Figure 5 - uploaded by Javier Sotres
Content may be subject to copyright.
![Schematic drawing of the oral cavity [97].](profile/Javier-Sotres/publication/259357833/figure/fig5/AS:297123783430169@1447851238813/Schematic-drawing-of-the-oral-cavity-97.png)
Source publication
![Figure 5. Schematic drawing of the oral cavity [97].](profile/Javier-Sotres/publication/259357833/figure/fig5/AS:297123783430169@1447851238813/Schematic-drawing-of-the-oral-cavity-97_Q320.jpg)
Interactions between surfaces are ubiquitous phenomena in living organisms. Nature has developed sophisticated strategies for lubricating these systems, increasing their efficiency and life span. This includes the use of water-based lubricants, such as saliva and synovial fluid. These fluids overcome the limitations of water as a lubricant by the p...
Context in source publication
Context 1
... serves as a secondary respiratory conduit, it enables speech by modifying the sound produced at the vocal folds and it also functions as a chemosensory organ. The oral cavity is bound by the lips, the oropharynx, the cheeks, and the hard and soft palates ( Figure 5). Oral surfaces are constantly exposed to mechanical stresses and strains during high-load bearing processes such as mastication [89] as well as during low-load bearing processes such as speech modulation [90]. ...
Similar publications
Our understanding of friction and mechanism of energy dissipation has undoubtedly experienced a tremendous profit after the introduction of scanning probe microscopy. Nowadays the tribological response of a sliding asperity can be easily traced down to the atomic scale. Still, many important aspects of friction on the nanoscale are scarcely studied...
Citations
... The viscosity was in the range of 12-65 mPa·s and depended on the concentration of hyaluronic acid. The higher the concentration, the higher the viscosity [23,41,42]. As in the case of our research, the shear thinning characteristic of non-Newtonian fluids was observed, which means that the viscosity of solutions decreases with increasing shear rate [21]. ...
... The obtained test results were promising. Furthermore, it is worth noting that density has a significant impact on the lubricating properties of hyaluronic acid solutions, and it grows with the concentration of HA [42]. ...
Synovial joints are a basic part of the human body. Lack of proper lubrication of joints can lead to significant wear of their surfaces. The tribological and rheological properties of artificial synovial fluid solutions based on hyaluronic acid were studied. It was found that the concentration of selected hyaluronic acid solutions significantly affects the investigated parameters. The most promising results were obtained for 8 wt% hyaluronic acid solution, which showed the highest viscosity and wettability, and the lowest wear.
... Given the vast range of possibilities for nanoparticles, additional reviews have highlighted numerous studies including organic and inorganic based nanoparticles effective in direct therapeutics and as delivery systems [7][8][9] What is lacking from many of these studies, however, is the consideration of joint movement and the impact of nanoparticle additives on sliding. An extensive collection of literature examines joint friction [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and mimetic materials such as hydrogels [26][27][28][29][30][31][32] (note the literature cited here is not a comprehensive list), yet few connect nanoparticles in synovial joints to sliding, and tend to focus on polymeric-based nanoparticles. In simulations by Jamalabadi [13] hollow silica nanoparticles with core/shell charged polymer brushes were evaluated in a modeled knee, finding that an increase in nanoparticle concentration decreased the maximum pressure on the squeeze film. ...
Nanoparticles are promising candidates as direct therapeutics and delivery systems for osteoarthritis treatments, primarily via intraarticular injection, but little is known about the impact on sliding behavior for a soft material surface like cartilage that would be encountered in a joint. Nanoparticle additives have primarily been studied in the context of hard material interfaces, such as metals or metal oxides, where different lubricating or anti-wear mechanisms depend sensitively on chemical composition, size, and concentration. To understand what nanoparticle parameters influence in situ (in a fluid environment) frictional behavior of soft materials, polyacrylamide (PAM) hydrogels were used as a model soft material platform. Friction tests were conducted in a rheometer with a tribology adapter, with PAM hydrogels molded in a petri dish and immersed in different nanoparticle containing fluid environments. A range of nanoparticle compositions were selected to compare broad categories: gold (metal) with a citrate capping ligand, nanodiamond (carbon), and zirconium dioxide (metal oxide). Comparing surface chemistry, concentration, and degree of aggregation, both nanoparticle surface chemistry and nanoparticle solution viscosity were found to modulate in situ hydrogel friction.
