Sorting Technology for Circulating Tumor Cells Based on Microfluidics

Label-free microfluidic chip for segregation and recovery of circulating leukemia cells: clinical applications in acute myeloid leukemia

We present a label-free microfluidic chip for the segregation of circulating leukemia cells (CLCs) from blood samples, with a focus on its clinical applications in Acute Myeloid Leukemia (AML). The microfluidic chip achieved an approximate capture efficiency of 92%. The study analyzed a comprehensive set of 66 blood specimens from AML patients in different disease stages, including newly diagnosed and relapsing cases, patients in complete remission, and those in partial remission. The results showed a significant difference in CLC counts between active disease stages and remission stages (p < 0.0001), with a proposed threshold of 5 CLCs to differentiate between the two. The microfluidic chip exhibited a sensitivity of 95.4% and specificity of 100% in predicting disease recurrence. Additionally, the captured CLCs were subjected to downstream molecular analysis using droplet digital PCR, allowing for the identification of genetic mutations associated with AML. Comparative analysis with bone marrow aspirate processing by FACS demonstrated the reliability and accuracy of the microfluidic chip in tracking disease burden, with highly agreement results obtained between the two methods. The non-invasive nature of the microfluidic chip and its ability to provide real-time insights into disease progression make it a promising tool for the proactive monitoring and personalized patient care of AML.

High-Throughput Separation and Enrichment of Rare Malignant Tumor Cells from Large-Volume Effusions by Inertial Microfluidics

Detection of malignant tumor cells (MTCs) in pleural effusions is essential for determining the malignancy. However, the sensitivity of MTC detection is significantly decreased due to the existence of a massive number of background blood cells in large-volume samples. Herein, we provide a method for on-chip separation and enrichment of MTCs from malignant pleural effusions (MPEs) by integrating an inertial microfluidic sorter with an inertial microfluidic concentrator. The designed sorter and concentrator are capable of focusing cells toward the specified equilibrium positions by inducing intrinsic hydrodynamic forces, enabling the size-based sorting of cells and the removal of cell-free fluids for cell enrichment. A 99.9% removal of background cells and a nearly 1400-fold ultrahigh enrichment of MTCs from large-volume MPEs can be achieved by this method. The concentrated high-purity MTC solution can be used directly for cytological examination by immunofluorescence staining, enhancing the accurate identification of MPEs. The proposed method can also be employed for the detection and count of rare cells in various clinical samples.

Recent advances in micro-/nanostructure array integrated microfluidic devices for efficient separation of circulating tumor cells

Circulating tumor cells (CTCs) released from the primary tumor to peripheral blood are promising targets for liquid biopsies. Their biological information is vital for early cancer detection, efficacy assessment, and prognostic monitoring. Despite the tremendous clinical applications of CTCs, development of effective separation techniques are still demanding. Traditional separation methods usually use batch processing for enrichment, which inevitably destroy cell integrity and affect the complete information acquisition. Considering the rarity and heterogeneity of CTCs, it is urgent to develop effective separation methods. Microfluidic chips with precise fluid control at the micron level are promising devices for CTC separation. Their further combination with micro-/nanostructure arrays adds more biomolecule binding sites and exhibit unique fluid barrier effect, which significantly improve the CTC capture efficiency, purity, and sensitivity. This review summarized the recent advances in micro-/nanostructure array integrated microfluidic devices for CTC separation, including microrods, nanowires, and 3D micro-/nanostructures. The mechanisms by which these structures contribute to improved capture efficiency are discussed. Two major categories of separation methods, based on the physical and biological properties of CTCs, are discussed separately. Physical separation includes the design and preparation of micro-/nanostructure arrays, while chemical separation additionally involves the selection and modification of specific capture probes. These emerging technologies are expected to become powerful tools for disease diagnosis in the future.

ANN-Based Instantaneous Simulation of Particle Trajectories in Microfluidics

Microfluidics has shown great potential in cell analysis, where the flowing path in the microfluidic device is important for the final study results. However, the design process is time-consuming and labor-intensive. Therefore, we proposed an ANN method with three dense layers to analyze particle trajectories at the critical intersections and then put them together with the particle trajectories in straight channels. The results showed that the ANN prediction results are highly consistent with COMSOL simulation results, indicating the applicability of the proposed ANN method. In addition, this method not only shortened the simulation time but also lowered the computational expense, providing a useful tool for researchers who want to receive instant simulation results of particle trajectories.

