Publications by authors named "Christian A Zorman"

18 Publications

  • Page 1 of 1

Fabrication of a Silver-Based Thermistor on Flexible, Temperature-Sensitive Substrates Using a Low-Temperature Inkjet Printing Technique.

IEEE Sens Lett 2019 Jan;3(2)

Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, OH 44106 USA.

Inkjet printing has been identified as a cost-effective method to fabricate sensors on polymeric substrates. However, substrate materials suitable for printing are limited by the annealing temperature required by conventional inks. In this article, we describe the fabrication of an inkjet-printed thermistor on polyethylene and cellophane substrates that are not thermally compatible with the conventional inkjet printing processes. Fabrication on these substrates is made possible by a novel plasma-based postprint treatment step that limits the substrate temperature to <50 °C. The sensors exhibited a temperature sensitivity of 0.25 Ω°C that was independent of substrate material. The utility of the fabrication process was demonstrated by fabricating thermistors for common indoor and outdoor applications.
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http://dx.doi.org/10.1109/LSENS.2019.2893741DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7032546PMC
January 2019

Vascular Pressure-Flow Measurement Using CB-PDMS Flexible Strain Sensor.

IEEE Trans Biomed Circuits Syst 2019 12 10;13(6):1451-1461. Epub 2019 Oct 10.

Regular monitoring of blood flow and pressure in vascular reconstructions or grafts would provide early warning of graft failure and improve salvage procedures. Based on biocompatible materials, we have developed a new type of thin, flexible pulsation sensor (FPS) which is wrapped around a graft to monitor blood pressure and flow. The FPS uses carbon black (CB) nanoparticles dispersed in polydimethylsiloxane (PDMS) as a piezoresistive sensor layer, which was encapsulated within structural PDMS layers and connected to stainless steel interconnect leads. Because the FPS is more flexible than natural arteries, veins, and synthetic vascular grafts, it can be wrapped around target conduits at the time of surgery and remain implanted for long-term monitoring. In this study, we analyze strain transduction from a blood vessel and characterize the electrical and mechanical response of CB-PDMS from 0-50% strain. An optimum concentration of 14% CB-PDMS was used to fabricate 300-μm thick FPS devices with elastic modulus under 500 kPa, strain range of over 50%, and gauge factor greater than 5. Sensors were tested in vitro on vascular grafts with flows of 0-1,100 mL/min. In vitro testing showed linear output to pulsatile flows and pressures. Cyclic testing demonstrated robust operation over hundreds of cardiac cycles, with ±2.6 mmHg variation in pressure readout. CB-PDMS composite material showed excellent potential in biologic strain sensing applications where a flexible sensor with large maximum strain range is needed.
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http://dx.doi.org/10.1109/TBCAS.2019.2946519DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6944770PMC
December 2019

Wearable sensors for monitoring the internal and external workload of the athlete.

NPJ Digit Med 2019 29;2:71. Epub 2019 Jul 29.

1Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 USA.

The convergence of semiconductor technology, physiology, and predictive health analytics from wearable devices has advanced its clinical and translational utility for sports. The detection and subsequent application of metrics pertinent to and indicative of the physical performance, physiological status, biochemical composition, and mental alertness of the athlete has been shown to reduce the risk of injuries and improve performance and has enabled the development of athlete-centered protocols and treatment plans by team physicians and trainers. Our discussions in this review include commercially available devices, as well as those described in scientific literature to provide an understanding of wearable sensors for sports medicine. The primary objective of this paper is to provide a comprehensive review of the applications of wearable technology for assessing the biomechanical and physiological parameters of the athlete. A secondary objective of this paper is to identify collaborative research opportunities among academic research groups, sports medicine health clinics, and sports team performance programs to further the utility of this technology to assist in the return-to-play for athletes across various sporting domains. A companion paper discusses the use of wearables to monitor the biochemical profile and mental acuity of the athlete.
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http://dx.doi.org/10.1038/s41746-019-0149-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6662809PMC
July 2019

Wearable sensors for monitoring the physiological and biochemical profile of the athlete.

