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Zhang Y, Luo Y, Zhao J, Zheng W, Zhan J, Zheng H, Luo F. Emerging delivery systems based on aqueous two-phase systems: A review. Acta Pharm Sin B 2024; 14:110-132. [PMID: 38239237 PMCID: PMC10792979 DOI: 10.1016/j.apsb.2023.08.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2023] [Revised: 07/24/2023] [Accepted: 07/28/2023] [Indexed: 01/22/2024] Open
Abstract
The aqueous two-phase system (ATPS) is an all-aqueous system fabricated from two immiscible aqueous phases. It is spontaneously assembled through physical liquid-liquid phase separation (LLPS) and can create suitable templates like the multicompartment of the intracellular environment. Delicate structures containing multiple compartments make it possible to endow materials with advanced functions. Due to the properties of ATPSs, ATPS-based drug delivery systems exhibit excellent biocompatibility, extraordinary loading efficiency, and intelligently controlled content release, which are particularly advantageous for delivering drugs in vivo . Therefore, we will systematically review and evaluate ATPSs as an ideal drug delivery system. Based on the basic mechanisms and influencing factors in forming ATPSs, the transformation of ATPSs into valuable biomaterials is described. Afterward, we concentrate on the most recent cutting-edge research on ATPS-based delivery systems. Finally, the potential for further collaborations between ATPS-based drug-carrying biomaterials and disease diagnosis and treatment is also explored.
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Affiliation(s)
- Yaowen Zhang
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu 610041, China
| | - Yankun Luo
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu 610041, China
| | - Jingqi Zhao
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu 610041, China
| | - Wenzhuo Zheng
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu 610041, China
| | - Jun Zhan
- Department of Obstetrics and Gynecology, West China Second University Hospital, Sichuan University, Chengdu 610041, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children (Sichuan University), Ministry of Education, Chengdu 610041, China
| | - Huaping Zheng
- Department of Dermatology, Rare Diseases Center, Institutes for Systems Genetics, Frontiers Science Center for Disease-related Molecular Network, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Feng Luo
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu 610041, China
- Department of Prosthodontics, West China School of Stomatology, Sichuan University, Chengdu 610041, China
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2
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Jeyhani M, Navi M, Chan KWY, Kieda J, Tsai SSH. Water-in-water droplet microfluidics: A design manual. BIOMICROFLUIDICS 2022; 16:061503. [PMID: 36406338 PMCID: PMC9674389 DOI: 10.1063/5.0119316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 11/03/2022] [Indexed: 06/16/2023]
Abstract
Droplet microfluidics is utilized in a wide range of applications in biomedicine and biology. Applications include rapid biochemical analysis, materials generation, biochemical assays, and point-of-care medicine. The integration of aqueous two-phase systems (ATPSs) into droplet microfluidic platforms has potential utility in oil-free biological and biomedical applications, namely, reducing cytotoxicity and preserving the native form and function of costly biomolecular reagents. In this review, we present a design manual for the chemist, biologist, and engineer to design experiments in the context of their biological applications using all-in-water droplet microfluidic systems. We describe the studies achievable using these systems and the corresponding fabrication and stabilization methods. With this information, readers may apply the fundamental principles and recent advancements in ATPS droplet microfluidics to their research. Finally, we propose a development roadmap of opportunities to utilize ATPS droplet microfluidics in applications that remain underexplored.
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3
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Aqueous two-phase emulsions toward biologically relevant applications. TRENDS IN CHEMISTRY 2022. [DOI: 10.1016/j.trechm.2022.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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4
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Daradmare S, Lee CS. Recent progress in the synthesis of all-aqueous two-phase droplets using microfluidic approaches. Colloids Surf B Biointerfaces 2022; 219:112795. [PMID: 36049253 DOI: 10.1016/j.colsurfb.2022.112795] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 08/10/2022] [Accepted: 08/21/2022] [Indexed: 12/21/2022]
Abstract
An aqueous two-phase system (ATPS) is a system with liquid-liquid phase separation and shows great potential for the extraction, separation, purification, and enrichment of proteins, membranes, viruses, enzymes, nucleic acids, and other biomolecules because of its simplicity, biocompatibility, and wide applicability [1-4]. The clear aqueous-aqueous interface of ATPSs is highly advantageous for their implementation, therefore making ATPSs a green alternative approach to replace conventional emulsion systems, such as water-in-oil droplets. All aqueous emulsions (water-in-water, w-in-w) hold great promise in the biomedical field as glucose sensors [5] and promising carriers for the encapsulation and release of various biomolecules and nonbiomolecules [6-10]. However, the ultralow interfacial tension between the two phases is a hurdle in generating w-in-w emulsion droplets. In the past, bulk emulsification and electrospray techniques were employed for the generation of w-in-w emulsion droplets and the fabrication of microparticles and microcapsules in the later stage. Bulk emulsification is a simple and low-cost technique; however, it generates polydisperse w-in-w emulsion droplets. Another technique, electrospray, involves easy experimental setups that can generate monodisperse but nonspherical w-in-w emulsion droplets. In comparison, microfluidic platforms provide monodisperse w-in-w emulsion droplets with spherical shapes, deal with the small volumes of solutions and short reaction times and achieve portability and versatility in their design through rapid prototyping. Owing to several advantages, microfluidic approaches have recently been introduced. To date, several different strategies have been explored to generate w-in-w emulsions and multiple w-in-w emulsions and to fabricate microparticles and microcapsules using conventional microfluidic devices. Although a few review articles on ATPSs emulsions have been published in the past, to date, few reviews have exclusively focused on the evolution of microfluidic-based ATPS droplets. The present review begins with a brief discussion of the history of ATPSs and their fundamentals, which is followed by an account chronicling the integration of microfluidic devices with ATPSs to generate w-in-w emulsion droplets. Furthermore, the stabilization strategies of w-in-w emulsion droplets and microfluidic fabrication of microparticles and microcapsules for modern applications, such as biomolecule encapsulation and spheroid construction, are discussed in detail in this review. We believe that the present review will provide useful information to not only new entrants in the microfluidic community wanting to appreciate the findings of the field but also existing researchers wanting to keep themselves updated on progress in the field.
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Affiliation(s)
- Sneha Daradmare
- Department of Chemical Engineering and Applied Chemistry, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Republic of Korea
| | - Chang-Soo Lee
- Department of Chemical Engineering and Applied Chemistry, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Republic of Korea.
