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Khilko Y, Weyman PD, Glass JI, Adams MD, McNeil MA, Griffin PB. DNA assembly with error correction on a droplet digital microfluidics platform. BMC Biotechnol 2018; 18:37. [PMID: 29859085 PMCID: PMC5984785 DOI: 10.1186/s12896-018-0439-9] [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] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 04/24/2018] [Indexed: 12/02/2022] Open
Abstract
Background Custom synthesized DNA is in high demand for synthetic biology applications. However, current technologies to produce these sequences using assembly from DNA oligonucleotides are costly and labor-intensive. The automation and reduced sample volumes afforded by microfluidic technologies could significantly decrease materials and labor costs associated with DNA synthesis. The purpose of this study was to develop a gene assembly protocol utilizing a digital microfluidic device. Toward this goal, we adapted bench-scale oligonucleotide assembly methods followed by enzymatic error correction to the Mondrian™ digital microfluidic platform. Results We optimized Gibson assembly, polymerase chain reaction (PCR), and enzymatic error correction reactions in a single protocol to assemble 12 oligonucleotides into a 339-bp double- stranded DNA sequence encoding part of the human influenza virus hemagglutinin (HA) gene. The reactions were scaled down to 0.6-1.2 μL. Initial microfluidic assembly methods were successful and had an error frequency of approximately 4 errors/kb with errors originating from the original oligonucleotide synthesis. Relative to conventional benchtop procedures, PCR optimization required additional amounts of MgCl2, Phusion polymerase, and PEG 8000 to achieve amplification of the assembly and error correction products. After one round of error correction, error frequency was reduced to an average of 1.8 errors kb− 1. Conclusion We demonstrated that DNA assembly from oligonucleotides and error correction could be completely automated on a digital microfluidic (DMF) platform. The results demonstrate that enzymatic reactions in droplets show a strong dependence on surface interactions, and successful on-chip implementation required supplementation with surfactants, molecular crowding agents, and an excess of enzyme. Enzymatic error correction of assembled fragments improved sequence fidelity by 2-fold, which was a significant improvement but somewhat lower than expected compared to bench-top assays, suggesting an additional capacity for optimization. Electronic supplementary material The online version of this article (10.1186/s12896-018-0439-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yuliya Khilko
- Stanford Genome Technology Center, Stanford University, 3165 Porter Drive, Palo Alto, CA, 94304, USA.,Department of Biomedical, Chemical and Materials Engineering, San Jose State University, 1 Washington Sq, San Jose, CA, 95192, USA
| | - Philip D Weyman
- J. Craig Venter Institute, 4120 Capricorn Lane, La Jolla, CA, 92037, USA
| | - John I Glass
- J. Craig Venter Institute, 4120 Capricorn Lane, La Jolla, CA, 92037, USA
| | - Mark D Adams
- J. Craig Venter Institute, 4120 Capricorn Lane, La Jolla, CA, 92037, USA
| | - Melanie A McNeil
- Department of Biomedical, Chemical and Materials Engineering, San Jose State University, 1 Washington Sq, San Jose, CA, 95192, USA
| | - Peter B Griffin
- Stanford Genome Technology Center, Stanford University, 3165 Porter Drive, Palo Alto, CA, 94304, USA.
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Madison AC, Royal MW, Vigneault F, Chen L, Griffin PB, Horowitz M, Church GM, Fair RB. Scalable Device for Automated Microbial Electroporation in a Digital Microfluidic Platform. ACS Synth Biol 2017; 6:1701-1709. [PMID: 28569062 DOI: 10.1021/acssynbio.7b00007] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [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: 11/28/2022]
Abstract
Electrowetting-on-dielectric (EWD) digital microfluidic laboratory-on-a-chip platforms demonstrate excellent performance in automating labor-intensive protocols. When coupled with an on-chip electroporation capability, these systems hold promise for streamlining cumbersome processes such as multiplex automated genome engineering (MAGE). We integrated a single Ti:Au electroporation electrode into an otherwise standard parallel-plate EWD geometry to enable high-efficiency transformation of Escherichia coli with reporter plasmid DNA in a 200 nL droplet. Test devices exhibited robust operation with more than 10 transformation experiments performed per device without cross-contamination or failure. Despite intrinsic electric-field nonuniformity present in the EP/EWD device, the peak on-chip transformation efficiency was measured to be 8.6 ± 1.0 × 108 cfu·μg-1 for an average applied electric field strength of 2.25 ± 0.50 kV·mm-1. Cell survival and transformation fractions at this electroporation pulse strength were found to be 1.5 ± 0.3 and 2.3 ± 0.1%, respectively. Our work expands the EWD toolkit to include on-chip microbial electroporation and opens the possibility of scaling advanced genome engineering methods, like MAGE, into the submicroliter regime.
