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Baban NS, Saha S, Jancheska S, Singh I, Khapli S, Khobdabayev M, Kim J, Bhattacharjee S, Song YA, Chakrabarty K, Karri R. Material-level countermeasures for securing microfluidic biochips. Lab Chip 2023; 23:4213-4231. [PMID: 37605818 DOI: 10.1039/d3lc00335c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
Flow-based microfluidic biochips (FMBs) have been rapidly commercialized and deployed in recent years for biological computing, clinical diagnostics, and point-of-care-tests (POCTs). However, outsourcing FMBs makes them susceptible to material-level attacks by malicious actors for illegitimate monetary gain. The attacks involve deliberate material degradation of an FMB's polydimethylsiloxane (PDMS) components by either doping with reactive solvents or altering the PDMS curing ratio during fabrication. Such attacks are stealthy enough to evade detection and deteriorate the FMB's function. Furthermore, material-level attacks can become prevalent in attacks based on intellectual property (IP) theft, such as counterfeiting, overbuilding, etc., which involve unscrupulous third-party manufacturers. To address this problem, we present a dynamic material-level watermarking scheme for PDMS-based FMBs with microvalves using a perylene-labeled fluorescent dye. The dyed microvalves show a unique excimer intensity peak under 405 nm laser excitation. Moreover, when pneumatically actuated, the peak shows a predetermined downward shift in intensity as a function of mechanical strain. We validated this protection scheme experimentally using fluorescence microscopy, which showed a high correlation (R2 = 0.971) between the normalized excimer intensity change and the maximum principal strain of the actuated microvalves. To detect curing ratio-based attacks, we adapted machine learning (ML) models, which were trained on the force-displacement data obtained from a mechanical punch test method. Our ML models achieved more than 99% accuracy in detecting curing ratio anomalies. These countermeasures can be used to proactively safeguard FMBs against material-level attacks in the era of global pandemics and diagnostics based on POCTs.
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Affiliation(s)
- Navajit Singh Baban
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
| | - Sohini Saha
- Department of Electrical and Computer Engineering, Duke University, Durham, USA
| | - Sofija Jancheska
- Department of Electrical and Computer Engineering, Tandon School of Engineering, New York University, New York, USA
| | - Inderjeet Singh
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
| | - Sachin Khapli
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
| | - Maksat Khobdabayev
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
| | - Jongmin Kim
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
| | - Sukanta Bhattacharjee
- Department of Computer Science and Engineering, Indian Institute of Technology Guwahati, India
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
- Department of Chemical and Biomolecular Engineering, Tandon School of Engineering, New York University, New York, USA
- Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, USA
| | - Krishnendu Chakrabarty
- School of Electrical, Computer and Energy Engineering, Arizona State University, Phoenix, Arizona, USA
| | - Ramesh Karri
- Department of Electrical and Computer Engineering, Tandon School of Engineering, New York University, New York, USA
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Baban NS, Saha S, Orozaliev A, Kim J, Bhattacharjee S, Song YA, Karri R, Chakrabarty K. Structural Attacks and Defenses for Flow-Based Microfluidic Biochips. IEEE Trans Biomed Circuits Syst 2022; 16:1261-1275. [PMID: 36350866 DOI: 10.1109/tbcas.2022.3220758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Flow-based microfluidic biochips (FMBs) have seen rapid commercialization and deployment in recent years for point-of-care and clinical diagnostics. However, the outsourcing of FMB design and manufacturing makes them susceptible to susceptible to malicious physical level and intellectual property (IP)-theft attacks. This work demonstrates the first structure-based (SB) attack on representative commercial FMBs. The SB attacks maliciously decrease the heights of the FMB reaction chambers to produce false-negative results. We validate this attack experimentally using fluorescence microscopy, which showed a high correlation ( R2 = 0.987) between chamber height and related fluorescence intensity of the DNA amplified by polymerase chain reaction. To detect SB attacks, we adopt two existing deep learning-based anomaly detection algorithms with ∼ 96% validation accuracy in recognizing such deliberately introduced microstructural anomalies. To safeguard FMBs against intellectual property (IP)-theft, we propose a novel device-level watermarking scheme for FMBs using intensity-height correlation. The countermeasures can be used to proactively safeguard FMBs against SB and IP-theft attacks in the era of global pandemics and personalized medicine.
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3
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Baban NS, Song YA. Rational design of bioinspired tissue adhesives. Clin Transl Med 2022; 12:e784. [PMID: 35389563 PMCID: PMC8989077 DOI: 10.1002/ctm2.784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 03/10/2022] [Indexed: 11/15/2022] Open
Affiliation(s)
- Navajit S Baban
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.,Department of Chemical and Biomolecular Engineering, Tandon School of Engineering, New York University, New York, USA.,Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, USA
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4
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Baban NS, Orozaliev A, Stubbs CJ, Song YA. Biomimicking interfacial fracture behavior of lizard tail autotomy with soft microinterlocking structures. Bioinspir Biomim 2022; 17:036002. [PMID: 35073538 DOI: 10.1088/1748-3190/ac4e79] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
Biological soft interfaces often exhibit complex microscale interlocking geometries to ensure sturdy and flexible connections. If needed, the interlocking can rapidly be released on demand leading to an abrupt decrease of interfacial adhesion. Here, inspired by lizard tail autotomy where such apparently tunable interfacial fracture behavior can be observed, we hypothesized an interlocking mechanism between the tail and body based on the muscle-actuated mushroom-shaped microinterlocks along the fracture planes. To mimic the fracture behavior of the lizard tail, we developed a soft bilayer patch that consisted of a dense array of soft hemispherical microstructures in the upper layer acting as mechanical interlocks with the counter body part. The bottom control layer contained a microchannel that allowed to deflect the upper layer when applying the negative pressure, thus mimicking muscle contraction. In the microinterlocked condition, the biomimetic tail demonstrated a 2.7-fold and a three-fold increase in adhesion strength and toughness, respectively, compared to the pneumatically released microinterlocks. Furthermore, as per the computational analysis, the subsurface microchannel in the control layer enabled augmented adhesion by rendering the interface more compliant as a dissipative matrix, decreasing contact opening and strain energy dissipation by 50%. The contrasting features between the microinterlocked and released cases demonstrated a highly tunable adhesion of our biomimetic soft patch. The potential applications of our study are expected in soft robotics and prosthetics.