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5
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Seo S, Prabhakar RG, Disney-McKeethen S, Song X, Shamoo Y. Microfluidic platform for spatially segregated experimental evolution studies with E. coli. STAR Protoc 2022; 3:101332. [PMID: 35496805 PMCID: PMC9048157 DOI: 10.1016/j.xpro.2022.101332] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Microdroplet emulsions allow investigators to build controllable microenvironments for applications in experimental evolution and synthetic ecology. We designed a microfluidic platform that uses highly homogenous microdroplets to enable these experiments. We also present a step-by-step protocol for the rapid production of highly homogeneous microdroplets suitable for experimental evolution. We also describe protocols for the propagation and serial passage of microbial populations across a range of selection schemes and potential spatial structures. For complete details on the use and execution of this protocol, please refer to Seo et al. (2021). Microfluidics for the study of microbial evolution and biomarker discovery Highly homogenous microdroplets as spatially segregated microenvironments Platform to identify evolutionary trajectories leading to antimicrobial resistance
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6
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Zhou C, Zhu P, Tian Y, Shi R, Wang L. Progress in all-aqueous droplets generation with microfluidics: Mechanisms of formation and stability improvements. BIOPHYSICS REVIEWS 2022; 3:021301. [PMID: 38505416 PMCID: PMC10914135 DOI: 10.1063/5.0054201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Accepted: 01/27/2022] [Indexed: 03/21/2024]
Abstract
All-aqueous systems have attracted intensive attention as a promising platform for applications in cell separation, protein partitioning, and DNA extraction, due to their selective separation capability, rapid mass transfer, and good biocompatibility. Reliable generation of all-aqueous droplets with accurate control over their size and size distribution is vital to meet the increasingly growing demands in emulsion-based applications. However, the ultra-low interfacial tension and large effective interfacial thickness of the water-water interface pose challenges for the generation and stabilization of uniform all-aqueous droplets, respectively. Microfluidics technology has emerged as a versatile platform for the precision generation of all-aqueous droplets with improved stability. This review aims to systematize the controllable generation of all-aqueous droplets and summarize various strategies to improve their stability with microfluidics. We first provide a comprehensive review on the recent progress of all-aqueous droplets generation with microfluidics by detailing the properties of all-aqueous systems, mechanisms of droplet formation, active and passive methods for droplet generation, and the property of droplets. We then review the various strategies used to improve the stability of all-aqueous droplets and discuss the fabrication of biomaterials using all-aqueous droplets as liquid templates. We envision that this review will benefit the future development of all-aqueous droplet generation and its applications in developing biomaterials, which will be useful for researchers working in the field of all-aqueous systems and those who are new and interested in the field.
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Affiliation(s)
| | - Pingan Zhu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China
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7
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Seo S, Disney-McKeethen S, Prabhakar RG, Song X, Mehta HH, Shamoo Y. Identification of Evolutionary Trajectories Associated with Antimicrobial Resistance Using Microfluidics. ACS Infect Dis 2022; 8:242-254. [PMID: 34962128 PMCID: PMC10022597 DOI: 10.1021/acsinfecdis.1c00564] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In vitro experimental evolution of pathogens to antibiotics is commonly used for the identification of clinical biomarkers associated with antibiotic resistance. Microdroplet emulsions allow exquisite control of spatial structure, species complexity, and selection microenvironments for such studies. We investigated the use of monodisperse microdroplets in experimental evolution. Using Escherichia coli adaptation to doxycycline, we examined how changes in environmental conditions such as droplet size, starting lambda value, selection strength, and incubation method affected evolutionary outcomes. We also examined the extent to which emulsions could reveal potentially new evolutionary trajectories and dynamics associated with antimicrobial resistance. Interestingly, we identified both expected and unexpected evolutionary trajectories including large-scale chromosomal rearrangements and amplification that were not observed in suspension culture methods. As microdroplet emulsions are well-suited for automation and provide exceptional control of conditions, they can provide a high-throughput approach for biomarker identification as well as preclinical evaluation of lead compounds.
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Affiliation(s)
- Seokju Seo
- Department of BioSciences, Rice University, Houston, Texas 77005, United States
| | | | | | - Xinhao Song
- Department of BioSciences, Rice University, Houston, Texas 77005, United States
| | - Heer H Mehta
- Department of BioSciences, Rice University, Houston, Texas 77005, United States
| | - Yousif Shamoo
- Department of BioSciences, Rice University, Houston, Texas 77005, United States
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8
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Ahmed T, Yamanishi C, Kojima T, Takayama S. Aqueous Two-Phase Systems and Microfluidics for Microscale Assays and Analytical Measurements. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2021; 14:231-255. [PMID: 33950741 DOI: 10.1146/annurev-anchem-091520-101759] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Phase separation is a common occurrence in nature. Synthetic and natural polymers, salts, ionic liquids, surfactants, and biomacromolecules phase separate in water, resulting in an aqueous two-phase system (ATPS). This review discusses the properties, handling, and uses of ATPSs. These systems have been used for protein, nucleic acid, virus, and cell purification and have in recent years found new uses for small organics, polysaccharides, extracellular vesicles, and biopharmaceuticals. Analytical biochemistry applications such as quantifying protein-protein binding, probing for conformational changes, or monitoring enzyme activity have been performed with ATPSs. Not only are ATPSs biocompatible, they also retain their properties at the microscale, enabling miniaturization experiments such as droplet microfluidics, bacterial quorum sensing, multiplexed and point-of-care immunoassays, and cell patterning. ATPSs include coacervates and may find wider interest in the context of intracellular phase separation and origin of life. Recent advances in fundamental understanding and in commercial application are also considered.
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Affiliation(s)
- Tasdiq Ahmed
- Walter H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory School of Medicine, Atlanta, Georgia 30332, USA;
| | - Cameron Yamanishi
- Walter H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory School of Medicine, Atlanta, Georgia 30332, USA;
| | - Taisuke Kojima
- Walter H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory School of Medicine, Atlanta, Georgia 30332, USA;
| | - Shuichi Takayama
- Walter H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory School of Medicine, Atlanta, Georgia 30332, USA;
- Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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9
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Zhou C, Zhu P, Han X, Shi R, Tian Y, Wang L. Microfluidic generation of ATPS droplets by transient double emulsion technique. LAB ON A CHIP 2021; 21:2684-2690. [PMID: 34170274 DOI: 10.1039/d1lc00351h] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
An aqueous two-phase system (ATPS) is considered as a promising candidate for biological applications due to its excellent permeability, selective separation, rapid mass transfer and all-biocompatible nature. However, it remains difficult to generate ATPS emulsions with controllable and prolonged stability due to ultra-low interfacial tension. Here, we present a transient double emulsion (TDE) technique to address this challenge. The method involves two steps: (i) water-in-oil-in-water (W1/O/W2) transient double emulsion droplets are first produced with droplet microfluidics by introducing an additional middle oil phase, and (ii) the W1/O/W2 droplets dewet into oil-in-water and ATPS droplets in a controllable manner. Using the TDE method, both dextran-in-polyethylene glycol (PEG) and PEG-in-dextran ATPS droplets can be generated with high uniformity (coefficient of variation (CV) ranging from 0.66% to 2.55%), a wide range of droplet sizes (∼100 to 250 μm in radius), and tunability in the generation frequency (∼4 to 170 Hz). Tuning the oil viscosity controls the destabilization time for on-demand dewetting and releasing of aqueous core droplets. The stability of ATPS droplets is significantly improved by storing aqueous droplets in double emulsion vessels, which would benefit various applications, such as small molecule encapsulation.
