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Biomedical subjects

Yuehe Lin

Publications and source records attributed to Yuehe Lin.

At least 19 recordsLinked to original sources
PubMed2006

Microanalyzer for biomonitoring lead (Pb) in blood and urine.

Biomonitoring of lead (Pb) in blood and urine enables quantitative evaluation of human occupational and environmental exposures to Pb. State-of-the-art ICP-MS instruments can only analyze metals in laboratories, resulting in lengthy turnaround times, and they are expensive. In response to the growing need for a metal analyzer capable of on-site, real-time monitoring of trace toxic metals in individuals, we developed a portable microanalyzer based on flow-injection/stripping voltammetry (ASV), and validated the system using rat blood and urine spiked with known amounts of Pb. Fouling of electrodes by proteins often prevents the effective use of electrochemical sensors in biological matrices. Minimization of such fouling was accomplished with suitable sample pretreatment and by establishing turbulent flow of blood and urine containing Pb onto the electrode inside the microanalyzer, which resulted in no apparent electrode fouling even when the samples contained 50% urine or 10% blood by volume. No matrix effect was observed for the voltammetric Pb signals, even when the samples contained 10% blood or 10% urine. The microanalyzer offered linear concentration ranges relevant to Pb exposure levels in humans (0-20 ppb in 10% blood samples, 0-50 ppb in 50% urine samples). The device showed excellent sensitivity and reproducibility; Pb detection limits were 0.44 ppb and 0.46 ppb, and % R.S.D. was 4.9 and 2.4 in 50% urine and 10% blood samples, respectively. It gave similar Pb concentrations in blood and urine to those measured by ICP-MS. It offered high throughput (3 min per sample) and economical use of samples (60 microL per measurement) as well as low reagent consumption (1 microg of Hg per measurement), thus minimizing environmental concerns associated with mercury use. Since it is miniaturized, the microanalyzer is portable and field-deployable. Thus, it shows much promise as the next-generation analyzer for the biomonitoring of toxic metals.

Animals↗
PubMed2006

Versatile apoferritin nanoparticle labels for assay of protein.

A versatile bioassay label based on marker-loaded apoferritin nanoparticles (MLANs) has been developed for sensitive protein detection. Dissociation and reconstitution characteristics at different pH as well as the special cavity structure of apoferritin provides a facile route to prepare nanoparticle labels and avoid the complicated and tedious synthesis process of conventional nanoparticle labels. The optical and electrochemical characteristics of the prepared nanoparticle labels are easily controlled by loading different optical or electrochemical markers. A fluorescence marker (fluorescein anion) and a redox marker [hexacyanoferrate(III)] were used as model markers to load into the cavity of apoferritin nanoparticles for microscopic fluorescence immunoassay and electrochemical immunoassay, respectively. Detection limits of 0.06 (0.39 pM) and 0.08 ng mL(-1) (0.52 pM) IgG were obtained with fluorescein MLAN and hexacyanoferrate MLANs, respectively. The new nanoparticle labels hold great promise for multiplex protein detection (in connection with nanoparticles loaded with different markers) and for enhancing the sensitivity of other bioassays.

Apoferritins↗
PubMed2006

Voltammetric analysis of europium at screen-printed electrodes modified with salicylamide self-assembled on mesoporous silica.

Mercury-free sensors for europium (Eu(3+)) assay based on the chemical modification of screen-printed carbon electrodes (SPCEs) with self-assembled salicylamide on mesoporous silica (Sal-SAMMS) have been developed. The preconcentration of Eu(3+) at SAMMS-based sensors utilizes the binding affinity of the salicylamide and Eu(3+), accomplished at open circuit potential without electrolyte and solution de-gassing. Optimal Eu detection was obtained after 3-5 min preconcentration in Eu solution (pH 2-6), electrolysis at -0.9 V for 60 s in a new medium (0.1-0.2 M NH(4)Cl, pH 3.5), followed by a square-wave voltammetric detection of Eu in the same electrolyte. Attributed to the strong covalent bonding of the functional groups on mesoporous silica and silane cross-linking, the SAMMS-modified SPCEs with a built-in 3-electrode system can be re-used for tens of measurements with minimal degradation, enabling the establishment of the calibration curve and lowering the costs. A linear calibration curve was found in the range of 75 to at least 500 ppb Eu(3+) after 5 min preconcentration. The experimental detection limit was 10 ppb after 10 min preconcentration, which can be improved with increased preconcentration time. Reproducibility (% RSD) of 100 ppb Eu(2+) was 10% for a single sensor and 10% for 5 sensors, which can be improved through the precision of sensor manufacturing, in which SAMMS modification can be made in-situ.

