Lab on a Chip最新文献

Digital microfluidics (DMF), is an emerging liquid-handling technology, that shows promising potential in various biological and biomedical applications. However, the fabrication of conventional DMF chips is usually complicated, time-consuming, and costly, which seriously limits their widespread applications, especially in the field of point-of-care testing (POCT). Although the paper- or film-based DMF devices can offer an inexpensive and convenient alternative, they still suffer from the planar addressing structure, and thus, limited electrode quantity. To address the above issues, we herein describe the development of a laser-induced graphene (LIG) based digital microfluidics chip (gDMF). It can be easily made (within 10 min, under ambient conditions, without the need of costly materials or cleanroom-based techniques) by a computer-controlled laser scribing process. Moreover, both the planar addressing DMF (pgDMF) and vertical addressing DMF (vgDMF) can be readily achieved, with the latter offering the potential of a higher electrode density. Also, both of them have an impressively low cost of below $1 ($0.85 for pgDMF, $0.59 for vgDMF). Experiments also show that both pgDMF and vgDMF have a comparable performance to conventional DMF devices, with a colorimetric assay performed on vgDMF as proof-of-concept to demonstrate their applicability. Given the simple fabrication, low cost, full function, and the ease of modifying the electrode pattern for various applications, it is reasonably expect that the proposed gDMF may offer an alternative choice as a versatile platform for POCT.

Yield stress, τ_y, is a key rheological property of complex materials such as gels, dense suspensions, and dense emulsions. While there is a range of established techniques to measure τ_y in the order of tens to thousands of pascals, the measurement of low τ_y, specifically below 1 Pa, remains underexplored. In this article, we present the measurement of low apparent τ_y using a Hele-Shaw microfluidic extensional flow device (MEFD). Using the MEFD, we observe a gradient in shear stress, τ, such that τ is lower near the center or stagnation point, and higher away from the stagnation point. For a yield stress fluid, we observe that, below a certain flow rate, τ exceeds τ_y only in the outer region, leading to stagnation or unyielding of the fluid in the inner region. We use scaling analysis based on a Hele-Shaw linear extensional flow to deduce τ_y by measuring the size of the unyielded region, S. We validate this scaling relationship using Carbopol solutions with concentrations ranging between 0.015 to 0.3%, measuring τ_y as low as ∼10 mPa to ∼1 Pa, and comparing it with τ_y measured using a standard rheometer. While the experimental lower limit of our technique is 5 mPa, modifying the geometry or improving the image analysis can reduce this limit to the order of 10⁻⁴ Pa. The MEFD facilitates rapid measurement of τ_y, allowing for its real-time assessment. We further report τ_y of human blood samples between 30 to 80 mPa with their hematocrit ranging between 14 to 63%. Additionally, we determine τ_y for a mucus simulant (∼0.7 Pa), and lactic drink (∼7 mPa) to demonstrate the versatility of the MEFD technique.

Synthetic biology is the design and modification of biological systems for specific functions, integrating several disciplines like engineering, genetics, and computer science. The field of synthetic biology is to understand biological processes within host organisms through the manipulation and regulation of their genetic pathways and the addition of biocontrol circuits to enhance their production capabilities. This pursuit serves to address global challenges spanning diverse domains that are difficult to tackle through conventional routes of production. Despite its impact, achieving precise, dynamic, and high-throughput manipulation of biological processes is still challenging. Microfluidics offers a solution to those challenges, enabling controlled fluid handling at the microscale, offering lower reagent consumption, faster analysis of biochemical reactions, automation, and high throughput screening. In this review, we diverge from conventional focus on automating the synthetic biology design-build-test-learn cycle, and instead, focus on microfluidic platforms and their role in advancing synthetic biology through its integration with host organisms – bacterial cells, yeast, fungi, animal cells – and cell-free systems. The review illustrates how microfluidic devices have been instrumental in understanding biological systems by showcasing microfluidics as an essential tool to create synthetic genetic circuits, pathways, and organisms within controlled environments. In conclusion, we show how microfluidics expedite synthetic biology applications across diverse domains including but not limited to personalized medicine, bioenergy, and agriculture.

The impact of fluid flow shear stresses, generated by the movement of blood through vasculature, on the organization and maturation of vessels is widely recognized. Nevertheless, it remains uncertain whether external fluid flows outside of the vasculature in the surrounding tissue can similarly play a role in governing these processes. In this research, we introduce an innovative technique called superfusion-induced vascular steering (SIVS). SIVS involves the controlled imposition of external fluid flow patterns onto the vascularized chick chorioallantoic membrane (CAM), allowing us to observe how this impacts the organization of vascular networks. To investigate the concept of SIVS, we conducted superfusion experiments on the intact chick CAM cultured within an engineered eggshell system, using phosphate buffered saline (PBS). To capture and analyze the effects of superfusion, we employed a custom-built microscopy setup, enabling us to image both superfused and non-superfused regions within the developing CAM. This study provides valuable insights into the practical application of fluid superfusion within an in vivo context, shedding light on its significance for understanding tissue development and manipulation in an engineering setting.

Concentration–polarization electroosmosis (CPEO) refers to steady-state electroosmotic flows around charged dielectric micro-particles induced by low-frequency AC electric fields. Recently, these flows were shown to cause repulsion of colloidal particles from the wall of a microfluidic channel when an electric field is applied along the length of the channel. In this work, we exploit this mechanism to demonstrate fractionation of micron-sized polystyrene particles and bacteria in a flow-focusing device. The results are in agreement with predictions of the CPEO theory. The ease of implementation of CPEO-based fractionation in microfluidics makes it an ideal candidate for combining with current techniques commonly used to generate particle lift, such as inertial or viscoelastic focusing, requiring no extra fabrication steps other than inserting two electrodes.