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Affiliation(s)
- Navajit S Baban
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Ajymurat Orozaliev
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Christopher J Stubbs
- Gildart Haase School of Computer Science and Engineering, Fairleigh Dickinson University, Teaneck, NJ 07666, United States of America
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
- Department of Chemical and Biomolecular Engineering, Tandon School of Engineering, New York University, NY, United States of America
- Department of Biomedical Engineering, Tandon School of Engineering, New York University, NY, United States of America
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5
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Abstract
Lizard tail autotomy is an antipredator strategy consisting of sturdy attachment at regular times but quick detachment during need. We propose a biomimetic fracture model of lizard tail autotomy using multiscale hierarchical structures. The structures consist of uniformly distributed micropillars with nanoporous tops, which recapitulate the high-density mushroom-shaped microstructures found on the lizard tail's muscle fracture plane. The biomimetic experiments showed adhesion enhancement when combining nanoporous interfacial surfaces with flexible micropillars in tensile and peel modes. The fracture modeling identified micro- and nanostructure-based toughening mechanisms as the critical factor. Under wet conditions, capillarity-assisted energy dissipation pertaining to liquid-filled microgaps and nanopores further increased the adhesion performance. This research presents insights on lizard tail autotomy and provides new biomimetic ideas to solve adhesion problems.
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Affiliation(s)
- Navajit S Baban
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Ajymurat Orozaliev
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Sebastian Kirchhof
- Division of Science, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Christopher J Stubbs
- Gildart Haase School of Computer Sciences and Engineering, Fairleigh Dickinson University, Teaneck, NJ 07666, USA
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.,Department of Chemical and Biomolecular Engineering, Tandon School of Engineering, New York University, New York, NY 11201, USA.,Department of Biomedical Engineering, Tandon School of Engineering, New York University, New York, NY 11201, USA
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6
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Sofela S, Sahloul S, Song YA. Biophysical analysis of drug efficacy on C. elegans models for neurodegenerative and neuromuscular diseases. PLoS One 2021; 16:e0246496. [PMID: 34115761 PMCID: PMC8195402 DOI: 10.1371/journal.pone.0246496] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 05/25/2021] [Indexed: 11/25/2022] Open
Abstract
Caenorhabditis elegans has emerged as a powerful model organism for drug screening due to its cellular simplicity, genetic amenability and homology to humans combined with its small size and low cost. Currently, high-throughput drug screening assays are mostly based on image-based phenotyping with the focus on morphological-descriptive traits not exploiting key locomotory parameters of this multicellular model with muscles such as its thrashing force, a critical biophysical parameter when screening drugs for muscle-related diseases. In this study, we demonstrated the use of a micropillar-based force assay chip in combination with a fluorescence assay to evaluate the efficacy of various drugs currently used in treatment of neurodegenerative and neuromuscular diseases. Using this two-dimensional approach, we showed that the force assay was generally more sensitive in measuring efficacy of drug treatment in Duchenne Muscular Dystrophy and Parkinson’s Disease mutant worms as well as partly in Amyotrophic Lateral Sclerosis model. These results underline the potential of our force assay chip in screening of potential drug candidates for the treatment of neurodegenerative and neuromuscular diseases when combined with a fluorescence assay in a two-dimensional analysis approach.
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Affiliation(s)
- Samuel Sofela
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
- Tandon School of Engineering, New York University, New York, NY, United States of America
| | - Sarah Sahloul
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
- Tandon School of Engineering, New York University, New York, NY, United States of America
- * E-mail:
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Sofela S, Sahloul S, Bhattacharjee S, Bose A, Usman U, Song YA. Quantitative fluorescence imaging of mitochondria in body wall muscles of Caenorhabditis elegans under hyperglycemic conditions using a microfluidic chip. Integr Biol (Camb) 2020; 12:150-160. [DOI: 10.1093/intbio/zyaa011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 03/15/2020] [Accepted: 04/28/2020] [Indexed: 12/25/2022]
Abstract
Abstract
Type 2 diabetes is the most common metabolic disease, and insulin resistance plays a role in the pathogenesis of the disease. Because completely functional mitochondria are necessary to obtain glucose-stimulated insulin from pancreatic beta cells, dysfunction of mitochondrial oxidative pathway could be involved in the development of diabetes. As a simple animal model, Caenorhabditis elegans renders itself to investigate such metabolic mechanisms because it possesses insulin/insulin-like growth factor-1 signaling pathway similar to that in humans. Currently, the widely spread agarose pad-based immobilization technique for fluorescence imaging of the mitochondria in C. elegans is laborious, batchwise, and does not allow for facile handling of the worm. To overcome these technical challenges, we have developed a single-channel microfluidic device that can trap a C. elegans and allow to image the mitochondria in body wall muscles accurately and in higher throughput than the traditional approach. In specific, our microfluidic device took advantage of the proprioception of the worm to rotate its body in a microfluidic channel with an aspect ratio above one to gain more space for its undulation motion that was favorable for quantitative fluorescence imaging of mitochondria in the body wall muscles. Exploiting this unique feature of the microfluidic chip-based immobilization and fluorescence imaging, we observed a significant decrease in the mitochondrial fluorescence intensity under hyperglycemic conditions, whereas the agarose pad-based approach did not show any significant change under the same conditions. A machine learning model trained with these fluorescence images from the microfluidic device could classify healthy and hyperglycemic worms at high accuracy. Given this significant technological advantage, its easiness of use and low cost, our microfluidic imaging chip could become a useful immobilization tool for quantitative fluorescence imaging of the body wall muscles in C. elegans.
