Works (33)

Updated: July 26th, 2023 21:17

2023 article

Assessing MTT and sulforhodamine B cell proliferation assays under multiple oxygen environments

Yao, M., Walker, G., & Gamcsik, M. P. (2023, July 5). CYTOTECHNOLOGY.

By: M. Yao n, G. Walker n & M. Gamcsik n

author keywords: MTT assay; SRB; Oxygen partial pressure; Hypoxia; Proliferation; Cancer
TL;DR: It is found that the MTT readings do not correlate with cell number for the Caco-2 and PANC-1 cell lines under different oxygen conditions, whereas the sulforhodamine B protein assays perform well under all conditions. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: July 24, 2023

2021 journal article

A multiwell plate-based system for toxicity screening under multiple static or cycling oxygen environments

SCIENTIFIC REPORTS, 11(1).

By: M. Yao n, G. Walker* & M. Gamcsik n

MeSH headings : Cell Culture Techniques / instrumentation; Cell Culture Techniques / methods; Cell Hypoxia / drug effects; Cell Hypoxia / physiology; Cell Line, Tumor / metabolism; Doxorubicin / pharmacology; High-Throughput Screening Assays / methods; Humans; Neoplasms / metabolism; Oxygen / metabolism; Pancreatic Neoplasms / metabolism; Tirapazamine / pharmacology; Toxicity Tests / methods; Triazines / pharmacology; Tumor Microenvironment / physiology
TL;DR: A novel 96-well plate design is presented that recirculates the local oxygen environment to shield cells during media changes and facilitates toxicity studies of cells cultured under varying oxygen levels, ideal for assessing the effects of oxygen as a variable in toxicity screens. (via Semantic Scholar)
Source: Web Of Science
Added: March 22, 2021

2019 journal article

Characterization of glass frit capillary pumps for microfluidic devices

MICROFLUIDICS AND NANOFLUIDICS, 23(5).

By: M. Rich n, O. Mohd n, F. Ligler n & G. Walker*

author keywords: Porous; Glass; Capillary forces; Pump; Microfluidic; Point-of-care
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: May 6, 2019

2019 journal article

Flow-Encoded Oxygen Control to Track the Time-Dependence of Molecular Changes Induced by Static or Cycling Hypoxia

ANALYTICAL CHEMISTRY, 91(23), 15032–15039.

MeSH headings : Aldehyde Dehydrogenase / metabolism; Caco-2 Cells; Cell Hypoxia; Cell Line, Tumor; Glucose / pharmacokinetics; Humans; Hypoxia-Inducible Factor 1, alpha Subunit / drug effects; Hypoxia-Inducible Factor 1, alpha Subunit / metabolism; Oxygen / metabolism; Oxygen / pharmacology; Pancreatic Neoplasms / pathology; Time Factors
TL;DR: A manifold designed to use flow-encoding to produce sequential changes in gas mixtures delivered to a permeable-bottom 96-well plate is fabricated and shown how this manifold and plate design can be used to expose cells to either static or cycling hypoxic conditions for eight different time periods thereby facilitating the study of the time-response of cells to altered oxygen environments. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: December 30, 2019

2019 journal article

Paper-based passive pumps to generate controllable whole blood flow through microfluidic devices

LAB ON A CHIP, 19(22), 3787–3795.

By: M. Sotoudegan n, O. Mohd*, F. Ligler n & G. Walker*

MeSH headings : Animals; Blood Component Removal / instrumentation; Microfluidic Analytical Techniques / instrumentation; Paper; Particle Size; Porosity; Swine
TL;DR: The promising performance of grooved paper pumps with whole blood offers potential applications of these small, disposable pumps in point-of-care diagnostics in which time is crucial and access to external power is limited. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: November 25, 2019

2018 journal article

Mixing and delivery of multiple controlled oxygen environments to a single multiwell culture plate

AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY, 315(5), C766–C775.

