Nanomechanical Properties of Phospholipid Microbubbles

Abstract

This study uses atomic force microscopy (AFM) force-deformation (F-Δ) curves to investigate for the first time the Young's modulus of a phospholipid microbubble (MB) ultrasound contrast agent. The stiffness of the MBs was calculated from the gradient of the F-Δ curves, and the Young's modulus of the MB shell was calculated by employing two different mechanical models based on the Reissner and elastic membrane theories. We found that the relatively soft phospholipid-based MBs behave inherently differently to stiffer, polymer-based MBs [Glynos, E.; Koutsos, V.; McDicken, W. N.; Moran, C. M.; Pye, S. D.; Ross, J. A.; Sboros, V. Langmuir2009, 25 (13), 7514-7522] and that elastic membrane theory is the most appropriate of the models tested for evaluating the Young's modulus of the phospholipid shell, agreeing with values available for living cell membranes, supported lipid bilayers, and synthetic phospholipid vesicles. Furthermore, we show that AFM F-Δ curves in combination with a suitable mechanical model can assess the shell properties of phospholipid MBs. The "effective" Young's modulus of the whole bubble was also calculated by analysis using Hertz theory. This analysis yielded values which are in agreement with results from studies which used Hertz theory to analyze similar systems such as cells.

Nanomechanics of phospholipid LB film studied layer by layer with AFM

“…Therefore, the mechanics of both the first lipid layer and the second layer are closely related to the biological functions of cells. Nanomechanical properties have been explored by Atomic Force Microscope (AFM), micropipet or other techniques in phospholipid microbubbles [ 10 ], vesicles [ 7 ] and living cells [ 11 ]. Recently, studies on nanomechanical properties of phospholipid layers have been focused by experimental and numerical analysis [ 12 ].…”

Spatial selective manipulation of microbubbles by tunable surface acoustic waves

“…MBs were chosen to demonstrate the performance of the microfluidic device since the response of MBs to acoustic wave is sensitive and the behavior of MBs in acoustic field is similar to the cells 43 . The octafluoropropane (C 3 F 8 ) gas-filled MBs were fabricated in-house by the mechanical agitation method 44 .…”

Atomic force microscopy of food assembly: Structural and mechanical insights at the nanoscale and potential opportunities from other fields

“…The use of AFM indentation at liquid/liquid or liquid/air interfaces to measure the stiffness of sessile liquid droplets has been explored but is still difficult to implement (Costa, Li-Destri, Pontoni, Konovalov, & Thomson, 2017;Munz & Mills, 2014;Wang et al, 2016). Similarly, calculation of the stiffness or the Young's modulus of filled microcapsules (Berry, Mettu, & Dagastine, 2017;Sarrazin et al, 2016;Tan et al, 2016) or phospholipid-shelled microbubbles (Buchner Santos, Morris, Glynos, Sboros, & Koutsos, 2012;Grant et al, 2012) requires further mathematical developments. These approaches have only been used limitedly with food systems, e.g., edible~1 MPa microcapsules of pea proteins (Ye et al, 2016) or emulsion droplets (Wackerbarth et al, 2009).…”