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Affiliation(s)
- Samuel Sofela
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
- Tandon School of Engineering, New York University, Brooklyn, NY, USA
| | - Sarah Sahloul
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Sukanta Bhattacharjee
- Department of Computer Science and Engineering, Indian Institute of Technology Guwahati, Guwahati, India
| | - Ambar Bose
- Kallistos Infotech Private Limited, Kolkata, India
| | - Ushna Usman
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
- Tandon School of Engineering, New York University, Brooklyn, NY, USA
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8
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Kim J, Sahloul S, Orozaliev A, Do VQ, Pham VS, Martins D, Wei X, Levicky R, Song YA. Microfluidic Electrokinetic Preconcentration Chips: Enhancing the detection of nucleic acids and exosomes. IEEE Nanotechnology Mag 2020. [DOI: 10.1109/mnano.2020.2966064] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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9
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Sofela S, Sahloul S, Stubbs C, Orozaliev A, Refai FS, Esmaeel AM, Fahs H, Abdelgawad MO, Gunsalus KC, Song YA. Phenotyping of the thrashing forces exerted by partially immobilized C. elegans using elastomeric micropillar arrays. Lab Chip 2019; 19:3685-3696. [PMID: 31576392 DOI: 10.1039/c9lc00660e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
As a simple model organism, C. elegans plays an important role in gaining insight into the relationship between bodily thrashing forces and biological effects, such as disease and aging, or physical stimuli, like touch and light. Due to their similar length scale, microfluidic chips have been extensively explored for use in various biological studies involving C. elegans. However, a formidable challenge still exists due to the complexity of integrating external stimuli (chemical, mechanical or optical) with free-moving worms and subsequent imaging on the chip. In this report, we use a microfluidic device to partially immobilize a worm, which allows for measurements of the relative changes in the thrashing force under different assay conditions. Using a device adapted to the natural escape-like coiling response of a worm to immobilization, we have quantified the relative changes in the thrashing force during different developmental stages (L1, L3, L4, and young adult) and in response to various glucose concentrations and drug treatment. Our findings showed a loss of thrashing force following the introduction of glucose into a wild type worm culture that could be reversed upon treatment with the type 2 diabetes drug metformin. A morphological study of the actin filament structures in the body wall muscles provided supporting evidence for the force measurement data. Finally, we demonstrated the multiplexing capabilities of our device through recording the thrashing activities of eight worms simultaneously. The multiplexing capabilities and facile imaging available using our device open the door for high-throughput neuromuscular studies using C. elegans.
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Affiliation(s)
- Samuel Sofela
- Division of Engineering, New York University Abu Dhabi, United Arab Emirates. and Tandon School of Engineering, New York University, New York, USA
| | - Sarah Sahloul
- Division of Engineering, New York University Abu Dhabi, United Arab Emirates.
| | | | - Ajymurat Orozaliev
- Division of Engineering, New York University Abu Dhabi, United Arab Emirates.
| | - Fathima Shaffra Refai
- Center for Genomics and Systems Biology, New York University Abu Dhabi, United Arab Emirates
| | | | - Hala Fahs
- Center for Genomics and Systems Biology, New York University Abu Dhabi, United Arab Emirates
| | - Mohamed Omar Abdelgawad
- Department of Mechanical Engineering, Assiut University, Egypt and Department of Mechanical Engineering, American University of Sharjah, United Arab Emirates
| | - Kristin C Gunsalus
- Center for Genomics and Systems Biology, New York University Abu Dhabi, United Arab Emirates
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi, United Arab Emirates. and Tandon School of Engineering, New York University, New York, USA
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10
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Cheung LS, Sahloul S, Orozaliev A, Song YA. Rapid Detection and Trapping of Extracellular Vesicles by Electrokinetic Concentration for Liquid Biopsy on Chip. Micromachines (Basel) 2018; 9:E306. [PMID: 30424239 PMCID: PMC6187315 DOI: 10.3390/mi9060306] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/11/2018] [Accepted: 06/15/2018] [Indexed: 01/04/2023]
Abstract
Exosomes have gained immense importance since their proteomic and genetic contents could potentially be used for disease diagnostics, monitoring of cancer progression, metastasis, and drug efficacy. However, establishing the clinical utility of exosomes has been restricted due to small sizes and high sample loss from extensive sample preparation. Sample loss is particularly critical for body fluids limited in volume and difficult to access, e.g., cerebrospinal fluid. We present a microfluidic technique that locally enhances the concentration of extracellular vesicles extracted from MDA-MB-231 human breast cancer cell lines by using an ion concentration polarization (ICP)-based electrokinetic concentrator. Our design incorporates a trapping mechanism near the conductive polymer membrane; therefore, we can preconcentrate and capture extracellular vesicles simultaneously. Compared with standard fluorescence detection, our method increased the limit of detection (LOD) of extracellular vesicles by two orders of magnitude in 30 min. Our concentrator increased the extracellular vesicle concentration for 5.0 × 10⁷ particles/1 mL (LOD), 5.0 × 10⁸ particles/1 mL, and 5.0 × 10⁸ particles/1 mL by ~100-fold each within 30 min using 45 V. This study demonstrates an alternative platform to simultaneously preconcentrate and capture extracellular vesicles that can be incorporated as part of a liquid biopsy-on-a-chip system for the detection of exosomal biomarkers and analysis of their contents for early cancer diagnosis.