By: M. Yao n, T. Sattler n, Z. Rabbani n, T. Pulliam n, G. Walker n & M. Gamcsik n

author keywords: cell culture; cycling hypoxia; finite element analysis; oxygen diffusion; permeability
MeSH headings : Caco-2 Cells; Cell Culture Techniques / instrumentation; Cell Hypoxia / genetics; Cell Proliferation / genetics; Humans; Hypoxia-Inducible Factor 1, alpha Subunit / chemistry; Hypoxia-Inducible Factor 1, alpha Subunit / metabolism; MCF-7 Cells; Oxygen / chemistry; Oxygen / metabolism
TL;DR: A 96-well plate-based device that is capable of delivering eight static or dynamically changing oxygen environments to different rows on a single plate that is amenable to multiwell Plate-based molecular assays or drug dose-response studies in static or cycling hypoxia conditions. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: December 10, 2018

2017 journal article

Modular pumps as programmable hydraulic batteries for microfluidic devices

TECHNOLOGY, 5(1), 21–30.

By: B. Cummins n, R. Chinthapatla n, B. Lenin n, F. Ligler n & G. Walker n

author keywords: Paper Microfluidics; Capillary Pump; Microfluidic; Lateral Flow; Microfluidic Pump; Point of Care
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2017 journal article

Time-Dependent Model for Fluid Flow in Porous Materials with Multiple Pore Sizes

Analytical Chemistry, 89(8), 4377–4381.

By: B. Cummins n, R. Chinthapatla n, F. Ligler n & G. Walker n

TL;DR: A new transport model is presented that incorporates a range of pore sizes to more accurately predict the capillary transport of fluid in porous materials. (via Semantic Scholar)
Sources: Web Of Science, Crossref
Added: August 6, 2018

2016 journal article

Drug Delivery: Microneedles Integrated with Pancreatic Cells and Synthetic Glucose-Signal Amplifiers for Smart Insulin Delivery (Adv. Mater. 16/2016)

Advanced Materials, 28(16), 3223–3223.

By: Y. Ye n, J. Yu n, C. Wang n, N. Nguyen n, G. Walker n, J. Buse*, Z. Gu n

TL;DR: A bio-responsive microneedle-based patch, integrated with a rhodamine-stained glucose-signal amplifier and calcein-AM-stained pancreatic β-cell capsules, effectively regulates the blood glucose level of type-1 diabetic mice, achieving a reduction for over 10 h. (via Semantic Scholar)
Source: Crossref
Added: December 17, 2020

2016 journal article

Improving the analytical performance and versatility of paper spray mass spectrometry via paper microfluidics

ANALYST, 141(13), 4065–4073.

By: I. Murray n, G. Walker n & M. Bereman n

TL;DR: Two paper-based microfluidic techniques, photolithography and wax patterning, were investigated for their potential to improve upon the sensitivity, reproducibility, and versatility of paper spray mass spectrometry. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: August 6, 2018

2016 journal article

Microneedles Integrated with Pancreatic Cells and Synthetic Glucose-Signal Amplifiers for Smart Insulin Delivery

Advanced Materials, 28(16), 3115–3121.

By: Y. Ye n, J. Yu n, C. Wang n, N. Nguyen n, G. Walker n, J. Buse*, Z. Gu n

MeSH headings : Animals; Blood Glucose / analysis; Blood Glucose / metabolism; Diabetes Mellitus, Experimental / blood; Diabetes Mellitus, Experimental / metabolism; Diabetes Mellitus, Experimental / pathology; Insulin / metabolism; Insulin Secretion; Islets of Langerhans / metabolism; Mice; Needles; Time Factors
TL;DR: An innovative microneedle (MN)-based cell therapy is developed for glucose-responsive regulation of the insulin secretion from exogenous pancreatic β-cells without implantation that can quickly reduce the blood-sugar levels of chemically induced type-1 diabetic mice. (via Semantic Scholar)
Sources: Crossref, Web Of Science
Added: August 6, 2018

2016 journal article

Point-of-care diagnostics for niche applications

Biotechnology Advances, 34(3), 161–176.

