Kotnala Abhay, Zheng Yi, Fu Jianping, Cheng Wei
Department of Pharmaceutical Sciences, University of Michigan, 428 Church Street, Ann Arbor, Michigan 48109, USA.
Department of Mechanical Engineering, University of Michigan, 2350 Hayward Street, Ann Arbor, Michigan 48109, USA.
Rev Sci Instrum. 2019 Feb;90(2):023107. doi: 10.1063/1.5074194.
Nanoparticles are important in several areas of modern biomedical research. However, detection and characterization of nanoparticles is challenging due to their small size. Back-focal-plane interferometry (BFPI) is a highly sensitive technique that has been used in laser tweezers for quantitative measurement of force and displacement. The utility of BFPI for detection and characterization of nanoparticles, however, has not yet been achieved. Here we show that BFPI can be used for rapid probing of a suspension of nanoparticles in a spatially confined microfluidic channel. We show that the Gaussian Root-mean-squared noise of the BFPI signal is highly sensitive to the nanoparticle size and can be used as a parameter for rapid detection of nanoparticles at a single-particle level and characterization of particle heterogeneities in a suspension. By precisely aligning the optical trap relative to the channel boundaries, individual polystyrene particles with a diameter as small as 63 nm can be detected using BFPI with a high signal-to-noise ratio.
纳米颗粒在现代生物医学研究的多个领域都很重要。然而，由于其尺寸小，纳米颗粒的检测和表征具有挑战性。背焦平面干涉测量法（BFPI）是一种高度灵敏的技术，已用于激光镊子中进行力和位移的定量测量。然而，BFPI在纳米颗粒检测和表征方面的应用尚未实现。在此我们表明，BFPI可用于在空间受限的微流控通道中对纳米颗粒悬浮液进行快速探测。我们表明，BFPI信号的高斯均方根噪声对纳米颗粒尺寸高度敏感，可作为在单颗粒水平快速检测纳米颗粒以及表征悬浮液中颗粒异质性的参数。通过将光阱相对于通道边界精确对齐，使用BFPI可以高信噪比检测到直径小至63 nm的单个聚苯乙烯颗粒。