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Affiliation(s)
- Lucia S Cheung
- Division of Engineering, New York University Abu Dhabi, PO Box 129188, Abu Dhabi, UAE.
| | - Sarah Sahloul
- Division of Engineering, New York University Abu Dhabi, PO Box 129188, Abu Dhabi, UAE.
| | - Ajymurat Orozaliev
- Division of Engineering, New York University Abu Dhabi, PO Box 129188, Abu Dhabi, UAE.
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi, PO Box 129188, Abu Dhabi, UAE.
- Department of Chemical and Biomolecular Engineering, New York University Tandon School of Engineering, Brooklyn, NY 11201, USA.
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Sofela S, Sahloul S, Rafeie M, Kwon T, Han J, Warkiani ME, Song YA. High-throughput sorting of eggs for synchronization of C. elegans in a microfluidic spiral chip. Lab Chip 2018; 18:679-687. [PMID: 29372209 DOI: 10.1039/c7lc00998d] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
In this study, we report the use of a high-throughput microfluidic spiral chip to screen out eggs from a mixed age nematode population, which can subsequently be cultured to a desired developmental stage. For the sorting of a mixture containing three different developmental stages, eggs, L1 and L4, we utilized a microfluidic spiral chip with a trapezoidal channel to obtain a sorting efficiency of above 97% and a sample purity (SP) of above 80% for eggs at different flow rates up to 10 mL min-1. The result demonstrated a cost-effective, simple, and highly efficient method for synchronizing C. elegans at a high throughput (∼4200 organisms per min at 6 mL min-1), while eliminating challenges such as clogging and non-reusability of membrane-based filtration. Due to its simplicity, our method can be easily adopted in the C. elegans research community.
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Affiliation(s)
- Samuel Sofela
- Division of Engineering, New York University Abu Dhabi, United Arab Emirates
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12
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Zhang Q, Kaisti M, Prabhu A, Yu Y, Song YA, Rafailovich MH, Rahman A, Levon K. Polyaniline-functionalized ion-sensitive floating-gate FETs for the on-chip monitoring of peroxidase-catalyzed redox reactions. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2017.12.130] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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13
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Cheung LS, Wei X, Martins D, Song YA. Rapid detection of exosomal microRNA biomarkers by electrokinetic concentration for liquid biopsy on chip. Biomicrofluidics 2018; 12:014104. [PMID: 30867851 PMCID: PMC6404950 DOI: 10.1063/1.5009719] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 12/12/2017] [Indexed: 06/09/2023]
Abstract
An ion concentration polarization (ICP)-based electrokinetic concentration device is used for accelerating the surface hybridization reaction between exosomal microRNAs (miRNAs) and morpholinos (MOs) as a synthetic oligo capture probe in the nanomolar concentration range in a microfluidic channel. Compared with standard hybridization at the same concentration, the hybridization time of the miRNA target on MO capture probes could be reduced from ∼24 h to 30 min, with an increase in detection speed by 48 times. This ICP-enhanced hybridization method not only significantly decreases the detection time but also makes workflow simple to use, circumventing use of quantitative reverse transcription polymerase chain reaction or other conventional enzyme-based amplification methods that can cause artifacts.
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Affiliation(s)
- Lucia S Cheung
- Division of Engineering, New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | | | - Diogo Martins
- NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
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14
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Desta IT, Al-Sharif A, AlGharibeh N, Mustafa N, Orozaliev A, Giakoumidis N, Gunsalus KC, Song YA. Detecting and Trapping of a Single C. elegans Worm in a Microfluidic Chip for Automated Microplate Dispensing. SLAS Technol 2016; 22:431-436. [PMID: 27630097 DOI: 10.1177/2211068216669688] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Microfluidic devices offer new technical possibilities for a precise manipulation of Caenorhabditis elegans due to the comparable length scale. C. elegans is a small, free-living nematode worm that is a popular model system for genetic, genomic, and high-throughput experimental studies of animal development and neurobiology. In this paper, we demonstrate a microfluidic system in polydimethylsiloxane (PDMS) for dispensing of a single C. elegans worm into a 96-well plate. It consists of two PDMS layers, a flow and a control layer. Using five microfluidic pneumatic valves in the control layer, a single worm is trapped upon optical detection with a pair of optical fibers integrated perpendicular to the constriction channel and then dispensed into a microplate well with a dispensing tip attached to a robotic handling system. Due to its simple design and facile fabrication, we expect that our microfluidic chip can be expanded to a multiplexed dispensation system of C. elegans worms for high-throughput drug screening.
