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11 pages, 1714 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Towards a Point-of-Care Test of CD4⁺ T Lymphocyte Concentrations for Immune Status Monitoring with Magnetic Flow Cytometry

by Moritz Leuthner, Mathias Reisbeck, Michael Helou and Oliver Hayden

Micromachines 2024, 15(4), 520; https://doi.org/10.3390/mi15040520 - 13 Apr 2024

Cited by 1 | Viewed by 4370

Abstract

For the treatment of human immunodeficiency virus (HIV)-infected patients, the regular assessment of the immune status is indispensable. The quantification of CD4⁺ T lymphocytes in blood by gold standard optical flow cytometry is not point-of-care testing (POCT) compatible. This incompatibility is due [...] Read more.

For the treatment of human immunodeficiency virus (HIV)-infected patients, the regular assessment of the immune status is indispensable. The quantification of CD4⁺ T lymphocytes in blood by gold standard optical flow cytometry is not point-of-care testing (POCT) compatible. This incompatibility is due to unavoidable pre-analytics, expensive and bulky optics with limited portability, and complex workflow integration. Here, we propose a non-optical, magnetic flow cytometry (MFC) workflow that offers effortless integration opportunities, including minimal user interaction, integrated sample preparation and up-concentration, and miniaturization. Furthermore, we demonstrate immunomagnetic CD4⁺ T lymphocyte labeling in whole blood with subsequent quantification using sheath-less MFC. Showing linearity over two log scales and being largely unimpaired by hematocrit, evidence is provided for POCT capabilities of HIV patients. Full article

(This article belongs to the Special Issue μ-TAS: A Themed Issue in Honor of Professor Andreas Manz)

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11 pages, 6992 KiB

Open AccessArticle

Glass Microdroplet Generator for Lipid-Based Double Emulsion Production

by Alessandra Zizzari and Valentina Arima

Micromachines 2024, 15(4), 500; https://doi.org/10.3390/mi15040500 - 5 Apr 2024

Viewed by 1480

Abstract

Microfluidics offers a highly controlled and reproducible route to synthesize lipid vesicles. In recent years, several microfluidic approaches have been introduced for this purpose, but double emulsions, such as Water-in-Oil-in-Water (W/O/W) droplets, are preferable to produce giant vesicles that are able to maximize [...] Read more.

Microfluidics offers a highly controlled and reproducible route to synthesize lipid vesicles. In recent years, several microfluidic approaches have been introduced for this purpose, but double emulsions, such as Water-in-Oil-in-Water (W/O/W) droplets, are preferable to produce giant vesicles that are able to maximize material encapsulation. Flow focusing (FF) is a technique used to generate double emulsion droplets with high monodispersity, a controllable size, and good robustness. Many researchers use polydimethylsiloxane as a substrate material to fabricate microdroplet generators, but it has some limitations due to its hydrophobicity, incompatibility with organic solvents, and the molecular adsorption on the microchannel walls. Thus, specific surface modification and functionalization steps, which are uncomfortable to perform in closed microchannels, are required to overcome these shortcomings. Here, we propose glass as a material to produce a chip with a six-inlet junction geometry. The peculiar geometry and the glass physicochemical properties allow for W/O/W droplet formation without introducing microchannel wall functionalization and using a variety of reagents and organic solvents. The robust glass chip can be easily cleaned and used repeatedly, bringing advantages in terms of cost and reproducibility in emulsion preparation. Full article

(This article belongs to the Special Issue μ-TAS: A Themed Issue in Honor of Professor Andreas Manz)

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11 pages, 2027 KiB

Open AccessArticle

Continuous Perfusion Experiments on 3D Cell Proliferation in Acoustic Levitation

by Luca Fabiano, Shilpi Pandey, Martin Brischwein, Morteza Hasanzadeh Kafshgari and Oliver Hayden

Micromachines 2024, 15(4), 436; https://doi.org/10.3390/mi15040436 - 25 Mar 2024

Cited by 1 | Viewed by 1986

Abstract

An acoustofluidic trap is used for accurate 3D cell proliferation and cell function analysis in levitation. The prototype trap can be integrated with any microscope setup, allowing continuous perfusion experiments with temperature and flow control under optical inspection. To describe the trap function, [...] Read more.

