Label-free enrichment of human adipose-derived stem cells using a continuous microfluidic sorting cascade

Inertial Microfluidics Enables Functional Analysis of Neutrophils Isolated from Ultralow Blood Volume Samples

Monitoring immune cell function is increasingly being recognized as a more relevant biomarker than traditional white blood cell counts, yet the need for repeated relatively large blood volumes still continues to pose a significant challenge. To overcome this, we developed a sample-sparing platform using inertial microfluidics that can process as little as 10 μL of blood to isolate leukocytes for downstream functional analysis. Our platform isolates leukocytes with ∼80% purity, >90% in-device recovery, and >95% viability. Neutrophils were our primary focus due to their sensitivity to external stimuli and their critical role in immune responses. Neutrophils isolated through our new method did not show inadvertent activation, as evidenced by unchanged expression of activation markers CD62L and CD11b, with phenotypes comparable to control cells in whole blood. We conducted a range of functional assays, including phagocytosis, ROS production, and NETosis with all tests confirming that neutrophils maintained their functionality after isolation. These assays were performed using standard laboratory workflows, demonstrating the platform's compatibility with techniques such as flow cytometry and cell culture assays. Furthermore, we showed the versatility of our platform by successfully isolating leukocytes from challenging samples, including mouse blood from the vena cava or tail vein, as well as human capillary blood obtained by fingerstick. This adaptability highlights the potential of this platform for clinical and research applications, particularly in frequent immune monitoring or cases where sample volume is limited.

The Latest Advances in Microfluidic DLD Cell Sorting Technology: The Optimization of Channel Design

Cell sorting plays a crucial role in both medical and biological research. As a key passive sorting technique in the field of microfluidics, deterministic lateral displacement (DLD) has been widely applied to cell separation and sorting. This review aims to summarize the latest advances in the optimization of channel design for microfluidic DLD cell sorting. First, we provide an overview of the design elements of microfluidic DLD cell sorting channels, focusing on key factors that affect separation efficiency and accuracy, including channel geometry, fluid dynamics, and the interaction between cells and channel surfaces. Subsequently, we review recent innovations and progress in channel design for microfluidic DLD technology, exploring its applications in biomedical fields and its integration with machine learning. Additionally, we discuss the challenges currently faced in optimizing channel design for microfluidic DLD cell sorting. Finally, based on existing research, we make a summary and put forward prospective views on the further development of this field.

Advanced methods to mechanically isolate stromal vascular fraction: A concise review

Adipose tissue is a highly attractive reservoir of stem cells due to its accessibility and abundance, and the SVF within it holds great promise for stem cell-based therapies. The use of mechanical methods for SVF isolation from adipose tissue is preferred over enzymatic methods, as it can be readily applied in clinical settings without additional processing steps. However, there is a lack of consensus on the optimal approach for mechanically isolating SVF. This comprehensive review aims to present and compare the latest mechanical isolation methods for SVF from adipose tissue, including centrifugation, filtration/washing, emulsification, vibration, and mincing/adiponizing. Each of these methods possesses unique advantages and limitations, and yet, no conclusive evidence has emerged demonstrating the superiority of one approach over the others, primarily due to the dearth of well-controlled prospective studies in this field.

Sorting differentiated mammalian cells using deterministic lateral displacement microfluidic devices

Separation of differentiated and undifferentiated cells without labeling is required for cell analyses and clinical application of cultured differentiated cells in vitro. To proceed with the passive separation of differentiated cells inside a clean bench, we developed a system of deterministic lateral displacement (DLD) microfluidic devices and applied this system to sort differentiated cells in vitro. The fluid flow is driven by compressed air to the buffer. Priming and sorting can be completed by air pressure control. We use this system to separate C2C12 mononuclear myocytes from multinuclear myotubes. Additionally, using a DLD microfluidic channel of Dc = 20 μm, multinuclear myotubes can be effectively sorted as larger particles. We prepared differentiated adipocytes from mouse embryonic fibroblast (MEF) cells and sorted those containing lipid droplets. The diameters of these sorted adipocytes considered larger particles, exceeded 20 μm, similar to the Dc of the DLD microfluidic channel. Differentiated cell sorting by cell size will contribute to single-cell analyses and in vitro tissue model preparation for drug discovery.