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Affiliation(s)
- Israel T Desta
- 1 Division of Engineering, New York University Abu Dhabi, Abu Dhabi, UAE
| | | | - Nour AlGharibeh
- 1 Division of Engineering, New York University Abu Dhabi, Abu Dhabi, UAE
| | - Nahal Mustafa
- 1 Division of Engineering, New York University Abu Dhabi, Abu Dhabi, UAE
| | - Ajymurat Orozaliev
- 1 Division of Engineering, New York University Abu Dhabi, Abu Dhabi, UAE
| | | | - Kristin C Gunsalus
- 2 Department of Biology, New York University, Center for Genomics and Systems Biology, NY, USA.,3 Division of Science, New York University Abu Dhabi, Abu Dhabi, UAE
| | - Yong-Ak Song
- 1 Division of Engineering, New York University Abu Dhabi, Abu Dhabi, UAE.,4 Tandon School of Engineering, Department of Chemical and Biomolecular Engineering, New York University, Brooklyn, NY, USA
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15
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Wei X, Panindre P, Zhang Q, Song YA. Increasing the Detection Sensitivity for DNA-Morpholino Hybridization in Sub-Nanomolar Regime by Enhancing the Surface Ion Conductance of PEDOT:PSS Membrane in a Microchannel. ACS Sens 2016. [DOI: 10.1021/acssensors.6b00169] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xi Wei
- Division
of Engineering, New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | | | | | - Yong-Ak Song
- Division
of Engineering, New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
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16
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Wei X, Syed A, Mao P, Han J, Song YA. Creating Sub-50 Nm Nanofluidic Junctions in PDMS Microfluidic Chip via Self-Assembly Process of Colloidal Particles. J Vis Exp 2016. [PMID: 27023724 DOI: 10.3791/54145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its transparency. Due to the softness of the PDMS material, however, it is challenging to use PDMS for building nanochannels. The channels tend to collapse easily during plasma bonding. In this paper, we present an evaporation-driven self-assembly method of silica colloidal nanoparticles to create nanofluidic junctions with sub-50 nm pores between two microchannels. The pore size as well as the surface charge of the nanofluidic junction is tunable simply by changing the colloidal silica bead size and surface functionalization outside of the assembled microfluidic device in a vial before the self-assembly process. Using the self-assembly of nanoparticles with a bead size of 300 nm, 500 nm, and 900 nm, it was possible to fabricate a porous membrane with a pore size of ~45 nm, ~75 nm and ~135 nm, respectively. Under electrical potential, this nanoporous membrane initiated ion concentration polarization (ICP) acting as a cation-selective membrane to concentrate DNA by ~1,700 times within 15 min. This non-lithographic nanofabrication process opens up a new opportunity to build a tunable nanofluidic junction for the study of nanoscale transport processes of ions and molecules inside a PDMS microfluidic chip.
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Affiliation(s)
- Xi Wei
- Division of Engineering, New York University Abu Dhabi (NYUAD); Department of Chemical and Biomolecular Engineering, New York University Tandon School of Engineering
| | - Abeer Syed
- Division of Engineering, New York University Abu Dhabi (NYUAD)
| | | | - Jongyoon Han
- Department of Electrical Engineering and Computer Science, Department of Biological Engineering, MIT
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi (NYUAD); Department of Chemical and Biomolecular Engineering, New York University Tandon School of Engineering;
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Martins D, Wei X, Levicky R, Song YA. Integration of Multiplexed Microfluidic Electrokinetic Concentrators with a Morpholino Microarray via Reversible Surface Bonding for Enhanced DNA Hybridization. Anal Chem 2016; 88:3539-47. [PMID: 26916577 DOI: 10.1021/acs.analchem.5b03875] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
UNLABELLED We describe a microfluidic concentration device to accelerate the surface hybridization reaction between DNA and morpholinos (MOs) for enhanced detection. The microfluidic concentrator comprises a single polydimethylsiloxane (PDMS) microchannel onto which an ion-selective layer of conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) ( PEDOT PSS) was directly printed and then reversibly surface bonded onto a morpholino microarray for hybridization. Using this electrokinetic trapping concentrator, we could achieve a maximum concentration factor of ∼800 for DNA and a limit of detection of 10 nM within 15 min. In terms of the detection speed, it enabled faster hybridization by around 10-fold when compared to conventional diffusion-based hybridization. A significant advantage of our approach is that the fabrication of the microfluidic concentrator is completely decoupled from the microarray; by eliminating the need to deposit an ion-selective layer on the microarray surface prior to device integration, interfacing between both modules, the PDMS chip for electrokinetic concentration and the substrate for DNA sensing are easier and applicable to any microarray platform. Furthermore, this fabrication strategy facilitates a multiplexing of concentrators. We have demonstrated the proof-of-concept for multiplexing by building a device with 5 parallel concentrators connected to a single inlet/outlet and applying it to parallel concentration and hybridization. Such device yielded similar concentration and hybridization efficiency compared to that of a single-channel device without adding any complexity to the fabrication and setup. These results demonstrate that our concentrator concept can be applied to the development of a highly multiplexed concentrator-enhanced microarray detection system for either genetic analysis or other diagnostic assays.
