IEEE Trans Ultrason Ferroelectr Freq Control. 2014 Jan;61(1):5-15. doi: 10.1109/TUFFC.2014.6689771.
Liquid-core nanoparticles are promising candidates for targeted ultrasound-controlled therapy, but their acoustic detection remains challenging. High-frequency (20 to 40 MHz) tone burst sequences were implemented with a programmable ultrasound biomicroscope to characterize acoustic response from perfluorooctyl bromide-core nanoparticles with thick poly(lactide-coglycolide) (PLGA) shells. Radio-frequency signals were acquired from flowing solutions of nanoparticles with two different shell-thickness-to-particle-radius ratios, solid PLGA nanoparticles, and latex nanobeads (linear controls). Normalized fundamental (20 MHz) and second-harmonic power spectral density (PSD) increased with particle concentration and was highest for the thinnest shelled particles. The second- harmonic PSD was detectable from the nanoparticles for peak rarefactional pressures (PRP) from 0.97 to 2.01 MPa at 23 cycles and for tone bursts from 11 to 23 cycles at 2.01 MPa. Their second-harmonic¿to¿fundamental ratio increased as a function of PRP and number of cycles. Within the same PRP and cycle ranges, the second-harmonic¿to¿fundamental ratios from matched concentration solutions of latex nanobeads and solid PLGA nanoparticles was more weakly detectable but also increased with PRP and number of cycles. Nanoparticles were detectable under flow conditions in vitro using the contrast agent mode of a high-frequency commercial scanner. These results characterize linear acoustic response from the nanoparticles (20 to 40 MHz) and demonstrate potential for their highfrequency detection.
液芯纳米颗粒是靶向超声控制治疗的有前途的候选者，但它们的声学检测仍然具有挑战性。使用可编程超声生物显微镜实现了高频（20 至 40 MHz）脉冲序列，以表征具有厚聚（乳酸-共-乙醇酸）（PLGA）壳的全氟辛基溴芯纳米颗粒的声学响应。从具有两种不同壳厚与颗粒半径比的流动纳米颗粒溶液、固态 PLGA 纳米颗粒和乳胶纳米珠（线性对照）中获取射频信号。归一化基频（20 MHz）和二次谐波功率谱密度（PSD）随颗粒浓度增加而增加，壳最薄的颗粒的 PSD 最高。二次谐波 PSD 可从纳米颗粒在峰值稀疏压力（PRP）下检测到，PRP 为 0.97 至 2.01 MPa，23 个周期，在 2.01 MPa 时为 11 至 23 个周期。它们的二次谐波与基波的比值随着 PRP 和周期数的增加而增加。在相同的 PRP 和周期范围内，乳胶纳米珠和固态 PLGA 纳米颗粒匹配浓度溶液的二次谐波与基波的比值虽然更弱，但也随 PRP 和周期数的增加而增加。纳米颗粒在体外使用高频商业扫描仪的造影剂模式下在流动条件下可检测到。这些结果表征了纳米颗粒的线性声学响应（20 至 40 MHz），并证明了它们在高频检测方面的潜力。
