Investigation of Leukocyte Viability and Damage in Spiral Microchannel and Contraction-Expansion Array

Abstract

Inertial separation techniques in a microfluidic system have been widely employed in the field of medical diagnosis for a long time. Despite no requirement of external forces, it requires strong hydrodynamic forces that could potentially cause cell damage or loss during the separation process. This might lead to the wrong interpretation of laboratory results since the change of structures and functional characteristics of cells due to the hydrodynamic forces that occur are not taken into account. Therefore, it is important to investigate the cell viability and damage along with the separation efficacy of the device in the design process. In this study, two inertial separation techniques—spiral microchannel and contraction-expansion array (CEA)—were examined to evaluate cell viability, morphology and intracellular structures using a trypan blue assay (TB), Scanning Electron Microscopy (SEM) and Wright-Giemsa stain. We discovered that cell loss was not significantly found in a feeding system, i.e., syringe, needle and tube, but mostly occurred in the inertial separation devices while the change of cell morphology and intracellular structures were found in the feeding system and inertial separation devices. Furthermore, percentage of cell loss was not significant in both devices (7–10%). However, the change of cell morphology was considerably increased (30%) in spiral microchannel (shear stress dominated) rather than in CEA (12%). In contrast, the disruption of intracellular structures was increased (14%) in CEA (extensional and shear stress dominated equally) rather than spiral microchannel (2%). In these experiments, leukocytes of canine were used as samples because their sizes are varied in a range between 7–12 µm, and they are commonly used as a biomarker in many clinical and medical applications.

High-Throughput, Label-Free Isolation of White Blood Cells from Whole Blood Using Parallel Spiral Microchannels with U-Shaped Cross-Section

“…Cell loss and damage due to fluid shear stress is a function of both stress magnitude and exposure time. The less exposure time to a particular shear stress, the less the chances of having cells damaged [ 49 ]. The critical magnitude of shear stress in this study for a 14 µm particle which is set to represent a WBC, remains relatively below the known threshold of WBC damaging shear stress [ 49 ].…”

“…The less exposure time to a particular shear stress, the less the chances of having cells damaged [ 49 ]. The critical magnitude of shear stress in this study for a 14 µm particle which is set to represent a WBC, remains relatively below the known threshold of WBC damaging shear stress [ 49 ]. Additionally, the low exposure time of WBCs to these amounts of shear stress, which equals to the amount of time that a single cell manages to pass through the microchannel (about 0.306 s) further lessons the possibility of losing WBCs in the process.…”

Sublethal Damage to Erythrocytes during Blood Flow

“…Purvis et al showed that elongational stress induces platelet aggregation as well as impairs the platelet's response to ADP [48]. Leukocyte suspensions in contraction expansion array microchannels (dominated by shear and elongational stresses), used for inertial cell separation, showed increased intracellular damage over spiral microchannel designs (dominated only by shear stress) [49]. This suggests that the elongational stresses are the main contributing factor to the observed intracellular damage.…”

Microfluidic Technology and Biomedical Field

“…The use of immobile microfluidics without the external force among cell manipulation techniques has attracted great interest. Recently, microfluidic systems used are suitable for simple and highly efficient cell separation and analysis [5]. Silicone is the first choice among microfluidic system manufacturing when considering advantages such as its readiness, chemical compatibility and thermostability.…”