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Enhanced glucose sensor linearity using poly(vinyl alcohol) hydrogels

Journal of Diabetes science and Technology 2009年第4期3卷 863-874页

作者： Vaddiraju, SanthiSagar Singh, Hardeep Burgess, Diane J. Jain, Faquir C. Papadimitrakopoulos, Fotios Polymer Program Institute of Material Science University of Connecticut Storrs CT 06269 United States Department of Pharmaceutical Sciences University of Connecticut Storrs CT United States Nanomaterials Optoelectronics Laboratory Electrical and Computer Engineering University of Connecticut Storrs CT United States Department of Chemistry University of Connecticut Storrs CT United States

Background: High linearities, sensitivities, and low oxygen dependence constitute prime requisites for electrochemical glucose sensors. However, for implantable sensors the need to control tissue inflammation requires the use of outer membranes that permit inward analyte diffusion while continuously releasing anti-inflammatory drugs and other tissue response-modifying (TRM) agents. We have shown previously that while outer membranes based on layer-by-layer (LBL) assembly enhance linearity, poly(vinyl alcohol)(PVA) hydrogels loaded with TRM-containing microspheres enable a significant reduction in tissue inflammation. This article discusses the amperometric performance of glucose sensors coated with stacked LBL/PVA hydrogel outer membranes. Methods: Sensors were fabricated by immobilizing glucose oxidase enzyme on a 50-μm platinum wire followed by deposition of stacked LBL/PVA hydrogel outer membranes. The sensor response to various glucose concentrations was determined by applying 0.7 V vs an Ag/AgCl reference electrode in phosphate-buffered saline (37°C). Michaelis-Menten analysis was performed to quantify sensor performance in terms of linearity (Km,gluapp) and oxygen dependence (Km,O2app/[Glucose]). Results: When overlaid onto LBL-assembled outer membranes, PVA hydrogels improved sensor linearity by 60% from 10 to 16 m M of glucose and resulted in a twofold decrease in oxygen dependence. Conclusions: Enhancement in the performance of a PVA-coated sensor is attributed to the oxygen-storing capability of PVA hydrogel due to the formation of hydrophobic domains during its freezing and thawing employed to physical cross-link the PVA. Such membranes with the capability to release TRMs continuously while storing oxygen constitute a major improvement over current outer membrane technologies. © Diabetes Technology Society.

关键词： Apparent Michaelis-Menten constants Biosensor Freeze-thaw cycle Layer-by-layer assembly Linearity Outer membranes Oxygen content Oxygen dependence of biosensors PVA hydrogels

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Achievable Capacity of a Spectrum Sharing System over Hyper Fading Channels

Achievable Capacity of a Spectrum Sharing System over Hyper ...

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GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference

作者： Sabit Ekin Ferkan Yilmaz Hasari Celebi Khalid A. Qaraqe Mohamed-Slim Alouini Erchin Serpedin Department of Electrical and Computer Engineering Texas A and M University Qatar Doha Qatar Electrical Engineering Program King Abdullah University for Science and Technology Thuwal Saudi Arabia

Cognitive radio with spectrum sharing feature is a promising technique to address the spectrum under-utilization problem in dynamically changing environments. In this paper, achievable capacity gain of spectrum sharing systems over dynamic fading environments is studied. For the analysis, a theoretical fading model called hyper fading model that is suitable to the dynamic nature of cognitive radio channel is proposed. Closed-form expression of probability density function (PDF) and cumulative density function (CDF) of the signal-to-noise ratio (SNR) for secondary users in spectrum sharing systems are derived. In addition, the capacity gains achievable with spectrum sharing systems in high and low power regions are obtained. Numerical simulations are performed to study the effects of different fading figures, average powers, interference temperature, and number of secondary users on the achievable capacity.

关键词： Fading Power system modeling Rayleigh channels Temperature Cognitive radio Interference constraints Random variables computer science education Educational programs Systems engineering education

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Determination of Thermal Parameters of Nanostructures Exhibiting One-Dimensional Heat Flow Through a Thermal Transient Method

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MRS Online Proceedings Library 2009年第1期1172卷 54-59页

作者： Arriagada, Anton Yu, Edward T. Bandaru, Prabhakar R. Deparment of Electrical and Computer Engineering University of California at San Diego La Jolla USA Materials Science Program Mechanical Engineering Department University of California at San Diego La Jolla USA

We present an improved methodology for a thermal transient method enabling simultaneous measurement of thermal conductivity and specific heat of nanoscale structures with one-dimensional heat flow. The temporal response of a sample to finite duration heat pulse inputs for both short (1 ns) and long (5μs) pulses is analyzed and exploited to deduce the thermal properties. Excellent agreement has been obtained between the recovered physical parameters and computational simulations.

