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The effect of temperature on supported dipalmitoylphosphatidylcholine (DPPC) bilayers: Structure and lubrication performance
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
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2015 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 445, 84-92 p.Article in journal (Refereed) Published
Abstract [en]

Phospholipids fulfill an important role in joint lubrication. They, together with hyaluronan and glycoproteins, are the biolubricants that sustain low friction between cartilage surfaces bathed in synovial fluid. In this work we have investigated how the friction force and load bearing capacity of 1,2-dipalmitoyl-snglycero-3-phosphocholine (DPPC) bilayers on silica surfaces are affected by temperature, covering the temperature range 25-52 degrees C. Friction forces have been determined utilizing the AFM colloidal probe technique, which showed that DPPC bilayers are able to provide low friction forces over the whole temperature interval. However, the load bearing capacity is improved at higher temperatures. We interpret this finding as being a consequence of lower rigidity and higher self-healing capacity of the DPPC bilayer in the liquid disordered state compared to the gel state. The corresponding structure of solid supported DPPC bilayers at the silica-liquid interface has been followed using X-ray reflectivity measurements, which suggests that the DPPC bilayer is in the gel phase at 25 degrees C and 39 degrees C and in the liquid disordered state at 55 degrees C. Well-defined bilayer structures were observed for both phases. The deposited DPPC bilayers were also imaged using AFM PealcForce Tapping mode, and these measurements indicated a less homogeneous layer at temperatures below 37 degrees C.

Place, publisher, year, edition, pages
2015. Vol. 445, 84-92 p.
Keyword [en]
Phospholipid bilayer, DPPC, X-ray reflectivity, AFM, Surface forces, Friction, Lubrication, Load bearing capacity
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-156653DOI: 10.1016/j.jcis.2014.12.042ISI: 000350006700011PubMedID: 25596372ScopusID: 2-s2.0-84921024640OAI: diva2:767632
Swedish Research Council, B0330901

QC 20150409. Updated from manuscript to article in journal.

Available from: 2014-12-02 Created: 2014-12-02 Last updated: 2015-04-09Bibliographically approved
In thesis
1. Biolubricants and Biolubrication
Open this publication in new window or tab >>Biolubricants and Biolubrication
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main objective of this thesis work was to gain understanding of the principles of biolubrication, focusing on synergistic effects between biolubricants. To this end surface force and friction measurements were carried out by means of Atomic Force Microscopy, using hydrophilic and hydrophobic model surfaces in salt solutions of high ionic strength (≈ 150 mM) in presence of different biolubricants. There was also a need to gain information on the adsorbed layers formed by the biolubricants. This was achieved by using a range of methods such as Atomic Force Microscopy PeakForce imaging, Quartz Crystal Microbalance with Dissipation, Dynamic Light Scattering and X-Ray Reflectometry. By combining data from these techniques, detailed information about the adsorbed layers could be obtained.The biolubricants that were chosen for investigation were a phospholipid, hyaluronan, lubricin, and cartilage oligomeric matrix protein (COMP) that all exist in the synovial joint area. First the lubrication ability of these components alone was investigated, and then focus was turned to two pairs that are known or assumed to associate in the synovial area. Of the biolubricants that were investigated, it was only the phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) that was found to be an efficient lubricant on its own. Deposited DPPC bilayers on silica surfaces were found to be able to provide very low friction coefficients (≈ 0.01) up to high pressures, ≈ 50 MPa. A higher load bearing capacity was found for DPPC in the liquid crystalline state compared to in the gel state.The first synergy pair that was explored was DPPC and hyaluronan, that is known to associate on the cartilage surface, and we also noticed association between hyaluronan and DPPC vesicles as well as with adsorbed DPPC bilayers. By combining these two components a lubrication performance similar to that of DPPC alone could be achieved, even though the friction coefficient in presence of hyaluronan was found to be slightly higher. The synergy here is thus not in form of an increased performance, but rather that the presence of hyaluronan allows a large amount of the phospholipid lubricant to accumulate where it is needed, i.e. on the sliding surfaces.The other synergy pair was lubricin and COMP that recently has been shown to be co-localized on the cartilage surface, and thus suggested to associate with each other. Lubricin, as a single component, provided poor lubrication of PMMA surfaces, which we utilized as model hydrophobic surfaces. However, if COMP first was allowed to coat the surface, and then lubricin was added a low friction coefficient (≈ 0.03) was found. In this case the synergy arises from COMP facilitating strong anchoring of lubricin to the surface in conformations that provide good lubrication performance.

