Understanding mechanisms behind the oily mouthcoating perception of pure vegetable oils using tribology.

Tribology is the science of measuring friction between surfaces. While it has been widely used to investigate texture sensations of food applications, it is seldom applied in pure edible oil systems. In this research, we measured friction, viscosity, and solid fat content (SFC) of nine vegetable oils at 30 and 60°C. Polarized static microscopy was used to assess crystal formation between 60 and 30°C. Descriptive sensory analysis and quantification of oral oil coatings were performed on the oils at 60°C. Expressing the friction factor of oil over the Hersey number (calculated using high sheer-viscosity values) showed no differences in friction between 30 and 60°C, except for shea stearin. Static microscopy revealed crystallization occurred at 30°C for shea stearin, whereas no or few crystals were present for other oils. At 30°C, friction at 1 × 10-2 m/s showed an inverse correlation with SFC (R = -0.95) and with high shear rate viscosity (R = -0.84), as well as an inverse correlation (R = -0.73) with "oily mouthcoating" perception. These results suggest that friction could be a predictor of fat-related perceptions of simple oil systems. Additionally, we hypothesize that the presence of crystals in oils could lower friction via a ball-bearing lubrication mechanism.

The role of membrane components on the oleosome lubrication properties.

HYPOTHESIS: Oleosomes are natural oil droplets with a unique phospholipid/protein membrane, abundant in plant seeds, from which they can be extracted and used in emulsion-based materials, such as foods, cosmetics and pharmaceutics. The lubrication properties of such materials are essential, on one hand, due to the importance of the in-mouth creaminess for the consumed products or the importance of spreading the topical creams. Therefore, here, we will evaluate the lubrication properties of oleosomes, and how these properties are affected by the components at the oleosome membrane. EXPERIMENT: Oleosomes were extracted, and their oral lubricating properties were evaluated using tribology. To understand the influence of the oil droplet membrane composition, reconstituted oleosomes were also studied, with membranes that differed in protein/lecithin ratio. Additionally, whey protein- and lecithin-stabilised emulsions were used as reference samples. Confocal laser scattering microscopy was used to study the samples visually before and after tribological analysis. FINDINGS: Oleosomes followed a ball-bearing mechanism, which was probably related to their high physical stability due to the presence of membrane proteins. When the membrane protein concentration at the surface was reduced, the droplet stability weakened, leading to plating-out lubrication. Following our results, we elucidated the oleosome lubrication mechanism and showed their possible control by changing the membrane composition.

Carbon Quantum Dots Derived from Herbal Medicine as Therapeutic Nanoagents for Rheumatoid Arthritis with Ultrahigh Lubrication and Anti-inflammation.

As a typical chronic inflammatory joint disease with swelling and pain syndromes, rheumatoid arthritis (RA) is closely related to articular lubrication deficiency and excessive proinflammatory cytokines in its progression and pathogenesis. Herein, inspired by the dual effects of joint lubrication improvement and anti-inflammation to treat RA, two novel potential therapeutic nanoagents have been developed rationally by employing herbal medicine-derived carbon quantum dots (CQDs), i.e., safflower (Carthamus tinctorius L.) CQDs and Angelica sinensis CQDs, yielding ultrahigh lubrication and anti-inflammation bioefficacy. In vitro experimental results show that the two nanoagents display excellent friction reduction due to their good water solubility and spherical structure. Using RA rat models, it is indicated that the nanoagents significantly relieved swelling symptoms and inhibited the expression of related inflammatory cytokines, including IL-1, IL-6, and TNF-α, indicating their extraordinary anti-inflammation bioefficacy. Thus, combining the lubricating and anti-inflammation bioefficacy of CQDs derived from herbal medicine is an attractive strategy to develop new nanoagents for RA treatment.

Investigation on the lubrication component and mechanism for a biolubricant isolated from the agro-waste resource of Codonopsis pilosula.

