An energy conservation approach to adsorbate-induced surface stress and the extraction of binding energy using nanomechanics

Pinnaduwage, Lal A.; Boiadjiev, V.; Hawk, J. E.; Gehl, Anthony C.; Fernando, Gayanath; Wijewardhana, L. C. R.

doi:10.1088/0957-4484/19/10/105501

Cited by 10 publications

(19 citation statements)

References 33 publications

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“…We utilized microcantilever sensors to study the interactions of Pluronic copolymer with SLBs; these sensors are capable of sensitively measuring the surface stress changes associated with liquid-solid systems. 32 Surface-coated lms, which are either physisorbed or chemisorbed on a biomaterial cantilever, cause a surface free energy change that results in cantilever bending, 33 which can be readily detected using a positionsensitive detector. Conformational changes in the adsorbed molecular lms have been readily observed using microcantilevers.…”

Section: Introductionmentioning

confidence: 99%

Probing the association of triblock copolymers with supported lipid membranes using microcantilevers

2014

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Pluronics are a class of amphiphilic triblock copolymers that are known to interact with cellular membranes in interesting ways. The solubility of these triblock copolymers in free lipid membranes can be altered with temperature, allowing the possibility of tuning their membrane insertion. However, for supported lipid membranes, the asymmetric local environment and the strong influence of the solid support can alter the solubility of these triblock copolymers in lipid membranes. Here, we probe the interactions of these copolymers with supported lipid membranes using microcantilevers and fluorescence recovery after photobleaching (FRAP) measurements. We measure the solubility and interactions of triblock copolymers (F68 and F98) in supported lipid bilayers as a function of temperature and the length of the copolymer lipophilic block. A Langmuir isotherm model and a free mean area theory are applied to describe the polymer-lipid interactions at the microcantilever surface, determine association constants, and analyze the effect of triblock copolymers on lateral lipid diffusion.

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Section: Introductionmentioning

confidence: 99%

Probing the association of triblock copolymers with supported lipid membranes using microcantilevers

2014

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“…The vesicle solution flows through the measurement chamber from 240 to 720 s. As vesicles fuse onto the SiO 2 surface and rupture to form a planar lipid bilayer, a compressive surface stress is induced, causing the cantilever to bend toward the gold side. The free energy of adsorption is transferred to the solid as a surface free energy at the solid–water–lipid interface . This surface free energy disturbs the atoms of the solid surface, leading to a surface stress in the solid that deforms the material laterally.…”

Section: Resultsmentioning

confidence: 99%

“…The free energy of adsorption is transferred to the solid as a surface free energy at the solid−water−lipid interface. 25 This surface free energy disturbs the atoms of the solid surface, leading to a surface stress in the solid that deforms the material laterally. Because of a surface stress mismatch between bulk and surface, the cantilever bends toward the gold surface.…”

Section: ■ Thermal Expansion Coefficient Analysismentioning

confidence: 99%

“…Changes in the Gibbs free energy of surface-coated films, either physisorbed or chemisorbed on the cantilever surface, are coupled to changes in the surface free energy of the solid surface. These lead to changes in the surface stress, thus resulting in cantilever bending . Microcantilevers also respond to temperature variations, which enable them to function as temperature or heat flow sensors .…”

Section: Introductionmentioning

confidence: 99%

“…These lead to changes in the surface stress, thus resulting in cantilever bending. 25 Microcantilevers also respond to temperature variations, which enable them to function as temperature or heat flow sensors. 26 In this paper, we use microcantilevers to probe the solid−liquid phase transition temperature T m of phospholipid bilayers and monolayers supported on a silicon dioxide surface.…”

Section: ■ Introductionmentioning

confidence: 99%

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Lipid Bilayer Phase Transformations Detected Using Microcantilevers

et al. 2013

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We report the use of microcantilevers to measure the phase transition temperature (T(m)) of supported lipid bilayers or lipid monolayers. During the solid-liquid phase transition, a supported lipid bilayer or monolayer undergoes a conformational change in which the lipid acyl chains transition from an ordered state to a disordered state. This process is accompanied by a free energy change, which is coupled to changes in the surface stress in the underlying solid support layer. These surface stress changes can be readily detected using microcantilevers. The surface stress of the solid-like phase of 1-myristoyl-2-palmitoyl-sn-glycero-3-phosphocholine (MPPC) decreases linearly as the temperature increases and abruptly jumps at the main phase transition temperature. This phase transition temperature corresponds well with that found for free membranes. For an MPPC monolayer, this phase transition temperature is shifted, indicating that the existence of the solid support affects the monolayer structure. The addition of cholesterol into the bilayer decreases the phase transition temperature by ~0.38 °C per mol % of cholesterol. Differences in MPPC stability when it is either a bilayer or a monolayer can be detected through these sensitive surface stress measurements.

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Using Microcantilevers to Study the Interactions of Lipid Bilayers with Solid Surfaces

Liu

Biswal

2010

Anal. Chem.

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We report the use of free-standing microcantilever beams, which have been used as an ultrasensitive method for measuring the surface free energy changes on a substrate induced by the adsorption of thin films, to probe the interactions between a solid surface and a phospholipid bilayer. We relate the observed deflection of a cantilever to the changes in the surface free energy of the solid surface which supports the phospholipid bilayer. We observe that the deflection is influenced by electrostatic and intermolecular interactions of the bilayer with the substrate. Increasing the surface charge density in the supported lipid bilayer (SLB), by increasing the ratio of cationic to zwitterionic lipids in bilayer, resulted in an increase in cantilever deflection. The surface free energy changes due to lipid transfer between anionic unilamellar vesicles and a cationic supported bilayer were also observed using microcantilevers. Finally, the adsorption free energy of a mixed lipid and cholesterol bilayer was measured demonstrating a detectable decrease in affinity between the phospholipid bilayer and the solid surface as a result of the addition of cholesterol. Our results reveal a new technique to probe the adsorption free energy of a SLB system as a function of the interactions governing the structure of supported lipid membranes.

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An energy conservation approach to adsorbate-induced surface stress and the extraction of binding energy using nanomechanics

Cited by 10 publications

References 33 publications

Probing the association of triblock copolymers with supported lipid membranes using microcantilevers

Probing the association of triblock copolymers with supported lipid membranes using microcantilevers

Lipid Bilayer Phase Transformations Detected Using Microcantilevers

Using Microcantilevers to Study the Interactions of Lipid Bilayers with Solid Surfaces

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