Department of Biomedical Engineering, Lund University , 221 00 Lund, Sweden.
Department of Translational Medicine, Lund University , 221 00 Lund, Sweden.
Anal Chem. 2017 Sep 5;89(17):8917-8923. doi: 10.1021/acs.analchem.7b01388. Epub 2017 Aug 15.
We present an experimental method including error analysis for the measurement of the density and compressibility of cells and microbeads; these being the two central material properties in ultrasound-based acoustophoretic applications such as particle separation, trapping, and up-concentration. The density of the microparticles is determined by using a neutrally buoyant selection process that involves centrifuging of microparticles suspended in different density solutions, CsCl for microbeads and Percoll for cells. The speed of sound at 3 MHz in the neutrally buoyant suspensions is measured as a function of the microparticle volume fraction, and from this the compressibility of the microparticles is inferred. Finally, from the obtained compressibility and density, the acoustic scattering coefficients and contrast factor of the microparticles are determined, and in a sensitivity analysis, the impact of the measurement errors on the computed acoustic properties is reported. The determination of these parameters and their uncertainties allow for accurate predictions of the acoustophoretic response of the microparticles. The method is validated by determining the density (0.1-1% relative uncertainty) and compressibility (1-3% relative uncertainty) of previously well-characterized polymer microbeads and subsequently applied to determine the density (0.1-1% relative uncertainty), compressibility (1% relative uncertainty), scattering coefficients, and acoustic contrast factors for nonfixed and fixed cells, such as red blood cells, white blood cells, DU-145 prostate cancer cells, MCF-7 breast cancer cells, and LU-HNSCC-25 head and neck squamous carcinoma cells in phosphate buffered saline. The results show agreement with published data obtained by other methods.
我们提出了一种实验方法，包括误差分析，用于测量细胞和微球的密度和压缩性；这些是基于超声的声电泳应用中两个中心的材料特性，如粒子分离、捕获和上转换。微球的密度是通过使用中性浮力选择过程来确定的，该过程涉及将悬浮在不同密度溶液中的微球（CsCl 用于微球，Percoll 用于细胞）离心。在中性浮力悬浮液中，3MHz 的声速作为微球体积分数的函数进行测量，由此推断出微球的压缩性。最后，从获得的压缩性和密度，确定微球的声散射系数和对比因子，并在灵敏度分析中，报告测量误差对计算声特性的影响。这些参数及其不确定性的确定允许对微球的声电泳响应进行准确预测。该方法通过确定先前经过良好表征的聚合物微球的密度（相对不确定度为 0.1-1%）和压缩性（相对不确定度为 1-3%）得到验证，随后应用于确定非固定和固定细胞（如红细胞、白细胞、DU-145 前列腺癌细胞、MCF-7 乳腺癌细胞和 LU-HNSCC-25 头颈部鳞状癌细胞）的密度（相对不确定度为 0.1-1%）、压缩性（相对不确定度为 1%）、散射系数和声对比因子在磷酸盐缓冲盐溶液中。结果与其他方法获得的已发表数据一致。