Waste plant resource provides a new sustainable feedstock for the biolubricant, and purification of the effective components in biomass oil is vital to improve the performance of biolubricant. In this work, the crude extract of the aerial part of Codonopsis pilosula was divided into four different parts by petroleum ether, ethyl acetate, n-butanol and water, respectively. Their thermal stability, lubricating performances and mechanisms have been systematically investigated. In the four extracts, the petroleum ether extract displays the best thermal stability and lubricating performance over the entire test conditions, and other three extracts are confronted with lubrication failure at high loads and elevated temperatures. Triterpenoid saponin, typical for n-butanol extract exhibit the best lubricity at room temperature, followed by the fatty acid derivatives as phosphatidylcholine; flavonoid, and sugar exhibit poor lubricity. At high temperature, only the petroleum ether extract retains the good lubricity.

A cyclic brush zwitterionic polymer based pH-responsive nanocarrier-mediated dual drug delivery system with lubrication maintenance for osteoarthritis treatment.

Enhanced joint synergistic lubrication combined with anti-inflammatory therapy is an effective strategy to delay the progression of early osteoarthritis (OA) but has been rarely reported. The hydration lubrication of zwitterions and inherent super-lubrication properties of the cyclic brush, as well as the enhancement of the steric stability of the cyclic topology, can effectively improve the drug loading and utilization; herein we report a pH-responsive cyclic brush zwitterionic polymer (CB) with SBMA and DMAEMA as brushes and a cyclic polymer (c-P(HEMA)) as the core template, possessing a low coefficient of friction (0.017). After loading with hydrophobic curcumin and hydrophilic loxoprofen sodium it demonstrates high drug-loading efficiency. In vitro and in vivo experiments confirmed the triple function of the CB on superlubrication, sequence controlled release and anti-inflammatory effects demonstrated by Micro CT, histological analysis and qRT-PCR. Overall, the CB is a promising long-acting lubricating therapeutic agent, with potential for OA treatment or other diseases.

Cellulose nanocrystals as sustainable additives in water-based cutting fluids.

Cutting fluid is indispensable in the machining industry as a fluid for lubrication and cooling in the metalworking process due to their ability to significantly improve various properties of cutting fluid. Castor oil, as a common base oil and additive in cutting fluid, can be grafted onto the surface of cellulose nanocrystals (CNC) to further enhance the lubricating properties of cutting fluid. It has been shown that cellulose nanocrystals and castor oil modified cellulose nanocrystals (CO-CNC) as additives in cutting fluid have good dispersion stability and can effectively improve the lubricating properties. When the amount of CNC or CO-CNC was added in the working fluid at about 0.5 wt%, the friction coefficient was significantly reduced. According to the results from this study, cellulose nanocrystal is a promising candidate as the nontoxic and renewable additive for the improvement of diverse performances for the water-based cutting fluid.

Effect of different molecular characteristics on the lubrication behavior of polysaccharide solutions.

Polysaccharides strongly affect the sensorial properties of foods, which is partly related to the lubrication they provide. We investigated the lubrication performance of polysaccharides with different characteristics (i.e. molecular weight, conformation, stiffness, and charge density) to identify the most relevant structural features related to lubrication ability. The effect of viscosity was excluded using isoviscous systems. Conformation resulted to be a key factor in determining lubrication. Rigid rod-like polysaccharides (xanthan) showed higher lubricating capacity and better resistance to changes in pH and ionic strength compared to semi-flexible (pectin and carboxymethyl cellulose) and flexible polysaccharide (guar gum). The friction behavior of flexible polysaccharides was highly dependent on concentration and sliding speed, for which a model including parameters of friction, concentration, and speed was developed. The concentration-dependency of the lubrication was related to the shear-thinning behavior, and possible mechanisms to explain these differences in terms of molecular properties of the polysaccharides are proposed.

Can lubrication of the eyelid speculum reduce overall pain perception associated with cataract surgery by phacoemulsification performed under topical anesthesia?

