16 results on '"White, Ian M."'
Search Results
2. Inkjet printed surface enhanced Raman spectroscopy array on cellulose paper
- Author
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Yu, Wei W. and White, Ian M.
- Subjects
Raman spectroscopy -- Methods ,Raman spectroscopy -- Equipment and supplies ,Raman spectroscopy -- Technology application ,Cellulose -- Chemical properties ,Ink-jet printers -- Usage ,Surface chemistry -- Research ,Ink jet printer ,Technology application ,Chemistry - Abstract
A novel, ultra low-cost surface enhanced Raman spectroscopy (SERS) substrate has been developed by modifying the surface chemistry of cellulose paper and patterning nanoparticle arrays, all with a consumer inkjet printer. Micro/nanofabrication of SERS substrates for on-chip chemical and biomolecular analysis has been under intense investigation. However, the high cost of producing these substrates and the limited shelf life severely limit their use, especially for routine laboratory analysis and for point-of-sample analysis in the field. Paper-based microfluidic biosensing systems have shown great potential as low-cost disposable analysis tools. In this work, this concept is extended to SERS-based detection. Using an inexpensive consumer inkjet printer, cellulose paper substrates are modified to be hydrophobic in the sensing regions. Synthesized silver nanoparticles are printed onto this hydrophobic paper substrate with microscale precision to form sensing arrays. The hydrophobic surface prevents the aqueous sample from spreading throughout the paper and thus concentrates the analyte within the sensing region. A SERS fingerprint signal for Rhodamine 6G dye was observed for samples with as low as 10 femtomoles of analyte in a total sample volume of 1 [micro]L. This extraordinarily simple technique can be used to construct SERS microarrays immediately before sample analysis, enabling ultra low-cost chemical and biomolecular detection in the lab as well as in the field at the point of sample collection. 10.1021/ac102475k
- Published
- 2010
3. On-column micro gas chromatography detection with capillary-based optical ring resonators
- Author
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Shopova, Siyka I., White, Ian M., Sun, Yuze, Zhu, Hongying, Fan, Xudong, Frye-Mason, Greg, Thompson, Aaron, and Ja, Shiou-jyh
- Subjects
Resonators -- Usage ,Gas chromatography -- Equipment and supplies ,Chemical detectors -- Research ,Chemistry - Abstract
We developed a novel on-column micro gas chromatography ([micro]GC) detector using capillary based optical ring resonators (CBORRs). The CBORR is a thin-walled fused silica capillary with an inner diameter ranging from a few tens to a few hundreds of micrometers. The interior surface of the CBORR is coated with a layer of stationary phase for gas separation. The circular cross section of the CBORR forms a ring resonator and supports whispering gallery modes (WGMs) that circulate along the ring resonator circumference hundreds of times. The evanescent field extends into the core and is sensitive to the refractive index change induced by the interaction between the gas sample and the stationary phase. The WGM can be excited and monitored at any location along the CBORR by placing a tapered optical fiber against the CBORR, thus enabling on-column real-time detection. Rapid separation of both polar and nonpolar samples was demonstrated with subsecond detection speed. Theoretical work was also established to explain the CBORR detection mechanism. While low-nanogram detection limits are observed in these preliminary tests, many methods for improvements are under investigation. The CBORR is directly compatible with traditional capillary GC columns without any dead volumes. Therefore, the CBORR-based [micro]GC is a very promising technology platform for rapid, sensitive, and portable analytical devices.