... However, these lubrication models do not fully explain the mechanisms of the joint lubrication and it is likely that a mixed regime operates including both fluid-film and boundary lubrication [5]. In the latter case, the nature of the boundary layer at the cartilage surface gains particular importance [5,14,15]. Thus, it was concluded that both bulk SF composition and the elements of interaction at the cartilage level have relevance in the analysis of SF lubrication. ...
The quality of the lubricant between cartilaginous joint surfaces impacts the joint’s mechanistic properties. In this study, we define the biochemical, ultrastructural, and tribological signatures of synovial fluids (SF) from patients with degenerative (osteoarthritis-OA) or inflammatory (rheumatoid arthritis-RA) joint pathologies in comparison with SF from healthy subjects. Phospholipid (PL) concentration in SF increased in pathological contexts, but the proportion PL relative to the overall lipids decreased. Subtle changes in PL chain composition were attributed to the inflammatory state. Transmission electron microscopy showed the occurrence of large multilamellar synovial extracellular vesicles (EV) filled with glycoprotein gel in healthy subjects. Synovial extracellular vesicle structure was altered in SF from OA and RA patients. RA samples systematically showed lower viscosity than healthy samples under a hydrodynamic lubricating regimen whereas OA samples showed higher viscosity. In turn, under a boundary regimen, cartilage surfaces in both pathological situations showed high wear and friction coefficients. Thus, we found a difference in the biochemical, tribological, and ultrastructural properties of synovial fluid in healthy people and patients with osteoarthritis and arthritis of the joints, and that large, multilamellar vesicles are essential for good boundary lubrication by ensuring a ball-bearing effect and limiting the destruction of lipid layers at the cartilage surface.
... From the above discussion, it follows that understanding how the structure and hydration of mucin films change when mechanically confined would be of high interest not only for understanding how mucous films protect biological barriers, but also for the rational design of mucin-based coatings. The study of soft matter films under mechanical confinement was originally made possible by the emergence of the Surface Force Apparatus and the Atomic Force Microscope [12]. These techniques provide accurate interaction forces at different separations. ...
Hypothesis: Among other functions, mucins hydrate and protect biological interfaces from mechanical challenges. Mucins also attract interest as biocompatible coatings with excellent lubrication performance. Therefore, it is of high interest to understand the structural response of mucin films to mechanical challenges. We hypothesized that this could be done with Neutron Reflectometry using a novel sample environment where mechanical confinement is achieved by inflating a membrane against the films.
Experiments: Oral MUC5B mucin films were investigated by Force Microscopy/Spectroscopy and Neutron Reflectometry both at solid-liquid interfaces and under mechanical confinement.
Findings: NR indicated that MUC5B films were almost completely compressed and dehydrated when confined at 1 bar. This was supported by Force Microscopy/Spectroscopy investigations. Force Spectroscopy also indicated that MUC5B films could withstand mechanical confinement by means of steric interactions for pressures lower than ∼0.5 bar i.e., mucins could protect interfaces from mechanical challenges of this magnitude while keeping them hydrated. To investigate mucin films under these pressures by means of the employed sample environment for NR, further technological developments are needed. The most critical would be identifying or developing more flexible membranes that would still meet certain requirements like chemical homogeneity and very low roughness.
... Friction and wear occur between moving materials in contact, the study of which is of fundamental importance in many applied sciences [1]. Lubricants, such as neat oils [2][3][4] and oil-in-water emulsions [5,6], have been extensively used to reduce the friction and wear, and satisfactory results have been obtained. To further enhance the friction-reduction and anti-wear properties of the oil-containing lubricants, great efforts have been directed towards incorporating different types of nanoadditives into the base lubricants [7][8][9]. ...
... In addition, the viscosity decreases with the increase of temperature [263], and it is a function of pressure throughout the inlet zone in metal rolling [264]. Most importantly, a higher viscosity leads to a lower COF due to a transition of lubrication regime from boundary lubrication into mixed or hydrodynamic lubrication [241], which indicates an increase in the thickness of lubricating film as per the well-known Stribeck curve [4]. This increased film thickness restrains the work rolls and workpiece from direct contact, leading to decreased friction in the contact zone. ...
