The Viability of Single Cancer Cells after Exposure to Hydrodynamic Shear Stresses in a Spiral Microchannel: A Canine Cutaneous Mast Cell Tumor Model

Hydrodynamic shear stress' impact on mammalian cell properties and its applications in 3D bioprinting

As an effective cell assembly method, three-dimensional bioprinting has been widely used in building organ models and tissue repair over the past decade. However, different shear stresses induced throughout the entire printing process can cause complex impacts on cell integrity, including reducing cell viability, provoking morphological changes and altering cellular functionalities. The potential effects that may occur and the conditions under which these effects manifest are not clearly understood. Here, we review systematically how different mammalian cells respond under shear stress. We enumerate available experimental apparatus, and we categorise properties that can be affected under disparate stress patterns. We also summarise cell damaging mathematical models as a predicting reference for the design of bioprinting systems. We concluded that it is essential to quantify specific cell resistance to shear stress for the optimisation of bioprinting systems. Besides, as substantial positive impacts, including inducing cell alignment and promoting cell motility, can be generated by shear stress, we suggest that we find the proper range of shear stress and actively utilise its positive influences in the development of future systems.

Deployable extrusion bioprinting of compartmental tumoroids with cancer associated fibroblasts for immune cell interactions

Realizing the translational impacts of three-dimensional (3D) bioprinting for cancer research necessitates innovation in bioprinting workflows which integrate affordability, user-friendliness, and biological relevance. Herein, we demonstrate 'BioArm', a simple, yet highly effective extrusion bioprinting platform, which can be folded into a carry-on pack, and rapidly deployed between bio-facilities. BioArm enabled the reconstruction of compartmental tumoroids with cancer-associated fibroblasts (CAFs), forming the shell of each tumoroid. The 3D printed core-shell tumoroids showedde novosynthesized extracellular matrices, and enhanced cellular proliferation compared to the tumour alone 3D printed spheroid culture. Further, thein vivophenotypes of CAFs normally lost after conventional 2D co-culture re-emerged in the bioprinted model. Embedding the 3D printed tumoroids in an immune cell-laden collagen matrix permitted tracking of the interaction between immune cells and tumoroids, and subsequent simulated immunotherapy treatments. Our deployable extrusion bioprinting workflow could significantly widen the accessibility of 3D bioprinting for replicating multi-compartmental architectures of tumour microenvironment, and for developing strategies in cancer drug testing in the future.

Application of a novel rectangular filtering microfluidic device for microfilarial detection

The rectangular filtering microfluidic chip was invented using microfluidics device fabrication technology and can separate living microfilariae from blood samples without a syringe pump. The diagnostic results are highly effective. The device is based on the principle of separating millions of blood cells from microfilariae using a rectangular filter structure. It disperses fluid evenly into the flow-passage channel, and its rectangular filter structure is the key to success in reducing the pressure and separating blood cells from microfilariae effectively. The flow rate and blood cell concentration were optimized in our study. The chip is intended to be a point-of-care device that can reduce the use of superfluous instrumentation in the field. The technology is designed to be rapid, accurate, and easy-to-use for all users, especially those in remote areas.

Hydrodynamic dissection of Stentor coeruleus in a microfluidic cross junction

Stentor coeruleus, a single-cell ciliated protozoan, is a model organism for wound healing and regeneration studies. Despite Stentor's large size (up to 2 mm in extended state), microdissection of Stentor remains challenging. In this work, we describe a hydrodynamic cell splitter, consisting of a microfluidic cross junction, capable of splitting Stentor cells in a non-contact manner at a high throughput of ∼500 cells per minute under continuous operation. Introduction of asymmetry in the flow field at the cross junction leads to asymmetric splitting of the cells to generate cell fragments as small as ∼8.5 times the original cell size. Characterization of cell fragment viability shows reduced 5-day survival as fragment size decreases and as the extent of hydrodynamic stress imposed on the fragments increases. Our results suggest that cell fragment size and composition, as well as mechanical stress, play important roles in the long-term repair of Stentor cells and warrant further investigations. Nevertheless, the hydrodynamic splitter can be useful for studying phenomena immediately after cell splitting, such as the closure of wounds in the plasma membrane which occurs on the order of 100-1000 seconds in Stentor.

A Novel Microfluidic Method Utilizing a Hydrofoil Structure to Improve Circulating Tumor Cell Enrichment: Design and Analytical Validation

Being one of the major pillars of liquid biopsy, isolation and characterization of circulating tumor cells (CTCs) during cancer management provides critical information on the evolution of cancer and has great potential to increase the success of therapies. In this article, we define a novel strategy to effectively enrich CTCs from whole blood based on size, utilizing a spiral microfluidic channel embedded with a hydrofoil structure at the downstream of the spiral channel. The hydrofoil increases the distance between the streams of CTCs and peripheral blood cells, which are already distributed about two focal axes by the spiral channel, thereby improving the resolution of the separation. Analytical validation of the system has been carried out using Michigan Cancer Foundation-7 (MCF7) breast cancer cell lines spiked into blood samples from healthy donors, and the performance of the system in terms of white blood cell (WBC) depletion, CTC recovery rate and cell viability has been shown in single or two-step process: by passing the sample once or twice through the microfluidic chip. Single step process yielded high recovery (77.1%), viable (84.7%) CTCs. When the collected cell suspension is re-processed by the same chip, recovery decreases to 65.5%, while the WBC depletion increases to 88.3%, improving the purity. Cell viability of >80% was preserved after two-step process. The novel microfluidic chip is a good candidate for CTC isolation applications requiring high recovery rate and viability, including functional downstream analyses for variety of cancer types.

A Potential Application of Triangular Microwells to Entrap Single Cancer Cells: A Canine Cutaneous Mast Cell Tumor Model

Cellular heterogeneity is a major hindrance, leading to the misunderstanding of dynamic cell biology. However, single cell analysis (SCA) has been used as a practical means to overcome this drawback. Many contemporary methodologies are available for single cell analysis; among these, microfluidics is the most attractive and effective technology, due to its advantages of low-volume specimen consumption, label-free evaluation, and real-time monitoring, among others. In this paper, a conceptual application for microfluidic single cell analysis for veterinary research is presented. A microfluidic device is fabricated with an elastomer substrate, polydimethylsiloxane (PDMS), under standard soft lithography. The performance of the microdevice is high-throughput, sensitive, and user-friendly. A total of 53.1% of the triangular microwells were able to trap single canine cutaneous mast cell tumor (MCT) cells. Of these, 38.82% were single cell entrapments, while 14.34% were multiple cell entrapments. The ratio of single-to-multiple cell trapping was high, at 2.7:1. In addition, 80.5% of the trapped cells were viable, indicating that the system was non-lethal. OCT4A-immunofluorescence combined with the proposed system can assess OCT4A expression in trapped single cells more precisely than OCT4A-immunohistochemistry. Therefore, the results suggest that microfluidic single cell analysis could potentially reduce the impact of cellular heterogeneity.

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

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.