Journal Article↗
PubMed2006

Development of a non-invasive biomonitoring approach to determine exposure to the organophosphorus insecticide chlorpyrifos in rat saliva.

Non-invasive biomonitoring approaches are being developed using reliable portable analytical systems to quantify dosimetry utilizing readily obtainable body fluids, such as saliva. In the current study, rats were given single oral gavage doses (1, 10, or 50 mg/kg) of the insecticide chlorpyrifos (CPF). Saliva and blood were then collected from groups of animals (4/time-point) at 3, 6, and 12 h post-dosing, and were analyzed for the CPF metabolite trichloropyridinol (TCP). Trichloropyridinol was detected in both blood and saliva at all doses and the TCP concentration in blood exceeded saliva, although the kinetics in blood and saliva were comparable. A physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) model for CPF incorporated a compartment model to describe the time-course of TCP in blood and saliva. The model adequately simulated the experimental results over the dose ranges evaluated. A rapid and sensitive sequential injection (SI) electrochemical immunoassay was developed to monitor TCP, and the reported detection limit for TCP was 6 ng/L (in water). Computer model simulation in the range of the Allowable Daily Intake (ADI) or Reference Dose (RfD) for CPF (0.01-0.003 mg/kg/day) suggests that the electrochemical immunoassay has adequate sensitivity to detect and quantify TCP in saliva at these low exposure levels. However, to validate this approach, further studies are needed to more fully understand the pharmacokinetics of CPF and TCP excretion in saliva. These initial findings suggest that the utilization of saliva as a biomonitoring matrix, coupled to real-time quantitation and PBPK/PD modeling represents a novel approach with broad application for evaluating both occupational and environmental exposures to CPF.

Animals↗
PubMed2006

Sensitive immunoassay of a biomarker tumor necrosis factor-alpha based on poly(guanine)-functionalized silica nanoparticle label.

A novel electrochemical immunosensor for the detection of tumor necrosis factor-alpha (TNF-alpha) based on poly(guanine)-functionalized silica nanoparticles (NPs) label is presented. The detection of mouse TNF-alpha via immunological reaction is based on a dual signal amplification: (1) a large amount of guanine residues introduced on the electrode surface through sandwich immunoreaction and poly(guanine)-functionalized silica NP label; (2) Ru(bpy)3(2+)-induced catalytic oxidation of guanine, which results in great enhancement of anodic current. The synthesized silica NP conjugates were characterized with atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemistry. These experiments confirmed that poly(guanine) and avidin were immobilized on the surface of silica NPs. The performance of the electrochemical immunosensor was evaluated and some experiment parameters (e.g., concentration of Ru(bpy)3(2+), incubation time of TNF-alpha, etc.) were optimized. The detection limit for TNF-alpha is found to be 5.0 x 10(-11) g mL(-1) (2.0 pM), which corresponds to 60 amol of TNF-alpha in 30 microL of sample. This immunosensor based on the poly(guanine)-functionalized silica NP label offers great promise for rapid, simple, cost-effective analysis of biological samples.

Animals↗
PubMed2006

Electrochemical proteolytic beacon for detection of matrix metalloproteinase activities.

