A curved expansion-contraction microfluidic structure for inertial based separation of circulating tumor cells from blood samples

Spiral microchannels with concave cross-section for enhanced cancer cell inertial separation

Inertial microfluidic technologies have proven effective for particle focusing and separation in many microchannels, typically the channels with the rectangular and trapezoidal shapes. To advance particle focusing in complex channels, we propose a spiral channel combining rectangular and concave cross-sections for high-resolution particle and cell focusing and separation. Numerical simulations were conducted to illustrate the effects of channel geometry on secondary flow distribution and particle focusing positions. The simulation shows the concave cross-section generates two asymmetrical Dean vortices skewing towards the inner and outer channel walls, resulting to stronger flow velocity magnitudes near the walls than the channel center. Consequently, larger particles focus near the inner wall, while smaller particles are trapped closer to the outer wall under the influence of the stronger velocity magnitude near the walls. A microfluidic chip with the proposed channel geometry, along with a traditional rectangular channel, was fabricated by 3D printing and PDMS casting. Fluorescent microbeads were used to investigate inertial focusing and separation behaviors in the microfluidic chips. Experimental results show that the concave channel facilitates particle focusing or trapping much closer to the walls than the traditional rectangular channel, achieving better separation resolution. Finally, the proposed channel was applied to separate lung cancer A549 cells from human blood, achieving a cancer cell recovery rate of ~ 84.78% (enrichment ratio over 820-fold) and a blood cell rejection rate of ~ 99.88%. This innovative channel design in inertial microfluidics offers new insights for enhanced particle focusing and holds significant promise for cell manipulation with improved separation resolution.

Precise diagnosis of tumor cells and hemocytes using ultrasensitive, stable, selective cuprous oxide composite SERS bioprobes assisted with high-efficiency separation microfluidic chips

Efficient enrichment and accurate diagnosis of cancer cells from biological samples can guide effective treatment strategies. However, the accessibility and accuracy of rapid identification of tumor cells have been hampered due to the overlap of white blood cells (WBCs) and cancer cells in size. Therefore, a diagnosis system for the identification of tumor cells using reliable surface-enhanced Raman spectroscopy (SERS) bioprobes assisted with high-efficiency microfluidic chips for rapid enrichment of cancer cells was developed. According to this, a homogeneous flower-like Cu2O@Ag composite with high SERS performance was constructed. It showed a favorable spectral stability of 5.81% and can detect trace alizarin red (10-9 mol L-1). Finite-difference time-domain (FDTD) simulation of Cu2O, Ag and Cu2O@Ag, decreased the fluorescence lifetime of methylene blue after adsorption on Cu2O@Ag, and surface defects of Cu2O observed using a spherical aberration-corrected transmission electron microscope (AC-TEM) demonstrated that the combined effects of electromagnetic enhancement and promoted charge transfer endowed the Cu2O@Ag with good SERS activity. In addition, the modulation of the absorption properties of flower-like Cu2O@Ag composites significantly improved electromagnetic enhancement and charge transfer effects at 532 nm, providing a reliable basis for the label-free SERS detection. After the cancer cells in blood were separated by a spiral inertial microfluidic chip (purity >80%), machine learning-assisted linear discriminant analysis (LDA) successfully distinguished three types of cancer cells and WBCs with high accuracy (>90%). In conclusion, this study provides a profound reference for the rational design of SERS probes and the efficient diagnosis of malignant tumors.

Innovative PNA-LB mediated allele-specific LAMP for KRAS mutation profiling on a compact lab-on-a-disc device

Tailored healthcare, an approach focused on individual patients, requires integrating emerging interdisciplinary technologies to develop accurate and user-friendly diagnostic tools. KRAS mutations, prevalent in various common cancers, are crucial determinants in selecting patients for novel KRAS inhibitor therapies. This study presents a novel state-of-the-art Lab-on-a-Disc system utilizing peptide nucleic acids-loop backward (PNA-LB) mediated allele-specific loop-mediated isothermal amplification (LAMP) for detecting the frequent G12D KRAS mutation, signifying its superiority over alternative mutation detection approaches. The designed Lab-on-a-Disc system demonstrated exceptional preclinical and technical precision, accuracy, and versatility. By applying varying cutoff values to PNA- LB LAMP reactions, the assay's sensitivity and specificity were increased by 80 % and 90 %, respectively. The device's key advantages include a robust microfluidic Lab-on-a-Disc design, precise rotary control, and a cutting-edge induction heating module. These features enable multiplexing of LAMP reactions with high reproducibility and repeatability, with CV% values less than 3.5 % and 5.5 %, respectively. The device offers several methods for accurate endpoint result detection, including naked-eye observation, RGB image analysis using Python code, and time of fluorescence (Tf) values. Preclinical specificity and sensitivity, assessed using different cutoffs for Eva-Green fluorescence Tf values and pH-sensitive dyes, demonstrated comparable performance to the best standard methods. Overall, this study represents a significant step towards tailoring treatment strategies for cancer patients through precise and efficient mutation detection technologies.