Purpose: This study aimed to evaluate the effect of using the lubricated eyelid speculum on the overall pain perception by the subject patients who underwent cataract surgery by phacoemulsification technique under topical anesthesia. Methods: A prospective interventional randomized comparative study was conducted at the tertiary eye care center, wherein adult patients scheduled for bilateral cataract surgery with phacoemulsification techniques under topical anesthesia were randomized to undergo surgery with two different modes of eyelid speculum insertion, either with or without lubrication of the eyelid speculum. Fifty percent of the patients underwent surgery with eyelid speculum without lubrication, and 50% with lubrication of the eyelid speculum. The primary outcome was to compare the level of overall pain perception among the subject patients of the two groups by using the Visual Analogue Scale (VAS) in the immediate postoperative period. Results: The study included 130 patients who underwent bilateral cataract surgery (n = 260 eyes) under topical anesthesia, wherein n = 130 eyes underwent surgery using lubricated eyelid speculum and n = 130 eyes underwent surgery with dry eyelid speculum. Pain perception score assessed on the VAS (0-10 cm) ranged from 0.5 to 6, with a mean ± standard deviation of 2.06 ± 1.12. A significant correlation was found with two different methods of eyelid speculum insertion with reduced overall pain perception in patients with the use of lubricated eyelid speculum compared to the dry eyelid speculum (P = 0.0001). Conclusion: The overall pain perception associated with cataract surgery performed by phacoemulsification technique under topical anesthesia can be further minimized by lubricating the eyelid speculum prior to insertion for exposing the globe.

Bio-inspired robust superhydrophilic/underwater superoleophobic coating with lubrication, anti-crude oil fouling and anti-corrosion performances.

The crude oil spill accidents cause numerous crude oil contaminations and oily wastewater. Underwater superoleophobic coating has excellent ability to resist crude oil contamination and separate oily wastewater. But it's hard to keep stable performance against the physical or chemical attack. Herein, a robust underwater superoleophobic coating was fabricated by spraying the mixture of polyethyleneimine (PEI) and TiO2 on epoxy resin (E44) surface. Besides the good physical and chemical stability, the coating exhibited better drag reduction, anti-fouling performance and anti-corrosive performance in water compared with the commercially hydrophilic coating. The stainless steel mesh (SSM), coated by the E44/PEI/TiO2 coating, could separate different oil-water emulsions with a high oil rejection greater than 99.7%.

Green Superlubricity Enabled by Only One Water Droplet on Plant Oil-Infused Surfaces.

The increase in energy loss due to friction and the use of large amounts of lubricants to improve it are major challenges we face from a global environmental perspective. Pitcher-plant-inspired liquid-infused surfaces (LISs) are emerging super-repellent surfaces against liquids. However, their coefficient of friction (CoF) against solids is higher than that of conventional lubricant surfaces. Herein, we demonstrate superlubricity with a single water droplet placed on a LIS holding oleic acid, a component of plant oil. When a water droplet is placed on the fluid layer, the CoF under reciprocating and rotating friction is 0.012 and 0.0098, respectively. A force in the direction opposite to the loading due to the Laplace pressure on the droplet and an autonomous positional movement of the water accompanied by the optimization of surface energy maintain the fluid-lubrication state and prevent direct contact between the surface and the friction material, resulting in a decrease of the dependence of the CoF on the friction velocity. The key technology here will not only present a novel strategy for preparing LISs against solids but also serve as a step toward a sustainable green strategy for friction reduction and lubrication, which would greatly reduce energy loss and environmental degradation.

Frictional behaviour of molten chocolate as a function of fat content.

Soft tribology is used to probe the lubrication behaviour of molten chocolate between soft contacts, analogous to in-mouth interactions between the tongue and palate. Molten chocolate is a concentrated suspension of solid particles (sugar, cocoa and milk solids) in cocoa butter. We hypothesise that the complex frictional behaviour of molten chocolate depends on its particulate nature and thus solid volume fraction (sugar & cocoa solids/fat content). In this work, we assess the properties of molten chocolate as a function of fat content by diluting milk chocolate containing 26, 27 and 29% fat with cocoa butter. The tribological behaviour of molten chocolate deviates notably from the typical Stribeck curve of Newtonian fluids. Additional transitions are observed in mixed and elastohydrodynamic lubrication which are respectively attributed to the effect of shear-thinning rheology (i.e. breakdown of aggregates) and the selective entrainment or exclusion of particles depending on interfacial gap height. These transitions are more pronounced in chocolate of high solid fraction, and correlate with the influence of particle aggregation on rheology. In addition, we assess oral lubrication by preparing model chocolate boluses with aqueous buffer, which produces a ternary system of oil droplets and insoluble cocoa solids dispersed within a continuous aqueous phase. The frictional behaviour of chocolate boluses is determined by the viscosity ratio between cocoa butter and aqueous phase, in agreement with previous findings for oil-in-water emulsions. We provide a conceptual model to interpret how fat content influences the oral lubrication and mouthfeel of chocolate during consumption.