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Affiliation(s)
- Andrew C. Madison
- Department
of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, United States
| | - Matthew W. Royal
- Department
of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, United States
| | - Frederic Vigneault
- Wyss Institute for Biologically Inspired Engineering, Boston, Massachusetts 02115, United States
| | - Liji Chen
- Department
of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, United States
| | - Peter B. Griffin
- Stanford
Genome Technology Center, Stanford University, Palo Alto, California 94304, United States
| | | | - George M. Church
- Wyss Institute for Biologically Inspired Engineering, Boston, Massachusetts 02115, United States
- Department
of Genetics, Harvard Medical School, Harvard University, Boston, Massachusetts 02115, United States
| | - Richard B. Fair
- Department
of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708, United States
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Moore JA, Nemat-Gorgani M, Madison AC, Sandahl MA, Punnamaraju S, Eckhardt AE, Pollack MG, Vigneault F, Church GM, Fair RB, Horowitz MA, Griffin PB. Automated electrotransformation of Escherichia coli on a digital microfluidic platform using bioactivated magnetic beads. Biomicrofluidics 2017; 11:014110. [PMID: 28191268 PMCID: PMC5291792 DOI: 10.1063/1.4975391] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 01/20/2017] [Indexed: 05/06/2023]
Abstract
This paper reports on the use of a digital microfluidic platform to perform multiplex automated genetic engineering (MAGE) cycles on droplets containing Escherichia coli cells. Bioactivated magnetic beads were employed for cell binding, washing, and media exchange in the preparation of electrocompetent cells in the electrowetting-on-dieletric (EWoD) platform. On-cartridge electroporation was used to deliver oligonucleotides into the cells. In addition to the optimization of a magnetic bead-based benchtop protocol for generating and transforming electrocompetent E. coli cells, we report on the implementation of this protocol in a fully automated digital microfluidic platform. Bead-based media exchange and electroporation pulse conditions were optimized on benchtop for transformation frequency to provide initial parameters for microfluidic device trials. Benchtop experiments comparing electrotransformation of free and bead-bound cells are presented. Our results suggest that dielectric shielding intrinsic to bead-bound cells significantly reduces electroporation field exposure efficiency. However, high transformation frequency can be maintained in the presence of magnetic beads through the application of more intense electroporation pulses. As a proof of concept, MAGE cycles were successfully performed on a commercial EWoD cartridge using variations of the optimal magnetic bead-based preparation procedure and pulse conditions determined by the benchtop results. Transformation frequencies up to 22% were achieved on benchtop; this frequency was matched within 1% (21%) by MAGE cycles on the microfluidic device. However, typical frequencies on the device remain lower, averaging 9% with a standard deviation of 9%. The presented results demonstrate the potential of digital microfluidics to perform complex and automated genetic engineering protocols.
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Affiliation(s)
- J A Moore
- Stanford Genome Technology Center , 3165 Porter Drive, Palo Alto, California 94304, USA
| | - M Nemat-Gorgani
- Stanford Genome Technology Center , 3165 Porter Drive, Palo Alto, California 94304, USA
| | - A C Madison
- Department of Electrical Engineering, Duke University , Durham, North Carolina 27560, USA
| | - M A Sandahl
- Advanced Liquid Logic , 615 Davis Drive #800, Morrisville, North Carolina 27560, USA
| | - S Punnamaraju
- Advanced Liquid Logic , 615 Davis Drive #800, Morrisville, North Carolina 27560, USA
| | - A E Eckhardt
- Advanced Liquid Logic , 615 Davis Drive #800, Morrisville, North Carolina 27560, USA
| | - M G Pollack
- Advanced Liquid Logic , 615 Davis Drive #800, Morrisville, North Carolina 27560, USA
| | - F Vigneault
- Wyss Institute, Harvard University , Boston, Massachusetts 02115, USA
| | - G M Church
- Department of Genetics, Harvard Medical School , Boston, Massachusetts 02115, USA
| | - R B Fair
- Department of Electrical Engineering, Duke University , Durham, North Carolina 27560, USA
| | - M A Horowitz
- Department of Electrical Engineering, Stanford University , Stanford, California 94305, USA
| | - P B Griffin
- Stanford Genome Technology Center , 3165 Porter Drive, Palo Alto, California 94304, USA