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Affiliation(s)
- Diogo Martins
- Division of Engineering, New York University Abu Dhabi , P.O. Box 129188 , Abu Dhabi, United Arab Emirates
| | - Xi Wei
- Division of Engineering, New York University Abu Dhabi , P.O. Box 129188 , Abu Dhabi, United Arab Emirates.,Department of Chemical and Biomolecular Engineering, New York University Tandon School of Engineering , Brooklyn, New York 11201, United States
| | - Rastislav Levicky
- Department of Chemical and Biomolecular Engineering, New York University Tandon School of Engineering , Brooklyn, New York 11201, United States
| | - Yong-Ak Song
- Division of Engineering, New York University Abu Dhabi , P.O. Box 129188 , Abu Dhabi, United Arab Emirates.,Department of Chemical and Biomolecular Engineering, New York University Tandon School of Engineering , Brooklyn, New York 11201, United States
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Song YA, Wu L, Tannenbaum SR, Wishnok JS, Han J. Tunable membranes for free-flow zone electrophoresis in PDMS microchip using guided self-assembly of silica microbeads. Anal Chem 2013; 85:11695-9. [PMID: 24251795 DOI: 10.1021/ac402169x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this paper, we evaluate the strategy of using self-assembled microbeads to build a robust and tunable membrane for free-flow zone electrophoresis in a PDMS microfluidic chip. To fabricate a porous membrane as a salt bridge for free-flow zone electrophoresis, we used silica or polystyrene microbeads between 3-6 μm in diameter and packed them inside a microchannel. After complete evaporation, we infiltrated the porous microbead structure with a positively or negatively charged hydrogel to modify its surface charge polarity. Using this device, we demonstrated binary sorting (separation of positive and negative species at a given pH) of peptides and dyes in standard buffer systems without using sheath flows. The sample loss during sorting could be minimized by using ion selectivity of hydrogel-infiltrated microbead membranes. Our fabrication method enables building a robust membrane for pressure-driven free-flow zone electrophoresis with tunable pore size as well as surface charge polarity.
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Affiliation(s)
- Yong-Ak Song
- Department of Electrical Engineering and Computer Science, ‡Department of Biological Engineering, §Department of Chemistry, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, MA 02139, United States
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Song YA, Ibrahim AM, Rabie AN, Han J, Lin SJ. Microfabricated nerve–electrode interfaces in neural prosthetics and neural engineering. Biotechnol Genet Eng Rev 2013; 29:113-34. [DOI: 10.1080/02648725.2013.801231] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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20
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Ko SH, Song YA, Kim SJ, Kim M, Han J, Kang KH. Nanofluidic preconcentration device in a straight microchannel using ion concentration polarization. Lab Chip 2012; 12:4472-82. [PMID: 22907316 DOI: 10.1039/c2lc21238b] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
In this paper, we introduce a simple, straight microchannel design for a nanofluidic protein concentration device. Compared with concentration devices previously developed, the anode channel and cathode channel in this new concentration scheme are both integrated into a straight microchannel, with one inlet and one outlet. Most of the functions of a conventional two-channel concentration device can be achieved by this concentration device, and the efficiency of sample accumulation can be controlled by the dimension of the Nafion membrane. Also, the operating mechanism of this device was tested on various material combinations such as PDMS (polydimethyl-siloxane) channel-glass substrate and silicon channel-PDMS substrate. Using a combined PDMS-silicon device which was sealed reversibly without plasma bonding, surface based immunoassay for concentrator-enhanced detection of clinically relevant samples such as C-reactive protein (CRP) was demonstrated. As a result, it was possible to enhance the detection sensitivity of the immunoassay by more than 500 folds compared to the immunoassay without preconcentration process.
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Affiliation(s)
- Sung Hee Ko
- Department of Mechanical Engineering, Pohang University of Science and Technology, San 31, Hyojadong, Pohang, Gyeongbuk 790-784, Korea
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Song YA, Melik R, Rabie AN, Ibrahim AMS, Moses D, Tan A, Han J, Lin SJ. Electrochemical activation and inhibition of neuromuscular systems through modulation of ion concentrations with ion-selective membranes. Nat Mater 2011; 10:980-6. [PMID: 22019944 PMCID: PMC3223285 DOI: 10.1038/nmat3146] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Accepted: 09/16/2011] [Indexed: 05/04/2023]
Abstract
Conventional functional electrical stimulation aims to restore functional motor activity of patients with disabilities resulting from spinal cord injury or neurological disorders. However, intervention with functional electrical stimulation in neurological diseases lacks an effective implantable method that suppresses unwanted nerve signals. We have developed an electrochemical method to activate and inhibit a nerve by electrically modulating ion concentrations in situ along the nerve. Using ion-selective membranes to achieve different excitability states of the nerve, we observe either a reduction of the electrical threshold for stimulation by up to approximately 40%, or voluntary, reversible inhibition of nerve signal propagation. This low-threshold electrochemical stimulation method is applicable in current implantable neuroprosthetic devices, whereas the on-demand nerve-blocking mechanism could offer effective clinical intervention in disease states caused by uncontrolled nerve activation, such as epilepsy and chronic pain syndromes.