Contributions of viscosity and friction properties to oral and haptic texture perception of iced coffees.

Creaminess is affected by bulk properties (i.e. viscosity) and surfaces properties (i.e. friction). This study aimed (i) to assess contributions of viscosity and friction properties to creaminess, thickness and slipperiness perception; and (ii) to compare oral and haptic thickness and slipperiness perception of iced coffees. Three iced coffees differing in viscosity and friction properties were prepared: low viscosity - high friction (LV-HF); low viscosity - low friction (LV-LF) and high viscosity - low friction (HV-LF) iced coffee. Viscosity of iced coffees was adjusted by addition of maltodextrin, and viscosity of HV-LF was 2.5 times higher than that of LV-HF and LV-LF (10 vs. 4 mPa s at 100 s-1). Friction coefficients of LV-LF were reduced by addition of polyethylene glycol (PEG, Mw 6000), and were up to 25% lower than those of LV-HF. Forty-seven untrained panellists (18-27 years) performed two-alternative forced choice (2-AFC) and rank-rating tests to compare creaminess by oral assessment, and thickness and slipperiness by oral and haptic assessment. Results from 2-AFC and rank-rating congruently showed that HV-LF was creamier, thicker and more slippery than LV-HF and LV-LF, both orally and haptically. LV-LF was orally perceived as less creamy and less thick, but haptically as more slippery than LV-HF. Creaminess was more strongly correlated to thickness than to slipperiness. Oral and haptic evaluation of thickness was congruent, whereas differences between oral and haptic slipperiness evaluation were product-dependent. We conclude that increasing viscosity enhances creaminess, whereas increasing lubrication is not necessarily sufficient to increase creaminess in iced coffees.

Lubrication during root canal treatment.

Lubrication is involved in all root canal treatment phases, from dental dam placement to canal obturation. Most often associated with instrumentation, lubrication is required to facilitate the mechanical action of hand/rotary files and to help emulsify and suspend the debris produced. Aqueous irrigation solutions such as sodium hypochlorite and ethylenediaminetetraacetic acid (EDTA) should be regarded as lubricants, but paste-type substances are marketed specifically for this purpose. As more patients demand the retention of challenging teeth with narrow and curved root canals, the importance of lubrication in all aspects of root canal treatment must be acknowledged.

Anti-Inflammation and Joint Lubrication Dual Effects of a Novel Hyaluronic Acid/Curcumin Nanomicelle Improve the Efficacy of Rheumatoid Arthritis Therapy.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, which can cause endless suffering to the patients and severely impact their normal lives. To treat RA, the drugs in use have many serious side effects, high cost, or only focus on their anti-inflammatory mechanisms without taking joint lubrication into consideration. Therefore, in this study, we aim to construct a novel anti-RA drug composed of hyaluronic acid/curcumin (HA/Cur) nanomicelle to resolve these problems. Characterizations show that Cur is bound to HA by ester linkages and self-assembles to form a spherical nanomicelle with a diameter of around 164 nm under the main driving of the hydrophilic and hydrophobic forces. The nanomicelle enjoys excellent biocompatibility that effectively promotes the proliferation of chondrocytes. When injected to the RA rats, the nanomicelle significantly lowers the edema degree of the arthritic rats compared to other groups; more critically, a dramatic decrease in friction between the surfaces of cartilage around the joints has been found, which protects the cartilage from the RA-induced damage. Additionally, systematic mechanism investigation indicates that the nanomicelle diminishes the expression of related cytokines and vascular endothelial growth factor, finally leading to the excellent performance. The newfound nanomicelle has a potential for clinical practice of RA therapy, which will contribute significantly to alleviating the pain of patients and improving the quality of life for them.