Applying nanomaterials and nanotechnology in lubrication has become increasingly popular and important to further reduce the friction and wear in engineering applications. To achieve green manufacturing and its sustainable development, water-based nanolubricants are emerging as promising alternatives to the traditional oil-containing lubricants that inevitably pose environmental issues when burnt and discharged. This review presents an overview of recent advances in water-based nanolubricants, starting from the preparation of the lubricants using different types of nanoadditives, followed by the techniques to evaluate and enhance their dispersion stability, and the commonly used tribo-testing methods. The lubrication mechanisms and models are discussed with special attention given to the roles of the nanoadditives. Finally, the applications of water-based nanolubricants in metal rolling are summarised, and the outlook for future research directions is proposed.
... One method that has been used to overcome the shortage of HA in OA joints is its replenishment via intra-articular injection of high-MW HA (HHA), known as viscosupplementation. 6−11 In spite of the wide application of the HHA in viscosupplementation, there is still debate on whether it is significantly better than placebo. 8, 10,12,13 Indeed, the precise mechanistic role of HA in maintaining the health and effective lubrication of synovial joint is still not fully understood, 6,14 since HA solutions at the shear rates between cartilage surfaces in joints have viscosity close to water, 15,16 while boundary layers of HA on its own cannot provide the necessary lubrication to the healthy joints under high pressure, regardless of their MW. 17−20 Thus, it has been suggested that instead of working directly as a lubricant, HA is potentially interacting with other components in the cartilage to form supramolecular boundary layers, which in turn mediate the lubrication. ...
Osteoarthritic joints contain lower molecular weight (MW) hyaluronan (hyaluronic acid, HA) than healthy joints. To understand the relevance of this HA-size effect for joint lubrication, the friction and surface structure of cartilage-emulating surfaces with HA of different MW were studied using a surface force balance (SFB), and atomic force microscopy (AFM) . Gelatin (gel)-covered mica surfaces were coated with either high MW HA (HHA), medium MW HA (MHA) or low MW HA (LHA), and lipids of Hydrogenated Soy L-α-phosphatidylcholine (HSPC) in the form of small unilamellar vesicles, using a layer-by-layer assembly method. SFB results indicate that the gel-HHA-HSPC boundary layer provides very efficient lubrication, attributed to hydration lubrication at the phosphocholine head-groups exposed by the HA-attached lipids, with friction coefficients (COF) as low as l0-3-10-4 at contact stresses at least up to P = 120 atm. However, for the gel-MHA-HSPC and gel-LHA-HSPC surfaces, the friction, initially low, increases sharply at much lower pressures (up to 30-60 atm at most). This higher friction with the shorter chains may be due to their weaker total adhesion energy to the gelatin, where the attraction between the negatively-charged HA and the weakly-positively charged gelatin is attributed largely to counterion-release entropy. Thus the complexes of LHA and MHA with the lubricating HSPC lipids are more easily removed by shear during sliding, especially at high stresses, than is the HHA-HSPC complex which is strongly adhered to the gelatin. This is ultimately the reason for lower-pressure lubrication breakdown with the shorter polysaccharides. Our results provide molecular level insight into why the decrease in HA molecular weight in osteoarthritic joints may be associated with higher friction at the articular cartilage surface, and may have relevance for treatments of osteoarthritis involving intra-articular HA injections.
... Friction and wear inevitably occur during rolling process, which leads to loss of energy and wear of work rolls [2][3][4]. Lubricants, including traditional neat oils [5][6][7] and oil-in-water emulsions [8,9], have thus been applied to solve these issues due to their excellent lubricating properties. The use of oil-containing lubricants, however, unavoidably generates contamination to the environment, especially when burnt and discharged [6]. ...
... Prior to the understanding of possible lubrication mechanisms, it is imperative to determine the lubrication regime in the testing condition. As is well-known, there are three types of lubrication regimes as defined from the Stribeck curve, including boundary lubrication, mixed lubrication and hydrodynamic lubrication [7]. The lubrication regime can be approximately determined by the lambda ratio (λ) in equation (1), where λ is the minimum film thickness (h min ) in relation to the combined surface roughness of the friction pair (R ′ q ). ...
Novel water-based nanolubricants using TiO2 nanoparticles (NPs) were synthesised by adding sodium dodecyl benzene sulfonate (SDBS) and glycerol, which exhibited excellent dispersion stability and wettability. The tribological performance of the synthesised nanolubricants was investigated using an Rtec ball-on-disk tribometer, and their application in hot steel rolling was evaluated on a 2-high Hille 100 experimental rolling mill, in comparison to those without SDBS. The water-based nanolubricant containing 4 wt% TiO2 and 0.4 wt% SDBS demonstrated superior tribological performance by decreasing coefficient of friction and ball wear up to 70.5% and 84.3%, respectively, compared to those of pure water. In addition to the lubrication effect, the suspensions also had significant effect on polishing of the work roll surface. The resultant surface improvement thus enabled the decrease in rolling force up to 8.3% under a workpiece reduction of 30% at a rolling temperature of 850 °C. The lubrication mechanisms were primarily ascribed to the formation of lubricating film and ball-bearing effect of the TiO2 NPs.
