Biotinylated lipid-coated microbubbles
(composition in mol %: DSPC or DPPC 84.8; PEG40-stearate 8.2; DSPE-PEG2000
5.9; DSPE-PEG2000-biotin 1.1) with a C4F10 gas
core were made by probe sonication at 20 kHz with a Sonicator Ultrasonic
Processor XL2020 at power setting 10 (HeatSystems, Farmingdale, NY,
USA) for 10 s as described previously.27 (link) The coating components were prepared in two different ways. (1)
For the direct method, all components were dissolved in PBS with a
final concentration of 2.5 mg/mL DSPC or DPPC, 0.625 mg/mL PEG40-stearate,
0.625 mg/mL DSPE-PEG2000, and 0.125 mg/mL DSPE-PEG2000-biotin. Fluorescent
dye rhodamine-DHPE (0.01 mol %) was added to study the lipid phase
organization in the microbubble coating. (2) For the indirect method,
DSPC, PEG-40 stearate, DSPE-PEG2000, and DSPE-PEG2000-biotin were
dissolved in chloroform/methanol (9:1 vol/vol). The organic solvent
was then evaporated with argon gas and the obtained lipid film was
dried under vacuum overnight. Finally, the lipid film was dispersed
in PBS with a final concentration of 2.5 mg/mL DSPC or DPPC, 0.625
mg/mL PEG40-stearate, 0.625 mg/mL DSPE-PEG2000, and 0.125 mg/mL DSPE-PEG2000-biotin,
fluorescent dye rhodamine-DHPE (0.01 mol %) was added, the solution
was placed in a sonicator bath for 10 min, and a probe sonicator was
used at power setting 3 for 5 min. The three types of microbubbles
produced are referred to as “direct DPPC”, “direct
DSPC”, or “indirect DSPC” microbubbles.
(composition in mol %: DSPC or DPPC 84.8; PEG40-stearate 8.2; DSPE-PEG2000
5.9; DSPE-PEG2000-biotin 1.1) with a C4F10 gas
core were made by probe sonication at 20 kHz with a Sonicator Ultrasonic
Processor XL2020 at power setting 10 (HeatSystems, Farmingdale, NY,
USA) for 10 s as described previously.27 (link) The coating components were prepared in two different ways. (1)
For the direct method, all components were dissolved in PBS with a
final concentration of 2.5 mg/mL DSPC or DPPC, 0.625 mg/mL PEG40-stearate,
0.625 mg/mL DSPE-PEG2000, and 0.125 mg/mL DSPE-PEG2000-biotin. Fluorescent
dye rhodamine-DHPE (0.01 mol %) was added to study the lipid phase
organization in the microbubble coating. (2) For the indirect method,
DSPC, PEG-40 stearate, DSPE-PEG2000, and DSPE-PEG2000-biotin were
dissolved in chloroform/methanol (9:1 vol/vol). The organic solvent
was then evaporated with argon gas and the obtained lipid film was
dried under vacuum overnight. Finally, the lipid film was dispersed
in PBS with a final concentration of 2.5 mg/mL DSPC or DPPC, 0.625
mg/mL PEG40-stearate, 0.625 mg/mL DSPE-PEG2000, and 0.125 mg/mL DSPE-PEG2000-biotin,
fluorescent dye rhodamine-DHPE (0.01 mol %) was added, the solution
was placed in a sonicator bath for 10 min, and a probe sonicator was
used at power setting 3 for 5 min. The three types of microbubbles
produced are referred to as “direct DPPC”, “direct
DSPC”, or “indirect DSPC” microbubbles.
