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Jagannath A, Yu M, Li J, Zhang N, Gilchrist MD. Improving assay feasibility and biocompatibility of 3D cyclic olefin copolymer microwells by superhydrophilic modification via ultrasonic spray deposition of polyvinyl alcohol. BIOMATERIALS ADVANCES 2024; 163:213934. [PMID: 38954877 DOI: 10.1016/j.bioadv.2024.213934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 05/30/2024] [Accepted: 06/27/2024] [Indexed: 07/04/2024]
Abstract
Sample partitioning is a crucial step towards digitization of biological assays on polymer microfluidic platforms. However, effective liquid filling into microwells and long-term hydrophilicity remain a challenge in polymeric microfluidic devices, impeding the applicability in diagnostic and cell culture studies. To overcome this, a method to produce permanent superhydrophilic 3-dimensional microwells using cyclic olefin copolymer (COC) microfluidic chips is presented. The COC substrate is oxidized using UV treatment followed by ultrasonic spray coating of polyvinyl alcohol solution, offering uniform and long-term coating of high-aspect ratio microfeatures. The coated COC surfaces are UV-cured before bonding with a hydrophobic pressure-sensitive adhesive to drive selective filling into the wells. The surface hydrophilicity achieved using this method remains unchanged (water contact angle of 9°) for up to 6 months and the modified surface is characterized for physical (contact angle & surface energy, morphology, integrity of microfeatures and roughness), chemical composition (FTIR, Raman spectroscopy) and coating stability (pH, temperature, time). To establish the feasibility of the modified surface in biological applications, PVA-coated COC microfluidic chips are tested for DNA sensing (digital LAMP detection of CMV), and biocompatibility through protein adsorption and cell culture studies (cell adhesion, viability, and metabolic activity). Kidney and breast cells remained viable for the duration of testing (7 days) on this modified surface, and the coating did not affect the protein content, morphology or quality of the cultured cells. The ultrasonic spray coated system, coating with 0.25 % PVA for 15 cycles with 0.12 A current after UV oxidation, increased the surface energy of the COC (naturally hydrophobic) from 22.04 to 112.89 mJ/m2 and improved the filling efficiency from 40 % (native untreated COC) to 94 % in the microwells without interfering with the biocompatibility of the surface, proving to be an efficient, high-throughput and scalable method of microfluidic surface treatment for diagnostic and cell growth applications.
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Affiliation(s)
- Akshaya Jagannath
- School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin, 4, Ireland
| | - Mingzhi Yu
- School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin, 4, Ireland
| | - Jiaqi Li
- School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin, 4, Ireland
| | - Nan Zhang
- School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin, 4, Ireland; MiNAN Technologies Ltd., NovaUCD, Belfield, Dublin 4, Ireland.
| | - Michael D Gilchrist
- School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin, 4, Ireland; MiNAN Technologies Ltd., NovaUCD, Belfield, Dublin 4, Ireland
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Quan PL, Alvarez-Amador M, Jiang Y, Sauzade M, Brouzes E. Robust and rapid partitioning in thermoplastic. Analyst 2023; 149:100-107. [PMID: 37982399 PMCID: PMC10777811 DOI: 10.1039/d3an01869e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2023]
Abstract
Partitioning is the core technology supporting digital assays. It divides a sample into thousands of individual reactors prior to amplification and absolute quantification of target molecules. Thermoplastics are attractive materials for large scale manufacturing, however they have been seldomly used for fabricating partitioning arrays. Patitioning in thermoplastic devices has proven difficult due to the challenge of efficiently displacing the air trapped in the nanoliter structures during priming of thousands of chambers. Here, we report the design of an array of chambers made of thermoplastics where the progression of the liquid-air interface is controlled by capillary effects. Our device performs robust partitioning over a wide range of pressures and can be actuated at low pressure by a simple micropipette. Our thermoplastic device lays the foundation to cost-effective and instrument-free partitioning platforms, which could be deployed in low-resource settings.
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Affiliation(s)
- Phenix-Lan Quan
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA.
| | - Maria Alvarez-Amador
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA.
| | - Yuhe Jiang
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA.
| | - Martin Sauzade
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA.
| | - Eric Brouzes
- Department of Biomedical Engineering, Stony Brook University, Stony Brook, NY, 11794, USA.