- Published
- 2008
4. Integrated refractive index optical ring resonator detector for capillary electrophoresis
- Author
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Zhu, Hongying, White, Ian M., Suter, Jonathan D., Zourob, Mohammed, and Fan, Xudong
- Subjects
Electrophoresis -- Usage ,Refractive index -- Measurement ,Lasers -- Resonators ,Lasers -- Research ,Chemistry - Abstract
We developed a novel miniaturized and multiplexed, on-capillary, refractive index (RI) detector using liquid core optical ring resonators (LCORRs) for future development of capillary electrophoresis (CE) devices. The LCORR employs a glass capillary with a diameter of ~100 [micro]m and a wall thickness of a few micrometers. The circular cross section of the capillary forms a ring resonator along which the light circulates in the form of the whispering gallery modes (WGMs). The WGM has an evanescent field extending into the capillary core and responds to the RI change due to the analyte conducted in the capillary, thus permitting label-free measurement. The resonating nature of the WGM enables repetitive light-analyte interaction, significantly enhancing the LCORR sensitivity. This LCORR architecture achieves dual use of the capillary as a sensor head and a CE fluidic channel, allowing for integrated, multiplexed, and noninvasive on-capillary detection at any location along the capillary. In this work, we used electroosmotic flow and glycerol as a model system to demonstrate the fluid transport capability of the LCORRs. In addition, we performed flow speed measurement on the LCORR to demonstrate its flow analysis capability. Finally, using the LCORR's label-free sensing mechanism, we accurately deduced the analyte concentration in real time at a given point on the capillary. A sensitivity of 20 nm/ RIU (refractive index units) was observed, leading to an RI detection limit of [10.sup.-6] RIU. The LCORR marries photonic technology with microfluidics and enables rapid on-capillary sample analysis and flow profile monitoring. The investigation in this regard will open a door to novel high-throughput CE devices and lab-on-a-chip sensors in the future.
- Published
- 2007
5. Thermally Responsive Alkane Partitions for Assay Automation.
- Author
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Boegner, David J., Everitt, Micaela L., and White, Ian M.
- Published
- 2022
- Full Text
- View/download PDF
6. New Trimodal Phenotypic Reporter of Extended-Spectrum β-Lactamase Activity.
- Author
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Nguyen, Hieu T., Ganapati, Shweta, Watts, David, Nanayakkara, Imaly A., DeShong, Philip, and White, Ian M.
- Published
- 2019
- Full Text
- View/download PDF
7. Phase-Change Partitions for Thermal Automation of Multistep Reactions.
- Author
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Goertz, John P. and White, Ian M.
- Subjects
- *
PHASE transitions , *MICROFLUIDICS , *NUCLEIC acid amplification techniques , *METAL ions , *BETA lactamases - Abstract
Medical diagnostics and basic research in low-resource settings require automated reactions to be controlled in a simple, portable manner. Here, we present a novel platform that enables simple automation of multistep reactions to facilitate robust, hands-free assay operation without complex microfluidics or paperfluidics. We separate reagent zones in a conventional PCR tube via solid layers of purified higher alkanes. Reagents can be mixed on demand by simply raising the temperature above the melting point of the alkane partition that separates the two zones. We partitioned various reagents to enable hands-free thermally automated isothermal nucleic acid amplification, heavy metal ion detection, and β-lactamase detection with tandem antibiotic specificity characterization. We anticipate that this phase-change partition platform will find broad application in clinical diagnostics at the point-of-care and in low-resource settings. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
8. Simplifying Nucleic Acid Amplification from Whole Blood with Direct Polymerase Chain Reaction on Chitosan Microparticles.
- Author
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Nanayakkara, Imaly A., Weidong Cao, and White, Ian M.
- Published
- 2017
- Full Text
- View/download PDF
9. Capture and Direct Amplification of DNA on Chitosan Microparticles in a Single PCR-Optimal Solution.
- Author
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Pandit, Kunal R., Nanayakkara, Imaly A., Weidong Cao, Raghavan, Srinivasa R., and White, Ian M.
- Published
- 2015
- Full Text
- View/download PDF
10. Multiplexed Detection of DNA Sequences Using a Competitive Displacement Assay in a Microfluidic SERRS-Based Device.
- Author
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Yazdi, Soroush H., Giles, Kristen L., and White, Ian M.
- Published
- 2013
- Full Text
- View/download PDF
11. Optofluidic Surface Enhanced Raman Spectroscopy Microsystem for Sensitive and Repeatable On-Site Detection of Chemical Contaminants.
- Author
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Yazdi, Soroush H. and White, Ian M.