By: B. Cummins n, F. Ligler n & G. Walker n

author keywords: Point-of-care; Diagnostics; Space travel; Sports medicine; Veterinary; Emergency care; Operating room
MeSH headings : Animals; Emergency Service, Hospital / organization & administration; Humans; Operating Rooms / organization & administration; Point-of-Care Systems / statistics & numerical data; Point-of-Care Systems / trends; Space Flight; Sports Medicine; Veterinary Medicine
TL;DR: This review discusses five areas relevant to human and animal health where increased attention could produce significant impact: veterinary medicine, space travel, sports medicine, emergency Medicine, emergency medicine, and operating room efficiency. (via Semantic Scholar)
Sources: Web Of Science, Crossref
Added: August 6, 2018

2016 review

Review of Automated Microinjection Systems for Single Cells in the Embryogenesis Stage

[Review of ]. IEEE-ASME TRANSACTIONS ON MECHATRONICS, 21(5), 2391–2404.

By: S. Permana n, E. Grant n, G. Walker n & J. Yoder n

author keywords: Automation; biological cells; control system; mechatronics; reviews
TL;DR: A comprehensive review of the major research technologies used in automated cell microin injection and of their individual subsystems concludes that research into automated microinjection systems will focus on reducing the scale of microinject systems and developing appropriate controllers. (via Semantic Scholar)
Sources: Web Of Science, ORCID, NC State University Libraries
Added: August 6, 2018

2015 journal article

A temperature microsensor for measuring laser-induced heating in gold nanorods

ANALYTICAL AND BIOANALYTICAL CHEMISTRY, 407(3), 719–725.

By: D. Pacardo n, B. Neupane n, G. Wang n, Z. Gu n, G. Walker n & F. Ligler n

author keywords: Microsensor; Gold nanorods; Temperature; Nanoparticles; Microfluidics
MeSH headings : Chemistry Techniques, Analytical / instrumentation; Chemistry Techniques, Analytical / methods; Equipment Design; Gold; Heating; Hot Temperature; Lasers; Microtechnology; Nanotubes / analysis
TL;DR: The results demonstrate the suitability of this simple temperature microsensor for determining laser-induced heating profiles of metallic nanomaterials; such measurements will be essential for optimizing therapeutic and catalytic applications. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: August 6, 2018

2015 journal article

Biocompatibility of Tygon® tubing in microfluidic cell culture

Biomedical Microdevices, 17(1).

By: X. Jiang n, R. Jeffries n, M. Acosta n, A. Tikunov n, J. Macdonald n, G. Walker n, M. Gamcsik n

author keywords: Biomaterial; Cancer cell; Biocompatibility; Toxicity; Polyvinylchloride; Spectroscopy
MeSH headings : Cell Culture Techniques / instrumentation; Cell Culture Techniques / methods; Cell Line, Tumor; Female; Humans; Microfluidic Analytical Techniques / instrumentation; Microfluidic Analytical Techniques / methods
TL;DR: Results indicate leaching of a chemical species from microbore Tygon® tubing that can affect cell growth in microfluidic devices. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Crossref
Added: August 28, 2020

2014 journal article

A microfluidic device for thermal particle detection

Microfluidics and Nanofluidics, 17(5), 871–878.

By: A. Vutha*, B. Davaji*, C. Lee* & G. Walker*

author keywords: Microfluidics; Particle counting; Thermal
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Crossref
Added: December 21, 2020

2014 journal article

A microfluidic device to study cancer metastasis under chronic and intermittent hypoxia

Biomicrofluidics, 8(5), 054117.

