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Patternable nanowire sensors for electrochemical recording of dopamine.

ABSTRACT: Spatially resolved electrochemical recording of neurochemicals is difficult due to the challenges associated with producing nanometer-scale patternable and integrated sensors. We describe the lithographic fabrication and characterization of patternable gold (Au) nanowire (NW) based sensors for the electrochemical recording of dopamine (DA). We demonstrate a straightforward NW-size-independent approach to align contact pads to NWs. Sensors, with NW widths as small as 30 nm, exhibited considerable insensitivity to scan rates during cyclic voltammetry, a nonlinear increase in oxidation current with increasing NW width, and the selectivity to measure submaximal synaptic concentrations of DA in the presence of interfering ascorbic acid. The electrochemical sensitivity of Au NW electrode sensors was much larger than that of Au thin-film electrodes. In chronoamperometric measurements, the NW sensors were found to be sensitive for submicromolar concentration of DA. Hence, the patternable NW sensors represent an attractive platform for electrochemical sensing and recording.

SUBMITTER: Tyagi P

PROVIDER: S-EPMC2794995 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature

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Patternable nanowire sensors for electrochemical recording of dopamine.

Tyagi P P Postetter D D Saragnese D L DL Randall C L CL Mirski M A MA Gracias D H DH

Analytical chemistry 20091201 24

Spatially resolved electrochemical recording of neurochemicals is difficult due to the challenges associated with producing nanometer-scale patternable and integrated sensors. We describe the lithographic fabrication and characterization of patternable gold (Au) nanowire (NW) based sensors for the electrochemical recording of dopamine (DA). We demonstrate a straightforward NW-size-independent approach to align contact pads to NWs. Sensors, with NW widths as small as 30 nm, exhibited considerable ...[more]

PMID: 19904993

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Project description:Nanowire field-effect transistors (NW-FETs) have been shown to be powerful building blocks for nanoscale bioelectronic interfaces with cells and tissue due to their excellent sensitivity and their capability to form strongly coupled interfaces with cell membranes. Graphene has also been shown to be an attractive building block for nanoscale electronic devices, although little is known about its interfaces with cells and tissue. Here we report the first studies of graphene field effect transistors (Gra-FETs) as well as combined Gra- and NW-FETs interfaced to electrogenic cells. Gra-FET conductance signals recorded from spontaneously beating embryonic chicken cardiomyocytes yield well-defined extracellular signals with signal-to-noise ratio routinely >4. The conductance signal amplitude was tuned by varying the Gra-FET working region through changes in water gate potential, V(wg). Signals recorded from cardiomyocytes for different V(wg) result in constant calibrated extracellular voltage, indicating a robust graphene/cell interface. Significantly, variations in V(wg) across the Dirac point demonstrate the expected signal polarity flip, thus allowing, for the first time, both n- and p-type recording to be achieved from the same Gra-FET simply by offsetting V(wg). In addition, comparisons of peak-to-peak recorded signal widths made as a function of Gra-FET device sizes and versus NW-FETs allowed an assessment of relative resolution in extracellular recording. Specifically, peak-to-peak widths increased with the area of Gra-FET devices, indicating an averaged signal from different points across the outer membrane of the beating cells. One-dimensional silicon NW- FETs incorporated side by side with the two-dimensional Gra-FET devices further highlighted limits in both temporal resolution and multiplexed measurements from the same cell for the different types of devices. The distinct and complementary capabilities of Gra- and NW-FETs could open up unique opportunities in the field of bioelectronics in the future.

Project description:BackgroundThe development of wearable health monitoring systems is garnering tremendous interest in research, technology and commercial applications. Their ability of providing unique capabilities in continuous, real-time, and non-invasive tracking of the physiological markers of users can provide insights into the performance and health of individuals. Electrocardiogram (ECG) signals are of particular interest, as cardiovascular disease is the leading cause of death globally. Monitoring heart health and its conditions such as ventricular disturbances and arrhythmias can be achieved through evaluating various features of ECG such as R-peaks, QRS complex, T-wave, and P-wave. Despite recent advances in biosensors for wearable applications, most of the currently available solutions rely solely on a single system attached to the body, limiting the ability to obtain reliable and multi-location biosignals. However, in engineering systems, sensor fusion, which is the optimal integration and processing of data from multiple sensors, has been a common theme and should be considered for wearables. In recent years, due to an increase in the availability and variety of different types of sensors, the possibility of achieving sensor fusion in wearable systems has become more attainable. Sensor fusion in multi-sensing systems results in significant enhancements of information inferences compared to those from systems with a sole sensor. One step towards the development of sensor fusion for wearable health monitoring systems is the accessibility to multiple reliable electrophysiological signals, which can be recorded continuously.ResultsIn this paper, we develop a textile-based multichannel ECG band that has the ability to measure ECG from multiple locations on the waist. As a proof of concept, we demonstrate that ECG signals can be reliably obtained from different locations on the waist where the shape of the QRS complex is nearly comparable with recordings from the chest using traditional gel electrodes. In addition, we develop a probabilistic approach-based on prediction and update strategies-to detect R-peaks from noisy textile data in different statuses, including sitting, standing, and jogging. In this approach, an optimal search method is utilized to detect R-peaks based on the history of the intervals between previously detected R-peaks. We show that the performance of our probabilistic approach in R-peak detection is significantly better than that based on Pan-Tompkins and optimal-threshold methods.ConclusionA textile-based multichannel ECG band was developed to track the heart rate changes from multiple locations on the waist. We demonstrated that (i) the ECG signal can be detected from different locations on the waist, and (ii) the accuracy of the detected R-peaks from textile sensors was improved by using our proposed probabilistic approach. Despite the limitations of the textile sensors that might compromise the quality of ECG signals, we anticipate that the textile-based multichannel ECG band can be considered as an effective wearable system to facilitate the development of sensor fusion methodology for pervasive and non-invasive health monitoring through continuous tracking of heart rate variability (HRV) from the waist. In addition, from the commercialization point of view, we anticipate that the developed band has the potential to be integrated into garments such as underwear, bras or pants so that individuals can use it on a daily basis.

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Patternable nanowire sensors for electrochemical recording of dopamine.

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Patternable nanowire sensors for electrochemical recording of dopamine.

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