This communication describes a novel method for detecting matrix metalloproteinase-7 activity using a peptide substrate labeled with a ferrocene reporter. The substrate serves as a selective "electrochemical proteolytic beacon" (EPB) for this metalloproteinase. The EPB is immobilized on a gold electrode surface to enable "on-off" electrochemical signaling capability for uncleaved and cleaved events. The EPB is efficiently and selectively cleaved by MMP-7 as measured by the rate of decrease in redox current of ferrocene. Direct transduction of a signal corresponding to peptide cleavage events into an electronic signal thus provides a simple, sensitive route for detecting the MMP activity. The new method allows for identification of the activity of MMP-7 in concentrations as low as 3.4 pM. The concept can be extended to design a multiple peptide substrate labeled with different electroactive reporters for assaying multiple MMPs activities.

Electrochemistry↗
PubMed2006

Electrically controlled anion exchange based on polypyrrole and carbon nanotubes nanocomposite for perchlorate removal.

A simple and highly effective process for perchlorate removal based on electrically switched ion exchange (ESIX) was developed by using polypyrrole (PPy) deposited on high surface area carbon nanotubes. The redox switching of conducting polymers such as polypyrrole is accompanied by the exchange of ions into or out of the polymer. This effect could be used for the development of an electrically switchable ion-exchanger for water purification, particularly for the removal of anions. In the research presented in this paper, the anion-exchange behavior and ion-exchange capacity of electrochemically prepared polypyrrole on glassy carbon electrodes with and without carbon nanotube (CNT) backbones are characterized using cyclic voltammetry and X-ray photoelectron spectroscopy. It has been found that the presence of carbon nanotube backbone results in an improvement in the anion exchange stability of polypyrrole, which may be due to the stronger interaction between carbon nanotubes and polypyrrole. Chronoamperometric studies show that the process of electrically switched anion exchange could be finished within 10 s. The selectivity of PPy/CNTs films for the perchlorate ion is demonstrated using cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). The results of the present study point to the possibility of developing a green process for removing ClO4- from wastewater using such a novel nanostructured PPy/CNT composite thin film through an electrically switched anion exchange.

Anion Exchange Resins↗
PubMed2006

Amperometric choline biosensor fabricated through electrostatic assembly of bienzyme/polyelectrolyte hybrid layers on carbon nanotubes.

We report a flow injection amperometric choline biosensor based on the electrostatic assembly of the choline oxidase (ChO) enzyme and a bienzyme of ChO and horseradish peroxidase (HRP) onto multi-wall carbon nanotubes (MWCNT) modified glassy carbon (GC) electrodes. These choline biosensors were fabricated by immobilization of enzymes on the negatively charged MWCNT surface through alternately assembling a cationic poly(diallydimethylammonium chloride) (PDDA) layer and an enzyme layer. Using this layer-by-layer assembling approach, a bioactive nanocomposite film of PDDA/ChO/PDDA/HRP/PDDA/CNT (ChO/HRP/CNT) and PDDA/ChO/PDDA/CNT (ChO/CNT) was fabricated on the GC surface. Owing to the electrocatalytic effect of carbon nanotubes, the measurement of faradic responses resulting from enzymatic reactions has been realized at low potential with acceptable sensitivity. The ChO/HRP/CNT biosensor is more sensitive than the ChO/CNT one. Experimental parameters affecting the sensitivity of biosensors, e.g., applied potential, flow rate, etc., were optimized and potential interference was examined. The response time for this choline biosensor is fast (few seconds). The linear range of detection for the choline biosensor is from 5.0 x 10(-5) to 5.0 x 10(-3) M and the detection limit is about 1.0 x 10(-5) M.

Biosensing Techniques↗
PubMed2006

Biosensor based on self-assembling acetylcholinesterase on carbon nanotubes for flow injection/amperometric detection of organophosphate pesticides and nerve agents.