关键词： thermal conductivity nanoscale simulation

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Photonic crystal enhanced cytokine immunoassay

Photonic crystal enhanced cytokine immunoassay

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： Patrick C. Mathias Nikhil Ganesh Brian T. Cunningham Department of Electrical and Computer Engineering University of Illinois Urbana-Champaign USA Department of Material Science and Engineering University of Illinois Urbana-Champaign USA Department of Bioengineering University of Illinois Urbana-Champaign USA

Photonic crystal surfaces are demonstrated as a means for enhancing the detection sensitivity and resolution for assays that use a fluorescent tag to quantify the concentration of an analyte protein molecule in a liquid test sample. computer modeling of the spatial distribution of resonantly coupled electromagnetic fields on the photonic crystal surface are used to estimate the magnitude of enhancement factor compared to performing the same fluorescent assay on a plain glass surface, and the photonic crystal structure is fabricated and tested to experimentally verify the performance using a sandwich immunoassay for the protein Tumor Necrosis Factor-alpha (TNF-alpha). The demonstrated photonic crystal fabrication method utilizes a nanoreplica molding technique that allows for large-area inexpensive fabrication of the structure in a format that is compatible with confocal microarray laser scanners. The signal-to-noise ratio for fluorescent spots on the photonic crystal is increased by at least five-fold relative to the glass slide, allowing a TNF-alpha concentration of 1.6 pg/ml to be distinguished from noise on a photonic crystal surface. In addition, the minimum quantitative limit of detection on the photonic crystal surface is one-third the limit on the glass slide - a decrease from 18 pg/ml to 6 pg/ml. The increased performance of the immunoassay allows for more accurate quantitation of physiologically relevant concentrations of TNF-alpha in a protein microarray format that can be expanded to multiple cytokines.

关键词： Photonic crystals Immunity testing Fluorescence Proteins Glass Optical device fabrication Signal to noise ratio Spatial resolution Distributed computing Optical computing

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Reconstructing FT-IR spectroscopic imaging data with a sparse prior

Reconstructing FT-IR spectroscopic imaging data with a spars...

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IEEE International Conference on Image Processing

作者： Spencer P. Brady Minh N. Do Rohit Bhargava Department of Electrical and Computer Engineering and Coordinated Science Laboratory University of Illinois Urbana-Champaign USA Department of Bioengineering and Beckman Institute of Advanced Science and Technology University of Illinois Urbana-Champaign USA

Fourier Transform Infrared (FT-IR) spectroscopic imaging is a potentially valuable tool for diagnosing breast and prostate cancer, but its clinical deployment is limited due to long data acquisition times and vast storage requirements. To counter this limitation, we develop a sparse representation for FT-IR absorbance spectra using a learned dictionary. This sparse representation is used as prior knowledge in regularizing the compressed sensing inverse problem. The data size and acquisition time are directly proportional to the length of the measured signal, namely the interferogram. Hence, we model our measurement process as interferogram truncation, which we implement by low pass filtering and downsampling in the spectral domain. With a downsample factor of four, our reconstruction is adequate for tissue classification and provides a Peak Signal-to-noise Ratio (PSNR) of 41.92 dB, while standard interpolation of the same low resolution measurements can only provide a PSNR of 36.93 dB.

关键词： Image reconstruction Spectroscopy PSNR Optical imaging Infrared spectra Image storage Fourier transforms Infrared imaging Breast Prostate cancer

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Patterning of SU-8 resist with Digital Micromirror Device (DMD) maskless lithography

Patterning of SU-8 resist with Digital Micromirror Device (D...

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Optical Microlithography XXII

作者： Wang, Tao Quaglio, Marzia Pirri, Fabrizio Cheng, Yang-Chun Busacker, David Cerrina, Franco Center for Nanotechnology University of Wisconsin-Madison Madison WI 53706 United States Materials Science Program University of Wisconsin-Madison Madison WI 53706 United States Polytechnic of Torino Physics Department Materials and Microsystems Laboratory C. so Duca degli Abruzzi 24 I-10129 Torino Italy Department of Electrical and Computer Engineering University of Wisconsin-Madison Madison WI 53706 United States Department of Electrical and Computer Engineering Boston University Boston MA 02215 United States

ISBN: (纸本)9780819475275

Digital micromirror device (DMD) based maskless lithography has a number of advantages including process flexibility, no physical photomask requirement, fast turnaround time, cost effectiveness. It can be particularly useful in the development stage of microfluidic and bioMEMS applications. In this report, we describe the initial results of thick resist SU-8 patterning, soft lithography with polydimethylsiloxane (PDMS) and lift-off of Cr features using a modified DMD maskless system. Exposures of various patterns and microfluidic channels reveal that the system is well capable of printing 60 μm thick resist at a resolution as small as a single pixel (less than 13 μm) with an aspect ratio about 5:1. Both negatively and positively tapered sidewalls are achieved by projecting the UV light from front side of the SU-8 coated Si wafer and from the back side of the coated glass, respectively. The positive sidewall has an angle 88 which is ideal to serve as a mold for subsequent PDMS soft lithography. Both SU-8 and PDMS microfluidic devices for biomolecular synthesis were fabricated with this maskless system. In addition, a lift-off process was also developed with the intention to create built-in metal features such as electrodes and heaters. © 2009 SPIE.