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Affiliation(s)
- Chunmei Zhou
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China. and HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), 311300, Hangzhou, Zhejiang, China
| | - Pingan Zhu
- Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China.
| | - Xing Han
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China. and HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), 311300, Hangzhou, Zhejiang, China
| | - Rui Shi
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China. and HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), 311300, Hangzhou, Zhejiang, China
| | - Ye Tian
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China. and HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), 311300, Hangzhou, Zhejiang, China and College of Medicine and Biological Information Engineering, Northeastern University, Shenyang 110016, China
| | - Liqiu Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China. and HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), 311300, Hangzhou, Zhejiang, China
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10
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Gebhard F, Hartmann J, Hardt S. Interaction of proteins with phase boundaries in aqueous two-phase systems under electric fields. SOFT MATTER 2021; 17:3929-3936. [PMID: 33720237 DOI: 10.1039/d0sm01921f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The electric-field driven transport of proteins across the liquid-liquid interface in an aqueous two-phase system (ATPS) is studied in a microfluidic device using fluorescence microscopy. An ATPS containing polyethylene glycol (PEG) and dextran is employed, and bovine serum albumin (BSA) and bovine γ-globulins (BγG) are considered as model proteins. It is shown that both proteins, initially in the dextran-rich phase, accumulate at the liquid-liquid interface, preferably close to the three-phase contact line between the two liquid phases and the microchannel wall. It is in these regions where the proteins penetrate into the PEG-rich phase. The transport resistance of the liquid-liquid interface is higher for BγG than for BSA, such that a much larger molar flux of BSA into the PEG phase is observed. This opens up the opportunity of separating different protein species by utilizing differences in the transport resistance at the interface. A mathematical model is developed, accounting for adsorption and desorption processes at the liquid-liquid interface. The underlying theoretical concept is that of an electrostatic potential minimum formed by superposing the applied electric field and the field due to the Donnan potential at the interface. A fit of the model parameters to the experimental data results in good agreement between theory and experiments, thereby corroborating the underlying picture.
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Affiliation(s)
- Florian Gebhard
- Technische Universität Darmstadt, Fachbereich Maschinenbau, Alarich-Weiss-Str. 10, 64287 Darmstadt, Germany.
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11
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Rho HS, Veltkamp HW, Baptista D, Gardeniers H, Le Gac S, Habibović P. A 3D polydimethylsiloxane microhourglass-shaped channel array made by reflowing photoresist structures for engineering a blood capillary network. Methods 2020; 190:63-71. [PMID: 32247048 DOI: 10.1016/j.ymeth.2020.03.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 03/11/2020] [Accepted: 03/29/2020] [Indexed: 11/16/2022] Open
Abstract
This paper describes an innovative yet straightforward fabrication technique to create three-dimensional microstructures with controllable tapered geometries by combining conventional photolithography and thermal reflow of photoresist. Positive photoresist-based microchannel structures with varying width-to-length ratios were reflowed after their fabrication to generate three-dimensional funnel structures with varying curvatures. A polydimethylsiloxane hourglass-shaped microchannel array was next cast on these photoresist structures, and primary human lung microvascular endothelial cells were cultured in the device to engineer an artificial capillary network. Our work demonstrates that this cost-effective and straightforward fabrication technique has great potential in engineering three-dimensional microstructures for biomedical and biotechnological applications such as blood vessel regeneration strategies, drug screening for vascular diseases, microcolumns for bioseparation, and other fluid dynamic studies at microscale.
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Affiliation(s)
- Hoon Suk Rho
- Department of Instructive Biomaterials Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, The Netherlands; Mesoscale Chemical Systems Group, MESA+ Institute for Nanotechnology, University of Twente, The Netherlands; Applied Microfluidics for BioEngineering Research Group, TechMed Institute, MESA+ Institute for Nanotechnology, University of Twente, The Netherlands
| | - Henk-Willem Veltkamp
- Integrated Devices and Systems Group, MESA+ Institute for Nanotechnology, University of Twente, The Netherlands
| | - Danielle Baptista
- Department of Instructive Biomaterials Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, The Netherlands
| | - Han Gardeniers
- Mesoscale Chemical Systems Group, MESA+ Institute for Nanotechnology, University of Twente, The Netherlands
| | - Séverine Le Gac
- Applied Microfluidics for BioEngineering Research Group, TechMed Institute, MESA+ Institute for Nanotechnology, University of Twente, The Netherlands
| | - Pamela Habibović
- Department of Instructive Biomaterials Engineering, MERLN Institute for Technology-Inspired Regenerative Medicine, Maastricht University, The Netherlands.
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12
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Navi M, Abbasi N, Salari A, Tsai SSH. Magnetic water-in-water droplet microfluidics: Systematic experiments and scaling mathematical analysis. BIOMICROFLUIDICS 2020; 14:024101. [PMID: 32161632 PMCID: PMC7056455 DOI: 10.1063/1.5144137] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 02/23/2020] [Indexed: 05/30/2023]
Abstract
A major barrier to the clinical utilization of microfluidically generated water-in-oil droplets is the cumbersome washing steps required to remove the non-biocompatible organic oil phase from the droplets. In this paper, we report an on-chip magnetic water-in-water droplet generation and manipulation platform using a biocompatible aqueous two-phase system of a polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer (PEG-PPG-PEG) and dextran (DEX), eliminating the need for subsequent washing steps. By careful selection of a ferrofluid that shows an affinity toward the DEX phase (the dispersed phase in our microfluidic device), we generate magnetic DEX droplets in a non-magnetic continuous phase of PEG-PPG-PEG. We apply an external magnetic field to manipulate the droplets and sort them into different outlets. We also perform scaling analysis to model the droplet deflection and find that the experimental data show good agreement with the model. We expect that this type of all-biocompatible magnetic droplet microfluidic system will find utility in biomedical applications, such as long-term single cell analysis. In addition, the model can be used for designing experimental parameters to achieve a desired droplet trajectory.
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13
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Chao Y, Shum HC. Emerging aqueous two-phase systems: from fundamentals of interfaces to biomedical applications. Chem Soc Rev 2020; 49:114-142. [DOI: 10.1039/c9cs00466a] [Citation(s) in RCA: 138] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
This review summarizes recent advances of aqueous two-phase systems (ATPSs), particularly their interfaces, with a focus on biomedical applications.
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Affiliation(s)
- Youchuang Chao
- Department of Mechanical Engineering
- The University of Hong Kong
- China
| | - Ho Cheung Shum
- Department of Mechanical Engineering
- The University of Hong Kong
- China
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14
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De Lora JA, Fencl FA, Macias Gonzalez AD, Bandegi A, Foudazi R, Lopez GP, Shreve AP, Carroll NJ. Oil-Free Acoustofluidic Droplet Generation for Multicellular Tumor Spheroid Culture. ACS APPLIED BIO MATERIALS 2019; 2:4097-4105. [DOI: 10.1021/acsabm.9b00617] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Jacqueline A. De Lora
- Department of Chemical and Biological Engineering and Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131,United States
| | - Frank A. Fencl
- Department of Chemical and Biological Engineering and Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131,United States
| | - Aidira D.Y. Macias Gonzalez
- Department of Chemical and Biological Engineering and Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131,United States
| | - Alireza Bandegi
- Department of Chemical and Materials Engineering, New Mexico State University, Las Cruces, New Mexico 88003, United States
| | - Reza Foudazi
- Department of Chemical and Materials Engineering, New Mexico State University, Las Cruces, New Mexico 88003, United States
| | - Gabriel P. Lopez
- Department of Chemical and Biological Engineering and Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131,United States
| | - Andrew P. Shreve
- Department of Chemical and Biological Engineering and Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131,United States
| | - Nick J. Carroll
- Department of Chemical and Biological Engineering and Center for Biomedical Engineering, University of New Mexico, Albuquerque, New Mexico 87131,United States
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15
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Choi D, Lee E, Kim SJ, Han M. Passive droplet generation in aqueous two-phase systems with a variable-width microchannel. SOFT MATTER 2019; 15:4647-4655. [PMID: 31073554 DOI: 10.1039/c9sm00469f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Passive droplet generation for an aqueous two-phase system (ATPS) was performed with a fracture-based variable microchannel. A jet of dextran-rich phase (DEX) in a polyethylene-glycol (PEG)-rich phase was created by focused flow. The width of the inlet channel could be varied over the range 1-10 μm via mechanical strain, which extended the range of operational back pressure. This enabled the spontaneous formation of DEX droplets with an ultralow surface tension of 12 μN m-1. The production of DEX droplets were examined with regard to driving pressure, flow rate, DEX/PEG concentration. The droplet properties are analyzed in terms of production rate (2-20 droplets per s), droplet diameter (10-100 μm), and diameter variance (5-20%). Controlling the inlet-channel width with other operating conditions widened the range of droplet properties. This simple and robust method significantly strengthened droplet-generation in microfluidics, especially for ATPS of low solute concentrations relevant to live cells.
