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Williamson IA, Arnold JW, Samsa LA, Gaynor L, DiSalvo M, Cocchiaro JL, Carroll I, Azcarate-Peril MA, Rawls JF, Allbritton NL, Magness ST. A High-Throughput Organoid Microinjection Platform to Study Gastrointestinal Microbiota and Luminal Physiology. Cell Mol Gastroenterol Hepatol 2018; 6:301-319. [PMID: 30123820 PMCID: PMC6092482 DOI: 10.1016/j.jcmgh.2018.05.004] [Citation(s) in RCA: 141] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 05/14/2018] [Indexed: 12/16/2022]
Abstract
Background & Aims The human gut microbiota is becoming increasingly recognized as a key factor in homeostasis and disease. The lack of physiologically relevant in vitro models to investigate host-microbe interactions is considered a substantial bottleneck for microbiota research. Organoids represent an attractive model system because they are derived from primary tissues and embody key properties of the native gut lumen; however, access to the organoid lumen for experimental perturbation is challenging. Here, we report the development and validation of a high-throughput organoid microinjection system for cargo delivery to the organoid lumen and high-content sampling. Methods A microinjection platform was engineered using off-the-shelf and 3-dimensional printed components. Microinjection needles were modified for vertical trajectories and reproducible injection volumes. Computer vision (CVis) and microfabricated CellRaft Arrays (Cell Microsystems, Research Triangle Park, NC) were used to increase throughput and enable high-content sampling of mock bacterial communities. Modeling preformed using the COMSOL Multiphysics platform predicted a hypoxic luminal environment that was functionally validated by transplantation of fecal-derived microbial communities and monocultures of a nonsporulating anaerobe. Results CVis identified and logged locations of organoids suitable for injection. Reproducible loads of 0.2 nL could be microinjected into the organoid lumen at approximately 90 organoids/h. CVis analyzed and confirmed retention of injected cargos in approximately 500 organoids over 18 hours and showed the requirement to normalize for organoid growth for accurate assessment of barrier function. CVis analyzed growth dynamics of a mock community of green fluorescent protein- or Discosoma sp. red fluorescent protein-expressing bacteria, which grew within the organoid lumen even in the presence of antibiotics to control media contamination. Complex microbiota communities from fecal samples survived and grew in the colonoid lumen without appreciable changes in complexity. Conclusions High-throughput microinjection into organoids represents a next-generation in vitro approach to investigate gastrointestinal luminal physiology and the gastrointestinal microbiota.
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Key Words
- 2D, 2-dimensional
- 3D, 3-dimensional
- Anaerobic
- Barrier Function
- CAG, chicken beta-actin promoter with CMV enhancer
- CFU, colony-forming unit
- CRA, CellRaft Array
- CVis, computer vision
- EGFP, enhanced green fluorescent protein
- FITC, fluorescein isothiocyanate
- Fecal Microbiota
- GFP, green fluorescent protein
- GI, gastrointestinal
- HF, hydrogen fluoride
- High-Content Sampling
- High-Throughput
- Microinjection
- OUT, operational taxonomic unit
- Organoid
- PBS, phosphate-buffered saline
- PCR, polymerase chain reaction
- QIIME, Quantitative Insights Into Microbial Ecology
- WT, wild-type
- hiPS, Human Induced Pluripotent Stem Cell
- rRNA, ribosomal RNA
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Affiliation(s)
- Ian A. Williamson
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill/North Carolina State University, Chapel Hill, North Carolina
| | - Jason W. Arnold
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Leigh Ann Samsa
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill/North Carolina State University, Chapel Hill, North Carolina
| | - Liam Gaynor
- Graduate Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, Massachusetts
| | - Matthew DiSalvo
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill/North Carolina State University, Chapel Hill, North Carolina
| | - Jordan L. Cocchiaro
- Department of Molecular Genetics and Microbiology Medicine, Duke University, Durham, North Carolina
| | - Ian Carroll
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - M. Andrea Azcarate-Peril
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - John F. Rawls
- Department of Molecular Genetics and Microbiology Medicine, Duke University, Durham, North Carolina
| | - Nancy L. Allbritton
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill/North Carolina State University, Chapel Hill, North Carolina
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Scott T. Magness
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill/North Carolina State University, Chapel Hill, North Carolina