NPJ Digit Med 2019 22;2:72. Epub 2019 Jul 22.

1Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 USA.

Athletes are continually seeking new technologies and therapies to gain a competitive edge to maximize their health and performance. Athletes have gravitated toward the use of wearable sensors to monitor their training and recovery. Wearable technologies currently utilized by sports teams monitor both the internal and external workload of athletes. However, there remains an unmet medical need by the sports community to gain further insight into the internal workload of the athlete to tailor recovery protocols to each athlete. The ability to monitor biomarkers from saliva or sweat in a noninvasive and continuous manner remain the next technological gap for sports medical personnel to tailor hydration and recovery protocols per the athlete. The emergence of flexible and stretchable electronics coupled with the ability to quantify biochemical analytes and physiological parameters have enabled the detection of key markers indicative of performance and stress, as reviewed in this paper.
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http://dx.doi.org/10.1038/s41746-019-0150-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6646404PMC
July 2019

Nanoparticle based simple electrochemical biosensor platform for profiling of protein-nucleic acid interactions.

Talanta 2019 Apr 6;195:46-54. Epub 2018 Nov 6.

Department of Chemical and Biomolecular Engineering, Case Western Reserve University, Cleveland, OH 44106, USA; Electronics Design Center, Case Western Reserve University, Cleveland, OH 44106, USA. Electronic address:

The analysis of protein-nucleic acid interactions is essential for biophysics related research. However, simple, rapid, and accurate methods for quantitative analysis of biomolecular interactions are lacking. We herein establish an electrochemical biosensor approach for protein-nucleic acid binding analysis. Nanoparticle based sensors are fabricated by highly-controlled inkjet printing followed by plasma conversion. A novel bioconjugation method is demonstrated as a simple and rapid approach for protein-based biosensor fabrication. As a proof of concept, we analyzed the binding interaction between unwinding protein 1 (UP1) and SL3 RNA, confirming the accuracy of this nanoparticle based electrochemical biosensor approach with traditional biophysical methods. We further accurately profiled and differentiated a unique binding interaction pattern of multiple G-tract nucleic acid sequences with heterogeneous nuclear ribonucleoprotein H1. Our study provides insights into a potentially universal platform for in vitro biomolecule interaction analysis using a nanoparticle based electrochemical biosensor approach.
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http://dx.doi.org/10.1016/j.talanta.2018.11.021DOI Listing
April 2019

Direct, Transfer-Free Growth of Large-Area Hexagonal Boron Nitride Films by Plasma-Enhanced Chemical Film Conversion (PECFC) of Printable, Solution-Processed Ammonia Borane.

ACS Appl Mater Interfaces 2018 Dec 4;10(50):43936-43945. Epub 2018 Dec 4.

Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States.

Synthesis of large-area hexagonal boron nitride (h-BN) films for two-dimensional (2D) electronic applications typically requires high temperatures (∼1000 °C) and catalytic metal substrates which necessitate transfer. Here, analogous to plasma-enhanced chemical vapor deposition, a nonthermal plasma is employed to create energetic and chemically reactive states such as atomic hydrogen and convert a molecular precursor film to h-BN at temperatures as low as 500 °C directly on metal-free substrates-a process we term plasma-enhanced chemical film conversion (PECFC). Films containing ammonia borane as a precursor are prepared by a variety of solution processing methods including spray deposition, spin coating, and inkjet printing and reacted in a cold-wall reactor with a planar dielectric barrier discharge operated at atmospheric pressure in a background of argon or a mixture of argon and hydrogen. Systematic characterization of the converted h-BN films by micro-Raman spectroscopy shows that the minimum temperature for nucleation on silicon-based substrates can be decreased from 800 to 500 °C by the addition of a plasma. Furthermore, the crystalline domain size, as reflected by the full width at half-maximum, increased by more than 3 times. To demonstrate the potential of the h-BN films as a gate dielectric in 2D electronic devices, molybdenum disulfide field effect transistors were fabricated, and the field effect mobility was found to be improved by up to 4 times over silicon dioxide. Overall, PECFC allows h-BN films to be grown at lower temperatures and with improved crystallinity than CVD, directly on substrates suitable for electronic device fabrication.
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http://dx.doi.org/10.1021/acsami.8b17152DOI Listing
December 2018

Vascular Graft Pressure-Flow Monitoring Using 3D Printed MWCNT-PDMS Strain Sensors.