An acoustofluidic trap is used for accurate 3D cell proliferation and cell function analysis in levitation. The prototype trap can be integrated with any microscope setup, allowing continuous perfusion experiments with temperature and flow control under optical inspection. To describe the trap function, we present a mathematical and FEM-based COMSOL model for the acoustic mode that defines the nodal position of trapped objects in the spherical cavity aligned with the microscope field of view and depth of field. Continuous perfusion experiments were conducted in sterile conditions over 55 h with a K562 cell line, allowing for deterministic monitoring. The acoustofluidic platform allows for rational in vitro cell testing imitating in vivo conditions such as cell function tests or cell–cell interactions. Full article

(This article belongs to the Special Issue μ-TAS: A Themed Issue in Honor of Professor Andreas Manz)

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14 pages, 5901 KiB

Open AccessArticle

Enhancement of Molecular Transport into Film Stacked Structures for Micro-Immunoassay by Unsteady Rotation

by Hinata Maeno, Satoshi Ogata, Tetsuhide Shimizu and Ming Yang

Micromachines 2023, 14(4), 744; https://doi.org/10.3390/mi14040744 - 28 Mar 2023

Cited by 1 | Viewed by 1747

Abstract

A film-stacked structure consisting of polyethylene terephthalate (PET) films stacked in a gap of 20 µm that can be combined with 96-well microplates used in biochemical analysis has been developed by the authors. When this structure is inserted into a well and rotated, [...] Read more.

A film-stacked structure consisting of polyethylene terephthalate (PET) films stacked in a gap of 20 µm that can be combined with 96-well microplates used in biochemical analysis has been developed by the authors. When this structure is inserted into a well and rotated, convection flow is generated in the narrow gaps between the films to enhance the chemical/bio reaction between the molecules. However, since the main component of the flow is a swirling flow, only a part of the solution circulates into the gaps, and reaction efficiency is not achieved as designed. In this study, an unsteady rotation is applied to promote the analyte transport into the gaps using the secondary flow generated on the surface of the rotating disk. Finite element analysis is used to evaluate the changes in flow and concentration distribution for each rotation operation and to optimize the rotation conditions. In addition, the molecular binding ratio for each rotation condition is evaluated. It is shown that the unsteady rotation accelerates the binding reaction of proteins in an ELISA (Enzyme Linked Immunosorbent Assay), a type of immunoassay. Full article

(This article belongs to the Special Issue μ-TAS: A Themed Issue in Honor of Professor Andreas Manz)

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10 pages, 2896 KiB

Open AccessArticle

Cost-Effective Droplet Generator for Portable Bio-Applications

by Lin Du, Yuxin Li, Jie Wang, Zijian Zhou, Tian Lan, Dalei Jing, Wenming Wu and Jia Zhou

Micromachines 2023, 14(2), 466; https://doi.org/10.3390/mi14020466 - 17 Feb 2023

Cited by 1 | Viewed by 2436

Abstract

The convenient division of aqueous samples into droplets is necessary for many biochemical and medical analysis applications. In this article, we propose the design of a cost-effective droplet generator for potential bio-chemical application, featuring two symmetric tubes. The new droplet generator revisits the [...] Read more.

The convenient division of aqueous samples into droplets is necessary for many biochemical and medical analysis applications. In this article, we propose the design of a cost-effective droplet generator for potential bio-chemical application, featuring two symmetric tubes. The new droplet generator revisits the relationship between capillary components and liquid flow rates. The size of generated droplets by prototype depends only on generator dimensions, without precisely needing to control external flow conditions or driving pressure, even when the relative extreme difference in flow rate for generating nL level droplets is over 57.79%, and the relative standard deviation (RSD) of the volume of droplets is barely about 9.80%. A dropper working as a pressure resource is used to verify the rapidity and robustness of this principle of droplet generation, which shows great potential for a wide range of droplet-based applications. Full article

(This article belongs to the Special Issue μ-TAS: A Themed Issue in Honor of Professor Andreas Manz)

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9 pages, 2502 KiB

Open AccessArticle

Trophoblast Migration with Different Oxygen Levels in a Gel-Patterned Microfluidic System

by Gun Ko, Tae-Joon Jeon and Sun Min Kim

Micromachines 2022, 13(12), 2216; https://doi.org/10.3390/mi13122216 - 14 Dec 2022

Cited by 7 | Viewed by 2489

Abstract

In the placenta, substances such as nutrients, oxygen, and by-products are exchanged between the mother and the fetus, and the proper formation of the placenta determines the success of pregnancy, including the growth of the fetus. Preeclampsia is an obstetric disease in which [...] Read more.