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Balfe A, Lennon G, Lavelle A, Docherty NG, Coffey JC, Sheahan K, Winter DC, O'Connell PR. Isolation and gene expression profiling of intestinal epithelial cells: crypt isolation by calcium chelation from in vivo samples. Clin Exp Gastroenterol 2018; 11:29-37. [PMID: 29391821 PMCID: PMC5769583 DOI: 10.2147/ceg.s145224] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Aim The epithelial layer within the colon represents a physical barrier between the luminal contents and its underlying mucosa. It plays a pivotal role in mucosal homeostasis, and both tolerance and anti-pathogenic immune responses. Identifying signals of inflammation initiation and responses to stimuli from within the epithelial layer is critical to understanding the molecular pathways underlying disease pathology. This study validated a method to isolate and analyze epithelial populations, enabling investigations of epithelial function and response in a variety of disease setting. Materials and methods Epithelial cells were isolated from whole mucosal biopsies harvested from healthy controls and patients with active ulcerative colitis by calcium chelation. The purity of isolated cells was assessed by flow cytometry. The expression profiles of a panel of epithelial functional genes were investigated by reverse transcription-polymerase chain reaction (PCR) in isolated epithelial cells and corresponding mucosal biopsies. The expression profiles of isolated cells and corresponding mucosal biopsies were evaluated and compared between healthy and inflamed colonic tissue. Results Flow cytometry identified 97% of cells isolated as intestinal epithelial cells (IECs). Comparisons of gene expression profiles between the mucosal biopsies and isolated IECs demonstrated clear differences in the gene expression signatures. Sixty percent of the examined genes showed contrasting trends of expression between sample types. Conclusion The calcium chelation isolation method provided a reliable method for the isolation of a pure population of cells with preservation of epithelial cell-specific gene expression. This demonstrates the importance of sample choice when investigating functions directly affecting the colonic epithelial layer.
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Affiliation(s)
- Aine Balfe
- School of Medicine and Medical Science, University College Dublin, Belfield, Dublin.,Centre for Colorectal Disease, St Vincent's University Hospital Dublin, Dublin
| | - Grainne Lennon
- School of Medicine and Medical Science, University College Dublin, Belfield, Dublin.,Centre for Colorectal Disease, St Vincent's University Hospital Dublin, Dublin
| | - Aonghus Lavelle
- School of Medicine and Medical Science, University College Dublin, Belfield, Dublin.,Centre for Colorectal Disease, St Vincent's University Hospital Dublin, Dublin
| | - Neil G Docherty
- School of Medicine and Medical Science, University College Dublin, Belfield, Dublin
| | - J Calvin Coffey
- Graduate Entry Medical School, University Hospital Limerick, 4i Centre for Interventions in Infection, Inflammation and Immunity, University of Limerick, Limerick
| | - Kieran Sheahan
- Histopathology Department, St. Vincent's University Hospital Dublin, Dublin, Ireland
| | - Desmond C Winter
- Centre for Colorectal Disease, St Vincent's University Hospital Dublin, Dublin
| | - P Ronan O'Connell
- School of Medicine and Medical Science, University College Dublin, Belfield, Dublin.,Centre for Colorectal Disease, St Vincent's University Hospital Dublin, Dublin
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Highly efficient cellular cloning using Ferro-core Micropallet Arrays. Sci Rep 2017; 7:13081. [PMID: 29026113 PMCID: PMC5638909 DOI: 10.1038/s41598-017-13242-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 09/20/2017] [Indexed: 12/28/2022] Open
Abstract
Advancing knowledge of biological mechanisms has come to depend upon genetic manipulation of cells and organisms, relying upon cellular cloning methods that remain unchanged for decades, are labor and time intensive, often taking many months to come to fruition. Thus, there is a pressing need for more efficient processes. We have adapted a newly developed micropallet array platform, termed the “ferro-core micropallet array”, to dramatically improve and accelerate the process of isolating clonal populations of adherent cells from heterogeneous mixtures retaining the flexibility of employing a wide range of cytometric parameters for identifying colonies and cells of interest. Using transfected (retroviral oncogene or fluorescent reporter construct) rat 208 F cells, we demonstrated the capacity to isolate and expand pure populations of genetically manipulated cells via laser release and magnetic recovery of single micropallets carrying adherent microcolonies derived from single cells. This platform can be broadly applied to biological research, across the spectrum of molecular biology to cellular biology, involving fields such as cancer, developmental, and stem cell biology. The ferro-core micropallet array platform provides significant advantages over alternative sorting and cloning methods by eliminating the necessity for repetitive purification steps and increasing throughput by dramatically shortening the time to obtain clonally expanded cell colonies.
