising electrospun cyclodextrin nanofibers (NFs) by embedding OG. The resultant OG/HPβCD NFs (273.6 μg/mL) under UV-A irradiation for 30 min (14.58 J/cm) could cause a great reduction (>5-log) of viable bacterial counts of E. coli. The in situ photodynamic antibacterial activity of OG/HPβCD NF-based packaging was evaluated during the Chinese giant salamander storage. Overall, this research highlights the dual functionalities (antibacterial and photodynamic properties) of OG as both an antibacterial agent and photosensitizer and the effectiveness of electrospun NFs containing OG as an active antibacterial packaging material for food preservation upon UV light illumination.

Real-time fluorescence imaging of anthocyanins complexed with diphenylboric acid 2-aminoethyl inside B16-F10 melanoma cells

Anthocyanins (AN), natural compounds daily consumed by humans, have outstanding therapeutical potential if administered topically in melanoma pathology. However, the search for efficient therapy development is still in progress, owing to the lack of complete understanding of the AN intracellular path, once they are uptaken by the cells. This target is constrained by the need for an imaging strategy that would enable their intracellular detection and localization in-situ. In this light, diphenylboric acid 2-aminoethyl (DPBA), a non-fluorescent reagent, was here successfully used to form fluorescent complexes with AN. The AN used are the cyanidin aglycon as a free standard molecule (CY), and the glycosylated compounds, extracted and purified from chokeberry fruits (AE). In solution, it was observed that the fluorescence emission increased by 39% (CY@DPBA), and by 34% (AE@DPBA), which concludes that AN form fluorescent complexes with DPBA (CY@DPBA and AE@DPBA). In addition, using NMR (nuclear magnetic resonance) spectroscopy, and HRMS (high-resolution mass spectrometry) analysis, the structure of the CY@DPBA complex was efficiently elucidated. In-vitro experiments showed that the complexes formed after the treatment proved to be non-toxic on B16-F10 cells. The sub-cellular visualization of all AN was monitored by fluorescence microscopy and flow cytometry, demonstrating detectable signals of the non-metabolized CY and glycosylated CY inside melanoma cells. This study reports that the use of DPBA to image AN intracellularly is a sensitive, non-invasive and successful method that can extend its application in broad fields like drug development or metabolism-associated mechanisms.

Analysis of Fluorescence Spectra of Citrus Polymethoxylated Flavones and Their Incorporation into Mammalian Cells

Citrus polymethoxylated flavones (PMFs) influence biochemical cascades in human diseases, yet little is known about how these compounds interact with cells and how these associations influence the actions of these compounds. An innate attribute of PMFs is their ultraviolet-light-induced fluorescence, and the fluorescence spectra of 14 PMFs and 7 PMF metabolites were measured in methanol. These spectra were shown to be strongly influenced by the compounds' hydroxy and methoxy substituents. For a subset of these compounds, the fluorescence spectra were measured when bound to human carcinoma Huh7.5 cells. Emission-wavelength maxima of PMF metabolites with free hydroxyl substituents exhibited 70-80 nm red shifts when bound to the Huh7.5 cells. Notable solvent effects of water were observed for nearly all these compounds, and these influences likely reflect the effects of localized microenvironments on the resonance structures of these compounds when bound to human cells.

On mechanism behind UV-A light enhanced antibacterial activity of gallic acid and propyl gallate against Escherichia coli O157:H7

Possible mechanisms behind the enhanced antimicrobial activity of gallic acid (GA) and its ester propyl gallate (PG) in the presence of UV-A light against Escherichia coli O157:H7 were investigated. GA by itself is a mild antimicrobial and has a pro-oxidant ability. We found that the presence of UV-A light increases the uptake of GA by the bacteria. Once GA is internalized, the interaction between GA and UV-A induces intracellular ROS formation, leading to oxidative damage. Concurrently, GA + UV-A also inhibits the activity of superoxide dismutase (SOD), magnifying the imbalance of redox status of E. coli O157:H7. In addition to ROS induced damage, UV-A light and GA also cause injury to the cell membrane of E. coli O157:H7. UV-A exposed PG caused oxidative damage to the cell and significantly higher damage to the cell membrane than GA + UV-A treatment, explaining its higher effectiveness than GA + UV-A treatment. The findings presented here may be useful in developing new antimicrobial sanitation technologies for food and pharmaceutical industries.

Imaging and Detection of Carboxylesterase in Living Cells and Zebrafish Pretreated with Pesticides by a New Near-Infrared Fluorescence Off-On Probe

A new near-infrared fluorescence off-on probe was developed and applied to fluorescence imaging of carboxylesterase in living HepG-2 cells and zebrafish pretreated with pesticides (carbamate, organophosphorus, and pyrethroid). The probe was readily prepared by connecting (4-acetoxybenzyl)oxy as a quenching and recognizing moiety to a stable hemicyanine skeleton that can be formed via the decomposition of IR-780. The fluorescence off-on response of the probe to carboxylesterase is based on the enzyme-catalyzed spontaneous hydrolysis of the carboxylic ester bond, followed by a further fragmentation of the phenylmethyl unit and thereby the fluorophore release. Compared with the only existing near-infrared carboxylesterase probe, the proposed probe exhibits superior analytical performance, such as near-infrared fluorescence emission over 700 nm as well as high selectivity and sensitivity, with a detection limit of 4.5 × 10^-3 U/mL. More importantly, the probe is cell membrane permeable, and its applicability has been successfully demonstrated for monitoring carboxylesterase activity in living HepG-2 cells and zebrafish pretreated with pesticides, revealing that pesticides can effectively inhibit the activity of carboxylesterase. The superior properties of the probe make it of great potential use in indicating pesticide exposure.

Complexation of curcumin with 2-aminoethyl diphenyl borate and implications for spatiotemporal fluorescence monitoring

In this study, we successfully determined spatiotemporal distribution of curcumin in mice via simple and fast fluorescence detection of native curcumin and stabilized curcumin. We used 2-aminoethyl diphenyl borate (DPBA) as a stabilizer of curcumin, which binds to curcumin and enhances its aqueous stability. After intravenous injection, curcumin and DPBA-curcumin complexes showed similar fluorescence intensities in the brain, pancreas, lungs, and kidneys at 15min. However, stabilized DPBA-curcumin complexes exhibited much stronger fluorescent signals at metabolically active sites such as liver tissues than native curcumin. After incubation for 1-3h, native curcumin showed significantly rapid reduction of fluorescent signals, compared to DPBA-curcumin complexes, probably due to degradation and reduction. In addition, complicate extraction procedures inhibited precise fluorescent monitoring of unstable curcumin, which result in different biodistribution of curcumin before and after extraction. Direct fluorescent monitoring could allow evaluation of in vivo distribution and fate of curcumin, which could be also applied to diverse natural polyphenols with fluorescent signals.