Annu Int Conf IEEE Eng Med Biol Soc 2018 Jul;2018:2989-2992

Real-time monitoring of arteriovenous graft blood flow would provide early warning of graft failure to permit interventions such as angioplasty or graft replacement to avoid catastrophic failure. We have developed a new type of flexible pulsation sensor (FPS) consisting of a 3D printed elastic cuff wrapped around a graft and thus not in contact with blood. The FPS uses multi-walled carbon nanotubes (MWCNTs) dispersed in polydimethylsiloxane (PDMS) as a piezoresistive sensor layer, which is embedded within structural thixotropic PDMS. These materials were specifically developed to enable sensor additive manufacturing via 3D Bio-plotting, and the resulting strain sensor is more compliant and has a wider maximum strain range than graft materials. Here, we analyze the strain transduction mechanics on a vascular graft and describe the memristive properties of MWCNT-PDMS composites, which may be mitigated using AC biasing. In vitro testing of the FPS on a vascular graft phantom showed a robust, linear sensor output to pulsatile flows (170-650 mL/min) and pressures (62-175 mmHg). The FPS showed an RMS error when measuring pressure and flow of 7.7 mmHg and 29.3 mL/min, with a mean measurement error of 6.5% (pressure) and 8.0% (flow).
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http://dx.doi.org/10.1109/EMBC.2018.8512997DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6699158PMC
July 2018

Ultrawide Band Gap β-GaO Nanomechanical Resonators with Spatially Visualized Multimode Motion.

ACS Appl Mater Interfaces 2017 Dec 27;9(49):43090-43097. Epub 2017 Nov 27.

Department of Electrical Engineering & Computer Science, Case School of Engineering, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.

Beta gallium oxide (β-GaO) is an emerging ultrawide band gap (4.5 eV-4.9 eV) semiconductor with attractive properties for future power electronics, optoelectronics, and sensors for detecting gases and ultraviolet radiation. β-GaO thin films made by various methods are being actively studied toward such devices. Here, we report on the experimental demonstration of single-crystal β-GaO nanomechanical resonators using β-GaO nanoflakes grown via low-pressure chemical vapor deposition (LPCVD). By investigating β-GaO circular drumhead structures, we demonstrate multimode nanoresonators up to the sixth mode in high and very high frequency (HF/VHF) bands, and also realize spatial mapping and visualization of the multimode motion. These measurements reveal a Young's modulus of E = 261 GPa and anisotropic biaxial built-in tension of 37.5 MPa and 107.5 MPa. We find that thermal annealing can considerably improve the resonance characteristics, including ∼40% upshift in frequency and ∼90% enhancement in quality (Q) factor. This study lays a foundation for future exploration and development of mechanically coupled and tunable β-GaO electronic, optoelectronic, and physical sensing devices.
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http://dx.doi.org/10.1021/acsami.7b13930DOI Listing
December 2017

Tuning Optical Signatures of Single- and Few-Layer MoS by Blown-Bubble Bulge Straining up to Fracture.

Nano Lett 2017 08 6;17(8):4568-4575. Epub 2017 Jul 6.

Electrical Engineering, ‡Chemical and Biomolecular Engineering, Case School of Engineering, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.

