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Improved Detection By Ensemble-Decision Aliquot Ranking Of Circulating Tumor Cells With Low Numbers Of A Targeted Surface Antigen, Eleanor S. Johnson, Robbyn K. Anand, Daniel T. Chiu
Improved Detection By Ensemble-Decision Aliquot Ranking Of Circulating Tumor Cells With Low Numbers Of A Targeted Surface Antigen, Eleanor S. Johnson, Robbyn K. Anand, Daniel T. Chiu
Robbyn Anand
Circulating tumor cells (CTCs) are shed from a solid tumor into the bloodstream and can seed new metastases. CTCs hold promise for cancer diagnosis and prognosis and to increase our understanding of the metastatic process. However, their low numbers in blood and varied phenotypic characteristics make their detection and isolation difficult. One source of heterogeneity among CTCs is molecular: When they leave the primary tumor, these cells must undergo a molecular transition, which increases their mobility and chance of survival in the blood. During this molecular transition, the cells lose some of their epithelial character, which is manifested by the …
Negative Dielectrophoretic Capture And Repulsion Of Single Cells At A Bipolar Electrode: The Impact Of Faradaic Ion Enrichment And Depletion, Robbyn K. Anand, Eleanor S. Johnson, Daniel T. Chiu
Negative Dielectrophoretic Capture And Repulsion Of Single Cells At A Bipolar Electrode: The Impact Of Faradaic Ion Enrichment And Depletion, Robbyn K. Anand, Eleanor S. Johnson, Daniel T. Chiu
Robbyn Anand
This paper describes the dielectrophoretic (DEP) forces generated by a bipolar electrode (BPE) in a microfluidic device and elucidates the impact of faradaic ion enrichment and depletion (FIE and FID) on electric field gradients. DEP technologies for manipulating biological cells provide several distinct advantages over other cell-handling techniques including label-free selectivity, inexpensive device components, and amenability to single-cell and array-based applications. However, extension to the array format is nontrivial, and DEP forces are notoriously short-range, limiting device dimensions and throughput. BPEs present an attractive option for DEP because of the ease with which they can be arrayed. Here, we present …
New Generation Of Ensemble-Decision Aliquot Ranking Based On Simplified Microfluidic Components For Large-Capacity Trapping Of Circulating Tumor Cells, Mengxia Zhao, Wyatt C. Nelson, Bingchuan Wei, Perry G. Schiro, Bejan M. Hakimi, Eleanor S. Johnson, Robbyn K. Anand, Grace S. Gyurkey, Lisa M. White, Samuel H. Whiting, Andrew L. Coveler, Daniel T. Chiu
New Generation Of Ensemble-Decision Aliquot Ranking Based On Simplified Microfluidic Components For Large-Capacity Trapping Of Circulating Tumor Cells, Mengxia Zhao, Wyatt C. Nelson, Bingchuan Wei, Perry G. Schiro, Bejan M. Hakimi, Eleanor S. Johnson, Robbyn K. Anand, Grace S. Gyurkey, Lisa M. White, Samuel H. Whiting, Andrew L. Coveler, Daniel T. Chiu
Robbyn Anand
Ensemble-decision aliquot ranking (eDAR) is a sensitive and high-throughput method to analyze circulating tumor cells (CTCs) from peripheral blood. Here, we report the next generation of eDAR, where we designed and optimized a new hydrodynamic switching scheme for the active sorting step in eDAR, which provided fast cell sorting with an improved reproducibility and stability. The microfluidic chip was also simplified by incorporating a functional area for subsequent purification using microslits fabricated by standard lithography method. Using the reported second generation of eDAR, we were able to analyze 1 mL of whole-blood samples in 12.5 min, with a 95% recovery …
Label-Free Electrochemical Monitoring Of Concentration Enrichment During Bipolar Electrode Focusing, Eoin Sheridan, Dzmitry Hlushkou, Robbyn K. Anand, Derek R. Laws, Ulrich Tallrek, Richard M. Crooks
Label-Free Electrochemical Monitoring Of Concentration Enrichment During Bipolar Electrode Focusing, Eoin Sheridan, Dzmitry Hlushkou, Robbyn K. Anand, Derek R. Laws, Ulrich Tallrek, Richard M. Crooks
Robbyn Anand
We show that a label-free electrochemical method can be used to monitor the position of an enriched analyte band during bipolar electrode focusing in a microfluidic device. The method relies on formation of a depleted buffer cation region, which is responsible for concentration enrichment of the charged analyte. However, this depletion region also leads to an increase in the local electric field in the solution near a bipolar electrode (BPE), and this in turn results in enhanced faradaic reactions (oxidation and reduction of water) at the BPE. Therefore, it is possible to detect the presence of the concentrated analyte band …
Pressure-Driven Bipolar Electrochemistry, Ioana Dumitrescu, Robbyn K. Anand, Stephen E. Fosdick, Richard M. Crooks
Pressure-Driven Bipolar Electrochemistry, Ioana Dumitrescu, Robbyn K. Anand, Stephen E. Fosdick, Richard M. Crooks
Robbyn Anand
Here we report that pressure-driven flow alone (no external electrical energy) can be used to drive faradaic electrochemical reactions in microchannels with charged walls. Specifically, we show that solution flow can generate streaming potentials on the order of volts and that this is sufficient to carry out reactions on the anodic and cathodic poles of a bipolar electrode (BPE). The existence of faradaic reactions is proven by electrodissolution of Ag from the anodic end of the BPE.