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA
- Cancer Center, Stony Brook School of Medicine, Stony Brook, NY 11794, USA
- Institute for Engineering Driven Medicine, Stony Brook University, Stony Brook, NY 11794, USA
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Li S, Zhang J, He J, Liu W, Wang Y, Huang Z, Pang H, Chen Y. Functional PDMS Elastomers: Bulk Composites, Surface Engineering, and Precision Fabrication. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2304506. [PMID: 37814364 DOI: 10.1002/advs.202304506] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Indexed: 10/11/2023]
Abstract
Polydimethylsiloxane (PDMS)-the simplest and most common silicone compound-exemplifies the central characteristics of its class and has attracted tremendous research attention. The development of PDMS-based materials is a vivid reflection of the modern industry. In recent years, PDMS has stood out as the material of choice for various emerging technologies. The rapid improvement in bulk modification strategies and multifunctional surfaces has enabled a whole new generation of PDMS-based materials and devices, facilitating, and even transforming enormous applications, including flexible electronics, superwetting surfaces, soft actuators, wearable and implantable sensors, biomedicals, and autonomous robotics. This paper reviews the latest advances in the field of PDMS-based functional materials, with a focus on the added functionality and their use as programmable materials for smart devices. Recent breakthroughs regarding instant crosslinking and additive manufacturing are featured, and exciting opportunities for future research are highlighted. This review provides a quick entrance to this rapidly evolving field and will help guide the rational design of next-generation soft materials and devices.
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Affiliation(s)
- Shaopeng Li
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, 201620, China
| | - Jiaqi Zhang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, 201620, China
| | - Jian He
- Yizhi Technology (Shanghai) Co., Ltd, No. 99 Danba Road, Putuo District, Shanghai, 200062, China
| | - Weiping Liu
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, 201620, China
- Center for Composites, COMAC Shanghai Aircraft Manufacturing Co. Ltd, Shanghai, 201620, China
| | - YuHuang Wang
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA
- Maryland NanoCenter, University of Maryland, College Park, MD, 20742, USA
| | - Zhongjie Huang
- State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, 201620, China
| | - Huan Pang
- School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, Jiangsu, 225009, China
| | - Yiwang Chen
- National Engineering Research Center for Carbohydrate Synthesis/Key Lab of Fluorine and Silicon for Energy Materials and Chemistry of Ministry of Education, Jiangxi Normal University, 99 Ziyang Avenue, Nanchang, 330022, China
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Toppi A, Dufva M. Accessible, fast and easy fabrication of hydrophilic-in-hydrophobic microdroplet arrays. PLoS One 2022; 17:e0263282. [PMID: 35213568 PMCID: PMC8880433 DOI: 10.1371/journal.pone.0263282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 01/16/2022] [Indexed: 11/18/2022] Open
Abstract
Microdroplet arrays (MDAs) are powerful tools for digital immunoassays, high-throughput screening and single cell analysis. However, MDAs are usually produced with cleanroom processes, which are associated with high costs and low availability. Furthermore, in order to obtain robust and stable MDAs based on hydrophilic spots surrounded by a hydrophobic background, the chemistry must be strictly controlled, which is challenging using shared equipment. Here, we developed a new method to fabricate MDA substrates independently from the cleanroom. A small and low-cost in-house built system to collimate the light source was assembled for photopatterning a negative resist, and spots with diameters down to 4 μm were obtained, with only 3% to 5% spot-to-spot variation across the same sample and high batch-to-batch reproducibility. The use of a negative photoresist enabled the formation of a hydrophobic coating in solution which yielded high-quality MDAs. The feasibility for carrying out digital assays was demonstrated by measuring anti-Tau antibody in sample buffers containing bovine serum albumin, with no noticeable surface fouling. The reported, robust, cost-effective, and fast process could hence lower the threshold to fabricate and use MDAs for digital immunoassays and other microcompartmentalization-based applications.