Emerging atomic layer semiconducting crystals such as molybdenum disulfide (MoS) are promising candidates for flexible electronics and strain-tunable devices due to their ultrahigh strain limits (up to ∼20-30%) and strain-tunable bandgaps. However, high strain levels, controllable isotropic and anisotropic biaxial strains in single- and few-layer MoS on device-oriented flexible substrates permitting convenient and fast strain tuning, remain unexplored. Here, we demonstrate a "blown-bubble" bulge technique for efficiently applying large strains to atomic layer MoS devices on a flexible substrate. As the strain increases via bulging, we achieve continuous tuning of Raman and photoluminescence (PL) signatures in single- and few-layer MoS, including splitting of Raman peaks. With proper clamping of the MoS crystals, we apply up to ∼9.4% strain in the flexible substrate, which causes a doubly clamped single-layer MoS to fracture at 2.2-2.6% strain measured by PL and 2.9-3.5% strain measured by Raman spectroscopy. This study opens new pathways for exploiting 2D semiconductors on stretchable substrates for flexible electronics, mechanical transducers, tunable optoelectronics, and biomedical transducers on curved and bulging surfaces.
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http://dx.doi.org/10.1021/acs.nanolett.7b00730DOI Listing
August 2017

Transfer printing of self-folding polymer-metal bilayer particles.

ACS Appl Mater Interfaces 2014 Dec 4;6(24):22695-700. Epub 2014 Dec 4.

Department of Macromolecular Science and Engineering, and ‡Department of Electrical Engineering and Computer Science, Case Western Reserve University , Cleveland, Ohio 44106, United States.

A simple and robust alternative for fabricating stimuli-responsive 2D self-folding films was introduced. The approach combines metal-sputtering, layer-by-layer assembly of polyelectrolytes, and transfer-printing of the bilayer film onto a substrate coated with a sacrificial layer. With this technique, self-folding bilayer films can be fabricated without using harsh chemical etchants, complicated chemical synthesis, or complex lithographic techniques. Upon release, the microsized 2D film is shown to reconfigure into a 3D structure caused by a mismatch in the properties of the individual layers. The actuation of the bilayer film can be triggered by partial swelling due to absorption of water or by partial expansion of one of the layers due to an increase in temperature.
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http://dx.doi.org/10.1021/am5068172DOI Listing
December 2014

Fabrication of electrically conductive metal patterns at the surface of polymer films by microplasma-based direct writing.

ACS Appl Mater Interfaces 2014 Mar 25;6(5):3099-104. Epub 2014 Feb 25.

Department of Chemical Engineering, ‡Department of Electrical Engineering and Computer Science, and §Department of Macromolecular Sciences and Engineering, Case Western Reserve University , Cleveland, Ohio, United States.

We describe a direct-write process for producing electrically conductive metal patterns at the surface of polymers. Thin films of poly(acrylic acid) (PAA) loaded with Ag ions are reduced by a scanning, atmospheric-pressure microplasma to form crystalline Ag features with a line width of 300 μm. Materials analysis reveals that the metallization occurs in a thin layer of ∼5 μm near the film surface, suggesting that the Ag ions diffuse to the surface. Sheet resistances of 1-10 Ω/sq are obtained independent of film thickness and Ag volume concentration, which is desirable for producing surface conductivity on polymers while minimizing metal loading.
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http://dx.doi.org/10.1021/am406005aDOI Listing
March 2014

Environmentally-controlled microtensile testing of mechanically-adaptive polymer nanocomposites for ex vivo characterization.

J Vis Exp 2013 Aug 20(78):e50078. Epub 2013 Aug 20.

Advanced Platform Technology Center, Rehabilitation Research and Development, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, USA.