Preliminary results of a single-arm pilot study to assess the safety and efficacy of visnadine, prenylflavonoids and bovine colostrum in postmenopausal sexually active women affected by vulvovaginal atrophy.

This single-arm pilot study enrolled 47 post-menopausal women affected by vulvovaginal atrophy (VVA). The Vaginal Health Index Score (VHIS) was evaluated for all women and all completed the Female Sexual Function Index (FSFI) questionnaire at baseline (T0) and after 15 days of vaginal cream treatment with one application per day (T1). Following treatment there was a significant improvement in all VHIS parameters and total score (p < 0.0001). Similarly, there was a significant improvement on four FSFI domains (lubrication, orgasm, satisfaction and pain) and total score (p = 0.001). None of the patients reported any local or systemic side-effects during treatment.

Lubricant based determination of design space for continuously manufactured high dose paracetamol tablets.

The objective of this study was to devise robust and stable continuous manufacturing process settings, by exploring the design space after an investigation of the lubrication-based parameters influencing the continuous direct compression tableting of high dose paracetamol tablets. Experimental design was used to generate a structured study plan which involved 19 runs. The formulation variables studied were the type of lubricant (magnesium stearate or stearic acid) and its concentration (0.5, 1.0 and 1.5%). Process variables were total production feed rate (5, 10.5 and 16kg/h), mixer speed rpm (500, 850 and 1200rpm), and mixer inlet port for lubricant (A or B). The continuous direct compression tableting line consisted of loss-in-weight feeders, a continuous mixer and a tablet press. The Quality Target Product Profile (QTPP) was defined for the final product, as the flowability of powder blends (2.5s), tablet strength (147N), dissolution in 2.5min (90%) and ejection force (425N). A design space was identified which fulfilled all the requirements of QTPP. The type and concentration of lubricant exerted the greatest influence on the design space. For example, stearic acid increased the tablet strength. Interestingly, the studied process parameters had only a very minor effect on the quality of the final product and the design space. It is concluded that the continuous direct compression tableting process itself is insensitive and can cope with changes in lubrication, whereas formulation parameters exert a major influence on the end product quality.

Effect of Cholesterol on the Stability and Lubrication Efficiency of Phosphatidylcholine Surface Layers.

The lubrication properties of saturated PC lipid vesicles containing high cholesterol content under high loads were examined by detailed surface force balance measurements of normal and shear forces between two surface-attached lipid layers. Forces between two opposing mica surfaces bearing distearoylphosphatidylcholine (PC) (DSPC) small unilamellar vesicles (SUVs, or liposomes), or bilayers, with varying cholesterol content were measured across water, whereas dimyristoyl PC (DMPC), dipalmitoyl PC (DPPC), and DSPC SUVs containing 40% cholesterol were measured across liposome dispersions of SUVs of the same lipid composition as in the adsorbed layers. The results clearly demonstrate decreased stability and resistance to normal load with the increase in cholesterol content of DSPC SUVs. Friction coefficients between two 10% cholesterol PC-bilayers were in the same range as for 40% cholesterol bilayers (µ ≈ 10-3), indicating that cholesterol has a more substantial effect on the mechanical properties of a bilayer than on its lubrication performance. We further find that the lubrication efficiency of DMPC and DPPC with 40% cholesterol is superior to that of DSPC 40% cholesterol, most likely because of enhanced hydration-lubrication in these systems. We previously found that when experiments are performed in the presence of a lipid reservoir, layers can self-heal and therefore their robustness is less important under such conditions. We conclude that the effect of cholesterol in decreasing the stability is more pronounced than its effect on hydration, but the stability is, in turn, less important when a lipid reservoir is present. This study complements our previous work and sheds light on the effect of cholesterol, a prominent and important physiological lipid, on the mechanical and lubrication properties of gel-phase lipid layers.

