Lubrication
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The aim of the present paper is to provide a novel experimental approach enabling to assess the thickness of lubricant film within hip prostheses in meaning of the contribution of particular proteins. Thin film colorimetric interferometry was combined with fluorescent microscopy finding that a combination of optical methods can help to better understand the interfacial lubrication processes in hip replacements. The contact of metal femoral head against a glass disc was investigated under various operating conditions. As a test lubricant, the saline solution containing the albumin and γ-globulin in a concentration 2:1 was employed. Two different mean speeds were applied, 5.7 and 22mm/s, respectively. The measurements were carried out under pure rolling, partial negative and partial positive sliding conditions showing that kinematic conditions substantially affects the formation of protein film. Under pure rolling conditions, an increasing tendency of lubricant film independently on rolling speed was detected, while the total thickness of lubricant film can be attributed mainly to albumin. When the ball was faster than the disc (negative sliding), a very thin lubricant film was observed for lower speed with no significant effect of particular proteins. The increase in sliding speed led to the increase of film thickness mainly caused due to the presence of γ-globulin. On the contrary, when the disc was faster than the ball (positive sliding), the film formation was very complex and time dependent while both of the studied proteins have shown any qualitative change during the test, however the effect of albumin seems to be much more important. Since a very good agreement of the results was obtained, it can be concluded that the approach consisting of two optical methods can provide the fundamental information about the lubricant film formation in meaning of particular proteins while the simultaneous presence of other constituents in model synovial fluid.
The objective of the present study is to clarify the lubrication processes within artificial joints considering the ceramic femoral heads focusing on the role of particular proteins. Two optical methods were employed; colorimetric interferometry and fluorescent microscopy. The experiments were conducted in ball-on-disc configuration, where the ball is made from ceramic (Sulox(TM), BIOLOX(®)delta) and the disc from optical glass. The measurements were realized under pure rolling, partial negative and partial positive sliding, to get a complex information about the protein film behaviour under various conditions. Moreover, two different speeds were investigated; 5.7 and 22 mm/s, respectively. The contact was lubricated by saline solutions containing albumin and γ-globulin in a ratio 2:1, while the total protein concentration was 10.5 mg/ml. Under pure rolling conditions, the film thickness gradually increases with time/rolling distance independently of material and rolling speed, while the dominant fluid constituent is albumin. In the case of negative sliding, the film formation is time/distance/speed dependent. At lower speed, both proteins contribute to film thickness; at higher speed, the effect of γ-globulin is not substantial. When the disc is faster, the character of film formation is similar to the metal component in the case of Sulox ceramic. Biolox ceramic shows a different behaviour, while for both materials, the contribution of γ-globulin increases with increasing speed. As most of the results can be well explained in terms of specific proteins, it can be concluded that the experimental approach is suitable for the investigation of protein film formation considering the ceramic materials.
- MeSH
- albuminy chemie MeSH
- gama-globuliny chemie MeSH
- keramika * MeSH
- kyčelní protézy * MeSH
- lidé MeSH
- lubrikace * MeSH
- náhrada kyčelního kloubu MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Effective lubrication of synovial joints is important to prevent cartilage degeneration and to keep the joints healthy. This paper sets out the basics of engineering lubrication with respect to the composition and properties of synovial fluid constituents. Two basic types of boundary lubrication are discussed: the presence of highly hydrophilic proteoglycans that provide a water liquid film, and the existence of multilamellar phospholipids lubricating layers at the surface ofarticular cartilage. Based on current knowledge, we may conclude that no single mechanism of boundary lubrication exists, and that effective boundary lubrication of synovial joints is maintained by the synergic effect of all synovial fluid constituents.