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Affiliation(s)
- Daeho Choi
- Mechanical Engineering, Incheon National University, Incheon, 22012, Korea.
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16
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McQueen L, Lai D. Ionic Liquid Aqueous Two-Phase Systems From a Pharmaceutical Perspective. Front Chem 2019; 7:135. [PMID: 30931300 PMCID: PMC6428778 DOI: 10.3389/fchem.2019.00135] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 02/21/2019] [Indexed: 12/30/2022] Open
Abstract
Aqueous Two-Phase Systems (ATPSs) have been extensively studied for their ability to simultaneously separate and purify active pharmaceutical ingredients (APIs) and key intermediates with high yields and high purity. Depending on the ATPS composition, it can be adapted for the separation and purification of cells, nucleic acids, proteins, antibodies, and small molecules. This method has been shown to be scalable, allowing it to be used in the milliliter scale for early drug development to thousands of liters in manufacture for commercial supply. The benefits of ATPS in pharmaceutical separations is increasingly being recognized and investigated by larger pharmaceutical companies. ATPSs use identical instrumentation and similar methodology, therefore a change from traditional methods has a theoretical low barrier of adoption. The cost of typical components used to form an ATPS at large scale, particularly that of polymer-polymer systems, is the primary challenge to widespread use across industry. However, there are a few polymer-salt examples where the increase in yield at commercial scale justifies the cost of using ATPSs for macromolecule purification. More recently, Ionic Liquids (ILs) have been used for ATPS separations that is more sustainable as a solvent, and more economical than polymers often used in ATPSs for small molecule applications. Such IL-ATPSs still retain much of the attractive characteristics such as customizable chemical and physical properties, stability, safety, and most importantly, can provide higher yield separations of organic compounds, and efficient solvent recycling to lower financial and environmental costs of large scale manufacturing.
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Affiliation(s)
- Lisa McQueen
- Drug Product Design and Development, GlaxoSmithKline, Collegeville, PA, United States
| | - David Lai
- Product and Process Engineering, GlaxoSmithKline, Collegeville, PA, United States.,Advanced Manufacturing Technologies, GlaxoSmithKline, Collegeville, PA, United States
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Liu HT, Wang H, Wei WB, Liu H, Jiang L, Qin JH. A Microfluidic Strategy for Controllable Generation of Water-in-Water Droplets as Biocompatible Microcarriers. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1801095. [PMID: 30091845 DOI: 10.1002/smll.201801095] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 07/16/2018] [Indexed: 05/14/2023]
Abstract
Droplet microfluidics has been widely applied in functional microparticles fabricating, tissue engineering, and drug screening due to its high throughput and great controllability. However, most of the current droplet microfluidics are dependent on water-in-oil (W/O) systems, which involve organic reagents, thus limiting their broader biological applications. In this work, a new microfluidic strategy is described for controllable and high-throughput generation of monodispersed water-in-water (W/W) droplets. Solutions of polyethylene glycol and dextran are used as continuous and dispersed phases, respectively, without any organic reagents or surfactants. The size of W/W droplets can be precisely adjusted by changing the flow rate of dispersed and continuous phases and the valve switch cycle. In addition, uniform cell-laden microgels are fabricated by introducing the alginate component and rat pancreatic islet (β-TC6) cell suspension to the dispersed phase. The encapsulated islet cells retain high viability and the function of insulin secretion after cultivation for 7 days. The high-throughput droplet microfluidic system with high biocompatibility is stable, controllable, and flexible, which can boost various chemical and biological applications, such as bio-oriented microparticles synthesizing, microcarriers fabricating, tissue engineering, etc.
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Affiliation(s)
- Hai-Tao Liu
- Division of Biotechnology, CAS Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hui Wang
- Division of Biotechnology, CAS Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wen-Bo Wei
- Division of Biotechnology, CAS Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
| | - Hui Liu
- Division of Biotechnology, CAS Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
| | - Lei Jiang
- Division of Biotechnology, CAS Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
| | - Jian-Hua Qin
- Division of Biotechnology, CAS Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
- School of Future Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, 100101, China
- CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
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18
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Mastiani M, Seo S, Mosavati B, Kim M. High-Throughput Aqueous Two-Phase System Droplet Generation by Oil-Free Passive Microfluidics. ACS OMEGA 2018; 3:9296-9302. [PMID: 31459062 PMCID: PMC6645416 DOI: 10.1021/acsomega.8b01768] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 08/06/2018] [Indexed: 05/29/2023]
Abstract
Aqueous two-phase system (ATPS) droplet generation has significant potential in biological and medical applications because of its excellent biocompatibility. However, the ultralow interfacial tension of ATPS makes droplet generation extremely challenging when compared with the conventional water-in-oil (W/O) system. In this paper, we passively produced ATPS droplets with a wide range of droplet size and high production rate without the involvement of an oil phase and external forces. For the first time, we reported important information of the flow rate and capillary (Ca) number for passive, oil-free ATPS droplet generation. It was found that the range of Ca numbers of the continuous phase under the jetting flow regime is 0.3-1.7, as compared to less than 0.1 in the W/O system, indicating the ultralow interfacial tension in ATPS. In addition, we successfully generated ATPS droplets with a radius as small as 7 μm at the maximum frequency up to 300 Hz, which has not been achieved in previous studies. The size and generation frequency of ATPS droplets can be controlled independently by adjusting the inlet pressures and corresponding flow rates. We found that the droplet size is correlated with the pressure and flow rate ratios with the power-law exponents of 0.8 and 0.2, respectively.
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19
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Bleier BJ, Anna SL, Walker LM. Microfluidic Droplet-Based Tool To Determine Phase Behavior of a Fluid System with High Composition Resolution. J Phys Chem B 2018; 122:4067-4076. [DOI: 10.1021/acs.jpcb.8b01013] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Blake J. Bleier
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Shelley L. Anna
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Lynn M. Walker
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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20
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Teixeira AG, Agarwal R, Ko KR, Grant‐Burt J, Leung BM, Frampton JP. Emerging Biotechnology Applications of Aqueous Two-Phase Systems. Adv Healthc Mater 2018; 7:e1701036. [PMID: 29280350 DOI: 10.1002/adhm.201701036] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 10/30/2017] [Indexed: 02/06/2023]
Abstract
Liquid-liquid phase separation between aqueous solutions containing two incompatible polymers, a polymer and a salt, or a polymer and a surfactant, has been exploited for a wide variety of biotechnology applications throughout the years. While many applications for aqueous two-phase systems fall within the realm of separation science, the ability to partition many different materials within these systems, coupled with recent advances in materials science and liquid handling, has allowed bioengineers to imagine new applications. This progress report provides an overview of the history and key properties of aqueous two-phase systems to lend context to how these materials have progressed to modern applications such as cellular micropatterning and bioprinting, high-throughput 3D tissue assembly, microscale biomolecular assay development, facilitation of cell separation and microcapsule production using microfluidic devices, and synthetic biology. Future directions and present limitations and design considerations of this adaptable and promising toolkit for biomolecule and cellular manipulation are further evaluated.