Digital PCR is a powerful method for absolute nucleic acid quantification and is widely used in the absolute quantification of viral copy numbers, tumor marker detection, and prenatal diagnosis. However, for most of the existing droplet-based dPCR systems, the droplet generation, PCR reaction, and droplet detection are performed separately using different instruments. Making digital PCR both easy to use and practical by integrating the qPCR workflow into a superior all-in-one walkaway solution is one of the core ideas. A new innovative and integrated digital droplet PCR platform was developed that utilizes cutting-edge microfluidics to integrate dPCR workflows onto a single consumable chip. This makes previously complex workflows fast and simple; the whole process of droplet generation, PCR amplification, and droplet detection is completed on one chip, which meets the clinical requirement of “sample in, result out”. It provides high multiplexing capabilities and strong sensitivity while all measurements were within the 95% confidence interval. This study is the first validation of the DropXpert S6 system and focuses primarily on verifying its reliability, repeatability, and consistency. In addition, the accuracy, detection limit, linearity, and precision of the system were evaluated after sample collection. Among them, the accuracy assessment by calculating the absolute bias of each target gene yielded a range from −0.1 to 0.08, all within ±0.5 logarithmic orders of magnitude; the LOB for the assay was set at 0, and the LoD value calculated using probit curves is MR4.7 (0.002%); the linearity evaluation showed that the R² value of the BCR-ABL was 0.9996, and the R² value of the ABL metrics calculated using the ERM standard was 0.9999; and the precision evaluation showed that all samples had a CV of less than 4% for intra-day, inter-day, and inter-instrument variation. The CV of inter-batch variation was less than 7%. The total CV was less than 5%. The results of the study demonstrate that dd-PCR can be applied to molecular detection and the clinical evaluation of CML patients and provide more precise personal treatment guidance, and its reproducibility predicts the future development of a wide range of clinical applications.

Biological barriers such as the blood–brain barrier, skin, and intestinal mucosal barrier play key roles in homeostasis, disease physiology, and drug delivery – as such, it is important to create representative in vitro models to improve understanding of barrier biology and serve as tools for therapeutic development. Microfluidic cell culture and organ-on-a-chip (OOC) systems enable barrier modelling with greater physiological fidelity than conventional platforms by mimicking key environmental aspects such as fluid shear, accurate microscale dimensions, mechanical cues, extracellular matrix, and geometrically defined co-culture. As the prevalence of barrier-on-chip models increases, so does the importance of tools that can accurately assess barrier integrity and function without disturbing the carefully engineered microenvironment. In this review, we first provide a background on biological barriers and the physiological features that are emulated through in vitro barrier models. Then, we outline molecular permeability and electrical sensing barrier integrity assessment methods, and the related challenges specific to barrier-on-chip implementation. Finally, we discuss future directions in the field, as well important priorities to consider such as fabrication costs, standardization, and bridging gaps between disciplines and stakeholders.

In vitro display technologies such as yeast display have been instrumental in developing the selection of new antibodies, antibody fragments or nanobodies that bind to a specific target, with affinity towards the target being the main factor that influences selection outcome. However, the roles of mechanical forces are being increasingly recognized as a crucial factor in the regulation and activation of effector cell function. It would thus be of interest to isolate binders behaving optimally under the influence of mechanical forces. We developed a microfluidic assay allowing the selection of yeast displaying nanobodies through antigen-specific immobilization on a surface under controlled hydrodynamic flow. This approach enabled enrichment of model yeast mixtures using tunable antigen density and applied force. This new force-based selection method opens the possibility of selecting binders by relying on both their affinity and force resistance, with implications for the design of more efficient immunotherapeutics.

We investigate for the first time the compatibility of nanovials with microfluidic impedance cytometry (MIC). Nanovials are suspendable crescent-shaped single-cell microcarriers that enable specific cell adhesion, the creation of compartments for undisturbed cell growth and secretion, as well as protection against wall shear stress. MIC is a label-free single-cell technique that characterizes flowing cells based on their electrical fingerprints and it is especially targeted to cells that are naturally in suspension. Combining nanovial technology with MIC is intriguing as it would represent a robust framework for the electrical analysis of single adherent cells at high throughput. Here, as a proof-of-concept, we report the MIC analysis of mesenchymal stromal cells loaded in nanovials. The electrical analysis is supported by numerical simulations and validated by means of optical analysis. We demonstrate that the electrical diameter can discriminate among free cells, empty nanovials, cell-loaded nanovials, and clusters, thus grounding the foundation for the use of nanovials in MIC. Furthermore, we investigate the potentiality of MIC to assess the electrical phenotype of cells loaded in nanovials and we draw directions for future studies.

Liposomes have garnered significant attention owing to their favorable characteristics as promising carriers. Microfluidic based hydrodynamic flow focusing, or micro-mixing approaches enable precise control of liposome size during their synthesis due to the comparable size scale. However, current microfluidic approaches still have issues such as high flow rate dependency, complex chip structures, and ease of clogging. Herein, we present a novel microfluidic platform for size-tunable liposome synthesis based on an ultra-high-frequency acoustic resonator. By designing the shape and orientation of the acoustic resonator in the three-phase laminar flow, it combined the features of both hydrodynamic flow focusing and rapid micro-mixing. The distribution of lipid precursor solution in laminar flow and the mixing conditions could be regulated by the confined acoustic streaming vortex. We successfully synthesize liposomes with adjustable sizes and narrow size distributions. Notably, this platform regulates the product size by adjusting only the input power, which is less dependent on the flow rate. Furthermore, the vortex-like fluid flow generated along the device edge effectively prevents precipitation due to excessive lipid concentration or contact with the wall.