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Affiliation(s)
- Yong-Ak Song
- Department of Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology, Cambridge, MA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA
| | - Rohat Melik
- Department of Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology, Cambridge, MA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA
| | - Amr N. Rabie
- Divisions of Plastic Surgery and Otolaryngology, Beth Israel Deaconess Medical Center, and Harvard Medical School, Boston, MA
- Department of Otolaryngology, Ain Shams University, Cairo, Egypt
| | - Ahmed M. S. Ibrahim
- Divisions of Plastic Surgery and Otolaryngology, Beth Israel Deaconess Medical Center, and Harvard Medical School, Boston, MA
| | - David Moses
- Department of Bioengineering, Rice University, Houston, TX
| | - Ara Tan
- Department of Chemical Engineering, University of Minnesota, Twin Cities, MN
| | - Jongyoon Han
- Department of Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology, Cambridge, MA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA
| | - Samuel J. Lin
- Divisions of Plastic Surgery and Otolaryngology, Beth Israel Deaconess Medical Center, and Harvard Medical School, Boston, MA
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Chen CH, Sarkar A, Song YA, Miller MA, Kim SJ, Griffith LG, Lauffenburger DA, Han J. Enhancing protease activity assay in droplet-based microfluidics using a biomolecule concentrator. J Am Chem Soc 2011; 133:10368-71. [PMID: 21671557 PMCID: PMC3165005 DOI: 10.1021/ja2036628] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
We introduce an integrated microfluidic device consisting of a biomolecule concentrator and a microdroplet generator, which enhances the limited sensitivity of low-abundance enzyme assays by concentrating biomolecules before encapsulating them into droplet microreactors. We used this platform to detect ultralow levels of matrix metalloproteinases (MMPs) from diluted cellular supernatant and showed that it significantly (~10-fold) reduced the time required to complete the assay and the sample volume used.
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Affiliation(s)
- Chia-Hung Chen
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Aniruddh Sarkar
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Yong-Ak Song
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Miles A. Miller
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Sung Jae Kim
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | - Linda G. Griffith
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
| | | | - Jongyoon Han
- Department of Electrical Engineering and Computer Science, MIT, 36-841, 77 Massachusetts Avenue, Cambridge MA 02139
- Department of Biological Engineering, MIT, 56-651, 77 Massachusetts Avenue, Cambridge MA 02139
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Song YA, Chan M, Celio C, Tannenbaum SR, Wishnok JS, Han J. Free-flow zone electrophoresis of peptides and proteins in PDMS microchip for narrow pI range sample prefractionation coupled with mass spectrometry. Anal Chem 2010; 82:2317-25. [PMID: 20163146 DOI: 10.1021/ac9025219] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this paper, we are evaluating the strategy of sorting peptides/proteins based on the charge to mass without resorting to ampholytes and/or isoelectric focusing, using a single- and two-step free-flow zone electrophoresis. We developed a simple fabrication method to create a salt bridge for free-flow zone electrophoresis in PDMS chips by surface printing a hydrophobic layer on a glass substrate. Since the surface-printed hydrophobic layer prevents plasma bonding between the PDMS chip and the substrate, an electrical junction gap can be created for free-flow zone electrophoresis. With this device, we demonstrated a separation of positive and negative peptides and proteins at a given pH in standard buffer systems and validated the sorting result with LC/MS. Furthermore, we coupled two sorting steps via off-chip titration and isolated peptides within specific pI ranges from sample mixtures, where the pI range was simply set by the pH values of the buffer solutions. This free-flow zone electrophoresis sorting device, with its simplicity of fabrication, and a sorting resolution of 0.5 pH unit, can potentially be a high-throughput sample fractionation tool for targeted proteomics using LC/MS.
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Affiliation(s)
- Yong-Ak Song
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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24
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Liu V, Song YA, Han J. Capillary-valve-based fabrication of ion-selective membrane junction for electrokinetic sample preconcentration in PDMS chip. Lab Chip 2010; 10:1485-90. [PMID: 20480116 PMCID: PMC2926974 DOI: 10.1039/b923214a] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
In this paper, we report a novel method for fabricating ion-selective membranes in poly(dimethylsiloxane) (PDMS)/glass-based microfluidic preconcentrators. Based on the concept of capillary valves, this fabrication method involves filling a lithographically patterned junction between two microchannels with an ion-selective material such as Nafion resin; subsequent curing results in a high aspect-ratio membrane for use in electrokinetic sample preconcentration. To demonstrate the concentration performance of this high-aspect-ratio, ion-selective membrane, we integrated the preconcentrator with a surface-based immunoassay for R-Phycoerythrin (RPE). Using a 1x PBS buffer system, the preconcentrator-enhanced immunoassay showed an approximately 100x improvement in sensitivity within 30 min. This is the first time that an electrokinetic microfluidic preconcentrator based on ion concentration polarization (ICP) has been used in high ionic strength buffer solutions to enhance the sensitivity of a surface-based immunoassay.
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Affiliation(s)
- Vincent Liu
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Yong-Ak Song
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Jongyoon Han
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
- ; Fax: +1-617-258-5846; Tel: +1-617-253-2290
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Kim SJ, Song YA, Han J. Nanofluidic concentration devices for biomolecules utilizing ion concentration polarization: theory, fabrication, and applications. Chem Soc Rev 2010; 39:912-22. [PMID: 20179814 DOI: 10.1039/b822556g] [Citation(s) in RCA: 294] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recently, a new type of electrokinetic concentration devices has been developed in a microfluidic chip format, which allows efficient trapping and concentration of biomolecules by utilizing ion concentration polarization near nanofluidic structures. These devices have drawn much attention not only due to their potential application in biomolecule sensing, but also due to the rich scientific content related to ion concentration polarization, the underlying physical phenomenon for the operation of these electrokinetic concentration devices. This tutorial review provides an introduction to the scientific and engineering advances achieved, in-depth discussion about several interesting applications of these unique concentration devices, and their current limitations and challenges.