- Subjects
- *
OPTOFLUIDICS , *SURFACE enhanced Raman effect , *MICROFLUIDICS , *MELAMINE , *SILVER nanoparticles , *THIRAM , *FOOD contamination , *SPECTROMETERS - Abstract
We demonstrate highly sensitive detection of real-world food and water contaminants using a portable and automated optofluidic surface enhanced Raman spectroscopy (SERS) microsystem. The optofluidic SERS device utilizes a porous microfluidic matrix formed by packed silica microspheres to concentrate silver nanoparticles and adsorbed analyte molecules, resulting in greatly improved SERS detection performance. In addition, a passive micromixer that mixes silver nanoparticles into the sample solution is integrated into the device for improved automation. Furthermore, two optical fibers are integrated into the device and aligned to the detection volume to improve the automation as compared to confocal SERS, which requires focusing and alignment. The device exhibits up to 2 orders of magnitude improvement in SERS performance as compared to conventional microfluidic SERS in an open channel. Using the optofluidic SERS device, the food contaminant melamine was detected in low concentrations, with an estimated limit of detection (LOD) of 63 ppb, while the fungicide thiram was detected down to an estimated LOD of 50 ppt. In both cases, the reported results meet the U.S. federal requirements. Additionally, it is shown that the device continues to exhibit excellent performance even when mated to a commercially available portable spectrometer for the trace detection of thiram. This combination of the optofluidic SERS microsystem with a portable spectrometer will lead to highly sensitive and automated sensing systems for on-site detection of food and water contaminants in the field. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
12. Inkjet Printed Surface Enhanced Raman Spectroscopy Array on Cellulose Paper.
- Author
-
Wei W. Yu and White, Ian M.
- Subjects
- *
RAMAN spectroscopy , *MICROFLUIDIC analytical techniques , *CELLULOSE , *RHODAMINE B , *PRINTING properties of paper - Abstract
A novel, ultra low-cost surface enhanced Rainan spectroscopy (SEES) substrate has been developed by modiiing the suiface chemistry of cellulose paper and patterning nanoparticle arrays, all with a consumer inkjet printer. Micro/nanofabrication of SERS substrates for on-chip chemical and biomolecular analysis has been under intense investigation. However, the high cost of producing these substrates and the limited shelf life severely limit their use, especially for routine laboratory analysis and for point-of-sample analysis in the field. Paper-based microfluidic biosensing systems have shown great potential as low-cost disposable analysis tools. In this work, this concept is extended to SEES-based detection. Using an inexpensive consumer inkjet printer, cellulose paper substrates are modified to be hydrophobic in the sensing regions. Synthesized silver nanoparticles are printed onto this hydrophobic paper substrate with microscale precision to form sensing arrays. The hydrophobic surface prevents the aqueous sample from spreading throughout the paper and thus concentrates the analyte within the sensing region. A SEES fingerprint signal for Rhodamine 6G dye was observed for samples with as low as 10 femtomoles of analyte in a total sample volume of 1 μL This extraordinarily simple technique can be used to construct SEES microarrays immediately before sample analysis, enabling ultra low-cost chemical and biomolecular detection in the lab as weH as in the field at the point of sample collection. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
13. Integrated Refractive Index Optical Ring Resonator Detector for Capillary Electrophoresis.
- Author
-
Hongying Zhu, White, Ian M., Suter, Jonathan D., Zourob, Mohammed, and Xudong Fan
- Subjects
- *
REFRACTIVE index , *TOTAL internal reflection (Optics) , *OPTICAL resonance , *CAPILLARY electrophoresis , *MICROFLUIDICS , *PHOTONICS , *FLUID dynamics , *DETECTORS , *GEL electrophoresis - Abstract
We developed a novel miniaturized and multiplexed, on-capillary, refractive index (RI) detector using liquid core optical ring resonators (LCORRs) for future development of capillary electrophoresis (CE) devices. The LCORR employs a glass capillary with a diameter of ~100 µm and a wall thickness of a few micrometers. The circular cross section of the capillary forms a ring resonator along which the light circulates in the form of the whispering gallery modes (WGMs). The WGM has an evanescent field extending into the capillary core and responds to the RI change due to the analyte conducted in the capillary, thus permitting label-free measurement. The resonating nature of the WGM enables repetitive light-analyte interaction, significantly enhancing the LCORR sensitivity. This LCORR architecture achieves dual use of the capillary as a sensor head and a CE fluidic channel, allowing for integrated, multiplexed, and noninvasive on-capillary detection at any location along the capillary. In this work, we used electro-osmotic flow and glycerol as a model system to demonstrate the fluid transport capability of the LCORRs. In addition, we performed flow speed measurement on the LCORR to demonstrate its flow analysis capability. Finally, using the LCORR's label-free sensing mechanism, we accurately deduced the analyte concentration in real time at a given point on the capillary. A sensitivity of 20 nm/ RIU (refractive index units) was observed, leading to an RI detection limit of 10-6 RIU. The LCORR marries photonic technology with microfluidics and enables rapid on-capillary sample analysis and flow profile monitoring. The investigation in this regard will open a door to novel high-throughput CE devices and lab-on-a-chip sensors in the future. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
