Oxidative Stability of Vegetal Oil-Based Lubricants.

Lipids are widely distributed in nature and are one of the most important components of natural foods, synthetic compounds, and emulsions. To date, there is a strong social demand in the industrial sector for the use of sustainable products with a minimal environmental impact. Depending on their origin and composition, lipids can be employed as a plausible alternative as biodegradable lubricants in order to reduce the use of conventional mineral oil lubricants and mitigate their environmental impact. This perspective provides an overview of the advantages and constrains of vegetal oils under different lubrication regimes and the tribochemical reactions that can take place. Also, the different factors and pathways that influence their oxidation, the key role of moisture, and the changes of physical properties under pressure and temperature are reviewed. Special emphasis is devoted to the oxidation instability of fatty acids and vegetal oils and the physical and chemical approaches to improve oxidative and thermal stability are described in detail.

Cellular Uptake and Tissue Biodistribution of Functionalized Gold Nanoparticles and Nanoclusters.

In this study, the in vitro uptake by fibroblasts and in vivo biodistribution of 15 nm 11-mercaptoundecanoicacid-protected gold nanoparticles (AuNPs-MUA) and 3 nm glutathione- and 3 nm bovine serum albumin-protected gold nanoclusters (AuNCs@GSH and AuNCs@BSA, respectively) were evaluated. In vitro cell viability was examined after gold nanoparticle treatment for 48 h, based on MTT assays and analyses of morphological structure, the cycle cell, cellular doubling time, and the gold concentration in cells. No potential toxicity was observed at any studied concentration (up to 10 ppm) for AuNCs@GSH and AuNCs@BSA, whereas lower cell viability was observed for AuNPs-MUA at 10 ppm than for other treatments. Neither morphological damage nor modifications to the cell cycle and doubling time were detected after contact with nanoparticles. Associations between cells and AuNPs and AuNCs were demonstrated by inductively coupled plasma mass spectrometry (ICP-MS). AuNCs@GSH exhibited fluorescence emission at 611 nm, whereas AuNCs@BSA showed a band at 640 nm. These properties were employed to confirm their associations with cells by fluorescence confocal microscopy; both clusters were observed in cells and maintained their original fluorescence. In vivo assays were performed using 9 male mice treated with 1.70 µg Au/g body weight gold nanoparticles for 24 h. ICP-MS measurements showed a different biodistribution for each type of nanoparticle; AuNPs-MUA mainly accumulated in the brain, AuNCs@GSH in the kidney, and AuNCs@BSA in the liver and spleen. Spleen indexes were not affected by nanoparticle treatment; however, AuNCs@BSA increased the thymus index significantly from 1.28 to 1.79, indicating an immune response. These nanoparticles have great potential as organ-specific drug carriers and for diagnosis, photothermal therapy, and imaging.

Engineered silica nanoparticles as additives in lubricant oils.

Silica nanoparticles (SiO2 NPs) synthesized by the sol-gel approach were engineered for size and surface properties by grafting hydrophobic chains to prevent their aggregation and facilitate their contact with the phase boundary, thus improving their dispersibility in lubricant base oils. The surface modification was performed by covalent binding of long chain alkyl functionalities using lauric acid and decanoyl chloride to the SiO2 NP surface. The hybrid SiO2 NPs were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, simultaneous differential thermal analysis, nuclear magnetic resonance and dynamic light scattering, while their dispersion in two base oils was studied by static multiple light scattering at low (0.01% w/v) and high (0.50%w/v) concentrations. The nature of the functional layer and the functionalization degree seemed to be directly involved in the stability of the suspensions. The potential use of the functional SiO2 NPs as lubricant additives in base oils, specially designed for being used in hydraulic circuits, has been outlined by analyzing the tribological properties of the dispersions. The dendritic structure of the external layer played a key role in the tribological characteristics of the material by reducing the friction coefficient and wear. These nanoparticles reduce drastically the waste of energy in friction processes and are more environmentally friendly than other additives.

Molecularly imprinted sol-gels for nafcillin determination in milk-based products.

A study has been made of the analytical application of a nafcillin-imprinted sol-gel to the direct determination of the beta-lactamic antibiotic in spiked milk-based samples using a room temperature phosphorescent flow-through system. The influence of the sample matrix on the transduction and the recognition processes was statistically determined, and results demonstrated that the imprinted sol-gel optosensing system could be effectively applied to real sample analysis. The analytical performance characteristics were as follows: The detection limit results for aqueous and skimmed milk were 5.8 x 10(-6) and 3.3 x 10(-5) mol L(-1), respectively, and a relative standard deviation less than 5% was found for both matrices. Statistical analysis of variance studies have been shown to have no significant effect on different skimmed milk commercial products over the imprinted material recognition. This fact provides an indicator of the ruggedness/robustness of the proposed analytical system and the possibility to use external real matrix calibration. Application of the method to nafcillin analysis in other milk-based samples is outlined.