A highly sensitive flow injection amperometric biosensor for organophosphate pesticides and nerve agents based on self-assembled acetylcholinesterase (AChE) on a carbon nanotube (CNT)-modified glassy carbon (GC) electrode is described. AChE is immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(diallyldimethylammonium chloride) (PDDA) layer and an AChE layer. Transmission electron microscopy images confirm the formation of layer-by-layer nanostructures on carboxyl-functionalized CNTs. Fourier transform infrared reflectance spectrum indicates the AChE was immobilized successfully on the CNT/PDDA surface. The unique sandwich-like structure (PDDA/AChE/PDDA) on the CNT surface formed by self-assembling provides a favorable microenvironment to keep the bioactivity of AChE. The electrocatalytic activity of CNT leads to a greatly improved electrochemical detection of the enzymatically generated thiocholine product, including a low oxidation overvoltage (+150 mV), higher sensitivity, and stability. The developed PDDA/AChE/PDDA/CNT/GC biosensor integrated into a flow injection system was used to monitor organophosphate pesticides and nerve agents, such as paraoxon. The sensor performance, including inhibition time and regeneration conditions, was optimized with respect to operating conditions. Under the optimal conditions, the biosensor was used to measure as low as 0.4 pM paraoxon with a 6-min inhibition time. The biosensor had excellent operational lifetime stability with no decrease in the activity of enzymes for more than 20 repeated measurements over a 1-week period. The developed biosensor system is an ideal tool for online monitoring of organophosphate pesticides and nerve agents.

Acetylcholinesterase↗
PubMed2006

Preparation, characterization and anion exchange properties of polypyrrole/carbon nanotube nanocomposites.

In this study, polypyrrole (PPy) thin films were electrodeposited on carbon nanotube (CNT) backbones by applying a constant deposition potential in 0.1 M pyrrole solution with different electrolytes, such as NaCl, NaNO3, or NaClO4. The hybrid films were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, and cyclic voltammetry. SEM images revealed the nanostructrure of PPy films generated on CNT surface. The electrochemical and anion exchange properties of the PPy-CNT composite films have been investigated. Nanostructured composite thin films of PPy-CNTs were studied by cyclic voltammetry between 0.4 and -0.8 V in aqueous solution to evaluate their cycling stability and capacity for electrically switched anion exchange. The presence of the CNT backbone greatly improved the anion exchange capacity and stability of the PPy-CNT composite film, which may be attributed to the high surface area of CNT matrix, nanostructure of the PPy film, and the interaction between CNTs and PPy.

Anion Exchange Resins↗
PubMed2006

Carbon nanotube-templated assembly of protein.

This paper describes a novel general strategy for fabricating protein-polyion multilayers by electrostatic layer-by-layer (LBL) self-assembly on carbon nanotube templates. Such a noncovalent functionalization method is important for preserving the activity of biomolecular, the mechanical, and electrical properties of carbon nanotubes. Glucose oxidase and poly(diallyldimethylammonium) chloride polymer (PDDA) were used as models to investigate the LBL process on CNT templates. High-resolution TEM and electrochemical characterization confirm the formation of LBL nanostructures on carboxyl functionalized carbon nanotubes. We have also demonstrated the applications of these nanoshell bioreactors to direct electrochemistry of protein and biosensing. This strategy can be applied to assemble other biological molecules such as antibody, antigen, and DNA for wide bioassay applications.

Coated Materials, Biocompatible↗
PubMed2005

Monodispersed core-shell Fe3O4@Au nanoparticles.

The ability to synthesize and assemble monodispersed core-shell nanoparticles is important for exploring the unique properties of nanoscale core, shell, or their combinations in technological applications. This paper describes findings of an investigation of the synthesis and assembly of core (Fe(3)O(4))-shell (Au) nanoparticles with high monodispersity. Fe(3)O(4) nanoparticles of selected sizes were used as seeding materials for the reduction of gold precursors to produce gold-coated Fe(3)O(4) nanoparticles (Fe(3)O(4)@Au). Experimental data from both physical and chemical determinations of the changes in particle size, surface plasmon resonance optical band, core-shell composition, surface reactivity, and magnetic properties have confirmed the formation of the core-shell nanostructure. The interfacial reactivity of a combination of ligand-exchanging and interparticle cross-linking was exploited for molecularly mediated thin film assembly of the core-shell nanoparticles. The SQUID data reveal a decrease in magnetization and blocking temperature and an increase in coercivity for Fe(3)O(4)@Au, reflecting the decreased coupling of the magnetic moments as a result of the increased interparticle spacing by both gold and capping shells. Implications of the findings to the design of interfacial reactivities via core-shell nanocomposites for magnetic, catalytic, and biological applications are also briefly discussed.