Bipolar Electrode Focusing: Faradaic Ion Concentration Polarization, Robbyn K. Anand, Eoin Sheridan, Kyle N. Knust, Richard M. Crooks
Bipolar Electrode Focusing: Faradaic Ion Concentration Polarization, Robbyn K. Anand, Eoin Sheridan, Kyle N. Knust, Richard M. Crooks
Robbyn Anand
Bipolar electrode (BPE) focusing locally enriches charged analytes in a microchannel along an electric field gradient that opposes a counter-flow. This electric field gradient forms at the boundary of an ion depletion zone generated by the BPE. Here, we demonstrate concentration enrichment of a fluorescent tracer by up to 500 000-fold. The use of a dual-channel microfluidic configuration, composed of two microchannels electrochemically connected by a BPE, enhances the rate of enrichment (up to 71-fold/s). Faradaic reactions at the ends of the BPE generate ion depletion and enrichment zones in the two, separated channels. This type of device is equivalent …
Bipolar Electrodes: A Useful Tool For Concentration, Separation, And Detection Of Analytes In Microelectrochemical Systems, François Mavré, Robbyn K. Anand, Derek R. Laws, Kwok-Fan Show, Byoung-Yong Chang, John A. Crooks, Richard M. Crooks
Bipolar Electrodes: A Useful Tool For Concentration, Separation, And Detection Of Analytes In Microelectrochemical Systems, François Mavré, Robbyn K. Anand, Derek R. Laws, Kwok-Fan Show, Byoung-Yong Chang, John A. Crooks, Richard M. Crooks
Robbyn Anand
Over the past decade, bipolar electrochemistry has emerged from relative obscurity to provide a promising new means for integrating electrochemistry into lab-on-a-chip systems. This article describes the fundamental operating principles of bipolar electrodes, as well as several interesting applications. The graphic, by François Mavré, shows the principle of operation of a bipolar electrode within a microfluidic channel overlaid on a background image of electrogenerated chemiluminescence from an array of 1000 bipolar electrodes.
Bipolar Electrode Focusing: The Effect Of Current And Electric Field On Concentration Enrichment, Robbyn K. Perdue, Derek R. Laws, Dzmitry Hlushkou, Ulrich Tallarek, Richard M. Crooks
Bipolar Electrode Focusing: The Effect Of Current And Electric Field On Concentration Enrichment, Robbyn K. Perdue, Derek R. Laws, Dzmitry Hlushkou, Ulrich Tallarek, Richard M. Crooks
Robbyn Anand
Bipolar electrode focusing at discontinuous bipolar electrodes (BPEs) provides new insight into the faradaic current and electric field characteristics associated with the technique and allows for the controlled transport of a focused anionic tracer in a microfluidic channel. The findings corroborate our previously reported simulation results, which describe the formation of an extended electric field gradient leading to concentration enrichment. This gradient has been attributed to the passage of faradaic current through a BPE affixed to the floor of the microchannel. Our results demonstrate that the onset of faradaic current is coincident with the onset of concentration enrichment. Utilizing an …
Bipolar Electrode Focusing: Simultaneous Concentration Enrichment And Separation In A Microfluidic Channel Containing A Bipolar Electrode, Derek R. Laws, Dzmitry Hlushkou, Robbyn K. Perdue, Ulrich Tallarek, Richard M. Crooks
Bipolar Electrode Focusing: Simultaneous Concentration Enrichment And Separation In A Microfluidic Channel Containing A Bipolar Electrode, Derek R. Laws, Dzmitry Hlushkou, Robbyn K. Perdue, Ulrich Tallarek, Richard M. Crooks
Robbyn Anand
A method for simultaneously concentrating and separating analytes in a buffer-filled microfluidic channel is reported. The approach is based on modulation of the local electric field within the channel and the corresponding opposition of electrophoretic and electroosmotic flow (EOF) velocities. Dye molecules having different electrophoretic mobilities are focused at different locations within the channel where concentration takes place. At least three species, all small dye molecules, can be simultaneously concentrated and separated, with localized enrichment factors up to ∼600 achieved within 400 s. The enrichment zones affect the electric field profile, as evidenced by significant differences in focusing of single …