By: M. Acosta n, X. Jiang n, P. Huang n, K. Cutler n, C. Grant n, G. Walker n, M. Gamcsik n

TL;DR: This work presents the design and characterization of a microfluidic device that can simultaneously mimic the oxygenation conditions observed within the tumor and model the cell migration and intravasation processes. (via Semantic Scholar)
Sources: Web Of Science, Crossref, NC State University Libraries
Added: August 6, 2018

2012 journal article

A photo-defined membrane for precisely patterned cellular and microparticle arrays

AIP Advances, 2(1), 012153.

By: A. McPherson n & G. Walker n

Source: Crossref
Added: August 14, 2021

2012 journal article

Adjustable stiffness tubes via thermal modulation of a low melting point polymer

Smart Materials and Structures, 21(4), 042001.

By: H. Dong n & G. Walker n

TL;DR: An adjustable stiffness tube composed of high melting point polymers for the inner and outer layer and a low melting point polymer in the middle that could be incorporated into an adjustable stiffness catheter is reported on. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Crossref
Added: August 14, 2021

2012 journal article

Microfluidic Cytometer for the Characterization of Cell Lysis

ANALYTICAL CHEMISTRY, 84(5), 2195–2201.

By: J. SooHoo n, J. Herr*, J. Ramsey* & G. Walker n

MeSH headings : Diffusion; Erythrocytes / cytology; Hemolysis; Humans; Kinetics; Microfluidic Analytical Techniques / instrumentation; Microfluidic Analytical Techniques / methods; Quaternary Ammonium Compounds / chemistry
TL;DR: A microfluidic cytometer was fabricated and achieved complete erythrocyte lysis of a blood sample in 0.7 s under optimum conditions, and a maximum lysis reaction rate of 1.55 s(-1) was extrapolated from the data. (via Semantic Scholar)
UN Sustainable Development Goal Categories
6. Clean Water and Sanitation (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2011 article

PENSIONING OFF PIPETTES: Pensioning off pipettes

Walker, G. M. (2011, June). NATURE CHEMISTRY, Vol. 3, pp. 428–429.

By: G. Walker n

MeSH headings : Microfluidics / instrumentation; Nanotechnology; Robotics
TL;DR: A microfluidic device design that allows a nanolitre droplet to be trapped and sequentially diluted without the need for any moving parts opens up new possibilities in high-throughput screening. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: August 6, 2018

2010 journal article

A microfluidic passive pumping Coulter counter

MICROFLUIDICS AND NANOFLUIDICS, 9(4-5), 897–904.

By: A. McPherson n & G. Walker n

author keywords: Microfluidics; Resistive pulse; Colloid; Enumeration
TL;DR: A microfluidic device using on-chip passive pumping was characterized for use as a particle counter and particle counts were within 13% of counts from a device using syringe pumping and hydrodynamic focusing using passive pumping. (via Semantic Scholar)
Source: Web Of Science
Added: August 6, 2018

2010 journal article

Adjustable-Stiffness Films via Integrated Thermal Modulation

MACROMOLECULAR MATERIALS AND ENGINEERING, 295(8), 735–741.

By: H. Dong n & G. Walker n

author keywords: adjustable stiffness; low-melting-point polymer; polycaprolactone; thermal modulation; young's modulus
TL;DR: A microfabricated heater embedded within a composite film is used to modulate the temperature of a low melting point polymer to propose a new strategy for fabricating thermally responsive adjustable stiffness materials. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: August 6, 2018

2009 journal article

Microfabricated curtains for controlled cell seeding in high throughput microfluidic systems

LAB ON A CHIP, 9(12), 1756–1762.