Ferric Compounds↗
PubMed2005

PtRu/carbon nanotube nanocomposite synthesized in supercritical fluid: a novel electrocatalyst for direct methanol fuel cells.

Platinum/ruthenium nanoparticles were decorated on carbon nanotubes (CNT) in supercritical carbon dioxide, and the nanocomposites were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). TEM images show that the particles size is in the range of 5-10 nm, and XRD patterns show a face-centered cubic crystal structure. Methanol electrooxidation in 1 M sulfuric acid electrolyte containing 2 M methanol were studied onPtRu/CNT (Pt, 4.1 wt%; Ru, 2.3 wt%; molar ratio approximately Pt/Ru = 45:55) catalysts using cyclic voltammetry, linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. All the electrochemical results show that PtRu/CNT catalysts exhibit high activity for methanol oxidation which resulted from the high surface area of carbon nanotubes and the nanostructure of platinum/ruthenium particles. Compared with Pt/CNT, the onset potential is much lower and the ratio of forward anodic peak current to reverse anodic peak current is much higher for methanol oxidation, which indicates the higher catalytic activity of PtRu/CNT. The presence of Ru with Pt accelerates the rate of methanol oxidation. The results demonstrated the feasibility of processing bimetallic catalysts in supercritical carbon dioxide for fuel cell applications.

Journal Article↗
PubMed2005

Electrochemical sensor for organophosphate pesticides and nerve agents using zirconia nanoparticles as selective sorbents.

An electrochemical sensor for detection of organophosphate (OP) pesticides and nerve agents using zirconia (ZrO2) nanoparticles as selective sorbents is presented. Zirconia nanoparticles were electrodynamically deposited onto the polycrystalline gold electrode by cyclic voltammetry. Because of the strong affinity of zirconia for the phosphoric group, nitroaromatic OPs strongly bind to the ZrO2 nanoparticle surface. The electrochemical characterization and anodic stripping voltammetric performance of bound OPs were evaluated using cyclic voltammetric and square-wave voltammetric (SWV) analysis. SWV was used to monitor the amount of bound OPs and provide simple, fast, and facile quantitative methods for nitroaromatic OP compounds. The sensor surface can be regenerated by successively running SWV scanning. Operational parameters, including the amount of nanoparticles, adsorption time, and pH of the reaction medium have been optimized. The stripping voltammetric response is highly linear over the 5-100 ng/mL (ppb) methyl parathion range examined (2-min adsorption), with a detection limit of 3 ng/mL and good precision (RSD = 5.3%, n = 10). The detection limit was improved to 1 ng/mL by using 10-min adsorption time. The promising stripping voltammetric performances open new opportunities for fast, simple, and sensitive analysis of OPs in environmental and biological samples. These findings can lead to a widespread use of electrochemical sensors to detect OP contaminates.

Electrochemistry↗
PubMed2005

Rapid, quantitative and sensitive immunochromatographic assay based on stripping voltammetric detection of a metal ion label.

A novel, sensitive immunochromatographic electrochemical biosensor (IEB) which combines an immunochromatographic strip technique with an electrochemical detection technique has been demonstrated. The IEB takes advantages of the speed and low-cost of the conventional immunochromatographic test kits and high-sensitivity of stripping voltammetry. Bismuth ions (Bi(3+)) have been coupled with the antibody through the bifunctional chelating agent diethylenetriamine pentaacetic acid (DTPA). After immunoreactions, Bi(3+) was released and quantified by anodic stripping voltammetry at a built-in single-use screen-printed electrode. As an example for the applications of such novel device, the detection of human chorionic gonadotronphin (HCG) in a specimen was performed. This biosensor provides a more user-friendly, rapid, clinically accurate, less expensive immunoassay for such analysis in specimens than currently available test kits.

Biosensing Techniques↗