Implantable microdevices are gaining significant attention for several biomedical applications. Such devices have been made from a range of materials, each offering its own advantages and shortcomings. Most prominently, due to the microscale device dimensions, a high modulus is required to facilitate implantation into living tissue. Conversely, the stiffness of the device should match the surrounding tissue to minimize induced local strain. Therefore, we recently developed a new class of bio-inspired materials to meet these requirements by responding to environmental stimuli with a change in mechanical properties. Specifically, our poly(vinyl acetate)-based nanocomposite (PVAc-NC) displays a reduction in stiffness when exposed to water and elevated temperatures (e.g. body temperature). Unfortunately, few methods exist to quantify the stiffness of materials in vivo, and mechanical testing outside of the physiological environment often requires large samples inappropriate for implantation. Further, stimuli-responsive materials may quickly recover their initial stiffness after explantation. Therefore, we have developed a method by which the mechanical properties of implanted microsamples can be measured ex vivo, with simulated physiological conditions maintained using moisture and temperature control. To this end, a custom microtensile tester was designed to accommodate microscale samples with widely-varying Young's moduli (range of 10 MPa to 5 GPa). As our interests are in the application of PVAc-NC as a biologically-adaptable neural probe substrate, a tool capable of mechanical characterization of samples at the microscale was necessary. This tool was adapted to provide humidity and temperature control, which minimized sample drying and cooling. As a result, the mechanical characteristics of the explanted sample closely reflect those of the sample just prior to explantation. The overall goal of this method is to quantitatively assess the in vivo mechanical properties, specifically the Young's modulus, of stimuli-responsive, mechanically-adaptive polymer-based materials. This is accomplished by first establishing the environmental conditions that will minimize a change in sample mechanical properties after explantation without contributing to a reduction in stiffness independent of that resulting from implantation. Samples are then prepared for implantation, handling, and testing (Figure 1A). Each sample is implanted into the cerebral cortex of rats, which is represented here as an explanted rat brain, for a specified duration (Figure 1B). At this point, the sample is explanted and immediately loaded into the microtensile tester, and then subjected to tensile testing (Figure 1C). Subsequent data analysis provides insight into the mechanical behavior of these innovative materials in the environment of the cerebral cortex.
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http://dx.doi.org/10.3791/50078DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3855926PMC
August 2013

Polytype control of spin qubits in silicon carbide.

Nat Commun 2013 ;4:1819

Center for Spintronics and Quantum Computation, University of California, Santa Barbara, Santa Barbara, California 93106, USA.

Crystal defects can confine isolated electronic spins and are promising candidates for solid-state quantum information. Alongside research focusing on nitrogen-vacancy centres in diamond, an alternative strategy seeks to identify new spin systems with an expanded set of technological capabilities, a materials-driven approach that could ultimately lead to 'designer' spins with tailored properties. Here we show that the 4H, 6H and 3C polytypes of SiC all host coherent and optically addressable defect spin states, including states in all three with room-temperature quantum coherence. The prevalence of this spin coherence shows that crystal polymorphism can be a degree of freedom for engineering spin qubits. Long spin coherence times allow us to use double electron-electron resonance to measure magnetic dipole interactions between spin ensembles in inequivalent lattice sites of the same crystal. Together with the distinct optical and spin transition energies of such inequivalent states, these interactions provide a route to dipole-coupled networks of separately addressable spins.
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http://dx.doi.org/10.1038/ncomms2854DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3674240PMC
December 2013

Adhesion and Moisture Barrier Characteristics of Roller-Cast Polydimethylsiloxane Encapsulants for Implantable Microsystems.

Proc IEEE Sens 2012 Oct;2012:1-4

Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, OH USA.

Poly-dimethylsiloxane (PDMS) is a highly attractive polymer to encapsulate implantable micro-electromechanical systems (MEMS) due to its biocompatibility, simplicity in processing, and low Young's Modulus. However, conventional deposition processes introduce defects that prevent the use of PDMS as a long term packaging material. In order to address these issues, we have developed a novel roller-casting process for depositing PDMS. This paper presents the findings of a study to simultaneously investigate the adhesion properties and moisture barrier characteristics of roller-cast, multilayered PDMS encapsulants subjected to testing in saline at 85°C.
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http://dx.doi.org/10.1109/ICSENS.2012.6411369DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3571116PMC
October 2012

A low-cost automated streaming potential measurement system.

J Lab Autom 2012 Apr 24;17(2):125-33. Epub 2012 Jan 24.

Department of Electrical Engineering, Case Western Reserve University, Cleveland, OH 44106-1712, USA.