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Affiliation(s)
- Alyne G. Teixeira
- School of Biomedical Engineering Dalhousie University 5981 University Avenue Halifax NS B3H 4R2 Canada
| | - Rishima Agarwal
- School of Biomedical Engineering Dalhousie University 5981 University Avenue Halifax NS B3H 4R2 Canada
| | - Kristin Robin Ko
- School of Biomedical Engineering Dalhousie University 5981 University Avenue Halifax NS B3H 4R2 Canada
| | - Jessica Grant‐Burt
- School of Biomedical Engineering Dalhousie University 5981 University Avenue Halifax NS B3H 4R2 Canada
| | - Brendan M. Leung
- School of Biomedical Engineering Dalhousie University 5981 University Avenue Halifax NS B3H 4R2 Canada
- Department of Applied Oral Science Dalhousie University 5981 University Avenue Halifax NS B3H 4R2 Canada
| | - John P. Frampton
- School of Biomedical Engineering Dalhousie University 5981 University Avenue Halifax NS B3H 4R2 Canada
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21
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Mak SY, Chao Y, Rahman S, Shum HC. Droplet Formation by Rupture of Vibration-Induced Interfacial Fingers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:926-932. [PMID: 29094601 DOI: 10.1021/acs.langmuir.7b02633] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
By imposing vibration to a core-annular flow of an aqueous two-phase system (ATPS) with ultralow interfacial tension, we observe a liquid finger protruding from the interface of an expanding jet. We find that the protruded finger breaks up only when its length-to-width ratio exceeds a threshold value. The breakup follows a constant wavelength-to-width ratio that is consistent with that of breakup under Rayleigh-Plateau instability. The mechanism is applicable to aqueous two-phase systems with a large range of viscosity ratios. The protruded finger can break up into small droplets that are monodisperse in size, controllable in generation frequency under a wide range of flow rates. This work suggests a way to generate small water-water droplets with high monodispersity and production rate from a single nozzle.
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Affiliation(s)
- Sze Yi Mak
- Department of Mechanical Engineering, The University of Hong Kong , Pok Fu Lam 999077, Hong Kong
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI) , Shenzhen, Guangdong 518000, China
| | - Youchuang Chao
- Department of Mechanical Engineering, The University of Hong Kong , Pok Fu Lam 999077, Hong Kong
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI) , Shenzhen, Guangdong 518000, China
| | - Shakurur Rahman
- Department of Mechanical Engineering, The University of Hong Kong , Pok Fu Lam 999077, Hong Kong
| | - Ho Cheung Shum
- Department of Mechanical Engineering, The University of Hong Kong , Pok Fu Lam 999077, Hong Kong
- HKU-Shenzhen Institute of Research and Innovation (HKU-SIRI) , Shenzhen, Guangdong 518000, China
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22
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Abbasi N, Navi M, Tsai SSH. Microfluidic Generation of Particle-Stabilized Water-in-Water Emulsions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:213-218. [PMID: 29231744 DOI: 10.1021/acs.langmuir.7b03245] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Herein, we present a microfluidic platform that generates particle-stabilized water-in-water emulsions. The water-in-water system that we use is based on an aqueous two-phase system of polyethylene glycol (PEG) and dextran (DEX). DEX droplets are formed passively, in the continuous phase of PEG and carboxylated particle suspension at a flow-focusing junction inside a microfluidic device. As DEX droplets travel downstream inside the microchannel, carboxylated particles that are in the continuous phase partition to the interface of the DEX droplets due to their affinity to the interface of PEG and DEX. As the DEX droplets become covered with carboxylated particles, they become stabilized against coalescence. We study the coverage and stability of the emulsions, while tuning the concentration and the size of the carboxylated particles, downstream inside the reservoir of the microfluidic device. These particle-stabilized water-in-water emulsions showcase good particle adsorption under shear, while being flowed through narrow microchannels. The intrinsic biocompatibility advantages of particle-stabilized water-in-water emulsions make them a good alternative to traditional particle-stabilized water-in-oil emulsions. To illustrate a biotechnological application of this platform, we show a proof-of-principle of cell encapsulation using this system, which with further development may be used for immunoisolation of cells for transplantation purposes.
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Affiliation(s)
- Niki Abbasi
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital , Toronto M5B 2K3, Canada
- Institute for Biomedical Engineering, Science and Technology (iBEST)-A Partnership between Ryerson University and St. Michael's Hospital , Toronto M5B 1W8, Canada
| | - Maryam Navi
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital , Toronto M5B 2K3, Canada
- Institute for Biomedical Engineering, Science and Technology (iBEST)-A Partnership between Ryerson University and St. Michael's Hospital , Toronto M5B 1W8, Canada
| | - Scott S H Tsai
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital , Toronto M5B 2K3, Canada
- Institute for Biomedical Engineering, Science and Technology (iBEST)-A Partnership between Ryerson University and St. Michael's Hospital , Toronto M5B 1W8, Canada
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23
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Mastiani M, Seo S, Jimenez SM, Petrozzi N, Kim MM. Flow regime mapping of aqueous two-phase system droplets in flow-focusing geometries. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2017.07.083] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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24
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Zhou C, Zhu P, Tian Y, Tang X, Shi R, Wang L. Microfluidic generation of aqueous two-phase-system (ATPS) droplets by oil-droplet choppers. LAB ON A CHIP 2017; 17:3310-3317. [PMID: 28861566 DOI: 10.1039/c7lc00696a] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Existing approaches for droplet generation with an ultra-low interfacial tension using aqueous two-phase systems, ATPS, are either constricted by a narrow range of flow conditions using passive methods or subjected to complex chip fabrication with the integration of external components using active actuation. To address these issues, we present a simple approach to produce uniform ATPS droplets facilitated by oil-droplet choppers in microfluidics. Our solution counts on the synchronized formation of high-interfacial-tension oil-in-water and low-interfacial-tension water-in-water droplets, where the ATPS interface is distorted by oil droplets and decays into water-in-water droplets. In the synchronization regime, the size and generation frequency of ATPS droplets can be controlled independently by tuning the flow rates of the dispersed aqueous and oil phases, respectively. Our method demonstrates high uniformity of droplets (coefficient of variation between 0.75% and 2.45%), a wide range of available droplet size (droplet radius from 5 μm to 180 μm), and a maximum generation frequency of about 2.1 kHz that is nearly two orders of magnitude faster than that in existing methods. We develop theoretical models to precisely predict the minimum and maximum frequencies of droplet generation and the droplet size. The produced ATPS droplets and oil choppers are separated in the channel using density difference. Our method would boost emulsion-based biological applications such as cell encapsulation, biomolecule delivery, bioreactors, and biomaterials synthesis with ATPS droplets.
