Cytotoxicity and antibacterial activity of gold-supported cerium oxide nanoparticles.

BACKGROUND: Cerium oxide nanoparticles (CeO2) have been shown to be a novel therapeutic in many biomedical applications. Gold (Au) nanoparticles have also attracted widespread interest due to their chemical stability and unique optical properties. Thus, decorating Au on CeO2 nanoparticles would have potential for exploitation in the biomedical field. METHODS: In the present work, CeO2 nanoparticles synthesized by a chemical combustion method were supported with 3.5% Au (Au/CeO2) by a deposition-precipitation method. The as-synthesized Au, CeO2, and Au/CeO2 nanoparticles were evaluated for antibacterial activity and cytotoxicity in RAW 264.7 normal cells and A549 lung cancer cells. RESULTS: The as-synthesized nanoparticles were characterized by X-ray diffraction, scanning and transmission electron microscopy, and ultraviolet-visible measurements. The X-ray diffraction study confirmed the formation of cubic fluorite-structured CeO2 nanoparticles with a size of 10 nm. All synthesized nanoparticles were nontoxic towards RAW 264.7 cells at doses of 0-1,000 µM except for Au at >100 µM. For A549 cancer cells, Au/CeO2 had the highest inhibitory effect, followed by both Au and CeO2 which showed a similar effect at 500 and 1,000 µM. Initial binding of nanoparticles occurred through localized positively charged sites in A549 cells as shown by a shift in zeta potential from positive to negative after 24 hours of incubation. A dose-dependent elevation in reactive oxygen species indicated that the pro-oxidant activity of the nanoparticles was responsible for their cytotoxicity towards A549 cells. In addition, cellular uptake seen on transmission electron microscopic images indicated predominant localization of nanoparticles in the cytoplasmic matrix and mitochondrial damage due to oxidative stress. With regard to antibacterial activity, both types of nanoparticles had the strongest inhibitory effect on Bacillus subtilis in monoculture systems, followed by Salmonella enteritidis, Escherichia coli, and Staphylococcus aureus, while, in coculture tests with Lactobacillus plantarum, S. aureus was inhibited to a greater extent than the other bacteria. CONCLUSION: Gold-supported CeO2 nanoparticles may be a potential nanomaterial for in vivo application owing to their biocompatible and antibacterial properties.

Formation and inhibition of cholesterol oxidation products during marinating of pig feet.

Cholesterol oxidation products (COPs), formed during the heating of cholesterol-rich foods, have been shown to cause cancer and coronary heart disease. The objectives of this study were to develop a GC-MS method for the determination of COPs in pig feet meat, skin, and juice during marinating and to study the formation and inhibition of COPs as affected by the incorporation of soy sauce and sugar. Results showed that an HP-5MS column could provide an adequate separation of cholesterol, 5α-cholestane (internal standard), and seven COPs, including 7α-OH, 7ß-OH, 5,6ß-OH, 5,6α-OH, triol, 25-OH, and 7-keto, within 15 min with a temperature-programming method. Most COPs in pig feet meat were generated at a larger amount than in pig feet skin and marinating juice over a 24 h heating period at about 100 °C. The Maillard browning index rose with increasing heating time, whereas the pH showed a slight change in marinated juice. Both reducing sugar and free amino acid contributed to the formation of Maillard reaction products. The incorporation of soy sauce and crystal sugar into fresh juice was effective in inhibiting COPs formation in pig feet, skin, and juice over a 30 min preheating period.

Gas chromatography-mass spectrometry determination of conjugated linoleic acids and cholesterol oxides and their stability in a model system.

A gas chromatography-mass spectrometry (GC-MS) method was developed to simultaneously separate cholesterol, eight cholesterol oxidation products (COPs), and two conjugated linoleic acids (9-cis,11-trans-CLA and 10-trans,12-cis-CLA) and to evaluate their stability in a model system during heating. Among four capillary columns tested, an Equity-5 column with low-polar stationary phase provided better resolution within 30 min. A high-performance liquid chromatography method was also developed to determine cholesterol hydroperoxides by using a YMC C30 column with diphenyl-1-pyrenylphosphine as fluorescence reagent. No formation of COPs or degradation of cholesterol and CLAs occurred at 100 degrees C, but the levels of COPs rose drastically at 150 degrees C. The first-order rate of cholesterol degradation declined following a rise in CLA concentration. For 0-, 100-, and 500-microg/ml CLA levels, the formation profiles of 7-hydroxycholesterol, 7-ketocholesterol, and 5,6-epoxycholesterol at 150 degrees C were fitted as multiple first-order curves, whereas a single first-order model could adequately describe 7-hydroperoxycholesterol and cholestane-3beta,5alpha,6beta-triol formation. A CLA-to-cholesterol mole ratio of 0.49 was required to prevent cholesterol oxidation at 150 degrees C.

Determination of flavonoids and saponins in Gynostemma pentaphyllum (Thunb.) Makino by liquid chromatography-mass spectrometry.

Gynostemma pentaphyllum (Thunb.) Makino, a traditional Chinese herb possessing antitumor and antioxidant activities, has been shown to contain several functional components like saponins and flavonoids. However, their identities remain uncertain. The objectives of this study were to develop an appropriate extraction, purification and HPLC-MS method to determine saponins and flavonoids in G. pentaphyllum. Both flavonoids and saponins were extracted with methanol, followed by purification with a C18 cartridge to elute the former with 50% methanol and the latter with 100% methanol. A total of 34 saponins were separated within 40 min by a Gemini C18 column and a gradient mobile phase of acetonitrile and 0.1% formic acid in water, in which 18 saponins were identified by LC-MS with ESI mode and Q-TOF (LC/MS/MS). Similarly, a total of eight flavonoids were separated within 45 min by the same column and a gradient solvent system of methanol and 0.1% formic acid in water, with identification being carried out by a post-column derivatization method and LC-MS with ESI mode. The amounts of flavonoids in G. pentaphyllum ranged from 170.7 to 2416.5 mug g(-1), whereas saponins were from 491.0 to 89,888.9 mug g(-1).

Lack of formation of heterocyclic amines in fumes from frying French fries.

The formation of heterocyclic amines (HAs) in the fumes from frying French fries in soybean oil or lard was studied. A high-pressure liquid chromatography method was used to determine the various HAs in fumes. Results showed that the yields of fumes produced from soybean oil when heated alone for 2 or 4 h were higher than from lard; however, a reversed trend was found when frying French fries in soybean oil and lard. Most fumes from soybean oil and lard while frying French fries were adsorbed onto the condensation apparatus, while the other portions were adsorbed onto the wool and glass beads, which were incorporated in our experimental design for collecting the fumes. The fumes from soybean oil when heated alone were found to contain three HAs, namely, 2-amino-3-methylimidazo[4,5-f]quinoxaline (IQx), 2-amino-3-methylimidazo[4,5-f ]quinoline (IQ), and 1-methyl-9H-pyrido[4,3-b ]indole (Harman), whereas two more HAs, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 3-amino-1,4-dimethyl-5H-pyrido[4,3-b ]indole (Trp-P-1), were generated in lard. Lard was more susceptible to the formation of HAs than soybean oil when both were heated alone. No HAs were detected in the fumes from French fries fried in soybean oil and lard.