Lab on a Chip最新文献

An oxygen gradient across the retina plays a crucial role in its development and function. The inner retina resides in a hypoxic environment (2% O₂) adjacent to the vitreous cavity. Oxygenation levels rapidly increase towards the outer retina (18% O₂) at the choroid. In addition to retinal stratification, oxygen levels are critical for the health of retinal ganglion cells (RGCs), which relay visual information from the retina to the brain. Human stem cell derived retinal organoids are being engineered to mimic the structure and function of human retina for applications such as disease modeling, development of therapeutics, and cell replacement therapies. However, rapid degeneration of the retinal ganglion cell layers are a common limitation of human retinal organoid platforms. We report the design of a novel retinal organoid chip (ROC) that maintains a physiologically relevant oxygen gradient and allows the maturation of inner and outer retinal cell phenotypes for human retinal organoids. Our PDMS-free ROC holds 55 individual retinal organoids that were manually seeded, cultured for extended periods (over 150 days), imaged in situ, and retrieved. ROC was designed from first principles of liquid and gas mass transport, and fabricated from biologically- and chemically inert materials using rapid prototyping techniques such as micromachining, laser cutting, 3D printing and bonding. After computational and experimental validation of oxygen gradients, human induced pluripotent stem cell derived retinal organoids were transferred into the ROC, differentiated, cultured and imaged within the chip. ROCs that maintained active perfusion and stable oxygen gradients were successful in inducing higher viability of RGCs within retinal organoids than static controls, or ROC without oxygen gradients. Our physiologically relevant and higher-throughput retinal organoid culture system is well suited for applications in studying developmental perturbations to primate retinogenesis, including those driven by inherited traits, fetal environmental exposure to toxic agents, or acquired by genetic mutations, such as retinoblastoma.

Blood coagulation is a highly regulated injury response that features polymerization of fibrin fibers to prevent the passage of blood from a damaged vascular endothelium. A growing body of research seeks to monitor coagulation in microfluidic systems but fails to capture coagulation as a response to disruption of the vascular endothelium. Here we present a device that allows compression injury of a defined segment of a microfluidic vascular endothelium and the assessment of coagulation at the injury site. This pressure injury-on-a-chip (PINCH) device allows visualization of coagulation as the accumulation of fluorescent fibrin at injury sites. Quantification of fluorescent fibrin levels upstream of and at injury sites confirm that pre-treating vascular endothelium with fluid shear stress helps capture coagulation as an injury response. We leverage the PINCH devices to demonstrate the limited coagulation response of type A hemophiliacs and evaluate the performance of hemostatic microparticles and fibrinolytic nanoparticles. Our findings and the straightforward fabrication of the PINCH devices make it a promising choice for additional screening of hemostatic therapeutics.

Droplets are essential in a wide range of microfluidic applications, but traditional passive droplet generation methods suffer from slow response speed and the need for precise flow rate adjustment. Here, we present an active droplet generation method through electrowetting-on-dielectric (EWOD). Electrowetting is a technique that uses an electric field to change the wettability of a surface. In our method, we apply an electric field to the laminar flow of the dispersed and continuous phases in a microchannel, which induces the discretization of the dispersed thread and leads to droplet formation. A key feature of the proposed active droplet-generating microfluidic device is the reusability of the EWOD actuation substrate, dramatically reducing operational costs. In addition, this approach offers significant advantages over passive methods, including fast response speeds, a wider range of droplet sizes, and greater control over droplet size. In addition, the ultrathin polymer film used in this device allows for a low electrowetting voltage, which helps to prevent damage to encapsulated cells. We believe that our active droplet generation method is a promising new method for generating droplets in microfluidic applications. It is faster, more versatile, and more precise than passive methods, making it ideal for a wide range of applications, including single-cell genomics and drug discovery.

Colistin is essential for treating multidrug-resistant Gram-negative bacterial infections but has significant nephrotoxic side effects. Traditional approaches for studying colistin's nephrotoxicity are challenged by the rapid metabolism of its prodrug, colistin methanesulfonate and the difficulty of obtaining adequate plasma from critically ill patients. To address these challenges, we developed the Spheroid Nephrotoxicity Assessing Platform (SNAP), a microfluidic device that efficiently detects colistin-induced toxicity in renal proximal tubular epithelial cell (RPTEC) spheroids within 48 hours using just 200 μL of patient plasma. Our findings demonstrate that SNAP not only promotes higher expression of kidney-specific markers aquaporin-1 (AQP1) and low-density lipoprotein receptor-related protein 2 (LRP2) compared to traditional two-dimensional (2D) cultures, but also exhibits increased sensitivity to colistin, with significant toxicity detected at concentrations of 50 μg ml⁻¹ and above. Notably, SNAP's non-invasive method did not identify nephrotoxicity in plasma from healthy donors, thereby confirming its physiological relevance and showcasing superior sensitivity over 2D cultures, which yielded false-positive results. In clinical validation, SNAP accurately identified patients at risk of colistin-induced nephrotoxicity with 100% accuracy for both early and late onset and demonstrated a 75% accuracy rate in predicting the non-occurrence of nephrotoxicity. These results underline the potential of SNAP in personalized medicine, offering a non-invasive, precise and efficient tool for the assessment of antibiotic-induced nephrotoxicity, thus enhancing the safety and efficacy of treatments against resistant bacterial infections.