Dissecting human adipose tissue heterogeneity using single-cell omics technologies

Single-cell omics technologies that profile genes (genomic and epigenomic) and determine the abundance of mRNA (transcriptomic), protein (proteomic and secretomic), lipids (lipidomic), and extracellular matrix (matrisomic) support the dissection of adipose tissue heterogeneity at unprecedented resolution in a temporally and spatially defined manner. In particular, cell omics technologies may provide innovative biomarkers for the identification of rare specific progenitor cell subpopulations, assess transcriptional and proteomic changes affecting cell proliferation and immunomodulatory potential, and accurately define the lineage hierarchy and differentiation status of progenitor cells. Unraveling adipose tissue complexity may also provide for the precise assessment of a dysfunctional state, which has been associated with cancer, as cancer-associated adipocytes play an important role in shaping the tumor microenvironment supporting tumor progression and metastasis, obesity, metabolic syndrome, and type 2 diabetes mellitus. The information collected by single-cell omics has relevant implications for regenerative medicine because adipose tissue is an accessible source of multipotent cells; alternative cell-free approaches, including the use of adipose tissue stromal cell-conditioned medium, extracellular vesicles, or decellularized extracellular matrix, are clinically valid options. Subcutaneous white adipose tissue, which is generally harvested via liposuction, is highly heterogeneous because of intrinsic biological variability and extrinsic inconsistencies in the harvesting and processing procedures. The current limited understanding of adipose tissue heterogeneity impinges on the definition of quality standards appropriate for clinical translation, which requires consistency and uniformity of the administered product. We review the methods used for dissecting adipose tissue heterogeneity and provide an overview of advances in omics technology that may contribute to the exploration of heterogeneity and dynamics of adipose tissue at the single-cell level.

High-throughput microalgae sorting based on the deterministic lateral displacement technique

Microalgae are a group of photosynthetic organisms that can grow autotrophically, performing photosynthesis to synthesize abundant organic compounds and release oxygen. They are rich in nutritional components and chemical precursors, presenting wide-ranging application prospects. However, potential contamination by foreign strains or bacteria can compromise their analytical applications. Therefore, the obtaining of pure algal strains is crucial for the subsequent analysis and application of microalgae. This study designed a deterministic lateral displacement (DLD) chip with dual input and dual outlet of equal width for the separation of Haematococcus pluvialis and Chlorella vulgaris. Optimal separation parameters were determined through a series of experiments, resulting in a purity of 99.80 % for Chlorella vulgaris and 94.58 % for Haematococcus pluvialis, with recovery rates maintained above 90 %, demonstrating high efficiency. This study provides a reliable foundation for future research and applications of microalgae, which holds considerable significance for the subsequent analysis and utilization of microalgae.

Recent advances in nano/microfluidics-based cell isolation techniques for cancer diagnosis and treatments

Miniaturization has improved significantly in the recent decade, which has enabled the development of numerous microfluidic systems. Microfluidic technologies have shown great potential for separating desired cells from heterogeneous samples, as they offer benefits such as low sample consumption, easy operation, and high separation accuracy. Microfluidic cell separation approaches can be classified into physical (label-free) and biological (labeled) methods based on their working principles. Each method has remarkable and feasible benefits for the purposes of cancer detection and therapy, as well as the challenges that we have discussed in this article. In this review, we present the recent advances in microfluidic cell sorting techniques that incorporate both physical and biological aspects, with an emphasis on the methods by which the cells are separated. We first introduce and discuss the biological cell sorting techniques, followed by the physical cell sorting techniques. Additionally, we explore the role of microfluidics in drug screening, drug delivery, and lab-on-chip (LOC) therapy. In addition, we discuss the challenges and future prospects of integrated microfluidics for cell sorting.