Surface charge characterization is important in the design and testing of coatings and membranes for biological and industrial applications, but commercial zeta potential meters are expensive and difficult to adapt to a variety of membrane designs. We combined inexpensive off-the-shelf components, a test mount fabricated with a conventional rapid prototyping system, and software written using a no-cost integrated development environment to implement a low-cost, automated streaming potential meter. Software written in Visual C# managed a USB data acquisition and control pod to regulate the transmembrane pressure while simultaneously reading transmembrane voltages from a digital multimeter with 0.1-nV precision. The streaming potential was measured through a commercially available polyethersulfone membrane with repeatable results for transmembrane pressures between -15 and 15 kPa. The transmembrane voltages for each set of six pressures were linear, with R (2) values greater than 0.9995. The zeta potentials calculated from the measured streaming potentials are in agreement with previous results for the same commercial membrane previously reported in the literature. The material cost for the system is less than $4000.
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http://dx.doi.org/10.1177/2211068211425663DOI Listing
April 2012

Basal lamina secreted by MDCK cells has size- and charge-selective properties.

Am J Physiol Renal Physiol 2011 Jan 27;300(1):F86-90. Epub 2010 Oct 27.

Department of Biomedical Engineering, ND20, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, USA.

The role electrical charge plays in determining glomerular permeability to macromolecules remains unclear. If the glomerular basement membrane (GBM) has any significant role in permselectivity, physical principles would suggest a negatively charged GBM would reject similarly charged more than neutral species. However, recent in vivo studies with negative and neutral glomerular probes showed the opposite. Whether this observation is due to unique characteristics of the probes used or is a general physiological phenomenon remains to be seen. The goal of this study was to use the basement membrane deposited by Madin-Darby canine kidney epithelial cells as a simple model of a biologically derived, negatively charged filter to evaluate size- and charge-based sieving properties. Fluorescein isothiocyanate-labeled carboxymethylated Ficoll 400 (FITC-CM Ficoll 400) and amino-4-methyl-coumarin-labeled Ficoll 400 (AMC Ficoll 400) were used as negatively charged and neutral tracer molecules, respectively, during pressure-driven filtration. Streaming potential measurement indicated the presence of fixed, negative charge in the basal lamina. The sieving coefficient for neutral Ficoll 400 decreased by ∼0.0013 for each 1-Å increment in solute radius, compared with a decrease of 0.0023 per Å for the anionic Ficoll 400. In this system, molecular charge played a significant role in determining the sieving characteristics of the membrane, pointing to solute charge as a potential contributor to GBM permselectivity.
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http://dx.doi.org/10.1152/ajprenal.00484.2010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3023222PMC
January 2011

Molecular conformation and filtration properties of anionic Ficoll.

Am J Physiol Renal Physiol 2010 Oct 28;299(4):F752-7. Epub 2010 Jul 28.

Biomedical Engineering, Cleveland Clinic, Cleveland, OH 44195, USA.

The physiology of glomerular permselectivity remains mechanistically obscure, despite its importance in human disease. Although electrical contributions to glomerular permselectivity have long been considered important, two recent reports demonstrated enhanced glomerular permeability to anionic versus neutral polysaccharides. The interpretation of these observations is complicated by confounding of the effects of chemical modification on charge with effects on size and shape. In this report, neutral and anionic Ficoll are characterized by size-exclusion chromatography with online light scattering and viscometry and filtration through a highly defined anionic filtration membrane. Neutral and carboxymethylated Ficoll are nearly identical in size and conformation, yet carboxymethylated Ficoll is retained by an anionic membrane in excess of neutral Ficoll. This suggests that comparisons between clearances of neutral and carboxymethylated Ficoll may be a sensitive probe of electrostatic interactions independent of size and conformation.
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http://dx.doi.org/10.1152/ajprenal.00324.2010DOI Listing
October 2010

Nanoelectromechanical systems: Nanodevice motion at microwave frequencies.

Nature 2003 Jan;421(6922):496

Condensed Matter Physics, California Institute of Technology 114-36, Pasadena, California 91125, USA.

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http://dx.doi.org/10.1038/421496aDOI Listing
January 2003
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