A Review of Research Progress in Microfluidic Bioseparation and Bioassay

With the rapid development of biotechnology, the importance of microfluidic bioseparation and bioassay in biomedicine, clinical diagnosis, and other fields has become increasingly prominent. Microfluidic technology, with its significant advantages of high throughput, automated operation, and low sample consumption, has brought new breakthroughs in the field of biological separation and bioassay. In this paper, the latest research progress in microfluidic technology in the field of bioseparation and bioassay is reviewed. Then, we focus on the methods of bioseparation including active separation, passive separation, and hybrid separation. At the same time, the latest research results of our group in particle separation are introduced. Finally, some application examples or methods for bioassay after particle separation are listed, and the current challenges and future prospects of bioseparation and bioassay are discussed.

Elasto-inertial particle focusing in sinusoidal microfluidic channels

Dean flow existing in sinusoidal channels could enhance the throughput and efficiency for elasto-inertial particle focusing. However, the fundamental mechanisms of elasto-inertial focusing in sinusoidal channels are still unclear. This work employs four microfluidic devices with symmetric and asymmetric sinusoidal channels to explore the elasto-inertial focusing mechanisms over a wide range of flow rates. The effects of rheological property, flow rate, sinusoidal channel curvature, particle size, and asymmetric geometry on particle focusing performance are investigated. It is intriguing to find that the Dean flow makes a substantial contribution to the particle elasto-inertial focusing. The results illustrate that a better particle focusing performance and a faster focusing process are obtained in the sinusoidal channel with a small curvature radius due to stronger Dean flow. In addition, the particle focusing performance is also related to particle diameter and rheological properties, the larger particles show a better focusing performance than smaller particles, and the smaller flow rate is required for particles to achieve stable focusing at the outlet in the higher concentration of polyvinylpyrrolidone solutions. Our work offers an increased knowledge of the mechanisms of elasto-inertial focusing in sinusoidal channels. Ultimately, these results provide supportive guidelines into the design and development of sinusoidal elasto-inertial microfluidic devices for high-performance focusing.

Passive microfluidic devices for cell separation

The separation of specific cell populations is instrumental in gaining insights into cellular processes, elucidating disease mechanisms, and advancing applications in tissue engineering, regenerative medicine, diagnostics, and cell therapies. Microfluidic methods for cell separation have propelled the field forward, benefitting from miniaturization, advanced fabrication technologies, a profound understanding of fluid dynamics governing particle separation mechanisms, and a surge in interdisciplinary investigations focused on diverse applications. Cell separation methodologies can be categorized according to their underlying separation mechanisms. Passive microfluidic separation systems rely on channel structures and fluidic rheology, obviating the necessity for external force fields to facilitate label-free cell separation. These passive approaches offer a compelling combination of cost-effectiveness and scalability when compared to active methods that depend on external fields to manipulate cells. This review delves into the extensive utilization of passive microfluidic techniques for cell separation, encompassing various strategies such as filtration, sedimentation, adhesion-based techniques, pinched flow fractionation (PFF), deterministic lateral displacement (DLD), inertial microfluidics, hydrophoresis, viscoelastic microfluidics, and hybrid microfluidics. Besides, the review provides an in-depth discussion concerning cell types, separation markers, and the commercialization of these technologies. Subsequently, it outlines the current challenges faced in the field and presents a forward-looking perspective on potential future developments. This work hopes to aid in facilitating the dissemination of knowledge in cell separation, guiding future research, and informing practical applications across diverse scientific disciplines.

Real-time monitoring and actuation of a hybrid siphon valve for hematocrit-independent plasma separation from whole blood

Centrifugal microfluidics have emerged as a pivotal area of research spanning multiple domains, including medicine and chemistry. Among passive valving strategies, siphon valves have gained prominence due to their inherent simplicity and self-reliance, eliminating the need for external equipment. However, achieving optimal valve performance mandates supplementary elements like surface adjustments or pneumatic pressure. These introduce intricacies such as time-dependent behavior and augmented spatial demands. This research introduces inventive design and manufacturing methodologies to amplify siphon valve functionality. Our proposed innovation situates the siphon microchannel on the external surface of the primary chamber, linked via an inlet. The crux of novelty lies in the adaptable material selection for the microchannel's upper or lower surfaces, allowing the integration of hydrophilic materials such as glass or super hydrophilic coverslips, ensuring a leakage-free operation. Our approach offers a streamlined concept and manufacturing process, ensures consistent time-independent functionality, and accommodates the integration of multiple siphon valves within a solitary chamber, tailored for specific applications. Experimental evaluations validate a robust alignment between acquired data and analytical outcomes based on a modified equation. A customized disc is engineered, featuring four siphon valves meticulously calibrated for hematocrit (HCT) levels spanning from 20% to 50% at 10% intervals. Harnessing these valves yields a substantial surge in plasma separation efficiency, scaling up to 75%. Notably, this performance eclipses traditional single-valve reliant microfluidic methodologies, achieving a purity level exceeding 99% in plasma separation. These findings underscore the auspicious practical applicability of our proposed technique in plasma separation, fostering heightened platelet concentration, and expediting blood sample analysis.