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Affiliation(s)
- Chunmei Zhou
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
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25
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Liu Y, Nambu NO, Taya M. Cell-laden microgel prepared using a biocompatible aqueous two-phase strategy. Biomed Microdevices 2017; 19:55. [DOI: 10.1007/s10544-017-0198-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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26
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Dang VB, Kim SJ. Water-head-driven microfluidic oscillators for autonomous control of periodic flows and generation of aqueous two-phase system droplets. LAB ON A CHIP 2017; 17:286-292. [PMID: 28001158 DOI: 10.1039/c6lc00911e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Generating periodic flows with an oscillator driven only by water-head pressure has potential for the operation of microfluidic systems without any dynamic off-chip controllers. However, its operational characteristic is not well understood due to complex dynamic interactions of the microfluidic components. Here, we focus on the mechanism of a water-head-driven oscillator and analyze the functions of its flow-switching period (T) and flow rate (Q) in a wide range (0.1 s-5.9 h and 2 μL min-1-2 mL min-1). We show linear control of T and Q by their corresponding fluidic resistors even with the complex and nonlinear relation of the microfluidic components. This allows independent regulation of T and Q within their operational ranges but we found the two parameters mutually constrain their ranges via fluidic resistance. Also, we characterize the control of T by water-head pressure and present operational ranges of input water-head pressure decrease with increasing output water-head pressure. To show its utility, we apply the oscillator to generate droplets with low interfacial tension aqueous two-phase systems. Our study would be useful and provide the foundation for various functions of water-head-driven microfluidic circuits.
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Affiliation(s)
- Van Bac Dang
- Department of Mechanical Engineering, Konkuk University, Seoul, 05029, Republic of Korea.
| | - Sung-Jin Kim
- Department of Mechanical Engineering, Konkuk University, Seoul, 05029, Republic of Korea.
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27
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Mytnyk S, Ziemecka I, Olive AG, van der Meer JWM, Totlani KA, Oldenhof S, Kreutzer MT, van Steijn V, van Esch JH. Microcapsules with a permeable hydrogel shell and an aqueous core continuously produced in a 3D microdevice by all-aqueous microfluidics. RSC Adv 2017. [DOI: 10.1039/c7ra00452d] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
We report the continuous production of microcapsules composed of an aqueous core and permeable hydrogel shell, made stable by the controlled photo-cross-linking of the shell of an all-aqueous double emulsion.
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Affiliation(s)
- Serhii Mytnyk
- Advanced Soft Matter Group
- Chemical Engineering Department
- Delft University of Technology
- Delft
- The Netherlands
| | - Iwona Ziemecka
- Advanced Soft Matter Group
- Chemical Engineering Department
- Delft University of Technology
- Delft
- The Netherlands
| | - Alexandre G. L. Olive
- Advanced Soft Matter Group
- Chemical Engineering Department
- Delft University of Technology
- Delft
- The Netherlands
| | - J. Wim M. van der Meer
- Product and Process Engineering Group
- Chemical Engineering Department
- Delft University of Technology
- Delft
- The Netherlands
| | - Kartik A. Totlani
- Product and Process Engineering Group
- Chemical Engineering Department
- Delft University of Technology
- Delft
- The Netherlands
| | - Sander Oldenhof
- Advanced Soft Matter Group
- Chemical Engineering Department
- Delft University of Technology
- Delft
- The Netherlands
| | - Michiel T. Kreutzer
- Product and Process Engineering Group
- Chemical Engineering Department
- Delft University of Technology
- Delft
- The Netherlands
| | - Volkert van Steijn
- Product and Process Engineering Group
- Chemical Engineering Department
- Delft University of Technology
- Delft
- The Netherlands
| | - Jan H. van Esch
- Advanced Soft Matter Group
- Chemical Engineering Department
- Delft University of Technology
- Delft
- The Netherlands
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28
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29
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Soares RRG, Silva DFC, Fernandes P, Azevedo AM, Chu V, Conde JP, Aires-Barros MR. Miniaturization of aqueous two-phase extraction for biological applications: From micro-tubes to microchannels. Biotechnol J 2016; 11:1498-1512. [PMID: 27624685 DOI: 10.1002/biot.201600356] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 07/20/2016] [Accepted: 07/25/2016] [Indexed: 01/26/2023]
Abstract
Aqueous two-phase extraction (ATPE) is a biocompatible liquid-liquid (L-L) separation technique that has been under research for several decades towards the purification of biomolecules, ranging from small metabolites to large animal cells. More recently, with the emergence of rapid-prototyping techniques for fabrication of microfluidic structures with intricate designs, ATPE gained an expanded range of applications utilizing physical phenomena occurring exclusively at the microscale. Today, research is being carried simultaneously in two different volume ranges, mL-scale (microtubes) and nL-scale (microchannels). The objective of this review is to give insight into the state of the art at both microtube and microchannel-scale and to analyze whether miniaturization is currently a competing or divergent technology in a field of applications including bioseparation, bioanalytics, enhanced fermentation processes, catalysis, high-throughput screening and physical/chemical compartmentalization. From our perspective, both approaches are worthy of investigation and, depending on the application, it is likely that either (i) one of the approaches will eventually become obsolete in particular research areas such as purification at the preparative scale or high-throughput screening applications; or (ii) both approaches will function as complementing techniques within the bioanalytics field.
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Affiliation(s)
- Ruben R G Soares
- Instituto de Engenharia de Sistemas e Computadores - Microsistemas e Nanotecnologias (INESC MN) and IN - Institute of Nanoscience and Nanotechnology, Lisbon, Portugal.,IBB - Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Daniel F C Silva
- Instituto de Engenharia de Sistemas e Computadores - Microsistemas e Nanotecnologias (INESC MN) and IN - Institute of Nanoscience and Nanotechnology, Lisbon, Portugal.,IBB - Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Pedro Fernandes
- IBB - Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.,Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Ana M Azevedo
- IBB - Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.,Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - Virginia Chu
- Instituto de Engenharia de Sistemas e Computadores - Microsistemas e Nanotecnologias (INESC MN) and IN - Institute of Nanoscience and Nanotechnology, Lisbon, Portugal
| | - João P Conde
- Instituto de Engenharia de Sistemas e Computadores - Microsistemas e Nanotecnologias (INESC MN) and IN - Institute of Nanoscience and Nanotechnology, Lisbon, Portugal.,Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
| | - M Raquel Aires-Barros
- IBB - Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal.,Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
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30
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Moon BU, Hwang DK, Tsai SSH. Shrinking, growing, and bursting: microfluidic equilibrium control of water-in-water droplets. LAB ON A CHIP 2016; 16:2601-2608. [PMID: 27314278 DOI: 10.1039/c6lc00576d] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate the dynamic control of aqueous two phase system (ATPS) droplets in shrinking, growing, and dissolving conditions. The ATPS droplets are formed passively in a flow focusing microfluidic channel, where the dextran-rich (DEX) and polyethylene glycol-rich (PEG) solutions are introduced as disperse and continuous phases, respectively. To vary the ATPS equilibrium condition, we infuse into a secondary inlet the PEG phase from a different polymer concentration ATPS. We find that the resulting alteration of the continuous PEG phase can cause droplets to shrink or grow by approximately 45 and 30%, respectively. This volume change is due to water exchange between the disperse DEX and continuous PEG phases, as the system tends towards new equilibria. We also develop a simple model, based on the ATPS binodal curve and tie lines, that predicts the amount of droplet shrinkage or growth, based on the change in the continuous phase PEG concentration. We observe a good agreement between our experimental results and the model. Additionally, we find that when the continuous phase PEG concentration is reduced such that PEG and DEX phases no longer phase separate, the ATPS droplets are dissolved into the continuous phase. We apply this method to controllably release encapsulated microparticles and cells, and we find that their release occurs within 10 seconds. Our approach uses the dynamic equilibrium of ATPS to control droplet size along the microfluidic channel. By modulating the ATPS equilibrium, we are able to shrink, grow, and dissolve ATPS droplets in situ. We anticipate that this approach may find utility in many biomedical settings, for example, in drug and cell delivery and release applications.