Wear and surface degradation of commercial ZTA femoral heads under boundary lubrication conditions.

The effect of frictional sliding on the surface degradation of commercially available zirconia-toughened alumina (ZTA) femoral heads was studied using a pin-on-ball wear tester under three different lubricating conditions: dry, water, and squalene. Water and squalene were employed under boundary lubrication regimes. Despite the unique (non-standard) character of this apparatus, standard loading conditions could be applied, which effectively determined dynamic friction coefficients as basic material properties. Two types of surface degradation were observed: (i) the polymorphic tetragonal-to-monoclinic (t→m) transformation of the zirconia (ZrO2) dispersoids, and (ii) the off-stoichiometry drift caused by oxygen vacancy formation within the alumina matrix. Scanning laser microscopy (SLM), Raman spectroscopy (RS), scanning electron microscopy (SEM), cathodoluminescence (CL), and X-ray photoelectron spectroscopy (XPS) were utilized to evaluate the fractions of transformed zirconia phase and the stoichiometric evolution of the oxygen sub-lattice at the surface of wear-tested ZTA components. Wear tracks on the surface of the femoral heads were only detected under dry conditions. Dry wear also showed the highest frictional forces and the most pronounced formation of oxygen vacancies among the tested conditions. Conversely, equivalent or greater amounts of the t→m transformation were observed with water and squalene lubrication when compared to the dry wear condition.

Usefulness of oil lubrication during colonoscopy: A comparative study with the conventional technique.

BACKGROUND: The different forms of lubrication are among the most simple, accessible, and economic techniques that have been implemented for improving the diagnostic performance of colonoscopy. AIM: To determine whether the use of oil improved the number of complete colonoscopies, facilitated the procedure, reduced pain, or improved the study's diagnostic performance, compared with the conventional lubrication technique. PATIENTS AND METHODS: One hundred and seventy-five patients referred for colonoscopy were alternately allocated to receive treatment with the standard lubrication method with chlorhexidine gel (group 1) or lubrication with corn oil administered through the working channel (group II). The number of complete colonoscopies, the length of time needed to reach the cecum, the degree of difficulty estimated by the endoscopist and the assistant, the level of pain at the end of the study estimated by the patient, and the endoscopic findings were all determined. RESULTS: Eighty-eight patients made up group I and 87 made up group II. No statistically significant differences were found between the two groups in relation to general characteristics, the number of complete colonoscopies (93 vs. 97%, respectively), the time needed to reach the cecum (8:00 vs. 8:41min, respectively), the level of pain at the end of the study, or the detection of polyps. The degree of difficulty was slightly lower in group II, but with no statistical significance. CONCLUSIONS: Lubrication with oil during colonoscopy did not improve the number of complete colonoscopies, did not facilitate the study, nor did it reduce pain or increase the diagnostic performance of the study, when compared with the conventional technique.

New approach to evaluate the lubrication process in various granule filling levels and rotating mixer sizes using a thermal effusivity sensor.

The principles of thermal effusivity are applied to an understanding of the detailed mechanisms of the lubrication process in a rotating mixer. The relationships and impact of the lubrication process by the pattern of powder flow, the filling level, and the rotating mixer size were investigated. Thermal effusivity profiles of the lubrication process, as obtained, indicate that lubrication is a two-phase process. The intersection point of the first and second phases (IPFS) is influenced by changing the filling level, thus changing the resulting number of avalanche flows created. The slope of the second phase (SSP) is influenced by the relationship between the number and the length of avalanche flows. Understanding this difference between the first and second phases is important to successfully evaluate the impact of proposed changes in the lubrication process. From this knowledge, a predictive model of the lubrication profile can be generated to allow an evaluation of proposed changes to the lubrication process. This model allows estimation of the lubrication profile at different filling levels and in different rotating mixer sizes. In this study, the actual lubrication profile almost coincides with the model predicted lubrication profile. Based on these findings, it is assumed that lubrication profiles at a commercial scale can be predicted from data generated at the laboratory scale. Further, it is assumed that changes in the filling level can also be estimated from the laboratory or current data.