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Affiliation(s)
- Sung Jae Kim
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
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Abstract
In this paper, we report a new method of fabricating a high-throughput protein preconcentrator in poly(dimethylsiloxane) (PDMS) microfluidic chip format. We print a submicron thick ion-selective membrane on the glass substrate by using standard patterning techniques. By simply plasma-bonding a PDMS microfluidic device on top of the printed glass substrate, we can integrate the ion-selective membrane into the device and rapidly prototype a PDMS preconcentrator without complicated microfabrication and cumbersome integration processes. The PDMS preconcentrator shows a concentration factor as high as approximately 10(4) in 5 min. This printing method even allows fabricating a parallel array of preconcentrators to increase the concentrated sample volume, which can facilitate an integration of our microfluidic preconcentrator chip as a signal enhancing tool to various detectors such as a mass spectrometer.
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Affiliation(s)
| | | | - Jongyoon Han
- Corresponding author. Tel: 1-617-253-2290. Fax: 1-617-258-5846. E-mail:
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Lee JH, Song YA, Tannenbaum SR, Han J. Increase of reaction rate and sensitivity of low-abundance enzyme assay using micro/nanofluidic preconcentration chip. Anal Chem 2008; 80:3198-204. [PMID: 18358012 DOI: 10.1021/ac800362e] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report a novel method of increasing both the reaction rate and the sensitivity of low-abundance enzyme assay using a micro/nanofluidic preconcentration chip. The disposable preconcentration device made out of PDMS with a surface-patterned ion-selective membrane increases local enzyme/substrate concentrations for rapid monitoring of enzyme activity. As a model system, we used trypsin as the enzyme and BODIPY FL casein as the fluorogenic substrate. We demonstrated that the reaction rate of trypsin-BODIPY FL was significantly enhanced by increasing the local concentrations of both trypsin and BODIPY FL casein in the preconcentration chip. The reaction time required to turn over substrates at 1 ng/mL was only approximately 10 min compared to approximately 1 h without preconcentration, which demonstrates a significantly higher reaction rate through the increase of the concentrations of both the enzyme and substrate. Furthermore, trypsin activity can be measured down to a concentration level of 10 pg/mL, which is a approximately 100 fold enhancement in sensitivity compared to the result without the preconcentration step. This micro/nanofluidic preconcentrator chip could be used as a generic micro reaction platform to study any enzyme-substrate systems, or other biochemical reaction systems in low concentration ranges.
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Affiliation(s)
- Jeong Hoon Lee
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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Abstract
Efficient sample preparation tools are the key to measuring molecular signals in a complex biological system. A novel continuous-flow isoelectric point (pI)-based sorting technique has been developed for proteins and peptides in a microfluidic chip format. It can sort biomolecules at a relatively high flow rate of up to 10 microL/min and does not require carrier ampholytes, which can create molecular backgrounds for subsequent analysis. Furthermore, the electrophoretic field required to run the pI-based sorting is generated by the diffusion of buffer ions in situ, at the liquid junction between two laminar flows within the microfluidic channel. Utilizing the diffusion potential in combination with a pH difference between the buffers, we demonstrated a separation of binary mixtures of pI markers and proteins without applying any external field. The sorting resolution and its efficiency are sufficiently high for sample preparation and could be further improved by optimizing buffers or with an additional transverse electric field. Once fully developed, it can potentially be a pI-based sample fractionation tool for proteomic analysis of complex biomolecule samples.
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Affiliation(s)
- Yong-Ak Song
- Department of Electrical Engineering and Computer Science, Biological Engineering Division, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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Kim SJ, Song YA, Skipper PL, Han J. Electrohydrodynamic generation and delivery of monodisperse picoliter droplets using a poly(dimethylsiloxane) microchip. Anal Chem 2006; 78:8011-9. [PMID: 17134134 PMCID: PMC2577391 DOI: 10.1021/ac061127v] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We developed a drop-on-demand microdroplet generator for the discrete dispensing of biosamples into a bioanalytical unit. This disposable PDMS microfluidic device can generate monodisperse droplets of picoliter volume directly out of a plane sidewall of the microfluidic chip by an electrohydrodynamic mechanism. The droplet generation was accomplished without using either an inserted capillary or a monolithically built-in tip. The minimum droplet volume was approximately 4 pL, and the droplet generation was repeatable and stable for at least 30 min, with a typical variation of less than 2.0% of drop size. The Taylor cone, which is usually observed in electrospray, was suppressed by controlling the surface wetting property of the PDMS device as well as the surface tension of the sample liquids. A modification of the channel geometry right before the opening of the microchannel also enhanced the continuous droplet generation without applying any external pumping. A simple numerical simulation of the droplet generation verified the importance of controlling the surface wetting conditions for the droplet formation. Our microdroplet generator can be effectively applied to a direct interface of a microfluidic chip to a biosensing unit, such as AMS, MALDI-MS or protein microarray-type biochips.
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Affiliation(s)
- Sung Jae Kim
- Department of Electrical Engineering and Computer Science, Biological Engineering Division, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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