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.

Low-cost inertial microfluidic device for microparticle separation: A laser-Ablated PMMA lab-on-a-chip approach without a cleanroom

Although microparticles are frequently used in chemistry and biology, their effectiveness largely depends on the homogeneity of their particle size distribution. Microfluidic devices to separate and purify particles based on their size have been developed, but many require expensive cleanroom manufacturing processes. A cost-effective, passive microfluidic separator is presented, capable of efficiently sorting and purifying particles spanning the size range of 15 µm to 40 µm. Fabricated from Polymethyl Methacrylate (PMMA) substrates using laser ablation, this device circumvents the need for cleanroom facilities. Prior to fabrication, rigorous optimization of the device's design was carried out through computational simulations conducted in COMSOL Multiphysics. To gauge its performance, chitosan microparticles were employed as a test case. The results were notably promising, achieving a precision of 96.14 %. This quantitative metric underscores the device's precision and effectiveness in size-based particle separation. This low-cost and accessible microfluidic separator offers a pragmatic solution for laboratories and researchers seeking precise control over particle sizes, without the constraints of expensive manufacturing environments. This innovation not only mitigates the limitations tied to traditional cleanroom-based fabrication but also widens the horizons for various applications within the realms of chemistry and biology.

Scaling up stem cell production: harnessing the potential of microfluidic devices

Stem cells are specialised cells characterised by their unique ability to both self-renew and transform into a wide array of specialised cell types. The widespread interest in stem cells for regenerative medicine and cultivated meat has led to a significant demand for these cells in both research and practical applications. Despite the growing need for stem cell manufacturing, the industry faces significant obstacles, including high costs for equipment and maintenance, complicated operation, and low product quality and yield. Microfluidic technology presents a promising solution to the abovementioned challenges. As an innovative approach for manipulating liquids and cells within microchannels, microfluidics offers a plethora of advantages at an industrial scale. These benefits encompass low setup costs, ease of operation and multiplexing, minimal energy consumption, and the added advantage of being labour-free. This review presents a thorough examination of the prominent microfluidic technologies employed in stem cell research and explores their promising applications in the burgeoning stem cell industry. It thoroughly examines how microfluidics can enhance cell harvesting from tissue samples, facilitate mixing and cryopreservation, streamline microcarrier production, and efficiently conduct cell separation, purification, washing, and final cell formulation post-culture.

Blood component separation in straight microfluidic channels

Separation of blood components is required in many diagnostic applications and blood processes. In laboratories, blood is usually fractionated by manual operation involving a bulk centrifugation equipment, which significantly increases logistic burden. Blood sample processing in the field and resource-limited settings cannot be readily implemented without the use of microfluidic technology. In this study, we developed a small footprint, rapid, and passive microfluidic channel device that relied on margination and inertial focusing effects for blood component separation. No blood dilution, lysis, or labeling step was needed as to preserve sample integrity. One main innovation of this work was the insertion of fluidic restrictors at outlet ports to divert the separation interface into designated outlet channels. Thus, separation efficiency was significantly improved in comparison to previous works. We demonstrated different operation modes ranging from platelet or plasma extraction from human whole blood to platelet concentration from platelet-rich plasma through the manipulation of outlet port fluidic resistance. Using straight microfluidic channels with a high aspect ratio rectangular cross section, we demonstrated 95.4% platelet purity extracted from human whole blood. In plasma extraction, 99.9% RBC removal rate was achieved. We also demonstrated 2.6× concentration of platelet-rich plasma solution to produce platelet concentrate. The extraction efficiency and throughput rate are scalable with continuous and clog-free recirculation operation, in contrast to other blood fractionation approaches using filtration membranes or affinity-based purification methods. Our microfluidic blood separation method is highly tunable and versatile, and easy to be integrated into multi-step blood processing and advanced sample preparation workflows.