关键词： Microfluidics

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A neuromorphic head direction cell system

A neuromorphic head direction cell system

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： Tarek M. Massoud Timothy K. Horiuchi Electrical and Computer Engineering Department Institute of Systems Research Neuroscience and Cognitive Science Program University of Maryland College Park MD USA

ISBN: (纸本)9781424438273

The head direction (HD) cell system in the brain of mammals is thought to be part of the neural circuitry supporting their spatial navigation capabilities. In this paper we present a neuromorphic VLSI system that mimics the operation of the HD system. Relying on spiking neurons and attractor dynamics, this system can be used to represent and retain the current estimate of head orientation in the environment and integrate angular velocity to update this estimate. The presented system is a first step towards more general odometry systems that could be used for modeling biological navigation systems.

关键词： Neuromorphics Neurons High definition video Navigation Very large scale integration Biological system modeling Brain Neuroscience Cognitive science Educational institutions

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Photonic crystals: A platform for label-free and enhanced fluorescence biomolecular and cellular assays

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MRS Online Proceedings Library 2009年第1期1133卷 1-10页

作者： T. Cunningham Brian Leo Chan C. Mathias Patrick Nikhil Ganesh Sherine George Erich Lidstone James Heeres J. Hergenrother Paul Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign Urbana USA Department of Bioengineering University of Illinois at Urbana-Champaign Urbana USA Department of Material Science and Engineering University of Illinois at Urbana-Champaign Urbana USA Department of Chemistry University of Illinois at Urbana-Champaign Urbana USA

Photonic crystal surfaces represent a class of resonant optical structures that are capable of supporting high intensity electromagnetic standing waves with near-field and far-field properties that can be exploited for high sensitivity detection of biomolecules and cells. While modulation of the resonant wavelength of a photonic crystal by the dielectric permittivity of adsorbed biomaterials enables label-free detection, the resonance can also be tuned to coincide with the excitation wavelength of common fluorescent tags - including organic molecules and semiconductor quantum dots. Photonic crystals are also capable of efficiently channeling fluorescent emission into a preferred direction for enhanced extraction efficiency. Photonic crystals can be designed to support multiple resonant modes that can perform label free detection, enhanced fluorescence excitation, and enhanced fluorescence extraction simultaneously on the same device. Because photonic crystal surfaces may be inexpensively produced over large surface areas by nanoreplica molding processes, they can be incorporated into disposable labware for applications such as pharmaceutical high throughput screening. In this talk, the optical properties of surface photonic crystals will be reviewed and several applications will be described, including results from screening a 200,000-member chemical compound library for inhibitors of protein-DNA interactions, gene expression microarrays, and high sensitivity of protein biomarkers.

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Coalition formation through learning in autonomic networks

Coalition formation through learning in autonomic networks

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International Conference on Game Theory for Networks, GameNets

作者： Tao Jiang John S. Baras Institute of Systems Research University of Maryland College Park MD USA Institute of Systems Research Department of Electrical and Computer Engineering Department of Computer Science The Fischell Department of Bioengineering University of Maryland College Park MD USA

Autonomic networks rely on the cooperation of participating nodes for almost all their functions. However, due to resource constraints, nodes are generally selfish and try to maximize their own benefit when participating in the network. Therefore, it is important to study mechanisms, which can be used as incentives for cooperation inside the network. In this paper, the interactions among nodes are modelled as games. A node joins a coalition if it decides to cooperate with at least one node in the coalition. The dynamics of coalition formation proceed via nodes that interact strategically and adapt their behavior to the observed behavior of others. We present conditions that the coalition formed is stable in terms of Nash stability and the core of the coalitional game.

关键词： Costs Game theory Collaborative work Spread spectrum communication Educational institutions Nash equilibrium Communication networks Stability Communication system control Routing

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LFP beta power predicts cursor stationarity in BMI task

LFP beta power predicts cursor stationarity in BMI task

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2009 4th International IEEE/EMBS Conference on Neural engineering, NER '09

作者： Ranade, Gireeja V. Ganguly, Karunesh Carmena, Jose Department of Electrical Engineering and Computer Sciences University of California Berkeley CA United States Helen Wills Neruoscience Institute University of California Berkeley CA United States Program in Cognitive Science University of California Berkeley CA United States Department of Neurology University of California San Francisco CA United States

ISBN: (纸本)9781424420735

Beta band oscillations in the local field potential (LFP) have been previously related to behavior in motor tasks. We investigated the correlations between beta oscillations and movement state for brain-machine interfaces. Two macaque monkeys were trained to perform a center-out motor task on a computer under normal movement control and under a 'brain control' paradigm, where neural firing directly controls the cursor. In both cases, LFP beta power decreased after movement onset. High beta power was predominantly observed with low movement velocity and vice versa. This observation was used to predict the stationarity of a computer cursor during brain control. ©2009 IEEE.

关键词： Interface states

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