Multiplexed fluidic plunger mechanism for the measurement of red blood cell deformability

Abstract

The extraordinary deformability of red blood cells gives them the ability to repeatedly transit through the microvasculature of the human body. The loss of this capability is part of the pathology of a wide range of diseases including malaria, hemoglobinopathies, and micronutrient deficiencies. We report on a technique for multiplexed measurements of the pressure required to deform individual red blood cell through micrometer-scale constrictions. This measurement is performed by first infusing single red blood cells into a parallel array of ~1.7 μm funnel-shaped constrictions. Next, a saw-tooth pressure waveform is applied across the constrictions to squeeze each cell through its constriction. The threshold deformation pressure is then determined by relating the pressure-time data with the video of the deformation process. Our key innovation is a self-compensating fluidic network that ensures identical pressures are applied to each cell regardless of its position, as well as the presence of cells in neighboring constrictions. These characteristics ensure the consistency of the measurement process and robustness against blockages of the constrictions by rigid cells and debris. We evaluate this technique using in vitro cultures of RBCs infected with P. falciparum, the parasite that causes malaria, to demonstrate the ability to profile the deformability signature of a heterogeneous sample.

Constriction Channel Based Single-Cell Mechanical Property Characterization

“…To address this issue, a few studies have been conducted to model the cellular entry process into the constriction channel which can translate these raw parameters into intrinsic cellular mechanical parameters such as Young's Modulus and Cortical Tension [35,36,[45][46][47]51,52]. Ma et al, are pioneers in this field and they used a Newtonian liquid drop to model a RBC where the cell deformability is indicated by a persistent cortical tension of the cell membrane (see Figure 6) [35,46].…”

“…Initially, the constriction channel design was used to quantify the mechanical properties of RBCs [23,[27][28][29][30][31][32][33][34][35][36][37][38][39][40]. In 2003, Chiu et al, characterized complex behaviors of Plasmodium falciparum infected RBCs using the constriction channels with sizes at 8, 6, 4, and 2 µm in width [23] (see Figure 1a).…”

“…[47] Meanwhile, the microfluidic constriction channel is used to quantify the cellular entry and transition process through a micro channel with a cross-sectional area smaller than the dimensions of a single cell, enabling high-throughput single-cell mechanical property characterization [23][24][25][26] (see Table 1). This technique was first used to evaluate the mechanical properties of RBCs [23,[27][28][29][30][31][32][33][34][35][36][37][38][39][40], which was then expanded to study the deformability of WBCs [24,41,42] and tumor cells [25,[43][44][45]. Leveraging mechanical modeling of the cellular entry process into the constriction channel, the microfluidic constriction channel design can collect size-independent intrinsic biomechanical markers such as cortical tension or Young's modulus [35,[46][47][48].…”

Microfluidic Device Design for Selective Enrichment of Biocolloids Based on their Deformability and Polarization

“…Microfluidic methods have been widely applied towards separation of individual cells based on their size [24], shape [25] and deformability [26] characteristics, such as blood cells from healthy versus from leukemia patients [27], oral squamous cells from healthy versus cancerous patients [28] and to distinguish the lineage of stem cells at various differentiation stages [29].. [30,31] These methods widely rely on the low Reynolds (Re) and Stokes (St) numbers associated with microfluidic systems. [30] Reynolds numbers are a non-dimensional factor that describes the ratio of inertial and viscus forces in a flow as given by the following equation:…”

“…Hence, methods to gauge deformation based on the application of force over small areas are likely to be ill-suited to gauge the deformability of cellular aggregates. In recent years, several high throughput microfluidic techniques for measuring deformability differences between individual cells have been developed [44], [46], wherein pressure driven flow across constricting structures is used to induce particle deformation, as measured by particle transit time, threshold bypass pressure [26], induced hydrodynamic or electrical resistance [47], and particle shape alterations under shear flow [48]. Since these microfluidic methods probe the ability of the particle to deform through a constriction, they can be more easily translated towards a separation application than other characterization methods.…”