Toward Label-Free Optical Fractionation of Blood—Optical Force Measurements of Blood Cells

Abstract

There is a compelling need to develop systems capable of processing blood and other particle streams for detection of pathogens that are sensitive, selective, automated, and cost/size effective. Our research seeks to develop laser-based separations that do not rely on prior knowledge, antibodies, or fluorescent molecules for pathogen detection. Rather, we aim to harness inherent differences in optical pressure, which arise from variations in particle size, shape, refractive index, or morphology, as a means of separating and characterizing particles. Our method for measuring optical pressure involves focusing a laser into a fluid flowing opposite to the direction of laser propagation. As microscopic particles in the flow path encounter the beam, they are trapped axially along the beam and are pushed upstream from the laser focal point to rest at a point where the optical and fluid forces on the particle balance. On the basis of the flow rate at which this balance occurs, the optical pressure felt by the particle can be calculated. As a first step in the development of a label-free device for processing blood, a system has been developed to measure optical pressure differences between the components of human blood, including erythrocytes, monocytes, granulocytes, and lymphocytes. Force differentials have been measured between various components, indicating the potential for laser-based separation of blood components based upon differences in optical pressure. Potential future applications include the early detection of blood-borne pathogens for the prevention of sepsis and other diseases as well as the detection of biological threat agents.

Orthogonal optical force separation simulation of particle and molecular species mixtures under direct current electroosmotic driven flow for applications in biological sample preparation

“…The walls were modeled with a -potential of -0.08 V and all inlets/outlets as open boundaries [23]. The potential fabrication of these models could be achieved using laser-patterned etching in fused silica [24]. The use of fused silica allows for the least amount of laser power dissipation while also supporting EOF.…”

Concurrent Isolation of Lymphocytes and Granulocytes Using Prefocused Free Flow Acoustophoresis

“…4,15–19 However, there is a significant unmet need for strategies to handle small volumes and to perform label-free or simultaneous fractionation into multiple subpopulations. We propose to address these challenges by using free flow acoustophoresis (FFA), which is based on the intrinsic acoustic properties of particles or cells and does not require any excessive pretreatment of the sample.…”

Optical separation of ellipsoidal particles in a uniform flow

“…Among the various applications of the laser light, the optical force can be utilized to manipulate micro-sized objects in a non-contacting manner, 3 e.g., to trap single cells or particles [4][5][6] and to separate multiple cells or particles, [7][8][9][10][11][12][13][14] as first demonstrated in the pioneering work of Ashkin. 15 In conjunction with the experimental approaches, theoretical models were developed, which were categorized according to the particle size.…”

“…Multiple cells or particles may be separated by combining optical methods with fluid flows, as in optical lattice, [7][8][9] optical chromatography (OC), 10,11 and cross-type optical particle separation (COPS). [12][13][14] In the optical lattice, an array of optical traps in the fluid flow was used.…”