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Optical painting and fluorescence activated sorting of single adherent cells labelled with photoswitchable Pdots. Nat Commun 2016; 7:11468. [PMID: 27118210 PMCID: PMC4853474 DOI: 10.1038/ncomms11468] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 03/30/2016] [Indexed: 12/19/2022] Open
Abstract
The efficient selection and isolation of individual cells of interest from a mixed population is desired in many biomedical and clinical applications. Here we show the concept of using photoswitchable semiconducting polymer dots (Pdots) as an optical 'painting' tool, which enables the selection of certain adherent cells based on their fluorescence, and their spatial and morphological features, under a microscope. We first develop a Pdot that can switch between the bright (ON) and dark (OFF) states reversibly with a 150-fold contrast ratio on irradiation with ultraviolet or red light. With a focused 633-nm laser beam that acts as a 'paintbrush' and the photoswitchable Pdots as the 'paint', we select and 'paint' individual Pdot-labelled adherent cells by turning on their fluorescence, then proceed to sort and recover the optically marked cells (with 90% recovery and near 100% purity), followed by genetic analysis.
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Shah PK, Herrera-Loeza SG, Sims CE, Yeh JJ, Allbritton NL. Small sample sorting of primary adherent cells by automated micropallet imaging and release. Cytometry A 2014; 85:642-9. [PMID: 24939722 DOI: 10.1002/cyto.a.22480] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 03/15/2014] [Accepted: 04/14/2014] [Indexed: 12/20/2022]
Abstract
Primary patient samples are the gold standard for molecular investigations of tumor biology yet are difficult to acquire, heterogeneous in nature and variable in size. Patient-derived xenografts (PDXs) comprised of primary tumor tissue cultured in host organisms such as nude mice permit the propagation of human tumor samples in an in vivo environment and closely mimic the phenotype and gene expression profile of the primary tumor. Although PDX models reduce the cost and complexity of acquiring sample tissue and permit repeated sampling of the primary tumor, these samples are typically contaminated by immune, blood, and vascular tissues from the host organism while also being limited in size. For very small tissue samples (on the order of 10(3) cells) purification by fluorescence-activated cell sorting (FACS) is not feasible while magnetic activated cell sorting (MACS) of small samples results in very low purity, low yield, and poor viability. We developed a platform for imaging cytometry integrated with micropallet array technology to perform automated cell sorting on very small samples obtained from PDX models of pancreatic and colorectal cancer using antibody staining of EpCAM (CD326) as a selection criteria. These data demonstrate the ability to automate and efficiently separate samples with very low number of cells.
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Affiliation(s)
- Pavak K Shah
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina 27599 and North Carolina State University, Raleigh, North Carolina, 27695
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Alamdari OG, Seyedjafari E, Soleimani M, Ghaemi N. Micropatterning of ECM Proteins on Glass Substrates to Regulate Cell Attachment and Proliferation. Avicenna J Med Biotechnol 2013; 5:234-40. [PMID: 24285998 PMCID: PMC3838768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Accepted: 07/19/2013] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Micropatterning is becoming a powerful tool for studying cells in vitro. This method not only uses very small amount of material but also mimic the microenvironment structure present in living tissues better than flask culturing techniques. In previous studies using micropatterning of extracellular matrix proteins on glass surfaces, the rate of protein detachment from the surface was so high that the proteins and the cultivated cells detached after 3 three days of cell seeding. METHODS Here we optimized the glass surface modification method to fulfill the requirement of most in vitro studies. RESULTS In our study we showed that the optimum time for glass surface modification reaction is 1.5 hr, and the cells could be tracked in vitro for over 15 days after cell seeding which is enough for the most in vitro studies. As a model, we cultivated HEK 293T and HepG2 cells on the collagen micro-patterns and showed that they have normal growth and morphology on these micropatterns. The HEK cells also transfected with pmaxGFP plasmid vector to show that the cells on collagen micropatterns could also used in transfection studies. CONCLUSION Taking these together, this novel method is promising for efficient cell culture studies on micropatterened surfaces in the future.