... This makes media additives an attractive option for modifying spheroid surface interactions. Possible additives for future research include biological lubricants such as those found the synovial fluid [14], water-based lubricants such as methylcellulose, ionic and anionic detergents, and various poloxamers [15]. ...
Background:
In current cancer spheroid culturing methods, the transfer and histological processing of specimens grown in 96-well plates is a time consuming process. A centrifugal fluidic device was developed and tested for rapid extraction of spheroids from a 96-well plate and subsequent deposition into a molded agar receiver block. The deposited spheroids must be compact enough to fit into a standard histology cassette while also maintaining a highly planar arrangement. This size and planarity enable histological processing and sectioning of spheroids in a single section. The device attaches directly to a 96-well plate and uses a standard centrifuge to facilitate spheroid transfer. The agar block is then separated from the device and processed.
Results:
Testing of the device was conducted using six full 96-well plates of fixed Pa14C pancreatic cancer spheroids. On average, 80% of spheroids were successfully transferred into the agar receiver block. Additionally, the planarity of the deposited spheroids was evaluated using confocal laser scanning microscopy. This revealed that, on average, the optimal section plane bisected individual spheroids within 27% of their mean radius. This shows that spheroids are largely deposited in a planar fashion. For rare cases where spheroids had a normalized distance to the plane greater than 1, the section plane either misses or captures a small cross section of the spheroid volume.
Conclusions:
These results indicate that the proposed device is capable of a high capture success rate and high sample planarity, thus demonstrating the capabilities of the device to facilitate rapid histological evaluation of spheroids grown in standard 96-well plates. Planarity figures are likely to be improved by adjusting agar block handling prior to imaging to minimize deformation and better preserve the planarity of deposited spheroids. Additionally, investigation into media additives to reduce spheroid adhesion to 96-well plates would greatly increase the capture success rate of this device.
... Lubrication technology is one of the most useful approaches to solve these issues as the primary causes of energy loss in engineering fields are friction and wear [6]. It is welldocumented that the conventional lubricating system including base oils such as mineral oil [7], synthetic oil [8] and biological oil [9], oilin-water emulsions [10,11] and other oil-based lubricants [12][13][14] can decrease friction and wear to a certain extent. The application and discharge of oil, however, inevitably trigger environmental issues due to its nonbiodegradable nature and inherent toxicity [7]. ...
... 10 It is well-known that natural joints have an excellent tribological performance, with friction coefficient less than 0.001, 11 and average bearing capacity of 5 MPa (20 MPa in some areas). 12 The macromolecules in synovial fluid, such as hyaluronic acid (HA), lubricin, aggrecan, and phospholipids, 13,14 play an important role. It was reported that the HA had poor lubrication, 15 but it contributed greatly to the bearing capacity and the wear prevention of cartilage. ...
... It is known that the physiological pressure in human joints is 5−20 MPa and the friction coefficient is 0.001 or even lower. 11,12 Therefore, the high bearing capacity and the low friction are achieved in the first lubrication region, which is similar to the natural joints. ...
Liposomes have been considered as the boundary lubricant in natural joints. They are also the main component of bionic lubricant. In this study, the tribological properties of liposomes on Ti6Al4V/polymer surface were studied by atomic force microscope (AFM) at the nanoscale. The superlubricity with a friction coefficient of 0.007 was achieved under the maximal pressure of 15 MPa, consisting with the lubrication condition of natural joints. Especially, when the AFM probe was hydrophilically modified and pre-adsorbed, the friction coefficient and load bearing capacity could be further improved. In addition, probe with large radius could maintain the stable lubrication of liposomes in the contact zone. Finally, an optimal lubrication model of liposomes was established and the critical force for superlubricity was also proposed. It was the boundary between elastic deformation and plastic deformation for vesicles. It was also the indicator of plough effect appearing on the adsorbed layer. This work reveals the interfacial behavior of liposomes and realizes the controllable superlubricity system, providing more guidance for clinical application.