Abstract [sv]

Huvudsyftet med det här avhandlingsarbetet var att öka förståelsen för den låga friktion som finns i vissa biologiska system, med fokus på synergistiska effekter mellan de smörjande molekylerna. För detta ändamål studerades ytkrafter och friktion med hjälp av atomkraftsmikroskopi. Mätningarna utfördes med hydrofila och hydrofoba modellytor i lösningar med hög salthalt (≈ 150 mM) i närvaro av smörjande biomolekyler. Det var också nödvändigt att få information om de adsorberade skikten av biomolekyler. Det åstadkoms med hjälp av en rad tekniker så som AFM PeakForce avbildning, kvartskristallmikrovåg, dynamisk ljusspridning och röntgen reflektometri. Genom att kombinera data från dessa tekniker erhölls detaljerad information om de smörjande skikten.De smörjande biomolekyler som valdes ut för studierna var en fosfolipid, hyaluronan, lubricin, and cartilage oligomeric matrix protein (COMP) vilka alla finns i synovialledsområdet. Först undersöktes den smörjande förmågan hos dessa komponenter var för sig, och sedan fokuserade vi på två par av biomolekyler som man vet eller antar bildar associationsstrukturer i synovialleder. Av de enskilda biomolekyler som undersöktes var det endast fosfolipiden 1,2-dipalmitoyl-sn-glycero-3-fosfokoline (DPPC) som visade sig vara en effektivt smörjande molekyl. Deponerade biskikt av DPPC på silikaytor gav upphov till mycket låga friktionskoefficienter (≈ 0.01) upp till höga pålagda tryck, ≈ 50 MPa. DPPC bilager i flytande kristallin fas visade sig ha högre lastbärande förmåga än DPPC bilager i geltillstånd.Det första synergistiska par som undersöktes var DPPC och hyaluronan vilka man vet associerar på broskytan, och vi visade att hyaluronan associerar med såväl DPPC vesiklar som med DPPC bilager. Genom att kombinera dessa två komponenter uppmättes en smörjande förmåga som var jämförbar med den som DPPC ensam uppvisar. Även om friktionskoefficienten var något högre i närvaro av hyaluronan. Synergieffekten här består inte av en bättre smörjande förmåga, utan istället gör närvaron av hyaluronan att de smörjande fosfolipiderna kan ansamlas i stora mängder där de behövs, dvs. på de glidande ytorna.Det andra synergiparet var lubricin och COMP vilka nyligen har visats vara lokaliserade på samma platser på broskytan, vilket tyder på att de associerar med varandra. På egen hand var lubricins smörjande förmåga av PMMA, våra hydrofoba modellytor, dålig. Emellertid, om COMP först adsorberades på PMMA och sedan lubricin tillsattes uppmättes en låg friktionskoefficient (≈ 0.03). I det här fallet består synergin av att COMP möjliggör en stark inbindning till ytan av lubricin i konformationer som ger god smörjande förmåga.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. vi, 62 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:56
Hyaluronan, Phospholipid, Lubricin, Cartilage Oligomeric Matrix Protein, COMP, Adsorption, Surface Force, Friction, Biolubrication, Boundary Lubrication, Load Bearing Capacity, Synergistic Effects, DLS, QCM-D, AFM., Hyaluronan, Fosfolipid, Lubricin, Cartilage Oligomeric Matrix Protein, COMP, Adsorption, Ytkraft, Friktion, Biologisk smörjning, Gränsskiktssmörjning, Lastbärande förmåga, Synergieffekter, DLS, QCM-D, AFM.
National Category
Physical Chemistry Polymer Chemistry
Research subject
urn:nbn:se:kth:diva-156632 (URN)978-91-7595-348-9 (ISBN)
Public defence
2014-12-16, E3, Osquarsbacke 14, KTH, Stockholm, 10:00 (English)
Stiftelsen för strategisk forskning - SSF

QC 20141202

Available from: 2014-12-02 Created: 2014-12-01 Last updated: 2014-12-02Bibliographically approved

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