- MeSH
- bioinženýrství * MeSH
- fosfolipidy farmakologie MeSH
- glykoproteiny farmakologie MeSH
- hydrodynamika MeSH
- kloubní chrupavka fyziologie MeSH
- kyselina hyaluronová fyziologie MeSH
- lidé MeSH
- lubrikanty farmakologie MeSH
- nemoci chrupavky patofyziologie prevence a kontrola terapie MeSH
- osteoartróza patofyziologie prevence a kontrola terapie MeSH
- povrchové vlastnosti MeSH
- rozsah kloubních pohybů fyziologie MeSH
- synoviální tekutina fyziologie MeSH
- viskozita MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
Hyaluronan (HA) is widely used for eye drops as lubricant to counteract dry eye disease. High and low molecular weight HA are currently used in ophthalmology. However, a large portion of the current literature on friction and lubrication addresses articular (joint) cartilage. Therefore, eye drops compositions based on HA and its derivatized forms are extensively characterized providing data on the tribological and mucoadhesive properties. The physiochemical properties are investigated in buffers used commonly in eye drops formulations. The tribological investigation reveals that amphiphilic HA-C12 decreases the friction coefficient. At the same time, the combination of trehalose/HA or HAC12 enhances up to eighty-fold the mucoadhesiveness. Thus, it is predicted a prolonged residence time on the surface of the eye. The incorporation of trehalose enhances the protection of human keratinocytes (HaCaT) cells, as demonstrated in an in-vitro cell-desiccation model. The presence of trehalose increases the friction coefficient. Medium molecular weight HA shows significantly lower friction coefficient than high molecular weight HA. This research represents a first, wide array of features of diverse HA forms for eye drops contributing to increase the knowledge of these preparations. The results here presented also provide valuable information for the design of highly performing HA-formulations addressing specific needs before preclinic.
- MeSH
- adhezivita MeSH
- buněčné linie keratinocytů HaCaT MeSH
- filtrace MeSH
- hlen účinky léků MeSH
- kyselina hyaluronová chemická syntéza chemie farmakologie MeSH
- lékové transportní systémy * MeSH
- lidé MeSH
- lubrikace * MeSH
- nefelometrie a turbidimetrie MeSH
- oči účinky léků MeSH
- oční roztoky farmakologie MeSH
- protonová magnetická rezonanční spektroskopie MeSH
- reologie MeSH
- sterilizace MeSH
- tření MeSH
- viskozita MeSH
- vysoušení MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- artroplastiky kloubů metody využití MeSH
- biomechanika MeSH
- kyselina hyaluronová terapeutické užití MeSH
- lidé MeSH
- lubrikanty * chemie terapeutické užití MeSH
- mechanické jevy MeSH
- protézy a implantáty MeSH
- protézy kloubů * využití MeSH
- synoviální tekutina * MeSH
- testování materiálů metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
Co-processed dry binders for ODTs are important multifunctional excipients for tablet manufacturing by direct compression. Testing their binary mixtures with lubricants is an important aspect of their use in combination with drugs. The aim of this study was to evaluate the rheological and compression properties of lubricated mixtures of co-processed dry binders Parteck® ODT, Prosolv® ODT G2 and Ludiflash®, and subsequently also the compactability and disintegration time of the tablets made thereof. The lubricants employed were magnesium stearate and sodium stearyl fumarate in the concentrations of 0.5% and 1%. The best flowability was shown by Prosolv® ODT G2 combined with magnesium stearate in the concentration of 0.5%. Lubricated mixtures with Prosolv® ODT G2 showed a lower angle of internal friction as well as lower pre-compression energy values. The values of plastic deformation energy were the highest in the case of Prosolv® ODT G2, which was also reflected in the highest tablet strength. On the contrary, the ejection force values were the lowest for this co-processed dry binder. Magnesium stearate reduced the ejection force more effectively than sodium stearyl fumarate. Prosolv® ODT G2 tablets exhibited the highest tensile strength and shortest disintegration time.