In the placenta, substances such as nutrients, oxygen, and by-products are exchanged between the mother and the fetus, and the proper formation of the placenta determines the success of pregnancy, including the growth of the fetus. Preeclampsia is an obstetric disease in which the incomplete formation of the placenta occurs, which is known to occur when there is an abnormality in the invasion of trophoblast cells. The invasion of trophoblast cells is controlled by oxygen concentration, and HIF-1α changes according to oxygen concentration, showing a difference in cell mobility. MMP-2 and MMP-9 are observed to be high in the endometrium involved in trophoblast invasion, and the expression is regulated according to the oxygen concentration. In this experiment, cell culture was conducted using a gel-patterned system with a hypoxic chamber. Before the chip experiment, the difference in the expression of MMP-2 and MMP-9 according to the oxygen concentration was confirmed using a hypoxia chamber. After that, trophoblast cells (HTR8/SVneo) and endothelial cells (HUVECs) were separated and cultured through a physical barrier through a hydrogel on a microfluidic chip. Cells were cultured in a hypoxic chamber under controlled oxygen levels. It was confirmed that the mobility of trophoblast cells in culture on the chip was upregulated in a hypoxic environment through oxygen control. This suggests that the formation of a hypoxic environment in the endometrium where the invasion of trophoblast cells occurs plays a role in increasing cell mobility. Full article

(This article belongs to the Special Issue μ-TAS: A Themed Issue in Honor of Professor Andreas Manz)

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Review

Jump to: Research

14 pages, 2639 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Advanced Neural Functional Imaging in C. elegans Using Lab-on-a-Chip Technology

by Youngeun Kwon, Jihye Kim, Ye Bin Son, Sol Ah Lee, Shin Sik Choi and Yongmin Cho

Micromachines 2024, 15(8), 1027; https://doi.org/10.3390/mi15081027 - 12 Aug 2024

Viewed by 1234

Abstract

The ability to perceive and adapt to environmental changes is crucial for the survival of all organisms. Neural functional imaging, particularly in model organisms, such as Caenorhabditis elegans, provides valuable insights into how animals sense and process external cues through their nervous [...] Read more.

The ability to perceive and adapt to environmental changes is crucial for the survival of all organisms. Neural functional imaging, particularly in model organisms, such as Caenorhabditis elegans, provides valuable insights into how animals sense and process external cues through their nervous systems. Because of its fully mapped neural anatomy, transparent body, and genetic tractability, C. elegans serves as an ideal model for these studies. This review focuses on advanced methods for neural functional imaging in C. elegans, highlighting calcium imaging techniques, lab-on-a-chip technologies, and their applications in the study of various sensory modalities, including chemosensation, mechanosensation, thermosensation, photosensation, and magnetosensation. We discuss the benefits of these methods in terms of precision, reproducibility, and ability to study dynamic neural processes in real time, ultimately advancing our understanding of the fundamental principles of neural activity and connectivity. Full article

(This article belongs to the Special Issue μ-TAS: A Themed Issue in Honor of Professor Andreas Manz)

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32 pages, 7726 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Droplet Microfluidics for High-Throughput Screening and Directed Evolution of Biomolecules

by Goran T. Vladisavljević

Micromachines 2024, 15(8), 971; https://doi.org/10.3390/mi15080971 - 29 Jul 2024

Viewed by 2339

Abstract

Directed evolution is a powerful technique for creating biomolecules such as proteins and nucleic acids with tailor-made properties for therapeutic and industrial applications by mimicking the natural evolution processes in the laboratory. Droplet microfluidics improved classical directed evolution by enabling time-consuming and laborious [...] Read more.

Directed evolution is a powerful technique for creating biomolecules such as proteins and nucleic acids with tailor-made properties for therapeutic and industrial applications by mimicking the natural evolution processes in the laboratory. Droplet microfluidics improved classical directed evolution by enabling time-consuming and laborious steps in this iterative process to be performed within monodispersed droplets in a highly controlled and automated manner. Droplet microfluidic chips can generate, manipulate, and sort individual droplets at kilohertz rates in a user-defined microchannel geometry, allowing new strategies for high-throughput screening and evolution of biomolecules. In this review, we discuss directed evolution studies in which droplet-based microfluidic systems were used to screen and improve the functional properties of biomolecules. We provide a systematic overview of basic on-chip fluidic operations, including reagent mixing by merging continuous fluid streams and droplet pairs, reagent addition by picoinjection, droplet generation, droplet incubation in delay lines, chambers and hydrodynamic traps, and droplet sorting techniques. Various microfluidic strategies for directed evolution using single and multiple emulsions and biomimetic materials (giant lipid vesicles, microgels, and microcapsules) are highlighted. Completely cell-free microfluidic-assisted in vitro compartmentalization methods that eliminate the need to clone DNA into cells after each round of mutagenesis are also presented. Full article

(This article belongs to the Special Issue μ-TAS: A Themed Issue in Honor of Professor Andreas Manz)

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