14. Sample-to-Answer Diagnostic System for the Detection of Circulating Histones in Whole Blood.
- Author
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Everitt ML, Boegner DJ, Birukov KG, and White IM
- Subjects
- Biomarkers, Humans, Histones, Point-of-Care Systems
- Abstract
Severe internal trauma results in millions of hospitalizations each year, including thousands of deaths caused by subsequent multiple organ failure. The majority of these deaths occur within the first 24 h, and thus, rapid diagnosis of internal trauma severity is necessary for immediate treatment. For early organ damage identification, diagnosis in point-of-care settings is crucial for rapid triage and treatment. Recent reports suggest that circulating histones may serve as a biomarker for severe organ damage and the risk of multiple organ failure. Here, we report a point-of-care diagnostic system that utilizes the inherent interactions between histones and DNA for the fluorescence-based detection of histones in whole blood. In the assay, histones within the sample are wrapped by DNA, thus preventing an intercalating dye from binding the DNA and fluorescing. To allow for quantitative fluorescent measurements to be made in a point-of-care setting, we integrate a rapid, automated blood separation step into our assay. Furthermore, we eliminate manual reagent additions using a thermally responsive alkane partition (TRAP), thus making the system sample-to-answer. Finally, we demonstrate the assay in a portable fluorescence reader compatible with a point-of-care environment. We report a limit of detection 112 ng/mL in whole blood, suggesting that our device can be used to rapidly diagnose internal trauma severity and the likelihood of multiple organ failure in near-patient settings.
- Published
- 2021
- Full Text
- View/download PDF
15. Multistage Chemical Heating for Instrument-Free Biosensing.
- Author
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Goertz JP, Colvin KM, Lippe AB, Daristotle JL, Kofinas P, and White IM
- Subjects
- Temperature, Biosensing Techniques methods, Hot Temperature
- Abstract
Improving the portability of diagnostic medicine is crucial for alleviating global access-to-care deficiencies. This requires not only designing devices that are small and lightweight, but also autonomous and independent of electricity. Here, we present a strategy for conducting automated multistep diagnostic assays using chemically generated, passively regulated heat. Ligation and polymerization reagents for rolling circle amplification of nucleic acids are separated by meltable phase-change partitions, thus replacing precise manual reagent additions with automated partition melting. To actuate these barriers and individually initiate the various steps of the reaction, field ration heaters exothermically generate heat in a thermos, whereas fatty acids embedded in a carbonaceous matrix passively buffer the temperature around their melting points. Achieving multistage temperature profiles extend the capability of instrument-free diagnostic devices and improve the portability of reaction automation systems built around phase-change partitions.
- Published
- 2018
- Full Text
- View/download PDF
16. Context-dependent redox properties of natural phenolic materials.
- Author
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Kim E, Liu Y, Leverage WT, Yin JJ, White IM, Bentley WE, and Payne GF
- Subjects
- Antioxidants chemistry, Antioxidants metabolism, Electrochemical Techniques, Molecular Structure, Oxidation-Reduction, Particle Size, Phenols metabolism, Reactive Oxygen Species metabolism, Surface Properties, Phenols chemistry
- Abstract
Macromolecular phenolics are among the most abundant organic molecules in nature, yet their biological activities are largely unresolved because of their structural complexity and because of an inability to probe their functionality experimentally. We developed thin film and electrochemical methodologies to probe the redox properties of melanin, lignin, and humic acid, three of the most abundant phenolic materials. We observed that all three phenolic matrixes possess redox activity and can be repeatedly switched between oxidized and reduced states. Furthermore, we observed that melanin possesses pro-oxidant activities exemplified by the uncatalyzed generation of reactive oxygen species (ROS) upon exposure to air; however, this pro-oxidant activity is observed only for melanin films that are poised in their reduced state. Conversely, melanin's antioxidant radical-scavenging activities are insensitive to its redox state. These results demonstrate that natural phenolic matrixes are not inert but rather serve as open-source redox media with significant potential for impacting redox signaling and redox biology.
- Published
- 2014
- Full Text
- View/download PDF
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