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Affiliation(s)
- Omid G. Alamdari
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
- Department of Nanotechnology and Tissue engineering, Stem Cell Technology Research Center, Tehran, Iran
| | - Ehsan Seyedjafari
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
| | - Masoud Soleimani
- Department of Hematology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Nasser Ghaemi
- Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran
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Gach PC, Attayek PJ, Herrera G, Yeh JJ, Allbritton NL. Isolation and in vitro culture of rare cancer stem cells from patient-derived xenografts of pancreatic ductal adenocarcinoma. Anal Chem 2013; 85:7271-8. [PMID: 23815678 DOI: 10.1021/ac401165s] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Described is the construction of a large array of releasable microstructures (micropallets) along with screening and isolation protocols for sorting rare, approximately 1 in 10,000, cancer stem cells (CSCs) from a heterogeneous cell population. A 10.1 × 7.1 cm array of micropallets (50 × 50 × 75 μm structures and 25 μm micropallet gap) was fabricated on a large glass substrate, providing an array of approximately 1.3 million releasable microstructures. Image analysis algorithms were developed to permit array screening for identification of fluorescently labeled cells in less than 15 min using an epifluorescent wide-field microscope with a computer controlled translational stage. Device operation was tested by culturing HeLa cells transfected with green fluorescent protein (GFP) admixed with wild-type HeLa cells at ratios of 1:10(4) to 1:10(6) on the array followed by screening to identify flourescent cells. Micropallets containing cells of interest were then selectively released by a focused laser pulse and collected on a numbered poly(dimethylsiloxane) (PDMS) substrate with high viability. A direct comparison of this technology with fluorescence-activated cell sorting (FACS) demonstrated that micropallet arrays offered enhanced post sorting purity (100%), yield (100%), and viability (94-100%) for rare cell isolation. As a demonstration of the technology's value, pancreatic tumor cells from Panc-1 cell lines and patient-derived xenografts were screened for the presence of CD24, CD44, and CD326: surface markers of pancreatic CSCs. Following cell isolation and culture, 63 ± 23% of the isolated Panc-1 cells and 35% of sorted human xenograft cells formed tumor spheroids retaining high expression levels of CD24, CD44, and CD326. The ability to isolate rare cells from relatively small sample sizes will facilitate our understanding of cell biology and the development of new therapeutic strategies.
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Affiliation(s)
- Philip C Gach
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States
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He L, Wang M, Zhang Q, Lu Y, Yin Y. Magnetic assembly and patterning of general nanoscale materials through nonmagnetic templates. NANO LETTERS 2013; 13:264-71. [PMID: 23237533 DOI: 10.1021/nl3040256] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Applied magnetic field represents an effective tool to rapidly assemble micro- and nanoscale magnetic objects into defined structures. Ordered assembly is typically achieved by using magnetic micropatterns, for which the downside is that they require advanced microfabrication techniques to produce. In addition, most conventional magnetic assembly strategies are restricted to target objects that possess magnetic properties. Herein we present a general strategy that allows convenient magnetically driven assembly of nonmagnetic objects in defined locations with high spatial resolution. The process involves immersing a polymer relief pattern in a uniformly magnetized ferrofluid, which modulates the local magnetic fields around the pattern. Nonmagnetic target objects dispersed in the same ferrofluid can then be magnetically assembled at positions defined by the polymer pattern. As the nonmagnetic polymer patterns can be conveniently fabricated at low cost through photolithography and soft-lithography processes, our method provides a general yet very effective means to assemble a wide range of nonmagnetic objects with controlled spatial distribution, paving the way toward patterning functional microstructures.
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Affiliation(s)
- Le He
- Department of Chemistry, University of California, Riverside, California 92507, USA
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Pai JH, Kluckman K, Cowley DO, Bortner DM, Sims CE, Allbritton NL, Allbritton NL. Efficient division and sampling of cell colonies using microcup arrays. Analyst 2013; 138:220-8. [PMID: 23099535 PMCID: PMC3509232 DOI: 10.1039/c2an36065a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A microengineered array to sample clonal colonies is described. The cells were cultured on an array of individually releasable elements until the colonies expanded to cover multiple elements. Single elements were released using a laser-based system and collected to sample cells from individual colonies. A greater than an 85% rate in splitting and collecting colonies was achieved using a 3-dimensional cup-like design or "microcup". Surface modification using patterned titanium deposition of the glass substrate improved the stability of microcup adhesion to the glass while enabling minimization of the laser energy for splitting the colonies. Smaller microcup dimensions and slotting the microcup walls reduced the time needed for colonies to expand into multiple microcups. The stem cell colony retained on the array and the collected fraction within released microcups remained undifferentiated and viable. The colony samples were characterized by both reporter gene expression and a destructive assay (PCR) to identify target colonies. The platform is envisioned as a means to rapidly establish cell lines using a destructive assay to identify desired clones.