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Affiliation(s)
- Arianna Toppi
- Department of Health Technology, Technical University of Denmark, Lyngby, Denmark
| | - Martin Dufva
- Department of Health Technology, Technical University of Denmark, Lyngby, Denmark
- * E-mail:
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Toppi A, Busk LL, Hu H, Dogan AA, Jönsson A, Taboryski RJ, Dufva M. Photolithographic Patterning of FluorAcryl for Biphilic Microwell-Based Digital Bioassays and Selection of Bacteria. ACS APPLIED MATERIALS & INTERFACES 2021; 13:43914-43924. [PMID: 34491739 DOI: 10.1021/acsami.1c10096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
FluorAcryl 3298 (FA) is a UV-curable fluoroacrylate polymer commonly employed as a chemically resistant, hydrophobic, and oleophobic coating. Here, FA was used in a cleanroom-based microstructuring process to fabricate hydrophilic-in-hydrophobic (HiH) micropatterned surfaces containing femtoliter-sized well arrays. A short protocol involving direct UV photopatterning, an etching step, and final recovery of the hydrophobic properties of the polymer produced patterned substrates with micrometer resolution. Specifically, HiH microwell arrays were obtained with a well diameter of 10 μm and various well depths ranging from 300 nm to 1 μm with high reproducibility. The 300 nm deep microdroplet array (MDA) substrates were used for digital immunoassays, which presented a limit of detection in the attomolar range. This demonstrated the chemical functionality of the hydrophilic and hydrophobic surfaces. Furthermore, the 1 μm deep wells could efficiently capture particles such as bacteria, whereas the 300 nm deep substrates or other types of flat HiH molecular monolayers could not. Capturing a mixture of bacteria expressing red- and green-fluorescent proteins, respectively, served as a model for screening and selection of specific phenotypes using FA-MDAs. Here, green-fluorescent bacteria were specifically selected by overlaying a solution of gelatin methacryloyl (GelMA) mixed with a photoinitiator and using a high-magnification objective, together with custom pinholes, in a common fluorescence microscope to cross-link the hydrogel around the bacteria of interest. In conclusion, due to the straightforward processing, versatility, and low-price, FA is an advantageous alternative to more commonly used fluorinated materials, such as CYTOP or Teflon-AF, for the fabrication of HiH microwell arrays and other biphilic microstructures.
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Affiliation(s)
- Arianna Toppi
- Department of Health Technology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Louise L Busk
- Department of Health Technology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Hongxia Hu
- Department of Health Technology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Asli A Dogan
- Department of Health Technology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Alexander Jönsson
- Department of Health Technology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Rafael J Taboryski
- DTU Nanolab, National Centre for Nano Fabrication and Characterization, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Martin Dufva
- Department of Health Technology, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
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Padmanabhan S, Sposito A, Yeh M, Everitt M, White I, DeVoe DL. Reagent integration and controlled release for multiplexed nucleic acid testing in disposable thermoplastic 2D microwell arrays. BIOMICROFLUIDICS 2021; 15:014103. [PMID: 33520047 PMCID: PMC7816768 DOI: 10.1063/5.0039146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 01/05/2021] [Indexed: 06/12/2023]
Abstract
The seamless integration of reagents into microfluidic devices can serve to significantly reduce assay complexity and cost for disposable diagnostics. In this work, the integration of multiplexed reagents into thermoplastic 2D microwell arrays is demonstrated using a scalable pin spotting technique. Using a simple and low-cost narrow-bore capillary spotting pin, high resolution deposition of concentrated reagents within the arrays of enclosed nanoliter-scale wells is achieved. The pin spotting method is further employed to encapsulate the deposited reagents with a chemically modified wax layer that serves to prevent disruption of the dried assay components during sample introduction through a shared microchannel, while also enabling temperature-controlled release after sample filling is complete. This approach supports the arbitrary patterning and release of different reagents within individual wells without crosstalk for multiplexed analyses. The performance of the in-well spotting technique is characterized using on-chip rolling circle amplification to evaluate its potential for nucleic acid-based diagnostics.
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Affiliation(s)
- S. Padmanabhan
- Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - A. Sposito
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - M. Yeh
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, USA
| | - M. Everitt
- Department of Bioengineering, University of Maryland, College Park, Maryland 20742, USA
| | - I. White
- Department of Bioengineering, University of Maryland, College Park, Maryland 20742, USA
| | - D. L. DeVoe
- Author to whom correspondence should be addressed:. Tel.: +1-301-405-8125
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