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Affiliation(s)
- Byeong-Ui Moon
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Canada. and Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Canada and Institute for Biomedical Engineering, Science and Technology (iBEST), A partnership between Ryerson University and St. Michael's Hospital, Toronto, Canada
| | - Dae Kun Hwang
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Canada. and Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Canada and Department of Chemical Engineering, Ryerson University, Toronto, Canada
| | - Scott S H Tsai
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Canada. and Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Canada and Institute for Biomedical Engineering, Science and Technology (iBEST), A partnership between Ryerson University and St. Michael's Hospital, Toronto, Canada
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31
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Moon BU, Abbasi N, Jones SG, Hwang DK, Tsai SSH. Water-in-Water Droplets by Passive Microfluidic Flow Focusing. Anal Chem 2016; 88:3982-9. [PMID: 26959358 DOI: 10.1021/acs.analchem.6b00225] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present a simple microfluidic system that generates water-in-water, aqueous two phase system (ATPS) droplets, by passive flow focusing. ATPS droplet formation is achieved by applying weak hydrostatic pressures, with liquid-filled pipette tips as fluid columns at the inlets, to introduce low speed flows to the flow focusing junction. To control the size of the droplets, we systematically vary the interfacial tension and viscosity of the ATPS fluids and adjust the fluid column height at the fluid inlets. The size of the droplets scales with a power law of the ratio of viscous stresses in the two ATPS phases. Overall, we find a drop size coefficient of variation (CV; i.e., polydispersity) of about 10%. We also find that when drops form very close to the flow focusing junction, the drops have a CV of less than 1%. Our droplet generation method is easily scalable: we demonstrate a parallel system that generates droplets simultaneously and improves the droplet production rate by up to one order of magnitude. Finally, we show the potential application of our system for encapsulating cells in water-in-water emulsions by encapsulating microparticles and cells. To the best of our knowledge, our microfluidic technique is the first that forms low interfacial tension ATPS droplets without applying external perturbations. We anticipate that this simple approach will find utility in drug and cell delivery applications because of the all-biocompatible nature of the water-in-water ATPS environment.
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Affiliation(s)
- Byeong-Ui Moon
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital , Toronto, Canada.,Institute for Biomedical Engineering, Science and Technology (iBEST), a partnership between Ryerson University and St. Michael's Hospital , Toronto, Canada
| | - Niki Abbasi
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital , Toronto, Canada.,Institute for Biomedical Engineering, Science and Technology (iBEST), a partnership between Ryerson University and St. Michael's Hospital , Toronto, Canada
| | - Steven G Jones
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital , Toronto, Canada.,Institute for Biomedical Engineering, Science and Technology (iBEST), a partnership between Ryerson University and St. Michael's Hospital , Toronto, Canada
| | - Dae Kun Hwang
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital , Toronto, Canada.,Institute for Biomedical Engineering, Science and Technology (iBEST), a partnership between Ryerson University and St. Michael's Hospital , Toronto, Canada
| | - Scott S H Tsai
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital , Toronto, Canada.,Institute for Biomedical Engineering, Science and Technology (iBEST), a partnership between Ryerson University and St. Michael's Hospital , Toronto, Canada
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32
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Rounding of Negative Dry Film Resist by Diffusive Backside Exposure Creating Rounded Channels for Pneumatic Membrane Valves. MICROMACHINES 2015. [DOI: 10.3390/mi6111442] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Moon BU, Jones SG, Hwang DK, Tsai SSH. Microfluidic generation of aqueous two-phase system (ATPS) droplets by controlled pulsating inlet pressures. LAB ON A CHIP 2015; 15:2437-44. [PMID: 25906146 DOI: 10.1039/c5lc00217f] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We present a technique that generates droplets using ultralow interfacial tension aqueous two-phase systems (ATPS). Our method combines a classical microfluidic flow focusing geometry with precisely controlled pulsating inlet pressure, to form monodisperse ATPS droplets. The dextran (DEX) disperse phase enters through the central inlet with variable on-off pressure cycles controlled by a pneumatic solenoid valve. The continuous phase polyethylene glycol (PEG) solution enters the flow focusing junction through the cross channels at a fixed flow rate. The on-off cycles of the applied pressure, combined with the fixed flow rate cross flow, make it possible for the ATPS jet to break up into droplets. We observe different droplet formation regimes with changes in the applied pressure magnitude and timing, and the continuous phase flow rate. We also develop a scaling model to predict the size of the generated droplets, and the experimental results show a good quantitative agreement with our scaling model. Additionally, we demonstrate the potential for scaling-up of the droplet production rate, with a simultaneous two-droplet generating geometry. We anticipate that this simple and precise approach to making ATPS droplets will find utility in biological applications where the all-biocompatibility of ATPS is desirable.
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Affiliation(s)
- Byeong-Ui Moon
- Ryerson University, Mechanical and Industrial Engineering, Toronto, Canada.
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34
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Lai D, Frampton JP, Tsuei M, Kao A, Takayama S. Label-free direct visual analysis of hydrolytic enzyme activity using aqueous two-phase system droplet phase transitions. Anal Chem 2014; 86:4052-7. [PMID: 24654925 PMCID: PMC4004187 DOI: 10.1021/ac500657k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
![]()
Dextran hydrolysis-mediated conversion
of polyethylene glycol (PEG)-dextran
(DEX) aqueous two-phase system droplets to a single phase was used
to directly visualize Dextranase activity. DEX droplets were formed
either by manual micropipetting or within a continuous PEG phase by
computer controlled actuation of an orifice connecting rounded channels
formed by backside diffused light lithography. The time required for
the two-phase to one-phase transition was dependent on the Dextranase
concentration, pH of the medium, and temperature. The apparent Michaelis
constants for Dextranase were estimated based on previously reported
catalytic constants, the binodal polymer concentration curves for
PEG-DEX phase transition for each temperature, and pH condition. The
combination of a microfluidic droplet system and phase transition
observation provides a new method for label-free direct measurement
of enzyme activity.