Compartmentalization of multiple single cells and/or single microbeads holds significant potential for advanced biological research including single-cell transcriptome analysis or cell–cell interactions. To ensure reliable analysis and prevent misinterpretation, it is essential to achieve highly efficient pairing or combining of single objects. In this paper, we introduce a novel microfluidic device coupled with a multilayer interconnect Si/SiO² control circuit, named the deterministic single-cell combinatorial reactor (DSCR) device, for the highly efficient combination of multiple single cells. The deterministic combination of multiple single cells is realized by sequentially introducing and trapping each cell population into designated trap-wells within each DSCR. These cell-sized trap-wells, created by etching the SiO₂ passivation layer, generate a highly localized electric field that facilitates deterministic single-cell trapping. The device's multilayer interconnection of electrodes enables the sequential operation of each trap-well, allowing precise trapping of each cell population into designated trap-wells within an array of combinatorial reactors. We demonstrated the feasibility of the DSCR by sequentially trapping three distinct groups of PC3 cells, each stained with a different fluorescent dye (blue, green, or red). This method achieved a 93 ± 2% pairing efficiency for two cell populations and an 82 ± 7% combination efficiency for three cell populations. Our innovative system offers promising applications for analyzing multiple cell–cell communications and combinatorial indexing of single cells.

Correction for ‘Distal renal tubular system-on-a-chip for studying the pathogenesis of influenza A virus-induced kidney injury’ by Yueyue Huangfu et al., Lab Chip, 2023, 23, 4255–4264, https://doi.org/10.1039/D3LC00616F

Automatic and precise fluid manipulation is essential in microfluidic applications. Microfluidic metering, in particular, plays a critical role in achieving the multiplexity of assays, reaction consistency, quantitative analysis, and the scalability of microfluidic operations. However, existing fluid metering techniques often face limitations, such as high complexity, high cost, reliance on external accessories, and lack of precision, which have restricted their use in multiplexed and quantitative analysis, especially in portable applications. In this study, we present a novel portable gravity-driven metering system designed for automated multiplexed fluid metering, multistep fluid control, and multi-chamber signal readout. Our metering chip utilizes gravitational force to dispense sample liquids, allowing for versatile and precise metering. Guided by a series of numerical simulations, we optimized the design of our metering chip to achieve rapid and accurate liquid metering. Furthermore, thermal control valves were employed to facilitate automated and programmable fluid transfer, eliminating the need for external equipment. To enhance user experience, we developed a smartphone-assisted readout pod for seamless integration with the metering chip. We validated the efficacy of our platform through a proof-of-concept multiplexed analysis of urinary biomarkers, demonstrating high sensitivity, specificity, and absolute quantification capabilities. Our gravity-driven metering system shows significant potential for applications in multiplexed diagnostics, drug screening, and material synthesis, effectively addressing critical needs in fluid manipulation and analysis.

We present an innovative platform designed to mimic the mucociliary clearance system, an essential defense mechanism in the respiratory tract. Our system utilizes PDMS and iron powder to fabricate micro-ciliary arrays that dynamically respond to alternating magnetic fields. The cilia exhibit an asymmetric beating pattern under a cyclically varying magnetic field, which propels microspheres directionally in a fluid medium, simulating the movement of mucus. We use both experimental setups and numerical simulations to investigate factors that influence the efficiency of particle transport, such as cilia beating frequency, microsphere size, cilia density, and fluid viscosity. Our results elucidate the role of artificial cilia in surface cleaning processes and provide insights that enhance our understanding of mucociliary clearance. This novel experimental platform holds great promise for advancing research in respiratory health and microchannel cleaning technologies, and contributes to our ability to model and study human respiratory function in vitro.

Disrupted blood flow in conditions such as peripheral artery disease and critical limb ischemia leads to variations in oxygen supply within skeletal muscle tissue, creating regions of poorly perfused, hypoxic skeletal muscle surrounded by regions of adequately perfused, normoxic muscle tissue. These oxygen gradients may have significant implications for muscle injury or disease, as mediated by the exchange of paracrine factors between differentially oxygenated tissue. However, creating and maintaining heterogeneous oxygen landscapes within a controlled experimental setup to ensure continuous paracrine signaling is a technological challenge. Here, we engineer oxygen-controlled microphysiological systems to investigate paracrine interactions between differentially oxygenated engineered muscle tissue. We fabricated microphysiological systems with dual oxygen landscapes that also had engineered control over paracrine interactions between hypoxic and normoxic skeletal muscle tissues, which were differentiated from C2C12 myoblasts cultured on micromolded gelatin hydrogels. The microphysiological systems interfaced with a new 3D-printed oxygen control well plate insert, which we designed to distribute flow to multiple microphysiological systems and minimize evaporation for longer timepoints. With our system, we demonstrated that amphiregulin, a myokine associated with skeletal muscle injury, exhibits unique upregulation in both gene expression and secretion after 24 hours due to paracrine interactions between hypoxic and normoxic skeletal muscle tissue. Our platform can be extended to investigate other impacts of paracrine interactions between hypoxic and normoxic skeletal muscle and can more broadly be used to elucidate many forms of oxygen-dependent crosstalk in other organ systems.

Tumor organoids present a challenge in drug screening due to their considerable heterogeneity in morphology and size. To address this issue, we proposed a portable microfluidic device that employs image processing algorithms for specific target organoid recognition and microvalve-controlled deflection for sorting and collection. This morphology-activated organoid sorting system offers numerous advantages, such as automated classification, portability, low cost, label-free sample preparation, and gentle handling of organoids. We conducted classification experiments using polystyrene beads, F9 tumoroids and patient-derived tumor organoids, achieving organoid separation efficiency exceeding 88%, purity surpassing 91%, viability exceeding 97% and classification throughput of 800 per hour, thereby meeting the demands of clinical organoid medicine.