Liana Lara

Sniffing out cancer using the JPL electronic nose: A pilot study of a novel approach to detection and differentiation of brain cancer

UNLABELLED A proof-of-concept study was done to determine whether an electronic nose developed for air quality monitoring at the Jet Propulsion Laboratory (JPL) could be used to distinguish between the odors of organ and tumor tissues, with an eye to using such a device as one of several modes in multi-modal imaging and tumor differentiation during surgery. HYPOTHESIS We hypothesized that the JPL electronic nose (ENose) would be able to distinguish between the odors of various organ and tumor tissues. MATERIALS AND METHODS The odor signatures, or array response, of two organs, chicken heart and chicken liver, and cultured glioblastoma and melanoma tumor cell lines were recorded using the JPL Electronic Nose. The overall array responses were compared to determine whether they were sufficiently different to allow the organs and cell lines to be identified by their array responses. RESULTS The ENose was able to distinguish between the two types of organ tissue and between the two types of tumor cell lines. The variation in array response for the organ tissues was 19% and between the two types of cultured cell lines was 22%. CONCLUSION This study shows that it is possible to use an electronic nose to distinguish between two types of tumor cells and between two types of organ tissue. As we conducted the experiment with a sensor array built for air quality monitoring rather than for medical purposes, it may be possible to select an array that is optimized to distinguish between different types of cells and organ tissues. Further focused studies are needed to investigate the odor signatures of different cells as well as cellular proliferation, growth, differentiation and infiltration.

Lifetimes of AMTEC electrodes: Molybdenum, rhodium-tungsten, and titanium nitride

The lifetime of three types of AMTEC electrodes is predicted from the rate of grain growth in the electrode. Grain size is related to electrode performance, allowing performance to be correlated with grain growth rate. The rate of growth depends on physical characteristics of each material, including the rates of surface self-diffusion and molecule mobility along grain boundaries. Grain growth rates for molybdenum, rhodium-tungsten and titanium nitride electrodes have been determined experimentally and fit to models in order to predict operating lifetimes of AMTEC electrodes. For lifetimes of 10 years or more, RhxW electrodes may be used at any operating temperature supportable by the electrolyte. TiN electrodes may be used in AMTEC cells only at operating temperatures under 1150 K, and Mo may be used only below 1100 K.

The JPL electronic nose: Monitoring air in the U.S. Lab on the International Space Station

An electronic nose with a sensor array of 32 conductometric sensors has been developed at the Jet Propulsion Laboratory (JPL) to monitor breathing air in spacecraft habitat. The Third Generation ENose is designed to operate in the environment of the U.S. Lab on the International Space Station (ISS). It detects a selected group of analytes at target concentrations in the ppm regime at an environmental temperature range of 18 – 30 °C, relative humidity from 20 – 75% and pressure from 530 to 760 torr. The monitoring targets are anomalous events such as leaks and spills of solvents, coolants or other fluids. The JPL ENose operated as a technology demonstration for seven months in the U.S. Laboratory Destiny during 2008–2009. Analysis of ENose monitoring data shows that there was regular, periodic rise and fall of humidity and occasional releases of Freon 218 (perfluoropropane), formaldehyde, methanol and ethanol. There were also several events of unknown origin, half of them from the same source. Each event lasted from 20 to 100 minutes, consistent with the air replacement time in the U.S. Lab.

Ground Validation of the Third Generation JPL Electronic Nose

The Third Generation ENose is an air quality monitor designed to operate in the environment of the US Lab on the International Space Station. It detects a selected group of analytes at target concentrations in the ppm regime at an environmental temperature range of 18 30 o C, relative humidity from 25 - 75% and pressure from 530 to 760 torr. The abilities of the device to detect ten analytes, to reject confounders as “unknown” and to deconvolute mixtures of two analytes under varying environmental conditions has been tested extensively in the laboratory. Results of ground testing showed an overall success rate for detection, identification and quantification of analytes of 87% under nominal temperature and humidity conditions and 83% over all conditions.