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Boles DJ, Benton JL, Siew GJ, Levy MH, Thwar PK, Sandahl MA, Rouse JL, Perkins LC, Sudarsan AP, Jalili R, Pamula VK, Srinivasan V, Fair RB, Griffin PB, Eckhardt AE, Pollack MG. Droplet-based pyrosequencing using digital microfluidics. Anal Chem 2011; 83:8439-47. [PMID: 21932784 DOI: 10.1021/ac201416j] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The feasibility of implementing pyrosequencing chemistry within droplets using electrowetting-based digital microfluidics is reported. An array of electrodes patterned on a printed-circuit board was used to control the formation, transportation, merging, mixing, and splitting of submicroliter-sized droplets contained within an oil-filled chamber. A three-enzyme pyrosequencing protocol was implemented in which individual droplets contained enzymes, deoxyribonucleotide triphosphates (dNTPs), and DNA templates. The DNA templates were anchored to magnetic beads which enabled them to be thoroughly washed between nucleotide additions. Reagents and protocols were optimized to maximize signal over background, linearity of response, cycle efficiency, and wash efficiency. As an initial demonstration of feasibility, a portion of a 229 bp Candida parapsilosis template was sequenced using both a de novo protocol and a resequencing protocol. The resequencing protocol generated over 60 bp of sequence with 100% sequence accuracy based on raw pyrogram levels. Excellent linearity was observed for all of the homopolymers (two, three, or four nucleotides) contained in the C. parapsilosis sequence. With improvements in microfluidic design it is expected that longer reads, higher throughput, and improved process integration (i.e., "sample-to-sequence" capability) could eventually be achieved using this low-cost platform.
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Affiliation(s)
- Deborah J Boles
- Advanced Liquid Logic Incorporated, Research Triangle Park, North Carolina, United States
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Fair RB, Khlystov A, Tailor TD, Ivanov V, Evans RD, Srinivasan V, Pamula VK, Pollack MG, Griffin PB, Zhou J. Chemical and Biological Applications of Digital-Microfluidic Devices. ACTA ACUST UNITED AC 2007. [DOI: 10.1109/mdt.2007.8] [Citation(s) in RCA: 253] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Agah A, Aghajan M, Mashayekhi F, Amini S, Davis RW, Plummer JD, Ronaghi M, Griffin PB. A multi-enzyme model for Pyrosequencing. Nucleic Acids Res 2004; 32:e166. [PMID: 15576673 PMCID: PMC535692 DOI: 10.1093/nar/gnh159] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [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] [Received: 05/25/2004] [Revised: 08/25/2004] [Accepted: 10/30/2004] [Indexed: 11/12/2022] Open
Abstract
Pyrosequencing is a DNA sequencing technique based on sequencing-by-synthesis enabling rapid real-time sequence determination. This technique employs four enzymatic reactions in a single tube to monitor DNA synthesis. Nucleotides are added iteratively to the reaction and in case of incorporation, pyrophosphate (PPi) is released. PPi triggers a series of reactions resulting in production of light, which is proportional to the amount of DNA and number of incorporated nucleotides. Generated light is detected and recorded by a detector system in the form of a peak signal, which reflects the activity of all four enzymes in the reaction. We have developed simulations to model the kinetics of the enzymes. These simulations provide a full model for the Pyrosequencing four-enzyme system, based on which the peak height and shape can be predicted depending on the concentrations of enzymes and substrates. Simulation results are shown to be compatible with experimental data. Based on these simulations, the rate-limiting steps in the chain can be determined, and K(M) and kcat of all four enzymes in Pyrosequencing can be calculated.
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Affiliation(s)
- Ali Agah
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA, USA
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Affiliation(s)
- A Ural
- Department of Electrical Engineering Stanford University, Stanford, California 94305, USA
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Goodman MJ, Estioko-Griffin A, Griffin PB, Grove JS. Menarche, pregnancy, birth spacing and menopause among the Agta women foragers of Cagayan province, Luzon, the Philippines. Ann Hum Biol 1985; 12:169-77. [PMID: 3985568 DOI: 10.1080/03014468500007661] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The reproductive histories of 74 post-menarcheal Agta Negrito women, tropical foragers of Cagayan province, north-eastern Luzon, the Philippines are described and analysed in comparison with data collected by Howell on Dobe !Kung hunter-gatherers. Among the Agta, mean age at menarche is 17, mean age at first live birth is 20.14 years, mean completed parity is 6.53 and mean age at menopause is 44. Average height is 141.24 cm and average weight 36.72 kg. No time trends were detected in age at menarche and age at first live birth among the Agta. Average spacing between live births where an infant survives until the birth of the next sibling was 2.85 years. Compared to the Dobe !Kung, Agta women have later menarche, but shorter birth spacing and a longer active childbearing span.
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