Dielectrophoresis-Based SERS Sensors for the Detection of Cancer Cells in Microfluidic Chips

The detection of freely circulating cancer cells (CTCs) is one of the greatest challenges of modern medical diagnostics. For several years, there has been increased attention on the use of surface-enhanced Raman spectroscopy (SERS) for the detection of CTCs. SERS is a non-destructive, accurate and precise technique, and the use of special SERS platforms even enables the amplification of weak signals from biological objects. In the current study, we demonstrate the unique arrangement of the SERS technique combined with the deposition of CTCs cells on the surface of the SERS platform via a dielectrophoretic effect. The appropriate frequencies of an alternating electric field and a selected shape of the electric field can result in the efficient deposition of CTCs on the SERS platform. The geometry of the microfluidic chip, the type of the cancer cells and the positive dielectrophoretic phenomenon resulted in the trapping of CTCs on the surface of the SERS platform. We presented results for two type of breast cancer cells, MCF-7 and MDA-MB-231, deposited from the 0.1 PBS solution. The limit of detection (LOD) is 20 cells/mL, which reflects the clinical potential and usefulness of the developed approach. We also provide a proof-of-concept for these CTCs deposited on the SERS platform from blood plasma.

Process simplification and structure design of parallelized microslit isolator for physical property-based capture of tumor cells

A facile, scalable, and highly efficient approach to physically capturing CTCs from blood samples has been developed using a microfluidic isolator with parallelized microslit channels.

Recent Development of Nanomaterials-Based Cytosensors for the Detection of Circulating Tumor Cells

The accurate analysis of circulating tumor cells (CTCs) holds great promise in early diagnosis and prognosis of cancers. However, the extremely low abundance of CTCs in peripheral blood samples limits the practical utility of the traditional methods for CTCs detection. Thus, novel and powerful strategies have been proposed for sensitive detection of CTCs. In particular, nanomaterials with exceptional physical and chemical properties have been used to fabricate cytosensors for amplifying the signal and enhancing the sensitivity. In this review, we summarize the recent development of nanomaterials-based optical and electrochemical analytical techniques for CTCs detection, including fluorescence, colorimetry, surface-enhanced Raman scattering, chemiluminescence, electrochemistry, electrochemiluminescence, photoelectrochemistry and so on.

Size-tuneable isolation of cancer cells using stretchable inertial microfluidics

Inertial microfluidics is a simple, low cost, efficient size-based separation technique which is being widely investigated for rare-cell isolation and detection. Due to the fixed geometrical dimensions of the current rigid inertial microfluidic systems, most of them are only capable of isolating and separating cells with certain types and sizes. Herein, we report the design, fabrication, and validation of a stretchable inertial microfluidic device with a tuneable separation threshold that can be used for heterogenous mixtures of particles and cells. Stretchability allows for the fine-tuning of the critical sorting size, resulting in a high separation resolution that makes the separation of cells with small size differences possible. We validated the tunability of the separation threshold by stretching the length of a microchannel to separate the particle sizes of interest. We also evaluated the focusing efficiency, flow behaviour, and the positions of cancer cells and white blood cells (WBCs) in an elongated channel, separately. In addition, the performance of the device was verified by isolating cancer cells from WBCs which revealed a high recovery rate and purity. The stretchable chip showed promising results in the separation of cells with comparable sizes. Further validation of the chip using whole blood spiked with cancer cells delivered a 98.6% recovery rate with 90% purity. Elongating a stretchable microfluidic chip enables onsite modification of the dimensions of a microchannel leading to a precise tunability of the separation threshold as well as a high separation resolution.

Microfluidic chip for graduated magnetic separation of circulating tumor cells by their epithelial cell adhesion molecule expression and magnetic nanoparticle binding

The enumeration of circulating tumor cells (CTCs) in the peripheral bloodstream of metastatic cancer patients has contributed to improvements in prognosis and therapeutics. There have been numerous approaches to capture and counting of CTCs. However, CTCs have potential information beyond simple enumeration and hold promise as a liquid biopsy for cancer and a pathway for personalized cancer therapy by detecting the subset of CTCs having the highest metastatic potential. There is evidence that epithelial cell adhesion molecule (EpCAM) expression level distinguishes these highly metastatic CTCs. The few previous approaches to selective CTC capture according to EpCAM expression level are reviewed. A new two-stage microfluidic device for separation, enrichment and release of CTCs into subpopulations sorted by EpCAM expression level is presented here. It relies upon immunospecific magnetic nanoparticle labeling of CTCs followed by their field- and flow-based separation in the first stage and capture as discrete subpopulations in the second stage. To fine tune the separation, the magnetic field profile across the first stage microfluidic channel may be modified by bonding small Vanadium Permendur strips to its outer walls. Mathematical modeling of magnetic fields and fluid flows supports the soundness of the design.