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Affiliation(s)
- Jeng-Hao Pai
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, Fax: +1 (919) 962-2388, Tel: +1 (919) 966-2291
| | | | - Dale O. Cowley
- TransViragen, Inc., PO Box 110301, Research Triangle Park, NC 27709
| | - Donna M. Bortner
- TransViragen, Inc., PO Box 110301, Research Triangle Park, NC 27709
| | - Christopher E. Sims
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, Fax: +1 (919) 962-2388, Tel: +1 (919) 966-2291
| | - Nancy L. Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, Fax: +1 (919) 962-2388, Tel: +1 (919) 966-2291
| | - Nancy L. Allbritton
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC 27599, North Carolina State University, Raleigh, NC 27695
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Gach PC, Xu W, King SJ, Sims CE, Bear J, Allbritton NL. Microfabricated arrays for splitting and assay of clonal colonies. Anal Chem 2012; 84:10614-20. [PMID: 23153031 PMCID: PMC3525785 DOI: 10.1021/ac301895t] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A microfabricated platform was developed for highly parallel and efficient colony picking, splitting, and clone identification. A pallet array provided patterned cell colonies which mated to a second printing array composed of bridging microstructures formed by a supporting base and attached post. The posts enabled mammalian cells from colonies initially cultured on the pallet array to migrate to corresponding sites on the printing array. Separation of the arrays simultaneously split the colonies, creating a patterned replica. Optimization of array elements provided transfer efficiencies greater than 90% using bridging posts of 30 μm diameter and 100 μm length and total colony numbers of 3000. Studies using five mammalian cell lines demonstrated that a variety of adherent cell types could be cultured and effectively split with printing efficiencies of 78-92%. To demonstrate the technique's utility, clonal cell lines with siRNA knockdown of Coronin 1B were generated using the arrays and compared to a traditional FACS/Western Blotting-based approach. Identification of target clones required a destructive assay to identify cells with an absence of Coronin 1B brought about by the successful infection of interfering shRNA construct. By virtue of miniaturization and its parallel format, the platform enabled the identification and generation of 12 target clones from a starting sample of only 3900 cells and required only 5 man hours over 11 days. In contrast, the traditional method required 500,000 cells and generated only 5 target clones with 34 man hours expended over 47 days. These data support the considerable reduction in time, manpower, and reagents using the miniaturized platform for clonal selection by destructive assay versus conventional approaches.
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Affiliation(s)
- Philip C. Gach
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Wei Xu
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - Samantha J. King
- Department of Cell & Development Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Christopher E. Sims
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
| | - James Bear
- Department of Cell & Development Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Nancy L. Allbritton
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA
- Department of Biomedical Engineering, University of North Carolina, Chapel Hill, NC 27599 and North Carolina State University, Raleigh, NC 27695
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Ma H, Mismar W, Wang Y, Small DW, Ras M, Allbritton NL, Sims CE, Venugopalan V. Impact of release dynamics of laser-irradiated polymer micropallets on the viability of selected adherent cells. J R Soc Interface 2011; 9:1156-67. [PMID: 22158840 DOI: 10.1098/rsif.2011.0691] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We use time-resolved interferometry, fluorescence assays and computational fluid dynamics (CFD) simulations to examine the viability of confluent adherent cell monolayers to selection via laser microbeam release of photoresist polymer micropallets. We demonstrate the importance of laser microbeam pulse energy and focal volume position relative to the glass-pallet interface in governing the threshold energies for pallet release as well as the pallet release dynamics. Measurements using time-resolved interferometry show that increases in laser pulse energy result in increasing pallet release velocities that can approach 10 m s(-1) through aqueous media. CFD simulations reveal that the pallet motion results in cellular exposure to transient hydrodynamic shear stress amplitudes that can exceed 100 kPa on microsecond timescales, and which produces reduced cell viability. Moreover, CFD simulation results show that the maximum shear stress on the pallet surface varies spatially, with the largest shear stresses occurring on the pallet periphery. Cell viability of confluent cell monolayers on the pallet surface confirms that the use of larger pulse energies results in increased rates of necrosis for those cells situated away from the pallet centre, while cells situated at the pallet centre remain viable. Nevertheless, experiments that examine the viability of these cell monolayers following pallet release show that proper choices for laser microbeam pulse energy and focal volume position lead to the routine achievement of cell viability in excess of 90 per cent. These laser microbeam parameters result in maximum pallet release velocities below 6 m s(-1) and cellular exposure of transient hydrodynamic shear stresses below 20 kPa. Collectively, these results provide a mechanistic understanding that relates pallet release dynamics and associated transient shear stresses with subsequent cellular viability. This provides a quantitative, mechanistic basis for determining optimal operating conditions for laser microbeam-based pallet release systems for the isolation and selection of adherent cells.