Operation of Third Generation JPL Electronic Nose on the International Space Station

The Third Generation ENose is an air quality monitor designed to operate in the environment of the US Lab on the International Space Station (ISS). It detects a selected group of analytes at target concentrations in the ppm regime at an environmental temperature range of 18 - 30 o C, relative humidity from 25 - 75% and pressure from 530 to 760 torr. This device was installed and activated on ISS on Dec. 9, 2008 and has been operating continuously since activation. Data are downlinked and analyzed weekly. Results of analysis of ENose monitoring data show the short term presence of low concentration of alcohols, octafluoropropane and formaldehyde as well as frequent short term unknown events.

Temperature effects on polymer-carbon composite sensors: Evaluating the role of polymer molecular weight and carbon loading

We report the effect of temperature coupled with varying polymer molecular weight and carbon loadings on the performance of polymer-carbon black composite films, used as sensing media in the JPL Electronic Nose (ENose). While bulk electrical properties of polymer composites have been studied, with mechanisms of conductivity described by connectivity and tunneling, it is not fully understood how environmental conditions and intrinsic polymer and filler properties affect polymer composite sensor characteristics and responses. Composites of polyethylene oxide (PEO)-carbon black (CB) considered here include PEO polymers with molecular weights of 20K, 600 K and 1M. The effects of polymer molecular weight on the percolation threshold of PEO-carbon composite and incremental sensor temperature effects on PEO-carbon sensor response were investigated. Results show a correlation between the polymer molecular weight and percolation threshold. Changes in sensor properties as a function of temperature are also observed at different carbon loadings; these changes may be explained by a change in conduction mechanism.

Advances in electrode materials for AMTEC

A mixed conducting electrode for the Alkali Metal Thermal to Electric Converter (AMTEC) has been made and tested. The electrode is made from a slurry of metal and TiO2 powders which is applied to the electrolyte and fired to sinter the electrode material. During the first 48–72 hours of operation in a SETC, the electrode takes up Na from low pressure sodium vapor to make a metal-Na-Ti-O compound. This compound is electronically conducting and ionically conducting to sodium; electronic conduction is also provided by the metal in the electrode. With a mixed conducting electrode made from robust, low vapor pressure materials, the promise for improved performance and lifetime is high.

The thermal stability of sodium beta'-Alumina solid electrolyte ceramic in AMTEC cells

A critical component of alkali metal thermal-to electric converter (AMTEC) devices for long duration space missions is the beta″-alumina solid electrolyte ceramic (BASE), for which there exists no substitute. The temperature and environmental conditions under which BASE remains stable control operational parameters of AMTEC devices. We have used mass loss experiments in vacuum to 1573K to characterize the kinetics of BASE decomposition, and conductivity and exchange current measurements in sodium vapor filled exposure cells to 1223K to investigate changes in the BASE which affect its ionic conductivity. There is no clear evidence of direct thermal decomposition of BASE below 1273K, although limited soda loss may occur. Reactive metals such as Mn or Cr can react with BASE at temperatures at least as low as 1223K.

Performance parameters of TiN electrodes for AMTEC cells

In order to model the lifetime of the electrochemical cell in an Alkali Metal Thermal to Electric Converter (AMTEC), studies of TiN electrodes on beta″-alumina solid electrolytes (BASE) have been made to determine the performance parameters over time. Performance parameters include, G, the morphology factor, and B, the temperature independent exchange current. The results of several experiments, both AMTEC cells and Sodium Exposure Test Cells, in which TiN electrodes have been studied at 1120–1200 K are described here.

Polymer-based carbon monoxide sensors

Polymer-based sensors have been used primarily to detect volatile organics and inorganics; they are not usually used for smaller, gas phase molecules. We report the development and use of two types of polymer-based sensors for the detection of carbon monoxide. Further understanding of the experimental results is also obtained by performing molecular modeling studies to investigate the polymer-carbon monoxide interactions. The first type is a carbon-black-polymer composite that is comprised of a non-conducting polymer base that has been impregnated with carbon black to make it conducting. These chemiresistor sensors show good response to carbon monoxide but do not have a long lifetime. The second type of sensor has a non-conducting polymer base but includes both a porphyrin-functionalized polypyrrole and carbon black. These sensors show good, repeatable and reversible response to carbon monoxide at room temperature.