Abstract
Amphiphilic triblock (Atri) copolymers made of perfluorinated alkyl chain linked to hydrocarbon chain and methoxy-poly(ethylene glycol) of three different molecular weights were synthesized. In vitro evaluation demonstrated that these new compounds were noncytotoxic. Characterization and interaction of each triblock copolymer with a branched polyamine myristoyl lipid (2-{3[bis-(3-amino-propyl)-amino]-propylamino}- N-ditetradecyl carbamoyl methyl-acetamide, DMAPAP) were studied by the Langmuir film method and thermal analysis. The triblock copolymer/cationic lipids (1:10, w/w) were mixed with perfluorobutane gas to form microbubbles (MBs). The latter were characterized by optical microscopy to get the microbubble size and concentration by densimetry to determine the amount of encapsulated gas and by ultrasound to assess oscillation properties. Atri with the lowest and intermediate weights were shown to interact with the cationic lipid DMAPAP and stabilize the Langmuir film. In that case, monodisperse microbubbles ranging from 2.3 ± 0.1 to 2.8 ± 0.1 μm were obtained. The proportion of encapsulated gas within the MB shell increased up to 3 times after the incorporation of the copolymer with the lowest and intermediate weights. Moreover, the acoustic response of the microbubbles was maintained in the presence of the copolymers.
Highlights
Contrast agents constituted of a lipid shell are currently used in clinical treatments to increase the signal-to-noise ratio of ultrasound imaging and improve diagnoses.[1]
Amphiphilic triblock (Atri) copolymers are composed of a perfluorinated alkyl chain, a hydrocarbon chain, and a methoxy-poly(ethylene glycol) group of three different molecular weights (500, 1000, or 2000 g mol−1)
Boc deprotection was obtained by treatment with trifluoroacetic acid (TFA) in dichloromethane to obtain the amines as TFA salt
Summary
Contrast agents constituted of a lipid shell are currently used in clinical treatments to increase the signal-to-noise ratio of ultrasound imaging and improve diagnoses.[1]. Two options have been proposed to increase microbubble stability: increasing the molecular weight of insoluble gas, which led to microbubbles filled with perfluorinated gas, or increasing the thickness of the microbubble shell.[9,10] playing with the latter often inhibits the nonlinear oscillation of microbubbles and reduces their impact on membrane destabilization since the lipid shell is suited for microbubble nonlinear oscillation.[11] An alternative is to modulate the shell composition of the microbubbles In this context, fluorinated amphiphiles have been proposed and shown to interact with phospholipids to form more stable organized self-assemblies.[12,13]. We highlight their noncytotoxicity as well as their capacity to interact with the cationic lipid DMAPAP14 to form microbubbles containing perfluorobutane gas, increasing its loading, and maintaining the nonlinear oscillation characteristics of the microbubbles
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