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首页> 外文期刊>IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control >Vibrational Responses of Bound and Nonbound Targeted Lipid-Coated Single Microbubbles
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Vibrational Responses of Bound and Nonbound Targeted Lipid-Coated Single Microbubbles

机译：绑定和非绑定的目标脂质涂层单个微气泡的振动响应。

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One of the main challenges for ultrasound molecular imaging is acoustically distinguishing nonbound microbubbles from those bound to their molecular target. In this in vitro study, we compared two types of in-house produced targeted lipid-coated microbubbles, either consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, C16:0 (DPPC) or 1,2-distearoyl-sn-glycero-3-phosphocholine, C18:0 (DSPC) as the main lipid, using the Brandaris 128 ultrahigh-speed camera to determine vibrational response differences between bound and nonbound biotinylated microbubbles. In contrast to previous studies that studied vibrational differences upon binding, we used a covalently bound model biomarker (i.e., streptavidin) rather than physisorption, to ensure binding of the biomarker to the membrane. The microbubbles were insonified at frequencies between 1 and 4 MHz at pressures of 50 and 150 kPa. This paper shows lower acoustic stability of bound microbubbles, of which DPPC-based microbubbles deflated most. For DPPC microbubbles with diameters between 2 and 4 μm driven at 50 kPa, resonance frequencies of bound microbubbles were all higher than 1.8 MHz, whereas those of nonbound microbubbles were significantly lower. In addition, the relative radial excursions at resonance were also higher for bound DPPC microbubbles. These differences did not persist when the pressure was increased to 150 kPa, except for the acoustic stability which further decreased. No differences in resonance frequencies were observed between bound and nonbound DSPC microbubbles. Nonlinear responses in terms of emissions at the subharmonic and second harmonic frequencies were similar for bound and nonbound microbubbles at both pressures. In conclusion, we identified differences in vibrational responses of bound DPPC microbubbles with diameters between 2 and 4 μm that distinguish them from nonbound ones.
机译：超声分子成像的主要挑战之一是在声学上区分未结合的微泡和结合到其分子靶标的微泡。在这项体外研究中，我们比较了两种内部产生的靶向脂质包裹的微泡，它们由1,2-二棕榈酰-sn-甘油-3-磷酸胆碱，C16：0（DPPC）或1,2-二硬脂酰组成-sn-glycero-3-phosphocholine，C18：0（DSPC）作为主要脂质，使用Brandaris 128超高速相机确定结合和未结合的生物素化微气泡之间的振动响应差异。与以前研究结合时振动差异的研究相反，我们使用共价结合的模型生物标记物（即链霉亲和素）而非物理吸附来确保生物标记物与膜的结合。将微泡在50和150 kPa的压力下以1至4 MHz的频率声化。本文显示出结合微泡的声学稳定性较低，其中基于DPPC的微泡放气最多。对于以50 kPa驱动的直径在2和4μm之间的DPPC微泡，结合的微泡的共振频率均高于1.8 MHz，而未结合的微泡的共振频率则明显更低。另外，结合的DPPC微泡在共振时的相对径向偏移也更高。当压力增加到150 kPa时，这些差异不会持续，除了声稳定性会进一步降低。在结合和未结合的DSPC微泡之间没有观察到共振频率的差异。对于在两个压力下有界和无界微气泡，在次谐波和二次谐波频率处的发射，非线性响应是相似的。总之，我们确定了直径在2和4μm之间的绑定DPPC微气泡在振动响应方面的差异，从而将它们与非绑定微气泡区分开。

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