- MeSH
- lubrikanty * MeSH
- pevnost v tahu MeSH
- pomocné látky * MeSH
- tablety MeSH
- Publikační typ
- časopisecké články MeSH
Wear testing of total joint replacement (TJR) is mandatory in preclinical testing before implantation of TJR into the human body. Testing is governed by current international standards that recommend bovine serum (BS) as a lubricating fluid to replace synovial fluid (SF). Recently, the use of BS has been criticized because of differences in content, fluid characteristics, and nonhuman origin. As a result, a more realistic lubricant mimicking SF is needed. To define SF composition, we analyzed SF obtained during revisions of total hip and knee arthroplasties and compared it with SF obtained during primary arthroplasties and from patients without TJR. Samples were acquired from 152 patients. We found that the median total protein concentration for all SF was 36.8 mg/mL, which is significantly higher than concentrations currently recommended by the ISO standards. The γ-globulin concentration was significantly higher and the phospholipid concentration significantly lower in patients with revision of TJR compared with patients without TJR. No significant difference was found in hyaluronic acid concentration and viscosity among the groups. Our results support the need to improve the definition of a more clinically relevant wear testing lubricant in the ISO standards. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1422-1431, 2017.
- MeSH
- biomimetické materiály chemie MeSH
- dospělí MeSH
- fosfolipidy analýza metabolismus MeSH
- gama-globiny analýza metabolismus MeSH
- lidé středního věku MeSH
- lidé MeSH
- lubrikanty chemie MeSH
- náhrada kyčelního kloubu MeSH
- senioři MeSH
- synoviální tekutina chemie metabolismus MeSH
- totální endoprotéza kolene MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Total knee arthroplasty has become a routine procedure for patients suffering from joint diseases. Although the number of operations continuously increases, a limited service-life of implants represents a persisting challenge for scientists. Understanding of lubrication may help to suitably explain tribological processes on the way to replacements that become durable well into the third decade of service. The aim of the present study is to assess the formation of protein lubricating film in the knee implant. A developed knee simulator was used to observe the contact of real femoral and transparent polymer tibial component using fluorescent microscopy. The contact was lubricated by various protein solutions with attention to the behaviour of albumin and γ-globulin. In order to suitably mimic a human synovial fluid, hyaluronic acid and phospholipids were subsequently added to the solutions. Further, the change in shape and the migration of the contact zone were studied. The results showed considerable appearance differences of the contact over the swing phase of the simplified gait cycle. Regarding film formation, a strong interaction of the various molecules of synovial fluid was observed. It was found that the thickness of the lubricating layer stabilizes within around 50 s. Throughout the contact zone, protein agglomerations were present and could be clearly visualised using the applied optical technique.
- MeSH
- albuminy MeSH
- gama-globuliny MeSH
- kolenní kloub MeSH
- lidé MeSH
- lubrikace MeSH
- synoviální tekutina * MeSH
- totální endoprotéza kolene * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The aim of the present study is to provide an analysis of protein film formation in hip joint replacements considering real conformity based on in situ observation of the contact zone. The main attention is focused on the effect of implant nominal diameter, diametric clearance and material. For this purpose, a pendulum hip joint simulator equipped with electromagnetic motors enabling to apply continuous swinging flexion-extension motion was employed. The experimental configuration consists of femoral component (CoCrMo, BIOLOX®forte, BIOLOX®delta) and acetabular cup from optical glass fabricated according to the dimensions of real cups. Two nominal diameters were studied, 28 and 36mm, respectively, while different diametric clearances were considered. Initially, a static test focused on the protein adsorption onto rubbing surfaces was performed with 36mm implants. It was found that the development of adsorbed layer is much more stable in the case of metal head, indicating that the adsorption forces are stronger compared to ceramic. A consequential swinging test revealed that the fundamental parameter influencing the protein film formation is diametric clearance. Independently of implant diameter, film was much thicker when a smaller clearance was considered. An increase of implant size from 28mm to 36mm did not cause a substantial difference in film formation; however, the total film thickness was higher for smaller implant. In terms of material, metal heads formed a thicker film, while this fact can be, among others, also attributed to clearance, which is more than two times higher in the case of ceramic implant.
