Force spectroscopy of streptavidin conjugated lipid coated microbubbles

Targeted ultrasound contrast agents for ultrasound molecular imaging and therapy

“…However, our results clearly show an increase of the resonance frequency and thus of the elasticity, which corresponds with the results obtained using AFM [74,75]. The increase in elasticity after functionalisation is believed to be due to the presence of crystallisation of streptavidin around the lipid shell forming a stiffer external layer [75] as also observed on streptavidin-functionalised giant unilamellar phospholipid vesicles [79,80].…”

“…However, the increase in elasticity between PEGylated and nonPEGylated MBs might actually be a consequence of the different lipids that were used for both bubble types: DSPE or DOPE as it has recently been shown that the main lipid of non-targeted biotinylated MBs changes the distribution of the lipids in the shell and its shell properties [13,14]. The authors do not explain the large difference in stiffness values between both studies [74,75]. Indeed, there does not seem to be a straightforward explanation.…”

“…Using AFM, an elasticity was found that was almost 30 Â higher for streptavidin-functionalised bubbles than for bare lipid-coated bubbles (710 ± 41 vs. 25 ± 1.4 mN/m; DPPC:PE-biotin, 90:10 mol%) [74]. Recently, the same group performed AFM studies on bubbles with a C 3 F 8 core and a lipid-coating of DPPC:DSPE-PEG(2000)-biotin or DPPC:DOPE-biotin (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-biotin) in a 90:10 ratio [75].…”

Temperature dependent stiffness and visco-elastic behaviour of lipid coated microbubbles using atomic force microscopy

“…Increasing the temperature could either lead to an increase in the gas pressure, which would concomitantly lead to an increase in the stiffness due to the gas core (the opposite to that observed) or to an increase in bubble volume which would lead to a softer bubble. 25 However, for the temperature range considered here, we would only estimate $9% increase in volume (corresponding to a $3% increase in radius) and from our previous work expect this to correspond to only a change in stiffness of $1 mN m…”

“…24 Recently, we have shown that the compression stiffness of phospholipid microbubbles is significantly increased, by a factor of 30, via the adsorption of a streptavidin layer at bilayer/water interface. 25 Other research on microbubbles has determined the stiffness and elastic modulus of 'thick-shelled' and 'hollow thinshelled' polymeric microbubbles.…”