The Discovery of Novel Circulating Cancer‐Related Cells in Circulation Poses New Challenges to Microfluidic Devices for Enrichment and Detection

Abstract

cells (CTCs) are precursors of metastasis in various cancers. They are detached cells slough off the edges of a solid tumor, and then enter the bloodstream or lymphatic system, moving from the primary site to distal organs via the lymphatic channels or the circulation. Although an estimated number of 3.2 × 10 6 tumor cells detach from one gram of tumor tissues per day, [2] CTCs have a relatively short life span that most of them begin to apoptosis within 24 h due to the loss of adhesion to the extracellular matrix, the shear forces of blood flow, or attacks from the immune cells. [3,4] Only a tiny fraction of CTCs that have undergone epithelial-mesenchymal transition (EMT) or CTC clusters formation survive in the bloodstream. [5] After EMT, epithelial CTCs acquire a mesenchymal phenotype, and become invasive and motile. CTCs hold the genetic information of the primary tumor, due to their same origin, thus can act as the surrogate of primary tumor for the monitoring of tumor phenotype/genotype. [6] CTCs counts have been reported correlate to overall survival and/or metastatic relapse, and suggested as a surrogate predictive marker for early diagnoses, the evaluation of chemotherapy efficacy, and cancer prognosis. [7] However, CTCs detection and analysis have two major challenges: their rarity in a typically sampled blood volume (10-50 mL), as well as genetical and phenotypical heterogeneity. [8] Thus, enrichment and detection procedures are the foundation for developing the technologies of CTCs detection. Microfluidic chip is a promising technology for CTCs isolation, identification, and characterization by using their biological and physical properties. It owes unique advantages, such as low-cost, simplicity, reduction in reagent consumption, miniaturization, fast and precise control.The substantial heterogeneity of CTCs determines their variability in expression patterns, [9] which causes difficulties to define a CTC by using specific markers. The most widely used markers to identify CTCs are EpCAM and cytokeratins (CKs). Thus, a long time in the early days, CTCs are defined as EpCAM or CKs positive and CD45 negative. But only epithelial CTCs express these two proteins. CTCs undergoing EMT gradually lose their epithelial features, having no or very low expression of epithelial markers (e.g., EpCAM, CKs, Circulating tumor cells (CTCs) enumeration has been widely used as a surrogate predictive marker for early diagnoses, the evaluation of chemotherapy efficacy, and cancer prognosis. Microfluidic technologies for CTCs enrichment and detection have been developed and commercialized as automation platforms. Currently, in addition to CTCs, some new types of circulating cancer-related cells (e.g., CCSCs, CTECs, CAMLs, and heterotypic CTC clusters) in circulation are also reported to be correlated to cancer diagnosis, metastasis, or prognosis. And they widely differ from the conventional CTCs in positive markers, cellular morphology, or size, which presents a new technological challenge to microfluidic devices that use ...

Microfluidic Continuous Modification of Magnetic Nanoparticles for Circulating Tumor Cell Capture and Isolation

“…However, detecting the very low abundance of CTCs among the massive blood cells in the bloodstream remains a tremendous challenge. [5] Therefore, emerging technologies have been developed for the enrichment of CTCs before the capture and separation of target cells, such as density gradient centrifugation, immunomagnetic bead enrichment, ultra-micro membrane filtration, 2D electrophoresis, etc. [6][7][8] Among these techniques, magnetic beads, especially Fe 3 O 4 magnetic nanoparticles, represent a promising enrichment approach, due to the advantages of easy operation, quick response, and capability of remote control.…”

Chitosan: a green adhesive for surface functionalization and fabrication of thermoplastic biomedical microdevices

“…17 Microfluidic technology has been developed and evolved in various fields, such as molecular diagnostics, biomedical analysis, and cancer diagnostics. [18][19][20] Among the various materials, thermoplastics are popularly used for constructing microfluidic devices owing to their advantages of low cost, simple design, easy fabrication, high resistance to chemicals, and good optical properties. [21][22][23] Bonding and surface functionalization methods are also playing an increasingly important role in the fabrication of microdevices for biomedical research.…”

Efficient Capture and Separation of Cancer Cells Using Hyaluronic Acid-Modified Magnetic Beads in a Microfluidic Chip

“…Cancer is one of the biggest threats to human life, and most deaths are caused by tumor cells invading surrounding tissues . Recent studies have found that circulating tumor cells (CTCs) shed from tumors into the blood play an important role in tumor metastasis, and their levels are significantly associated with the prognosis and survival of cancer patients. − Therefore, the development of methods to capture CTCs in blood counts for much in the early diagnosis of cancer metastasis. − However, the difficulty of CTC detection lies in their extremely low concentration in the blood, with the occurrence probability of one CTC per 10 million white blood cells or 5 billion red blood cells . Thus, effective separation and enrichment of CTCs in a complex environment is crucial for accurate diagnosis of cancer metastasis. − …”