By: . Adrian T. O'Neill n, N. Monteiro-Riviere n & G. Walker n

Contributors: . Adrian T. O'Neill n, N. Monteiro-Riviere n & G. Walker n

MeSH headings : Cell Culture Techniques / instrumentation; Cell Movement; Cell Proliferation; Cell Survival / drug effects; Collagen / metabolism; Cytotoxins / toxicity; Dimethylpolysiloxanes; Humans; Keratinocytes / cytology; Keratinocytes / drug effects; Microfluidic Analytical Techniques / instrumentation; Nylons; Skin / cytology; Time Factors
TL;DR: Curtain use permitted high initial cell seeding densities and increased the amount of time cells can be cultured compared to multi-well plates and showed that cells exposed to 6% ethanol or less grew in population size, 8% ethanol exposure stunted growth, and higher concentrations led to population loss. (via Semantic Scholar)
UN Sustainable Development Goal Categories
2. Zero Hunger (OpenAlex)
Sources: Web Of Science, ORCID, NC State University Libraries
Added: August 6, 2018

2009 journal article

Microfluidic aqueous two phase system for leukocyte concentration from whole blood

BIOMEDICAL MICRODEVICES, 11(2), 323–329.

By: J. SooHoo n & G. Walker n

author keywords: Microfluidics; Leukocyte; Aqueous two phase separation; Blood; PEG; Dex
MeSH headings : Blood Component Removal / instrumentation; Blood Component Removal / methods; Cell Separation / instrumentation; Cell Separation / methods; Equipment Design; Equipment Failure Analysis; Humans; Leukocytes / cytology; Microfluidic Analytical Techniques / instrumentation; Microfluidic Analytical Techniques / methods; Phase Transition
TL;DR: The most effective configuration was the Dex-PEG-Dex stream pattern which on average increased the ratio of leukocytes to erythrocytes by a factor of 9.13 over unconcentrated blood. (via Semantic Scholar)
UN Sustainable Development Goal Categories
6. Clean Water and Sanitation (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2008 journal article

Characterization of microfluidic human epidermal keratinocyte culture

CYTOTECHNOLOGY, 56(3), 197–207.

By: . Adrian T. O'Neill*, N. Monteiro-Riviere* & G. Walker*

Contributors: . Adrian T. O'Neill*, N. Monteiro-Riviere* & G. Walker*

author keywords: cytotoxicity; high-throughput; keratinocyte; microfluidic; PDMS; toxicology
TL;DR: Human epidermal keratinocytes were shown to maintain 93.0%–99.6% viability at 72 h under medium perfusion ranging from 0.025–0.4 μl min−1, a level not possible in 96 well plates. (via Semantic Scholar)
Sources: Web Of Science, ORCID, NC State University Libraries
Added: August 6, 2018

2007 journal article

A linear dilution microfluidic device for cytotoxicity assays

LAB ON A CHIP, 7(2), 226–232.

By: G. Walker n, N. Monteiro-Riviere n, J. Rouse n & . Adrian T. O'Neill n

Contributors: G. Walker n, N. Monteiro-Riviere n, J. Rouse n & . Adrian T. O'Neill n

MeSH headings : Cells, Cultured; Combinatorial Chemistry Techniques; Diffusion; Drug Evaluation, Preclinical / instrumentation; Drug Evaluation, Preclinical / methods; Electrochemistry / methods; Equipment Design; Humans; Keratinocytes / cytology; Keratinocytes / drug effects; Microchemistry; Microfluidic Analytical Techniques / instrumentation; Microfluidic Analytical Techniques / methods; Microfluidics; Models, Statistical; Models, Theoretical
UN Sustainable Development Goal Categories
Sources: Web Of Science, ORCID, NC State University Libraries
Added: August 6, 2018

2006 chapter

A serial dilution microfluidic device for cytotoxicity assays

In 28th annual International Conference of the IEEE Engineering in Medicine and Biology Society (pp. 2836–2839). Piscataway, NJ: IEEE.

By: A. O'Neill, N. Monteiro-Riviere & G. Walker

Source: NC State University Libraries
Added: August 6, 2018

2006 journal article

The IL Sequence in the LLKIL Motif in CXCR2 Is Required for Full Ligand-induced Activation of Erk, Akt, and Chemotaxis in HL60 Cells

Journal of Biological Chemistry, 281(47), 35931–35941.

