Nanomechanical Control of Cell Rolling in Two Dimensions through Surface Patterning of Receptors

Abstract

We envisioned that label-free control of the transport of cells in two dimensions through receptorligand interactions would enable simple separation systems that are easy to implement, yet retain the specificity of receptor-ligand interactions. Here we demonstrate nanomechanical control of cell transport in two dimensions via transient receptor-ligand adhesive bonds by patterning of receptors that direct cell rolling through an edge effect. HL-60 cells rolling on P-selectin receptor patterns were deflected at angles of 5 -10° with respect to their direction of travel. Absence of this effect in the case of rigid microsphere models of cell rolling suggests that this twodimensional motion depends on nanomechanical properties of the rolling cell. This work suggests the feasibility of simple continuous-flow microfluidic cell separation systems that minimize processing steps and yet retain the specificity of receptor-ligand interactions.Techniques for separation of cells rely on the ability to control their transport based on specific characteristics such as size, density, or surface ligands. In particular, control of transport in two dimensions is highly advantageous for the design of continuous-flow separation systems [1][2][3] . Continuous-flow separation of cells based on specific receptor-ligand interactions is currently limited to external control techniques that harness dielectrophoretic, magnetic, or other forces 4, 5 and typically rely on capturing or labeling of the cells. These label-based approaches are very useful for cell separation, but involve special apparatus and multiple processing steps for labeling and label removal which are not desirable for sensitive cell samples or for point of care diagnostics, especially in third world countries. On the other hand, label-free approaches based on physical characteristics of the cells are often easy to implement, but lack the specificity provided by receptor-ligand interactions 4 . Control over the transport of cells based on specific receptor-ligand interactions without labeling and label-removal steps would enable cell separation devices for single use or continuous-flow separation, while retaining the specificity of receptor-ligand interactions. In this paper, we wanted to examine whether receptor patterning could be used to achieve nanomechanical control of the transport of cells in two dimensions in a label-free manner through the formation of transient receptor-ligand bonds that result in cell rolling.The formation of transient receptor-ligand bonds commonly occurs between cells flowing in the blood stream and the vascular endothelium in a physiological process known as cell rolling [6][7][8] . This phenomenon is mediated primarily by glycoprotein receptors known as selectins, among some other receptors can also enable cell rolling [8][9][10][11] . The adhesive bonds formed by selectins have high dissociation rates and are also responsive to shear stress [12][13][14] .As the cell rolls under shear force exerted by the flowing blood stream, bonds ...

Microfluidics for cell separation

“…Most affinity-based separation techniques are based on ''capture and release'' methods, while continuous flow sorting would be more desirable in terms of sorting efficiency and selectivity. Karnik et al [58] implemented a slanted affinity pattern, on which interacting cells are allowed to roll along the edges of the pattern, to separate cells continuously based on the surface affinity.…”

Secondary-flow-induced label-free continuous cell sorting using antibody-immobilized micro oblique grooves

“…Note that the residence time in the present device is 2 minuets, while it takes 2 hours for the cells to exit the tubing connected to the outlets. It is also noted that the cell speed is three orders of magnitude larger than that used in Karnik et al [7]. In order to demonstrate the feasibility of high-speed cell sorting with the present device, we employ the polystyrene beads and examine the effect of the flow velocity over 2 μm-deep grooves.…”

High-density antibody-immobilized surface for adhesion-based cell separation

“…9) and human umbilical-vein endothelial cells (HUVEC) has been successfully accomplished. Karnik et al [13] also reported lateral cell motion along the edge of a Pselectin pattern. However, the cell velocity in the present device is three orders of magnitude larger than that used in the their study, indicating much higher throughput.…”