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Affiliation(s)
- David Lai
- Department of Biomedical Engineering and Department of Macromolecular Science and Engineering, University of Michigan, Biointerfaces Institute , 2800 Plymouth Road, NCRC Building 10 A183, Ann Arbor, Michigan 48109, United States
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35
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Nge PN, Rogers CI, Woolley AT. Advances in microfluidic materials, functions, integration, and applications. Chem Rev 2013; 113:2550-83. [PMID: 23410114 PMCID: PMC3624029 DOI: 10.1021/cr300337x] [Citation(s) in RCA: 519] [Impact Index Per Article: 47.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Pamela N. Nge
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602
| | - Chad I. Rogers
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602
| | - Adam T. Woolley
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602
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36
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Boreyko JB, Mruetusatorn P, Retterer ST, Collier CP. Aqueous two-phase microdroplets with reversible phase transitions. LAB ON A CHIP 2013; 13:1295-301. [PMID: 23381219 DOI: 10.1039/c3lc41122b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Aqueous two-phase systems contained within microdroplets enable a bottom-up approach to mimicking the dynamic microcompartmentation of biomaterial that naturally occurs within the cytoplasm of cells. Here, we demonstrate the generation of femtolitre aqueous two-phase droplets within a microfluidic oil channel. Gated pressure pulses were used to generate individual, stationary two-phase microdroplets with a well-defined time zero for carrying out controlled and sequential phase transformations over time. Reversible phase transitions between single-phase, two-phase, and core-shell microbead states were obtained via evaporation-induced dehydration and water rehydration. In contrast to other microfluidic aqueous two-phase droplets, which require continuous flows and high-frequency droplet formation, our system enables the controlled isolation and reversible transformation of a single microdroplet and is expected to be useful for future studies in dynamic microcompartmentation and affinity partitioning.
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Affiliation(s)
- Jonathan B Boreyko
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6493, USA
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37
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Lai D, Labuz JM, Kim J, Luker GD, Shikanov A, Takayama S. Simple Multi-level Microchannel Fabrication by Pseudo-Grayscale Backside Diffused Light Lithography. RSC Adv 2013; 3:19467-19473. [PMID: 24976950 DOI: 10.1039/c3ra43834a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Photolithography of multi-level channel features in microfluidics is laborious and/or costly. Grayscale photolithography is mostly used with positive photoresists and conventional front side exposure, but the grayscale masks needed are generally costly and positive photoresists are not commonly used in microfluidic rapid prototyping. Here we introduce a simple and inexpensive alternative that uses pseudo-grayscale (pGS) photomasks in combination with backside diffused light lithography (BDLL) and the commonly used negative photoresist, SU-8. BDLL can produce smooth multi-level channels of gradually changing heights without use of true grayscale masks because of the use of diffused light. Since the exposure is done through a glass slide, the photoresist is cross-linked from the substrate side up enabling well-defined and stable structures to be fabricated from even unspun photoresist layers. In addition to providing unique structures and capabilities, the method is compatible with the "garage microfluidics" concept of creating useful tools at low cost since pGS BDLL can be performed with the use of only hot plates and a UV transilluminator: equipment commonly found in biology labs. Expensive spin coaters or collimated UV aligners are not needed. To demonstrate the applicability of pGS BDLL, a variety of weir-type cell traps were constructed with a single UV exposure to separate cancer cells (MDA-MB-231, 10-15 μm in size) from red blood cells (RBCs, 2-8 μm in size) as well as follicle clusters (40-50 μm in size) from cancer cells (MDA-MB-231, 10-15 μm in size).
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Affiliation(s)
- David Lai
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA ; Reproductive Sciences Program, University of Michigan, Ann Arbor, MI, USA
| | - Joseph M Labuz
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Jiwon Kim
- Reproductive Sciences Program, University of Michigan, Ann Arbor, MI, USA ; Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Gary D Luker
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA ; Department of Radiology, University of Michigan, Ann Arbor, MI, USA ; Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Ariella Shikanov
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA ; Reproductive Sciences Program, University of Michigan, Ann Arbor, MI, USA ; Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Shuichi Takayama
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA ; Reproductive Sciences Program, University of Michigan, Ann Arbor, MI, USA ; Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA ; Division of Nano-Bio and Chemical Engineering WCU Project, UNIST, Ulsan, Republic of Korea
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Kim SJ, Lai D, Park JY, Yokokawa R, Takayama S. Microfluidic automation using elastomeric valves and droplets: reducing reliance on external controllers. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2012; 8:2925-34. [PMID: 22761019 PMCID: PMC3463711 DOI: 10.1002/smll.201200456] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 05/02/2012] [Indexed: 05/04/2023]
Abstract
This paper gives an overview of elastomeric valve- and droplet-based microfluidic systems designed to minimize the need of external pressure to control fluid flow. This Concept article introduces the working principle of representative components in these devices along with relevant biochemical applications. This is followed by providing a perspective on the roles of different microfluidic valves and systems through comparison of their similarities and differences with transistors (valves) and systems in microelectronics. Despite some physical limitation of drawing analogies from electronic circuits, automated microfluidic circuit design can gain insights from electronic circuits to minimize external control units, while implementing high-complexity and high-throughput analysis.
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Affiliation(s)
- Sung-Jin Kim
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - David Lai
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Joong Yull Park
- School of Mechanical Engineering, Chung-Ang University, Seoul, Republic of Korea
| | - Ryuji Yokokawa
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Microengineering, Kyoto University, Yoshida-honmachi, Sakyo, Kyoto, 606-8501 JAPAN
| | - Shuichi Takayama
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, 48109, USA; Division of Nano-Bio and Chemical Engineering WCU Project, UNIST, Ulsan, Republic of Korea
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Geschiere SD, Ziemecka I, van Steijn V, Koper GJM, Esch JHV, Kreutzer MT. Slow growth of the Rayleigh-Plateau instability in aqueous two phase systems. BIOMICROFLUIDICS 2012; 6:22007-2200711. [PMID: 22536307 PMCID: PMC3331863 DOI: 10.1063/1.3700117] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 03/18/2012] [Indexed: 05/11/2023]
Abstract
This paper studies the Rayleigh-Plateau instability for co-flowing immiscible aqueous polymer solutions in a microfluidic channel. Careful vibration-free experiments with controlled actuation of the flow allowed direct measurement of the growth rate of this instability. Experiments for the well-known aqueous two phase system (ATPS, or aqueous biphasic systems) of dextran and polyethylene glycol solutions exhibited a growth rate of 1 s(-1), which was more than an order of magnitude slower than an analogous experiment with two immiscible Newtonian fluids with viscosities and interfacial tension that closely matched the ATPS experiment. Viscoelastic effects and adhesion to the walls were ruled out as explanations for the observed behavior. The results are remarkable because all current theory suggests that such dilute polymer solutions should break up faster, not slower, than the analogous Newtonian case. Microfluidic uses of aqueous two phase systems include separation of labile biomolecules but have hitherto be limited because of the difficulty in making droplets. The results of this work teach how to design devices for biological microfluidic ATPS platforms.
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Cheung Shum H, Varnell J, Weitz DA. Microfluidic fabrication of water-in-water (w/w) jets and emulsions. BIOMICROFLUIDICS 2012; 6:12808-128089. [PMID: 22662075 PMCID: PMC3365327 DOI: 10.1063/1.3670365] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 11/24/2011] [Indexed: 05/06/2023]
Abstract
We demonstrate the generation of water-in-water (w/w) jets and emulsions by combining droplet microfluidics and aqueous two-phase systems (ATPS). The application of ATPS in microfluidics has been hampered by the low interfacial tension between typical aqueous phases. The low tension makes it difficult to form w/w droplets with conventional droplet microfluidic approaches. We show that by mechanically perturbing a stable w/w jet, w/w emulsions can be prepared in a controlled and reproducible fashion. We also characterize the encapsulation ability of w/w emulsions and demonstrate that their encapsulation efficiency can be significantly enhanced by inducing formation of precipitates and gels at the w/w interfaces. Our work suggests a biologically and environmentally friendly platform for droplet microfluidics and establishes the potential of w/w droplet microfluidics for encapsulation-related applications.
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