Hybrid double-spiral microfluidic chip for RBC-lysis-free enrichment of rare cells from whole blood

Hypoxia stimulates CTC-platelet cluster formation to promote breast cancer metastasis

Circulating tumor cell clusters/micro-emboli (CTM) possess greater metastatic capacity and survival advantage compared to individual circulating tumor cell (CTC). However, the formation of CTM subtypes and their role in tumor metastasis remain unclear. In this study, we used a microfluidic Cluster-Chip with easy operation and high efficiency to isolate CTM from peripheral blood, which confirmed their correlation with clinicopathological features and identified the critical role of CTC-platelet clusters in breast cancer metastasis. The correlation between platelets and CTM function was further confirmed in a mouse model and RNA sequencing of CTM identified high-expressed genes related to hypoxia stimulation and platelet activation which possibly suggested the correlation of hypoxia and CTC-platelet cluster formation. In conclusion, we successfully developed the Cluster-Chip platform to realize the clinical capture of CTMs and analyze the biological properties of CTC-platelet clusters, which could benefit the design of potential treatment regimens to prevent CTM-mediated metastasis and tumor malignant progression.

The integrated on-chip isolation and detection of circulating tumour cells

Circulating tumour cells (CTCs) are cancer cells shed from a primary tumour which intravasate into the blood stream and have the potential to extravasate into distant tissues, seeding metastatic lesions. As such, they can offer important insight into cancer progression with their presence generally associated with a poor prognosis. The detection and enumeration of CTCs is, therefore, critical to guiding clinical decisions during treatment and providing information on disease state. CTC isolation has been investigated using a plethora of methodologies, of which immunomagnetic capture and microfluidic size-based filtration are the most impactful to date. However, the isolation and detection of CTCs from whole blood comes with many technical barriers, such as those presented by the phenotypic heterogeneity of cell surface markers, with morphological similarity to healthy blood cells, and their low relative abundance (∼1 CTC/1 billion blood cells). At present, the majority of reported methods dissociate CTC isolation from detection, a workflow which undoubtedly contributes to loss from an already sparse population. This review focuses on developments wherein isolation and detection have been integrated into a single-step, microfluidic configuration, reducing CTC loss, increasing throughput, and enabling an on-chip CTC analysis with minimal operator intervention. Particular attention is given to immune-affinity, microfluidic CTC isolation, coupled to optical, physical, and electrochemical CTC detection (quantitative or otherwise).

Cascaded elasto-inertial separation of malignant tumor cells from untreated malignant pleural and peritoneal effusions

Separation of malignant tumor cells (MTCs) from large background cells in untreated malignant pleural and peritoneal effusions (MPPEs) is critical for improving the sensitivity and efficiency of cytological diagnosis. Herein, we proposed a cascaded elasto-inertial cell separation (CEICS) device integrating an interfacial elasto-inertial microfluidic channel with a symmetric contraction expansion array (CEA) channel for pretreatment-free, high-recovery-ratio, and high-purity separation of MTCs from clinical MPPEs. First, the effects of flow-rate ratio, cell concentration, and cell size on separation performances in two single-stage channels were investigated. Then, the performances of the integrated CEICS device were characterized using blood cells spiked with three different tumor cells (MCF-7, MDA-MB-231, and A549 cells) at a high total throughput of 240 μL min-1. An average recovery ratio of ∼95% and an average purity of ∼61% for the three tumor cells were achieved. Finally, we successfully applied the CEICS device for the pretreatment-free separation of MTCs from clinical MPPEs of different cancers. Our CEICS device may provide a preparation tool for improving the sensitivity and efficiency of cytological examination.

Reverse flow enhanced inertia pinched flow fractionation

Particle separation plays a critical role in many biochemical analyses. In this article, we report a method of reverse flow enhanced inertia pinched flow fractionation (RF-iPFF) for particle separation. RF-iPFF separates particles by size based on the flow-induced inertial lift, and in the abruptly broadened segment, reverse flow is utilized to further enhance the separation distance between particles of different sizes. The separation performance can be significantly improved by reverse flow. Generally, compared with the case without reverse flow, this RF-iPFF technique can increase the particle throughput by about 10 times. To demonstrate the advantages of RF-iPFF, RF-iPFF was compared with traditional iPFF through a control experiment. RF-iPFF consistently outperformed iPFF across various conditions we studied. In addition, we use tumor cells spiked into the human whole blood to evaluate the separation performance of RF-iPFF.

Recent Developments in Inertial and Centrifugal Microfluidic Systems along with the Involved Forces for Cancer Cell Separation: A Review

The treatment of cancers is a significant challenge in the healthcare context today. Spreading circulating tumor cells (CTCs) throughout the body will eventually lead to cancer metastasis and produce new tumors near the healthy tissues. Therefore, separating these invading cells and extracting cues from them is extremely important for determining the rate of cancer progression inside the body and for the development of individualized treatments, especially at the beginning of the metastasis process. The continuous and fast separation of CTCs has recently been achieved using numerous separation techniques, some of which involve multiple high-level operational protocols. Although a simple blood test can detect the presence of CTCs in the blood circulation system, the detection is still restricted due to the scarcity and heterogeneity of CTCs. The development of more reliable and effective techniques is thus highly desired. The technology of microfluidic devices is promising among many other bio-chemical and bio-physical technologies. This paper reviews recent developments in the two types of microfluidic devices, which are based on the size and/or density of cells, for separating cancer cells. The goal of this review is to identify knowledge or technology gaps and to suggest future works.