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Affiliation(s)
- Huan Ma
- Department of Chemical Engineering and Materials Science, University of California, 916 Engineering Tower, Irvine, CA 92697-2575, USA
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Wang Y, Phillips C, Xu W, Pai JH, Dhopeshwarkar R, Sims CE, Allbritton N. Micromolded arrays for separation of adherent cells. LAB ON A CHIP 2010; 10:2917-24. [PMID: 20838672 PMCID: PMC2994190 DOI: 10.1039/c0lc00186d] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We present an efficient, yet inexpensive, approach for isolating viable single cells or colonies from a mixed population. This cell microarray platform possesses innovations in both the array manufacture and the manner of target cell release. Arrays of microwells with bases composed of detachable concave elements, termed microrafts, were fabricated by a dip-coating process using a polydimethylsiloxane mold as the template and the array substrate. This manufacturing approach enabled the use of materials other than photoresists to create the array elements. Thus microrafts possessing low autofluorescence could be fabricated for fluorescence-based identification of cells. Cells plated on the microarray settled and attached at the center of the wells due to the microrafts' concavity. Individual microrafts were readily dislodged by the action of a needle inserted through the compliant polymer substrate. The hard polymer material (polystyrene or epoxy resin) of which the microrafts were composed protected the cells from damage by the needle. For cell analysis and isolation, cells of interest were identified using a standard inverted microscope and microrafts carrying target cells were dislodged with the needle. The released cells/microrafts could be efficiently collected, cultured and clonally expanded. During the separation and collection procedures, the cells remained adherent and provided a measure of protection during manipulation, thus providing an extremely high single-cell cloning rate (>95%). Generation of a transfected cell line based on expression of a fluorescent protein demonstrated an important application for performing on-chip cell separations.
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Affiliation(s)
- Yuli Wang
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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Pai JH, Xu W, Sims CE, Allbritton NL. Microtable arrays for culture and isolation of cell colonies. Anal Bioanal Chem 2010; 398:2595-604. [PMID: 20644916 DOI: 10.1007/s00216-010-3984-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 06/07/2010] [Accepted: 06/29/2010] [Indexed: 01/09/2023]
Abstract
Cell microarrays with culture sites composed of individually removable microstructures or micropallets have proven benefits for isolation of cells from a mixed population. The laser energy required to selectively remove these micropallets with attached cells from the array depends on the microstructure surface area in contact with the substrate. Laser energies sufficient to release micropallets greater than 100 μm resulted in loss of cell viability. A new three-dimensional culture site similar in appearance to a table was designed and fabricated using a simple process that relied on a differential sensitivity of two photoresists to UV-mediated photopolymerization. With this design, the larger culture area rests on four small supports to minimize the surface area in contact with the substrate. Microtables up to 250 × 250 μm were consistently released with single 10-μJ pulses to each of the four support structures. In contrast, microstructures with a 150 × 150-μm surface area in contact with the substrate could not be reliably released at pulse energies up to 212 μJ. Cassie-Baxter wetting is required to provide a barrier of air to localize and sequester cells to the culture sites. A second asset of the design was an increased retention of this air barrier under conditions of decreased surface tension and after prolonged culture of cells. The improved air retention was due to the hydrophobic cavity created beneath the table and above the substrate which entrapped air when an aqueous solution was added to the array. The microtables proved an efficient method for isolating colonies from the array with 100% of selected colonies competent to expand following release from the array.
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Affiliation(s)
- Jeng-Hao Pai
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
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