By: J. Sai*, G. Walker*, J. Wikswo* & A. Richmond*

MeSH headings : Amino Acid Motifs; Cell Movement; Cell Separation; Chemokines / metabolism; Chemotaxis; Enzyme Activation; GTP Phosphohydrolases / metabolism; HL-60 Cells; Humans; Interleukin-8 / physiology; Ligands; Mutation; Protein Structure, Tertiary; Receptors, Interleukin-8B / chemistry; Receptors, Interleukin-8B / physiology; Signal Transduction
TL;DR: The data imply that IL amino acid residues in the LLKIL motif are key either for amplification or oscillation of crucial signaling events or for establishment of a threshold for signals required for chemotaxis. (via Semantic Scholar)
Source: Crossref
Added: September 18, 2021

2005 journal article

Effects of flow and diffusion on chemotaxis studies in a microfabricated gradient generator

Lab on a Chip, 5(6), 611.

By: G. Walker*, J. Sai*, A. Richmond*, M. Stremler*, C. Chung* & J. Wikswo*

MeSH headings : Cell Line, Tumor; Cell Movement / physiology; Chemokines, CXC / physiology; Chemotaxis / physiology; Diffusion; HL-60 Cells; Humans; Microfluidics / instrumentation; Microfluidics / methods; Receptors, Chemokine / physiology; Sensitivity and Specificity; Time Factors
TL;DR: When the microchannel flow rates were increased, cell trajectories along the x axis were found to be significantly affected and it may be possible to estimate the total tractile force exerted by a cell during chemotaxis, which would be particularly valuable for cells whose tractile forces are below the level of detection with standard techniques of traction-force microscopy. (via Semantic Scholar)
Source: Crossref
Added: September 18, 2021

2004 journal article

Cell infection within a microfluidic device using virus gradients

Sensors and Actuators B: Chemical, 98(2-3), 347–355.

By: G. Walker*, M. Ozers & D. Beebe

author keywords: microfluidics; baculovirus expression system; PDMS; microchannel; concentration gradient
TL;DR: In characterizing non-gradient infection at the microscale, average multiplicity of infections (MOIs) ranging from 8 to 25 were used and reduced GFP expression levels, compared to accepted macroscale values, were observed. (via Semantic Scholar)
Source: Crossref
Added: September 18, 2021

2004 journal article

Microenvironment design considerations for cellular scale studies

Lab on a Chip, 4(2), 91.

By: G. Walker*, H. Zeringue* & D. Beebe*

MeSH headings : Adsorption; Animals; Biocompatible Materials / chemistry; Bioreactors; Cell Adhesion; Cell Culture Techniques / instrumentation; Cell Culture Techniques / methods; Cells, Cultured; Diffusion; Equipment Design; Microfluidics / instrumentation; Microfluidics / methods; Stress, Mechanical
TL;DR: Feature of in vitro cellular microenvironments are discussed and compared to macroscale cell culture environments; the concept of an effective culture volume (ECV) is introduced to facilitate the comparison. (via Semantic Scholar)
Source: Crossref
Added: September 18, 2021

2004 journal article

Microfluidic glucose stimulation reveals limited coordination of intracellular Ca2+ activity oscillations in pancreatic islets

Proceedings of the National Academy of Sciences, 101(35), 12899–12903.

By: J. Rocheleau*, G. Walker*, W. Head*, O. McGuinness* & D. Piston*

author keywords: beta cell; ATP-sensitive K+ channels; NAD(P)H
MeSH headings : Animals; Calcium / metabolism; Glucose / metabolism; Islets of Langerhans / metabolism; Male; Mice; Microfluidics / instrumentation; Microscopy, Confocal; Time Factors
TL;DR: A microfluidic device capable of partially stimulating an islet, while allowing observation of the NAD(P)H and [Ca2+]i responses is developed and shows that the extent of Ca2+ propagation across the islet depends on a delicate interaction between the degree of coupling andThe extent of ATP-sensitive K+-channel activation. (via Semantic Scholar)
Source: Crossref
Added: September 18, 2021

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